I A I;nemlcal IThe School l ,a - web.usm.myweb.usm.my/chem/bulletin kimia/buletin kimia2005.pdf ·...

Bulletin Vo1.4 October 2005 I A I T h e S c h o o l o f l ,a -=- I;nemlcal - - 1 n i v e r s i t i S a i n s M a l a y s i a

, ar furher informati~n~please contact: Chief Editor, Bulletin of School of Chemical Sciences, Universiti Sains Malaysia, 1 7800 Penang, Malaysia

Fax: 604-657 4854; Tel : 604-653 3888 ext. 3262; E-mail: [email protected]

from the Dean

2 Bulletin Kimia USM

WELCOME to the fourth issue of Bulletin KIMIA-USM. This is the first issue since the new administration took office on 16 March 2005.1 would like to congratulate the Editorial Board and the contributors to this issue. It is noteworthy that Bulletin KIMIA-USM has been a very useful source of information for our prospective graduate students, our alumni and other potential 'clients' of the School.

The School of Chemical Sciences continues doing excellent teaching, research and

Prof. Madya Dr Wan Ahmad Kamll consultancy services despite uncertain times. Mahmood We are currentlv in the transient ~ e r i o d

between the Malaysian Plans. The 9Ih Malaysian Plan is due to commence in 2006 which will have implications on the physical development. It will also present a different outlook on the opportunities of research grants, be it from IRPA or other government agencies. With the Government's greater emphasis on agro-based industries, nanotechnology, advanced materials and biotechnology, it is more so important that the chemists seek out research collaborations with our colleagues in these areas to secure research grants. It is without doubt that we as chemists will be able to contribute to the fundamental aspects of the said thrust areas. Concurrently, we should also continuously secure research grants in our own respective areas from both local and international agencies. As the operational funds will not increase very much, grants obtained by staff will go a long way in supporting the graduate students.

As I write this preface, the School is busily preparing for new intake of students for the 2005106 Session and for the beginning of the new Session a week later. On July 4, 2005, we are receiving the new batch of students for the Session 2005106. We are expecting no more than 250 freshies for both programmes. The School has made preparations to ensure that quality education is provided by the School. While research has been given much emphasis, the teaching aspect is equally important. 1 seek cooperation from all members of the School to give their best in this endeavour as these 'captive-market' should not be taken for granted.

I would like to take this opportunity to thank the last administration for their relentless effort to maintain the excellent work at the School. We wish them a successful and productive sabbatical, they surely deserve it.

Thank you.

Assoc. Prof. Wan Ahmad Kamil Mahmood

Kandungan

From the Dean

From the Chief Editor

Research News --

4 From nematic to smectic phase - a progress in the liquid crystals display (LCD)

Bimetallic nanocatalysts - potential application in organic reaction selectivity

Tin chemical research for crop protection

Sequencing batch reactor treatment system

4 Crosslinking level assessments in polyolefin system

4 Chitosan research at the School of Chemical Sciences

w Trace metal speciation studies in natural waters

4 Molecular recognition using molecular imprinting techniques

Research Report - -- - -

4 Volatile constituents of some local fragrant flowers

Flavanoid monomers as steel corrosion inhibitors

4 Mangrove's pyroligneous acid: natural antioxidant and antimicrobial agents

4 Visible light environmental photocatalysis with natural polymers-doped TiO,.

4 Ruthenium-silica nano-fibres from rice husk?

4 Understanding natural rubber via nanoscience

General Article - -

Protecting the environment by consuming chemicals smartly

News About the School

MUPA activities

1 Highlight of activities in 2004

EDITORIAL BOARD - CHIEF EDITOR Professor Lim Poh Eng

EDITORS Assoc. Prof. Md. Sani lbrahim Assoc. Prof. Norita Mohamed Assoc. Prof. Yeap Guan Yeow Dr. Farook Adam Dr. Shafida Abdul Hamid

.

.

. .

WELCOME to this issue of the Bulletin KIMIA-USM

from

Editor

of the School of Chemical Sciences. As you may have

noticed, this issue presents a new format which hopefully

: will enhance the appeal of the Bulletin. We are encouraged by the overwhelming support shown by the

academic staff of the School in terms of the great number

: of contributed articles encompassing various topics from

nanoscience to trace metal speciation. It is also worth mentioning that Dr. Yeap prepared his article while he is

on sabbatical in Japan.

. The contributed articles reflect a very diverse research . interests among the academic staff of the School. . Nonetheless, they can broadly be classified into the

: research fields of nanoscience, environment, liquid crystals, tin chemistry, corrosion studies and natural . products. While cluster groups for some of these fields

: have been formally established, others are still in the process of formation. The Bulletin will try to bring to you in every issue the progress and achievements of these

cluster groups which provide a good benchmark for the

: School in its pursuit in attaining research excellence.

. We have been trying to make the content of the Bulletin . reader friendly without sacrificing the academic aspect

: of the publication. Although it is definitely a difficult balancing act, we are convinced that this is the best . approach for the Bulletin. . .

0

Bulletin Kimia USM 3

RESEARCH News

From Nematic To Smectic Phase - A Progress In The Liquid Crystals Display (LCD)

Bimetallic Nanocatalysts - Potential Application in Organic Reaction Selectivity

I Dr. Shafida Abdul Hamid

STRATEGIES for controlling the regio-and stereoselectivity of reactions are important in organic chemical research. Asymmetric catalysis using organometallic reagents has been successfully employed in the synthesis of enantiomerically pure compounds. One of the many rational approaches to design stereoselective catalysts involves studying the influence of the ligands, particularly their steric and electronic properties. For example, it was found that using phosphinites with electron donating bis(3,5-dimethylphenyl) groups at phosphorus provide high ee's in the Rh(l)-catalysed asymmetric hydrogenation of dehydroamino acid derivatives whereas electron-withdrawing aryl substituents decrease the enantiose1ectivity.l

In recent years, nanocatalysts have received increasing attention due to their unique chemical and physical properties and potential technological applications as compared to the conventional metal catalysts. Bimetallic catalysts particularly have attracted much interest and the syntheses of these particles with definite size and dispersion provide a great challenge to researcher^.^.^

The synthesis of highly active bimetallic nanocatalysts for various organic reactions have been widely studied. However, only a few have studied the role of each metal in the catalyst. It has been thought that one of the metals in the bimetallic catalyst will provide the electronic influence (like a ligand), while the other metal will act as the ~atalyst.~

We are currently focusing on synthesising bimetallic nanocatalysts and study their effects on some of selected organic reactions, particularly hydrogenation. The selectivity of each reaction will also be studied and compared with the conventional asymmetric organic reactions.

References:

1. Rajanbabu, T.V., Radetich, B., You, K.K., Ayers, TA., Casalnuovo, A.L. and Calabrese, J.C., J. Org. Chem., 1999, 64, 3429-2447 and references therein.

2. Thomas, J.M., Raja, R., Johnson, B.F.G., O'Connell, T.J., Sankar, G. and Khimyak, T., Chem. Comm., 2003, 1126- 1127.

3. Dubau, L., Hahn, F., Coutanceau, C., Leger, J.-M. and Lamy, C., J. Electroanal. Chem., 2003, 554-555, 407-415. 4. Zhang, W-X, Wang, C-B and Lien, H-L, Catalysis Tday, 1998, 40, 387-395 and references therein.

I Assoc. Prof. Yeap Guan Yeow crystal (SSFLC) owing to the existence of spontaneous polarization which responds to the external field with higher speed.

LIQUID crystals display (LCD) technology has experienced a The leap from nematic to smectic phase within the LC materials is


tremendous development even though ~rogressive transition is intangible since the last few decades ago. The conventional LCD- based electronic devices available in the Current market such as watch and flat panel of laptop rely very much on the ordering nature of nematic or super-twisted nematic LC molecules over certain temperature range. Although the I'Iematic and twisted nematic LC are common materials for LCD devices in the past and present days, the workability of the product using these materials are still subject to further investigation. Several parameters such as the viewing angle, shutter speed and response time need to be improved or upgraded.

In 1974, a first truly polar liquid crystal was reported by R.B.Meyer and his coworkers [I]. The materials that he recognized as a chiral tilted smectic substance possess an intrinsic ferroelectric properties in the sense that every smectic layer has an electric dipole density, P, which is perpendicular to the molecular tilt direction, n, and parallel to the smectic layer plane. The importance of this ferroelectricity has further been substantiated by Clark-Lagetwall [2] who was responsible for the discovery of ferroelectric liquid crystals FLC. This kind of FCL domains have subsequently been related to a unique substance called surface-stabilized ferroelectric liquid

not a sudden process but appears in gradual manner. The Liquid Crystal Research Laboratory in the School of Chemical Sciences has regarded it as one of the niche research areas years ago. The research in the past [3] and several projects being expedited currently have shown promising results of which the orientational ordering of the molecules thus synthesized seemed to exhibit smectic as well as nematic phases [4].

References:

1. R.B.Meyer, L. Liebert, et.al. (1975). Le J. de Physique-Lettres, 36? L-69.

2. N.A.Clark, S.T.Lagerwall, et.a/. (1 985). Proceedings of the S/D, 2612,133-1 39.

3. G.Y.Yeap, M.Nakata, eta/. (2000). Liquid crystals, 27, 1437- 1443.

4, G.Y.Yeap, S.T.Ha, et.al. (2004). Mol.Cryst.Liq.Cryst., 423, 73- 84.

Tin Chemical Research for Crop Protection

Professor Teoh Siang Guan

THERE are five main triorganotin ingredients used as pesticides for crop protection, namely triphenyltin hydroxide (TPTH or fentin hy-droxide), tricyclohexyltin hydroxide (TCTH or cyhexatin), tricyclohexyltin triazole (TClT or azocyclotin), trineophenyltin oxide (TNTO or fenbutatin oxide) and triphenyltin acetate (TPTA or fentin ace-tate).These products are used primarily as fungicides (pesticides which kill or inhibit the growth of fungi) and acaracides (pesticides which kill mites and ticks).

The research carried out by the group is aimed at improving the efficiency, lowering the costs and diversifying the range of organotin chemicals that could be used for crop protection. Amongst the products that are being synthesized are the amino, fluoro and chloro- substituted phenyltin(lV) carboxylates and pyridine tin(lV) carboxylates. The fundamental principles related to the effects of the substituents on the structure and bonding take centre place in the investigation. Some of the interesting structural features arising from the research include self assembly of the tin(lV) complex into a coordination polymer in the crystalline state. In the first instance, it was found that when the carboxylate substituent of pyridine is in the 4-position, the bridging occurs in an end-on manner.

Pyridine-4-carboxylic acid

l'-:+-LQ< toluene 7-p

However, for triphenyl-2-chloro-5-aminophenyl- carboxylatotin(lV) bridging occurs in a via the carboxylate group in a bidentate manner.

Polymeric 5-coordinate

bidentate . bridging

Triphenyl 2-CI-5-NH,

carboxylate

Steric hindrance arising from the placement of amino group on the 2-position results in the formation of tetrahedral tin(lV) complex with a long range intermolecular interaction between the Sn atom and the N atom of the amino group from an adjacent molecule via hydrogen bonding.

Hydrogen Bonding between Sn and N

Recently, there have been a number of concerns raised regarding possible human health effects associated with organotins. Unfortunately, many of these allegations fail to consider the weight of scientific evidence and important scientific research conducted over the last decade. On this score, our research group is continuing to look into the intrinsic factors of organotins that enhance the desired biological activity and minimize the health or environmental effects.


Sequencing Batch Reactor Treatment System

Assoc. Prof. Seng Chye Eng and Prof. Lim Poh Eng

THE sequencing batch reactor (SBR) is a well-tested technology with distinct advantages over the conventional activated sludge process. It is a batch process based on a single activated sludge treatment reactor [I]. This treatment method has been gaining considerable popularity in recent years because of its high efficiency and flexibility of operation and cost effectiveness for small-scale treatment facilities. This fact has been reflected by growing interest among researchers and also the publication of a large number of papers. The conventional SBR operation is based on the principle of four steps - i.e. FILL, REACT, SETTLE and DRAW - all steps being operated sequentially in a single reactor. The perceived merits of the SBR systems also include better tolerance towards shock load, good settling due to better control of filamentous growth, simplicity and compact layout.

The application of simultaneous adsorption and biodegradation processes in the same reactor is known to be effective in the removal of both biodegradable and non-biodegradable contaminants including toxic compounds in various kinds of wastewater. This approach may be a good alternative to employing an activated carbon adsorption process as pretreatment in the treatment of metal-containing wastewater. Previous studies had shown that the combination of powdered activated carbon (PAC) and biomass in the same aeration basin of the conventional continuous-flow activated sludge system, known as the PACT process, was effective in the removal of toxic pollutants present in various types of wastewater.The adsorption and biodegradation processes under SBR operation have been proven to be effective in treating metal-containing and dye-containing wastewaters with powdered activated carbon as the adsorbent [2-51. However, little work had been reported on PACT process under SBR operation in treating organic priority pollutants in industrial wastewater.

The treatment of organic pollutants by simultaneous adsorption and biodegradation processes is of particular interest because of the biodegradability of many organic compounds. This means that the adsorbent used in the PACT process can be bio-regenerated to a significant extent thus opening up a wide range of relatively low cost adsorbents, in comparison to the PAC, which can be used in the process [6,7].

Our current research activities on SBR include: Application of SBR in treating organic priority pollutant. Modeling of sorption of individual and simultaneous toxic pollutants onto biomass.

. Treatment of chromium (VI) and Nickel (11)-containing wastewater in SBR.

References:

1. Irvine, R.L. & Busch, A.W. (1979). Sequencing batch biological reactors-an overview. J. Water Pollut. Control Fed. 51, 235-243.

2. Lim RE. & Er C. C. (2000). Treatment of dye-containing wastewater by sequencing batch reactor with powdered activated carbon addition. Toxicol. Environ. Chem. 75, 75-88.

3. Lim P.E., Ong S.A. & Seng C.E. (2002), Simultaneous adsorption and biodegradation processes in sequencing batch reactor (SBR) for treating copper and cadmium-containing wastewater. Water Res. 36, 667-675.

4. Ong S.A, Lim PE. & Seng C.E. (2003). Effects of adsorbents and copper (11) on activated sludge microorganisms and sequencing batch reactor treatment process. J. Hazard. Mat. B103, 263-277.

5. Ong S.A, Lim PE., Seng C.E., Hirata M. & Hano Tadashi (2005). Effects of Cu(ll) and Cd(ll) on the performance of sequencing batch reactor treatment system. Process Biochemistry, 40, 453-460.

6. Lee K.M. & Lim PE. (2003). Treatment of phenolic wastewater using agricultural wastes as an adsorbent in a sequencing batch reactor. Water Sci. Technol. 47, 41-47.

7. Lee K.M. & Lim PE. (2005). Bioregeneration of powdered activated carbon in the treatment of alkyl- substituted phenolic compounds in simultaneous adsorption and biodegradation processes. Chemosphere 58, 407-41 6.


RESEARCH News

Crosslinking Level Assessments In Polyolefin System

Dr. Coswald Stephen Sipaut @ Mohd Nasri

POLYMER, known as macromolecule, is classified into three main categories, namely thermoplastic, thermoset and elastomer, based on their properties [I]. It is also known that polymer with excellent physical and mechanical properties can be obtained by altering processing techniques and formulations. Structural modification by molecular crosslinking (three dimensional network formation) is the main modification in the polymeric system to significantly alter their chemical, physical and mostly their mechanical properties [I]. This crosslinking material can be obtained by various techniques depending on the base polymer. Normally, for polyolefin and rubber-based polymers, crosslinking is achieved by using peroxide, irradiation and sianol techniques which involved free radical interaction. For epoxy/composite-based material, crosslinking is achieved by addition of hardener and involves either ionic or radical interaction.

Crosslinking can be formed at either the intra- or inter- 1 molecular level both of which give different properties [2,3]. Therefore, assessment of the crosslinking level (degree of crosslinking) formed in the polymeric system is important to predict or correlate with their properties. There are a few methods to assess the crosslinking level in the polymer depending on the type of the polymer. For polyolefin, gel content, swelling, melt tensile and rheological techniques are often employed, whereas for rubber system, swelling, melt tensile and rheological techniques are often used and for composite materials, their glass transition and melting temperature values are considered [3].

Crosslinking can be

formed at either the intra- or

inter-molecular level both of

which give different

properties [2,3]. Therefore,

assessment of the

crosslinking level (degree of

crosslinking) formed in the

polymeric system is

important to predict or

correlate with their

properties.


RESEARCH News I

For polyolefin, e.g. polyethylene, a standard measurement of crosslinking level is by gel content technique. It is determined by refluxing in boiling xylene for 24 hours and expressing the weight of the vacuum- dried insoluble fraction as a percentage of sample weight before extraction [4]. For the melt measurements, the solid crosslinked matrix is performed in an lnstron tensile testing machine fitted with an environmental chamber at elevated temperature. For the rheological technique, the sample is analyzed in the Dynamic Mechanical Thermal Analysis equipment to obtain the shear modulus at elevated temperature. Both melt and rheological measurements require either Young's modulus or shear modulus to calculate the degree of crosslinking (i.e. crosslink density) using Eq. (1) [I ,5]:

where c is the crosslink density, E the Young's Modulus, G the shear modulus at full crosslinking, R the gas constant and T the temperature of testing.

For the Swell technique, the crosslinking level is determined after immersion in p-xylene at elevated temperature for 24 hours [4]. The data obtained from swelling equilibrium could be used to estimate the crosslink density using Eq. (2) [5]:

where x is the polymer solvent interaction parameter (i.e. the Flory-Huggins interaction parameter for the polymer in p-xylene), !/,the molar volume of p-xylene at elevated temperature, c $ ~ the volume fraction of polymer in the polymer-solvent mixture and p the density of dried sample. It should be highlighted that the temperature used for all crosslinking level measurements depends on the melting temperature of the base polymer.

DCP concen8atlonI p k . . ,. . - . . . - ~.

Fig'ure 1 The effect of DCP concentration on gel content.

It is well documented that peroxides are the main chemical used as a crosslinking agent (initiator) to form molecular crosslinking in polyolefin material. It has also been reported that increasing peroxide concentration in the polymers will increase their mechanical strength and thermal resistance due to the crosslinking formations. Figure 1 shows the effect of increasing dicumyl peroxide (DCP) concentration on gel content (percentage of crosslinking) in low-density polyethylene (LDPE). The results support the phenomenon as the crosslinking level increases with increasing DCP concentration (21 whereas swelling, melt and rheological measurements of the same samples show an increase in crosslink density with increasing gel content (i.e. increasing DCP concentration) as shown in Fig. 2 [3]. Therefore, all measurement techniques are adequate to measure or determine the crosslinking level in polyolefin traditional system (polymer with peroxide alone).

References:

1. Klempner D. and Frisch K. C., 1991, Handbook of Polymeric Foams, Hanser Publishers, New York

2. Sims G. L. A. and Sipaut C. S., 2001, Crosslinking of Polyolefin Foams: I. Effect of Triallyl Cyanurate on Dicumyl Peroxide Crosslinking of Low-Density Polyethylene, Cell. Polym., 20, 255-278

3. Sims G. L. A. and Sipaut C. S., 2002, The Used of Polyfunctional Monomers in Compression-Moulded Low- Density Polyethylene Foam Formulations, Blowing Agents and Foaming Process, Paper 14, RAPRA Technology, Heildelberg Germany

4. ASTM D 2765-95., 1995, Standard Test Methods for Determination of Gel Content and Swell Ratio of Crosslinked Ethylene Plastics, ASTM, Philadelphia, Pa.

5. Flory P. J. and Rehner J. Jr., 1943, Statistical Mechanics of Crosslinked Polymer Networks 11. Swelling, J . Chem. Phys., 11, 521-530.

Figure 2 Comparison of crosslink density determined by variou methods as a function of gel content for DCP crosslinked LDPE.


Chitosan Research at The School of Chemical Sciences

Assoc. Prof. Mohamad Abu Bakar, Assoc. Prof. Wan Saime Wan Ngah, Dr. Rohana Adnan, M. Adlim and R. Ahmad Ramli

NATURAL polymers such as natural rubber, chitin and ' carbohydrates have attracted research activities at the School of Chemical Sciences (SCS) over the years. Recently, research on their derivatives, namely epoxidised natural rubber (ENR) and chitosan, has intensified as reflected by the numerous publications [I]. I Chitosan (Fig.1) is a deacetylated chitin which is a biopolymer found in exoskeleton of insects, crustaceans and also in other lower form organisms including fungi, algae, protozoas, cnidaria and aschelminthes. Applications of many types of fabricated chitosan have been introduced in literatures [2].

Figure 1 : Chitosan

At SCS, three areas relating to chitosan-based material studies are currently being explored. Each area is being led by an academic staff, whose group supports several postgraduate and final-year undergraduate students. Their activities managed to procure several short-term IRPA and FRGS grants. These activities also result in a number of publications.

The first area of research concerned the use and the modification of chitosan structure to enhance its durability. adsorption capacity and selectivity for separations of metal ions and dyes. This is conducted by a research group led by Assoc. Prof. Wan Saime. His group has published several papers on the performance of chitosan and its cross-link derivatives mth glutaraldehyde, epichlorohydrin and ethyleneglycol dgtycidyl ether [3-51. For future development, studies on various types of chitosan derivatives in the form of porous chitosan beads being durable toward organic acids are being undertaken.

Assoc. Prof. Mohamad's group conducts studies on the nanoscience aspects of chitosan-based materials. Chitosan has been employed as a matrix in the preparation of nanosize metals and metal oxides nanocomposites film, membrane or as support with or

without inert materials. These chitosan-based materials also found applications as stabilizer for nanoparticles in colloidal preparations as shown in Fig. 2(c). Chitosan- stabilized noble metal nanoparticles catalysts have narrow size distribution and their particle size can be controlled using appropriate reducing agent [6]. It is also proven that chitosan have dual functions, acting as the stabilizer as well as the reducing agent [7]. Morphology of the chitosan-stabilized noble metal particles has been studied and reported [8]. Studies on bimetallic noble metal nanoparticles as the core-shell structure and their catalytic properties have been carried out [9]. This includes comparisons of the catalytic activities among the chitosan-stabilized mono- as shown in Fig. 2(a) and bimetallic nanoparticles with regard to the type of metals, composition, stabilizers, substrates, reducing agents or techniques. Various techniques of immobilizing noble metal colloidal nanoparticles on inert support with regard to catalytic activities have been investigated as shown in Fig. 2(b). Chitosan stabilized multi-metals and metat oxides nanoclusters are in line for future projects.

Dr. Rohana and her group work on the development of both the theoretical and preparative aspects of chitosan- based biomaterial nanocomposites. Hydroxyapatite- chitosan (HAP-Chi) has been prepared with various techniques to enhance the mechanical properties for biomedical implants with several designed properties such as bioactive, biodegradable and osteoconductive. Co-precipitation and blending methods have been performed to prepare HAP-Chi nanocomposites as shown in Fig. 3. Organic solvents such as ethanol has been employed in both methods to develop well disperse HAP-Chi nanocomposites. Co-precipitation route has shown that the particles congregated to form fractals or scaffold-like structure as shown in Fig. 3(a). However, blending method afforded the HAP-Chi particles with higher dispersivity as shown in Fig. 3(c) and under certain experimental condition produced smaller and stouter particles as in Fig. 3 (b). For future study, metal incorporated HAP-Chi nanocomposites will be investigated.

Epilogue

Chitin, the parent compound of chitosan, is the second most abundant biopolymer after carbohydrate. This makes chitosan an easily available raw material. Coupled with innovativeness in experimental and theoretical approaches, chitosan chemistry can be interesting and fruitful. We welcome other staff researchers, postgraduates and graduates alike in exploring "the


I RESEARCH News

0 0 50 100

time (min)

gure 2: (a) Rate of hydrogen uptake of variously reduced chitosan-stabilized palladlum metal clusters [6], (b) TEM image of the bimetal11 I-Au nanopartlcles on the surface of chitosan coated-TiO, [a] and (c)TEM image of the chitosan-stabilized gold colloidal nanoparticles [7

Figure 3: TEM images of HAP-Chi prepared by (a) co-preclpitatlon, (b) and (c) blending techniques.

Chemistry of Chitosan at the School of Chemical Sciences".

References:

1. Publication 2002-2003: A Compilation, SCS, USM, December, 2003.

2. Adlim, M. (2003). Natural, 3 (1) 32-38. 3. Wan Ngah, W. S. & Isa, I. M. (1998). J. Appl. Polym.

Sci., 67, 1067-1 070. 4. Wan Ngah, W. S. & Liang, K. H. (1999). Ind. Eng.

Chem. Res., 38, 141 1-1414.

5. Wan Ngah, W. S., Endud, C. S & Mayanar, R. (2002). React. Funct. Polym. J., 50, 181 -1 90.

6. Adlim, M., Bakar, M. A., Liew, K.Y & Ismail, J. (2003). J. Mol. Catal. A: Chem., 212, 141-149.

7. Adlim, M., Abu Bakar, M. A., Liew, K. Y & Ismail, J. (2003). (accepted for publication; React. Funct. Polym. J.).

8. Adlim, M & Bakar, M. A. (2003). Microsom, Vol. 5- 6, (I), 6-10.

9. Adlim, M., Abu Bakar, M., Ismail, J. & Liew, K.Y., (2004). CD Proceedings Of RCYC, Vol. 2, pp 1-7, April, Penang.


Trace Metal Speciation studies in Natural Waters

Assoc. Prof. Norita Mohamed and Prof. Lim Poh Eng

THE total concentration of a metal in an ecosystem may not correlate well with its impact on various aquatic life forms. For instance, only a few metal species are available to plankton since most metal uptake occurs using a complexing agent produced by the plankton [I]. Essentially only rapidly dissociating complexes are available for uptake. A metal can either have toxic effects or function as a nutrient. Trace metals in natural waters tend to be complexed by organic and inorganic ligands and this will affect both their chemical reactivity and biological availability [2]. Speciation analysis of trace metals in water may be defined as the determination of the concentrations of the different physio-chemical forms of the metal which make up its total concentration in the sample. These forms may include particulate matter and dissolved forms such as simple inorganic species, organic complexes and the metal adsorbed on various colloidal particles. Several techniques and methods such as solvent extraction, ultrafiltration, dialysis, adsorption, ion-exchange, UV-irradiation, ion-selective electrode potentiometry and stripping voltammetry have been used in chemical speciation schemes to distinguish between chemical forms in natural waters [3]. Other speciation studies which involve sequential schemes or single extraction employing various kinds of sorbents have been developed to further enhance knowledge of metal speciation in terms of whether they are labile, non-polar, anionic or neutral [ I , 2, 4, 51. Kinetic studies of metal speciation together with studies on physical speciation of the metal species by their size fractionation and correlation of the size fractions with the dissociation kinetics of the metal complex have great potential [6,q. It was reported that free metal ions, namely the aqua ions. and the highly labile metal complexes in a water sample are the most bioavailable fraction of the total metal in the sample. The dissociation rate constants of metal complexes would be an indicator of the bioavailability and toxicity of the metal. The kinetics of the metal complex dissociation has been studied by anodic stripping voltammetry and by ion exchange at Chelex-100 cation exchange resin, using both the Chelex column and the Chelex batch technique [3, 61.

Our work involves the development of a speciation scheme for Pb, Cd, Cu and Zn in natural waters which

incorporates physical speciation by size using ultrafiltration of the soluble metal species and the

I subsequent chemical characterization of the various size fractions using different sorbents such as Chelex-100, Dowex 1 -X8 and silica C,, which will distinguish labile complexes, non-polar organic adsorbable matter and ion exchangeable substances [El. The retention behaviour of Pb, Cd, Cu and Zn as free hydrated ions and after conversion into negative or neutral complexes using various ligands on the sorbents are investigated. The combination of ultrafiltration with the use of various sorbents will help to explain the behaviour of colloidal species in natural waters. The kinetics of metal complex dissociation is studied using anodic stripping voltammetry and the Chelex batch technique [9].

It is hoped that this work will provide a more comprehensive picture and insight into the physical and chemical characteristics of metal species in natural waters. It is also expected to provide information for the correlation of the chemical characteristics (dissociation kinetics) of the metal species with their bioavailability and toxicity.

References:

C. Haraldsson, B. Lyven, M. Pollak & A. Skoog, Anal. Chim. Acta 284 (1993) 327. M. Groschner & P. Appriou, Anal. Chim. Acta 297 (1 994) 369. J. Cheng, C.L. Chakrabarti, M.H. Back & W.H. Schroeder, Anal. Chim. Acta 288 ( 1 9 9 4 ) 141. C. L. Chakrabarti, Y. Lu & J. Cheng, Anal. Chim. Acta 267 (1 993) 47. P. A. Sule & J. D. Ingle, Jr., Anal. Chim. Acta 326 (1 996) 85. 0. Abollino, M. Aceto, C. Sarzanini & E. Mentasti, Anal. Chim. Acta 41 1 (2000) 223. C.H. Langford & D. M. Gutzman, Anal. Chim. Acta 256 (1 992) 183. C. Suitcharit, N. Mohamed, P.E. Lim and W. Sirinawin, 2004. 'Determination of metal species using ultrafiltration and different solid sorbents', Regional Conference for Young Chemists, 2004, Penang, 13 -1 4 April 2004. P. Figura & B. McDuffle, Anal. Chem. 52 (1980) 1433.


IESEARCH News

Molecular Recognition Using Molecular Imprinting Techniques

Dr.Rohana Binti Adnan

THE development of systems capable of mimicking selectivity observed in nature has been the focus of intense research over the recent years. Among the artificial recognition system gaining popularity is the Molecular Imprinted Polymers (MIPS). Molecular imprinting involves pre-organization of monomers around a target (template) molecule (Fig. 1). Polymerization with an excess of cross-linker forms a highly crosslinked polymer network. Subsequent removal of the template molecules leaves behind functional cavities that are capable of selectively recognizing and rebinding the template. In other words, the imprint functions like a lock that is only compatible with the correct key.

MIPS are being used in an increasing number of applications including "tailor-made" separation materials, as antibodylreceptor binding site mimics, as enzyme mimics for catalytic applications, as well as recognition elements in biosensors [ I ,2]. To date, the most extensively investigated applications of MIPS have been as separation materials for the analysis of numerous compounds such as drugs, pesticides and amino

acids in techniques such as liquid chromatography and thin-layer chromatography PI.

MIPS research group at the School of Chemical Sciences comprises four researchers at the moment. Although at a very early stage, the progress of this MIPS related research has been very encouraging and helps to boost collaboration among other researchers in USM as well. The aim of our work is to investigate the possibility of preparing custom-designed polymers for the separation and, possibly, detection of a target compound. Ongoing MIPS research includes the synthesis of MIPS for the detection of nicotine smoke (in collaboration with Prof. Mohd. Noor Ahmad, KUKUM) and also the separation of

' lactose, a milk sugar. Fundamental issue involving the MIPS-template molecular recognition is being addressed as well.

References:

1. J. Steinke, D.C. Sherrington, I.R. Dunkin, Adv. Polym. Sci., 123 (1 995) 81.

2. C. Baggiani et, al, Analytica Chim. Acta, 504 (2004), 43.

3. K. Ensing, T. de Boer, Trends Anal. Chem., 18 (1 999) 138.


Fig. 1. Schematlc representation of the synthesis of MIPS

RESEARCH Report

Volatile Constituents of Some Local Fragrant Flowers

Assoc. Prof. Wong Keng Chong

THE campus of the Universiti Sains Malaysia and its neighbourhood are abound with a large variety of plants producing flowers which are rather fragrant. Mimusops elengi L. (Sapotaceae), Lawsonia inermis L. (Lythraceae) and Couroupita guianensis Aubl. (Lecythidaceae) are three examples. The first, known locally as bunga tanjung, is an evergreen medium- sized tree commonly planted in gardens or by roadsides for its ornamental appearance and white, fragrant flowers which are produced during the greater part of the year. The essential oil obtained from the flowers is used in perfumes and as a stimulant. The flowers are also used in folk medicine for treating diarrhoea, and when dried and powdered, used as a snuff (1,2). The second plant is commonly known as henna or inai. It is a bush which can often be found in gardens in the villages. There are many races with flowers of different colours, though in Penang the yellow and red types are prevalent. The volatile oil from the flowers has an odour which has been described as reminiscent of tea-rose. The third of the aforementioned plants is a straight tree with a crown of branches high up, and brightly-coloured flowers and curious-looking fruits which resemble cannon balls. There is only one tree growing in the USM campus, but quite a few can be found in the Penang Botanical Garden.

Volatile constituents of the flowers of these three plants were analysed by using capillary GC and GC- MS, following isolation either by headspace sampling of the freshly-picked flowers, or by soaking the freshly-picked flowers in aqueous ethanol for 36 hours at room temperature. The aromatic essences were recovered from the filtered extracts by continuous liquidlliquid extraction using pentane. Seventy-four constituents were identified among the flower volatiles of M. elengi, comprising mainly aromatic alcohols and esters derived from the phenylpropanoid metabolism (3). 2-Phenylpropanol was clearly dominant, accounting for about 38 % of the volatiles. This constituent has a mild rose odour. Other quantitatively significant components included methyl benzoate, p-methylanisole, 2-phenylethyl acetate, (Q-cinnamyl alcohol and the uncommon plant volatile, 3-hydroxy-4-phenyl-2-butanone. Mono- and sesquiterpenoids were minor constituents; their total contribution was about 3 %. Regarding L. inermis, the red and the yellow varieties were examined (4). Interestingly, both the yellow and red flowers yielded high levels (> 10 %) of linalool, and

The second plant is

commonly known as henna

or inai. It is a bush which

can often be found in

gardens in the villages.

There are many races with

flowers of different colours,

though in Penang the yellow

and red types are prevalent.

The volatile oil from the

flowers has an odour which

has been described as

reminiscent of tea-rose.


Report

most of the compounds found among the volatiles of the yellow flowers were also detected among those of the red flowers. There were, however, significant quantitative differences. For example, 2-ionone and other carotenoid degradation products constituted over 50% of the volatiles of the yellow flowers but such high proportions of these compounds were not found among the volatiles of the red flowers. The red flowers yielded high levels of 2-phenylpropanol, benzyl alcohol and C, alcohols and aldehydes instead. As to C. guianensis, geraniol, farnesol and linalool had been identified previously in a petroleum ether extract of the flowers (5). Our investigation of the flower volatiles confirmed the presence of these three terpenoids and revealed the presence of 38 other identified constituents (6). We found eugenol clearly the most abundant (> 40%); the other quantitatively significant constituents were linalool, (E, E)-farnesol, nerol, geraniol, 2-phenylpropanol and benzyl alcohol.

References:

Burkill IH. A Dictionary of the Economic Products of the Malay Peninsula, vol 11. Ministry of Agriculture and Cooperatives: Kuala Lumpur, 1966; 1501. The Useful Plants of India. Council of Scientific and Industrial Research: New Dehli, 1986; 375. Wong KC, Teng YE. J. Essent. Oil Res. 1994; 6: 453-458. Wong KC, Teng YE. J. Essent. Oil Res. 1995; 7: 425-428. Lewis YS, Nambudiri ES, Krishnamurthy N, Ananthakrishna SM. Perfum. Essent. Oil Rec. 1969; 60: 23-24. Wong KC, Tie DY. J. Essent. Oil Res. 1995; 7: 225-227.

Flavanoid monomers as steel corrosion inhibitors Afidah Abdul Rahim, Assoc. Prof. Mohd. Jain Noordin I Mohd. Kassirn, Prof. J. Steinrnetz, Dr. E. Rocca and 1 Assoc. Prof. Md. Sani Ibrahirn. I

mangrove tannin but the inhibitive performance was found to be dependent on concentration.

IN our previous study, the characterization of mangrove tannin was carried out by depolymerizing condensed tannin in the presence of phloroglucinol nucleophiles in acidic ethanol. This was followed by the separation of flavan-3-01s and their phloroglucinol adducts using reversed phase high performance liquid chromatography. As a result of the analysis, four major components constituting mangrove tannin were identified. These monomers are catechin, epicatechin, epicatechin gallate and epigallocatechin. The inhibitory performance on steel in 0.5 M HCI of these monomers were evaluated via electrochemical studies so as to have a better rationalization of mangrove tannin inhibitory action. It was found that all the monomers act as cathodic inhibitors (Fig.1) similarly shown by

As a comparison, the inhibitory performance of the monomers were compared with that of 2- napthalene sulfonic acid, a cathodic inhibitor as claimed by Vracar and Drazic. It was observed that 2-napthalene sulfonic acid exhibited similar inhibitory performance to the monomers. On inspection of the percentage inhibition curves (Fig. 2), catechin, epicatechin and epicatechin gallate proved to be better inhibitors at 5 ~ 1 0 . ~ M and 1 . 0 ~ 1 0 . ~ M. The percentage inhibition of 2- napthalene sulfonic acid decreased as the concentration was increased to 0.01 M and exceeded 85% only when concentrations were increased to 0.05 M and 0.1 M. Thus, the use of these monomers as cathodic inhibitors is very promising.

Reference :

Vracar, Lj.M. and Drazic, D.M, Corrosion Science, 44. (2002). 1669-1 680.

Fig. 1.0 : Potentiodynamic curves of steel in 0.5 M HCI Fig. 2.0: Effect of concentration of inhibitors on solution containing 5xlW M fiavanoids. percentage inhibition of steel in 0.5 M HCI based on I,


Mangrove's Pyroligneous Acid: Natural Antioxidant and Antimicrobial

agents

IASSOC. Prof. Mohd. Jain Noordin Mohd. Kassirn

PYROLIGNEOUS acid or generally known as wood vinegar is a dark brown colour liquid solution obtained as the by products from charcoal kiln. During the pyrolysis of wood in charcoal production, smoke would be generated and the condensation of this smoke resulted in pyroligneous acid. The temperature of the smoke coming out from the kiln during the condensation process is about 240 "C. It is believed that this liquid contains hundreds of beneficial chemicals such as organic acid, alcohol, ketones, aldehydes etc. Pyroligneous acid has a long history and has been known for its sterilizing properties. At present, pyroligneous acid is recognized by experts of various field as having positive health and beauty effects, such as a health tonic and body patches or pouches that are capable of improving blood circulation and promoting detoxification.

The Matang Mangrove Forest with an area of 40,151 hectares is recognized internationally as the most sustainable and well-managed mangrove forest in the world. The Kuala Sepetang Charcoal village there has 600 charcoal kilns that were built in the 1930' and are still in business today. The smoke that escapes from the chimneys of kilns was passed through a 30 m extension of air-cooled aluminium pipe for condensation purpose. The condensed smoke or pyroligneous acid was collected in a polycarbonate drum and used for the present study.

Mangrove's pyroligneous acid (MPA) shows the FTlR characteristic bands for phenolic compounds. The Folin-Ciocalteu assay for total phenolic contents indicated that the MPA possesses high amount of phenolic content of 85.0 mg GAE (gallic acid equivalent) in comparison with ascorbic acid of 72.0 mg GAE.The dichloromethane extract (CPAE) of MPA in fact contains much higher phenolic content of up to 236.0 mg GAE.

The Matang Mangrove Forest

with an area of 40,151 hectares

is recognized internationally as

the most sustainable and well-

managed mangrove forest in

the world. The Kuala Sepetang

Charcoal village there has 600

charcoal kilns that were built in

the 1930' and are still in

business today.


Recent studies have shown that many dietary Among the pathogenic microorganisms strongly polyphenolic constituents derived from plants are more effective antioxidants in vitro than vitamin E or C, and thus might contribute significantly to the protective effects in vivo [I]. The antioxidant activity of phenolics is mainly due to their redox properties, which allow them to act as reducing agents, hydrogen donors and singlet oxygen quenchers. The reduction capacity and radical scavenging of a compound may serve as a significant indicator of its potential antioxidant activity. Figure 1 shows the reductive capabilities of MPA on FeYFe2+ system compared with ascorbic acid (AA), butylated hydroxytoluene (BHT), and a-tocopherol. The concentrated MPA (CPA) and CPAE showed higher reductive capabilities than commonly known antioxidants, thus indicating that MPA possessed better antioxidant activity. At 0.1000 mg ml-I, CPAE possessed scavenging activities at 2.7 times higher than AA, 3.9 times higher than a-tocopherol, and 10.6 times higher than BHT. MPA also shows a significant radical scavenging activities on DPPH (1,l -diphenil-2-picrl- hydrazyl) radical compared with AA, BHT and a- tocopherol (Fig.2)[2].

Antimicrobial activity test by means of disc diffusion method (Fig.3) showed that MPA strongly inhibited the growth of bacteria, fungi and yeast species.

. in hi bi ted were Staphylocucus aureus, Escherichia coli, Salmonella paratyphi B, Bacillus subtilis, Candida albicans, Rhodotorula rubra, Cryptococcus . neoformans, Trichoderma viride, Aspergillus flavus, Penicillium sp. and Aspergillus niger [3,4].

. The results of this preliminary study showed that the mangrove's pyroligneous acid (MPA) can be used as an easily accessible source of natural antioxidant and . a possible food supplement or in pharmaceutical industry. However, the components responsible for

: the antioxidant and antimicrobial activities are currently unresolved. Therefore, further works should be performed on the isolation and identification of . the antioxidant and antimicrobial components.

References:

H.Y.Pyo, T.C. Lee, L. Logendra and R.T. Rosen, (2004). Food Chem., 85, 19-26.

Y.C. Tang, (2005). B.Sc (Hons) Thesis,Universiti Sains Malaysia

M.1 Nor Zilawati, (2005). B.Sc.(Hons) Thesis, Universiti Sains Malaysia

R. Wendy, (2003). B.Sc(Hons) Thesis, Universiti Sains Malaysia.

1.80 - 1.60 .

0.00 0.02 0.40 0.06 0.08 0.10

Concentration (mglrnl) - CPA -c CPAE +- AA -u- BHT -- tocophemi

Fig. 1. Antioxidant activity of different concentrations of MPA Fig. 2. Free radical scavenging activity of different concentrations of MPA compared to the well known antioxidants.

Fig. 3. MPA of different concentrations applied to Bacillus subtilis (A), Aspergillus niger (B).


Visible Light Environmental Photocatalysis With Natural

Polymers - Doped Ti0 2

IASSOC. Prof. Mohd. Asri Bin Nawi

TITANIUM dioxide (TiO,) photocatalyst is a semiconductor with many potential applications. The application of photocatalyst for the removal of toxic pollutants has been well researched by many scientists worldwide [1,2]. It provides the exciting possibility of a total destruction of pollutants without the conventional requirement of chemical dosages and production of hazardous sludges. All it takes is just a proper illumination of light onto polluted water or air in the presence of photocatalyst. This dream technology however suffers from the need of using high intensity UV irradiation and sophisticated filtration set up to remove the suspended catalyst prior to the discharge of treated effluent. These inherent drawbacks have up to now stalled the commercial application of this amazing technology. Immobilization of the catalyst on solid supports may solve the problem of filtration requirements but most researchers acknowledge a drastic drop of its photocatalytic activities and its poor sustainability.

We had developed a dip-coating technique via a prepared TiO, emulsion solution to solve the problem of filtration requirement. TiO, emulsion is a formulation prepared by adding an appropriate amount of epoxidized natural rubber (ENR), phenolformaldehyde and TiO, powder in organic solvent. Immobilization was done by dipping supporting substrates into the emulsion. The thickness of the photocatalyst layer was controlled via the dipping duration and the number of dippings onto the supports . Using this technique, fast and convenient immobilization of TiO, on any solid supports was achieved. The prepared photocatalyst plate was shown to be very sustainable without losing much activity even after 10 times of repeated usage.

In the past decade, Ti0,-photocatalytic degradation of organic pollutants under UV irradiation was proven to be a very effective process to accelerate the complete mineralization of organic substrates [3]. Unfortunately, ultra-violet light sources are not beneficial to personal health and are not easy to obtain for technological applications. Another

fundamental problem with TiO, photocatalysis is the charge recombination effect of electron hole-pairs. A rapid recombination of these pairs will lower TiO, efficiency. Therefore, it is necessary to design and synthesize highly efficient materials as sensitizers or band-gap bridgers for TiO, to overcome these two fundamental problems. One approach of sensitization has been the coupling method whereby TiO, is doped with low bandgap semiconductor and inorganic dyes [4]. This method however still suffers from poor efficiency and sustainability. Recently, considerable attention was focused on synthetic polymers of low bandgap energy due to their high absorption coefficient in the visible region, charge generation under illumination and easy deposition on substrates even at room temperature [5]. Among these polymers, conjugated polymers were thought to be the more promising candidates. Many attempts had also been done to utilize organic polymers that absorb visible light as dopants in TiO,. In such blends, the organic polymers act as electron donor and the inorganic particles as electron acceptor. The biggest problem for this approach is the high incurring cost of the low bandgap polymers as all of these polymers are novel compounds of research laboratories and are not commercially available.

Our laboratory has focused on sensitizers synthesized from natural products such as humic acids and tannins to overcome the problems of availability and cost. Zepp et al. [6] had reported that HAS act as a natural photosensitizer in heterogeneous as well as homogeneous solutions. By adsorbing HAS on the surface of TiO,, Vinodgopal[7] had demonstrated that there was electron injection from HAS into Ti02 conduction band. Using a similar approach, Espinoza et al. [8] recently utilized Tannins, another natural polymer, as photosensitizer. Tannins are polyphenols that are known to bind to many substrates. They had demonstrated that adsorbed tannin on TiO, surface acted as sensitizer whereby recombination losses were minimized. Our laboratory had completed a laborious study on the effect of humic acid and tannin as dopants in the immobilized photocatalyst and found that both had significant impact on the sensitization of TiO,. However, it was found that the sensitization process required the presence of small amount of doped metal ions such as Ag+. Figure 1 illustrates the impact of natural polymers-doped TiO, in speeding


up photocatalytic degradation of Cibacron red dye via 45 W visible light fluorescent lamp. Photocatalyst plates were found to have improved their respective photocatalytic efficiency on repeated use. This improved efficiency was due to the clean-up effect of the photocatalyst surface during each run.

One alternative is to use peat soil itself as the sensitizer. Peat soil is known to contain high concentrations of humic acid as well as tannin and fulvic acid. Peat soil by nature should be more photoresistant as compared to HAS or tannin. Since it has been shown that both HAS and tannins work as sensitizer, the hypothesis here is that peat soil and its chemically modified derivative shall be a better choice as sensitizer for TiO, under visible light operation. Furthermore, metal ions are normally present in peat soil thus additional doping of metal ions will not be necessary.

Figure 2 shows the photocatalytic efficiency of undoped TiO,, ENR-doped TiO,, peat soil-doped Ti0 and modified peat-doped TiO, in the degradation of methylene blue while Fig. 3 shows their respective effectiveness in the degradation of methylene blue under UV-filtered irradiation. The effectiveness of peat-doped TiO, is further illustrated in Fig. 4 whereby methyl orange was effectively degraded under total visible light whileTi0, without peat dopant failed to function at all.

This work adds another dimension to the usefulness of peat soil in environmental management. Our laboratory is currently pursuing a fundamental research in developing a theoretical understanding of the mechanism of this band-gap bridging of TiO, by humic acid, tannin and above all peat soil and its derivative. The success of this work will not only provide the understanding of the roles of these natural polymers in the sensitization of photocatalyst but also contribute towards the effective applications of TiO, in environmental photocatalysis and solar cells.

References:

A. Fujishima, T.N. Rao and D.A. Tryk, J. Photochem. Photobiol. C: Reviews,1(2000),1-21. F.J. Farrauto and R.M. Heck, Catalysis Today, 55 (2000). 179-187 A. Mills, S.Lee, J. Photochem. Photobiol. A: Chem,152 (2002),233-247 P.M. Sirimanne, T.Shirata, L.Damodare, Y. Hayashi, T.Soga and T. Jimbo, , Sol Energ Mater. Sol Cells, 77 (2003) 15. L. H. &oof, M. M. Wienk and J.M. Kroon, Thin Solid Film 451-452 (2004), 634. R.G.Zepp, N.L. Wolfe, G.L. Baughman, R.C. Hollis, Nature, 267 (1977) 421. K. Vinodao~al. Res. Chem. Intermed. 20 (1 994), g25 '

R. Espinosa, I. Zumeta, J.L. Santana, F.M. Luzardo. B. Gonzalez. S. Docteur and E. Vi il, ; Sol Energy ~ a t e r . Sol Cells, Article in t ress (2005)(available online at www.sciencedirect.com).

ImdkmUon TI- (ml-

Fig. 1: Photocatalytic degradation of 30 mg/L Cibacron Red dye (CBR) by various dopedTIO, photocatalyst plates under 45 W visible light fluorescent lamp.

100

n m trmn.) -no2 unmodified -TO2 wlth ENR -no2 wlth ENR + modined pest

Fig. 2: Photodegradation of 12.5 ppm methylene blue using 45 W visible light fluorescent lamp without UV filter.

. Fig. 3: Photodegradation of 12.5 mglL methylene blue using . 45 W visible light fluorescent lamp fitted with a UV filter to . filter any possible traces of UV rays.

I L ~ -

4 . Fig. 4: Comparison of TIOJENR and TlOJmodified peat system . in photodegradation of 10 ppm methil orange using 45 W . fluorescent lamp fitted with UV filter.


RESEARCH Report

Ruthenium-Silica Nano-Fibres From Rice Husk?

Dr. Farook Adam

IN our continued effort to find ways for the use of the agricultural waste, i.e, rice husk, we have managed to chemically modify its ash with ruthenium metal. The rice husk ash denoted as RHA, dissolves in sodium hydroxide producing sodium silicate solution, as shown in equation (I), where x is a variable that gives the ratio of the SiO, to Na20 in the sodium silicate solution that affects its properties [I].

The sodium silicate solution was neutralized using nitric acid containing the metal to produce silica gel with the metal ion chemically incorporated into the silica matrix.

The SEM micrographs of the samples are presented in figure 1. Fig. 1 (a) shows the amorphous structure of RHA-Ru at 2.00 K magnification, indicating a general porous solid. However, the bulk structure of RHA-Ru700 (RHA-RU calcined at 700 "C for 5 hours) was seen to retain the amorphous nature but this was interspersed with the presence of fine needles, which were observed to be rather elongated. The SEM micrograph of RHA-Ru700 shows the existence of these fine needles (Fig. la). On further magnification (Fig. I b) the needles looked like thin flat elongated

pieces of fibbers with sharp edges and of nano dimension.

The width of the needles can be estimated to be about 200 nanometers with the length stretching several micrometers. The fibres, which are crystalline, are also seen to be very flexible as observed in Fig. 1 (a). The flat and long nature of the fibres is evident from Fig. I(b).

The major chemical groups present in RHA-RU and RHA-Ru700 were identified by the respective FTlR spectrum. As can be seen in Fig. 2, in general the IR spectra of both samples had a broad band in the region of 3450-3500 cm.l due to the surface OH vibration. This band is due to the SiO-H groups and the HO-H vibration of the adsorbed water molecules bound to the silica surface. These modified silica gels are basically a high moisture product made up of a network of interconnected pores with a silicon dioxide core consisting of the silanol groups. The bending vibration for H-0-H is observed at 1637 cm-I and this value corresponds to the literature. The strong band at 1099 cm.l is due to the structural siloxane, Si-O- Si, bond. This band was observed in both RHA and metal incorporated RHA and is the main characteristic of any silica material having the Si-0-Si bond. The band at 802 cm-I was assigned to symmetric Si-0-Si stretching vibration [2] and this was shifted to 795 cm-I upon calcination. The Si-OH groups generally have a weak shoulder at around 980 cm-l. By adding metal to silica, it results in a weak shoulder at 950

Fig. 1: SEM images of RHA-Ru700. l(a): RHA-Ru700 (X 1.5 K) and l(b): RHA-Ru700 at 15 K magnification showing the flat fibbers along its length.


RESEARCH Report

The bending vibration for H-OH

is obsewed at 1637 cm-l and

this value corresponds to the

literature. The strong band at

1099 cm-I is due to the

structural siloxane, Si-0-Si,

bond, This band was observed

in both RHA and metal - - -

incorporated RHA and is the

main characteristic of any silica

material having the Si-0-Si

bond.

cm'l. Maxim et a/. recently prepared Fe-doped silica and attributed this shift to the presence of Fe-0-Si bond [2]. This peak was observed to disappear on calcination which makes such an assignment improbable. However work done by Stark et a/. on titanium-doped silica [2] proved to be inconclusive on the assignment of this particular band in the IR spectrum. In the FTlR spectrum of RHA-RU there is a slight shoulder at about 580 cm-l. This band becomes more pronounced after calcination and shifts to 619 cm-l. It is tempting to make the conclusion that this wave number could be due to the vibration of Ru-0-Si species that may be present in RHA-Ru700, although further confirmatory work need to be done. However, a band at this wave number was never observed in RHA or other metal modified rice husk ash silica.The sharp peak at 1384 cm.l is due to the vibrations of NO; anion.

The N, adsorption and desorption isotherms of RHA- Ru catalysts is shown in Fig. 3.The desorption branch does not follow the adsorption branch, but gives a distinct hysteresis loop, where the amount adsorbed is greater along the desorption branch compared to the adsorption branch. The hysteresis loop can be classified as type H3 according to the IUPAC classification [3]. Generally, this type of hysteresis

loop is believed to be found in solids with agglomerates, having slit-shaped pores. This model is assumed to have slab geometry with slit walls comprised of two infinite graphitic planes [4].

For RHA-Ru, there are two pore size ranges between 40 and 100 A and between 150 to 400 A. Both these ranges fall within the mesoporous region. The catalytic activities of these materials are currently being investigated in our laboratory.

Reference:

1. Farook Adam and Joo-Hann Chua, J. Colloid and Interface Sci. Accepted for publication, July 2004.

2. W.J. Stark, R. Strobel, D. Gunther, S.E. Pratsinis and A. Baiker, J. Mater. Chem., 12 (2002) 3620.

3. G. Leofanti, M. Padovan, G. Touola and B. Venturelli, Catalysis Today, 41 (1 998) 207-21 9.

4. E.F. Vansant, P.V.D. Voort and K.C. Vrancken, "Characterization and Chemical Modification of the Silica Surface", Vol. 93. Elsevier Science B. V. Amsterdam, Netherlands. (1 995) 22.

Fig. 2: The FllR spectra of RHA-Ru and RHA-Rd7OO

Fig. 3: The Nitrogen adsorption isotherm for RHA-Ru. " Is the adsorption branch, and D is the desorptlon branch. Inset: pore distribution graph of RHA-Ru.


RESEARCH Report

Understanding Natural Rubber via Nanoscience

N.H.H. Abu Bakar, Assoc. Prof. Mohamad Abu '

Bakar and Prof. Jamil lsmail

NOBLE metal with sizes below 100 nm possesses electronic structures as well as unique optical, electronic, conducting, and catalytic properties associated with quantum effect, which are not observed in its bulk state. Synthesis of a stable nano- sized metal stabilized either by a surfactant or a polymer solution has been a subject of interest among scientists. Colloidal or solid systems containing nanometal as materials with new functionality and capability have been reported. In the case of a polymer matrix containing metal nanoparticles, it is expected to exhibit properties mentioned above.

In one of our investigations, natural rubber latex was chosen as the matrix. An interesting phenomenon showed up in an experiment on photo reduction of silver ions in dry natural rubber latex film in which inhomogeneous dispersion of metallic silver nanoparticles were formed. The dispersion pattern of the silver nanoparticles has revealed the interfaces of the fused rubber particles that constitute the matrix of the dry natural rubber latex film. The morphology as shown in Fig. 1 (a) is a feature not seen or reported before in literature. The interfaces form a network of narrow strips with an average width of 8 nm in which discrete metallic silver particles are dispersed. Depending on the condition of reduction, the average particle size ranges between 4 to 7 nm as depicted in Fig. 2.

This unique feature is associated with insoluble proteins, which occurs on the surface of a rubber particle. Based on gathered evidences, we believe that water insoluble proteins influence the formation of silver particles and stabilize the nanoparticles. Our earlier observation has revealed that reduction of silver ions in aqueous albumin resulted in stable discrete metallic silver particles of average sizes in the range of 4 to 8 nm. In another study, reduction of silver ions at the same concentration and condition in de-proteinized natural rubber (DPNR) latex, where proteins were absent, was found to produce only aggregates as shown in Fig. 3 and no characteristic interface network was observed. The interface can be enhanced by grafting poly(viny1 pyrollidone), PVP, onto the rubber surface. PVP is soluble in water and the grafted PVP chains extend in aqueous phase

The dispersion pattern of the

silver nanoparticles has

revealed the interfaces of the

fused rubber particles that

constitute the matrix of the dry

natural rubber latex film. The

morphology as shown in Fig.

1 (a) is a feature not seen or

reported before in literature.


I AESEARCH Report

forming a hairy layer. Figure 1 (b) shows the interface network observed in dry PVP-grafted natural rubber latex film, PVP-g-NR, containing silver nanoparticles formed under the same conditions used previously in the NR latex. The interface network exhibits greater width in which discrete silver particles of about similar size range are dispersed due to PVP being a good stabilizer. The significance of the above finding lies in its potential as a possible technique to verify the presence of proteins in the NR latex.

The UV-VIS spectra of the silver nanoparticles-filled natural rubber film have a I- in the range 450 to 475 nm. This peak is a phenomenon known as the surface plasmon resonance, directly associated with

the electronic transition at specific UV wavelength. A blue shift occurs when the time of photo reduction is increased. This corresponds to decreasing size of the silver nanoparticles formed in the film as confirmed by TEM analysis. The results also imply possibility of the nanosize control by photo reduction.

In the case of nanometallic silver-filled natural rubber, more interesting properties related to the quantum effect are expected to be seen as our investigation continues. For now, we have shown that silver metal reduction provides new information and a basis for development of a novel technique to verify the existence of NR latex's proteins.

1 Figure l(a) TEM micrograph; metallic silver nanocrystals, 4.7 nm, and interface network of

I dry NR latex film

Figure 2.TEM micrographs, average particle size and size distribution of silver nanoparticles in NR - Ag composite films after (a) 20 minutes, (b) 60 minutes and (c) 90 mlnutes of UV exposure.

Figure 3. Aggregates of silver natural rubber.

particles formed


GENERAL Article

Protect the Enviroment by Consuming Chemicals Smartly

Dr. Moharnad Nasir Mohamad lbrahim

RECORD indicated that the School of Chemical Sciences alone discarded about 27 Carboy size barrels of chemical wastes last year. Each Carboy can contain 22 L of liquid. This number skyrockets to 22 barrels for only the first quarter of this year; not to mention the number of plastic and glass bottles, with a capacity of 2.5 L each, reaching 495 pieces for the same period.

Although the data above were obtained from one particular school/center, this trend is believed to be a good indicator of chemical consumption as the School of Chemical Sciences consumes the most chemicals than any other school or center in this campus. With the increase in graduate student intake as well as the number of research grants obtained by the faculty members, the use of chemicals in terms of amount and types has also gone up. However, these are not the reasons why we should forget our early worry about the amount of chemical waste that is keep increasing tremendously. There is a need to find a way to control the usage of chemicals and at the same time we could enjoy the luxury of having plenty research projects for quite a number graduate students.

It is the time for many of us, if not all, to start changing our strategy of conducting experiment from a traditional Trail-And-Error (TAE) method to a more systematic way or better known as Design of Experiment (DOE) technique. TAE experiments can be expensive and impractical especially when dealing with more than a few variables or when the

process is costly and consumes expensive chemicals.

Realizing these shortcomings, researchers especially the mathematicians and the statisticians had developed several experimental designs such as Full Factorial design and Fractional Factorial design, to name a few. In this article, we will look into one of the most rapidly adopted DOE technique in the United States and world wide known as Taguchi Method.

To illustrate better how this method works, allow me to share my experience in formulating the optimum electroless nickel bath with my graduate student. In this study, four factors which were concentrations of NiSO .6H 0 (nickel salt), NaH,PO,.H,O (reducing agent), (&,),c,H 0, (complexing agent) and pH of the bath were anabzed against the nickel deposition rate. Each factor was considered at 3 levels. The factors involved and their levels were shown in Table 1. If full factorial experimental design were used, it would require 81 (34) trial runs for all possible combinations of these factors. By using Taguchi orthogonal array L, for experimental design, the number of trial runs was reduced to 9 simple and effective experiments. It could save experimental cost and time.

The use of Taguchi orthogonal arrays helps determine the minimum number of experiments needed which may produce the most favorable information for a given set of factors. Table 2 illustrated the orthogonal array L . Since there were four of 3 levels factors, these facyors were assigned to all four columns in the L, array. For example in the first trial, we used the first level value for each factor. In other words, the first experiment involved the use of 30 g/L of NiSO .6H,O; 30 g/L of NaH2P02.H,0 and 40 g/L of (%IH~),c,H,o, at pH value equal to 8. In the second trial however, only [NiS04.6H,0] was remained the same at 30 g/L

Table 1 : Design Factors and Their Levels for Orthogonal Experimant


GENERAL Article

Table 2 : L Orthogonal Array

I

1 1 1 1 1

2 1 2 2 2

3 1 3 3 3 4 2 2 3

5 2 2 3 1

6 2 3 1 2 --

-- -

8 3 2 1 3 9 3 3 2 1

Table 3 :The Oatimun Bath Formulation

40 glL

whereas [NaH PO .H,O], [(NH,),C,H O,] and pH value have changed2to tke second level wiich were 40 g/L, 50 g/L and 9 respectively. The same process was applied to the rest of the trials as specified in Table 2. After completed all the nine trials, several calculation steps need to be carried out in order to rank the most influenced factor among those four. These calculations were based on the results obtained from the nine trial experiments performed earlier. This is how Taguchi Method tries to relate the real experiment results with mathematics.

From this study, we found that the optimum bath formulation for electroless nickel on mild steel may be predicted in general as shown in Table 3. Besides being able to rank the most influenced factor in this

-- experiment, which was pH followed by [NiSO .6H 01, w a v q q ? l m a n y €wp*% % h i - -

Method can also help you to pred~cj how much nickel were expected to be deposited i f the optimum condition (Table 3) was applied. In this study, we found that the expected value was 133.51 mg, which was not very much different from the actual experimental result when the optimum condition was applied.

Acknowledgment: The author would like to thank En. Khairul lzwan Saruddin, Science Officer at the School of Chemical Sciences, USM for supplying waste disposal data.

General References: M. N. Mohamad Ibrahim, C. W. Sia and Z. A. Ahmad: "Preliminary Step in Formulating The Optimum Electroless Nickel Bath Using A Taguchi Method", Jurnal Teknologi, 37(C), 2002, pp.67-74.

R. K. Roy: A Primer On The Taguchi Method, New York: Van Nostrand Reinhold, 1990.

1. "Determination of organochlorine pesticides and polychlorinated ' iphenyls in fresh water fish" - conducted by a team headed '" Assoc. Prof. Md Sani Ibrahi~,, - (RM9.000.00).

"Determination of chemical p r a s r v r r h (methyl panaben, ~ropyl paraben, benzoic and sorMc adds)" - conducted by Assoc. Prof. Behnrddin Saad and team members. A total of 67 samples, comprising matnly imported foods categorized as soft drinks, canned truits/vegetables. jam, sauces and dried fruits were analysed. A two day HPLC trainin workshop (5-6 April 2004) was also conducted for the client's laboratory perst a1 - (RM15.000.00).


NEWS About the school

Highlight of Activities in 2004

1 Syarahan Umum Peringkat Kebangsaan 1 (Public Lecture at the National Level) r The School of Chemical Science has organized the above lecture at the Lecture Theatre A on 12

April 2004. The invited speaker was Academician Tan Sri Datuk Dr. Augustine S. H. Ong who I presented the talk on "Chemistry in the Advancement of Science, Technology and Society: 1 Opportunities and Challenges".

Industrial Linkages

The school organized a series of technical lectures listed below presented by invited speakers from various industries to provide exposure for the students on related fields.


Date

9 January 2004

13 May 2004

29June2004

9 July 2004

3 September 2004

17 September 2004

26 November 2004

3 December 2004

17 December 2004

20 December 2004

Topic

Thermal design for microelectronic packaging

GC column selection, trouble shooting and maintenance of GC

Practical aspect of Gas Chromatography

Introduction to electronic packaging

Chip level interconnection metallurgy for high performance microproccesor

Kaolin and its industrial applications

Characterization technique and defect analysis for electronic packaging

Polymer materials for the semiconductor packaging

Thermal design for macroelectronic packaging

LECO Pegasus GC-TOF MS and Unique LC-TOF MS

Speaker

Mr. Goh Teck Joo Intel Technology Malaysia

Dr. Kuhn Eberhardt GC Application Specialist Agilent

Technology

Dr. Kuhn Eberhardt GC Application Specialist Agilent Technology

Mr. Kin Gan Intel Technology Malaysia

Dr. Sim Kian Sinlntel Technology Malaysia

Mr. Hwang Chni HorTinex Kaolin Corporation Sdn. Bhd

Mr. Tamil Selvy Sevamuniaday Intel Technology Malaysia

Dr. Chee Chong Kooi Intel Technology Malaysia

Mr. Logendran Bharatham Intel Technology Malaysia

Mr. David Nightingle LECO Corporation, USA

Invited speakers

The School has invited 8 speakers to present their seminars during the year.

1. Dr. Arthur M. Usmani, President & Chief Scientific Officer at ALTEC USA, on "Advancement in material research", 26 Jan. 2004.

2. Dr. Joachim Weiss, Technical Director, Dionex, on "Reagent free ion chromatography", 9 Feb. 2004.

3. Prof. David Littlejohn, University of Strathclyde, Glasgow, on "Developments in on-line and in-line process analysis", 18 March 2004.

4. John Wiley Staff on "Wiley's E-Grade", 25 March 2004.

5. Prof. Dr. S. Mohan, AIMST, Amanjaya, Sungai Petani, Kedah, on "Recent advances in techniques and industrial applications of infrared and Raman spectroscopy", 22 May 2004.

6. Prof. Wolkmar Vill, Department of Chemistry, University of Hamburg, Germany, on "Dialog", 31 Jul. 2004.

7. Prof. Lee Soo Ying, Department of Chemistry, National University of Singapore, on "Raman Spectroscopy, some ideas, experiments and theory", 15 Sept. 2004.

8. Dr. Tjandra Setiadi, lnstitute of Chemical Engineering, lnstitute Teknologi Bandung, Indonesia, on "Production of biodegradable plastics (Polyhydroxyalkanoates)", 27 Dec. 2004.

Posgraduate Seminars

This weekly activity was organized for the postgraduate students to present their latest research findings and to interact among themselves. A total of 20 students have presented their seminars in the year.

WorkshopslTraining Course

The following are workshopsltraining course organized by the School in the year:

2. "Laboratory Safety Rules" on 24 Nov 2004. The speakers were Mr Khairul lzwan Saruddin and Mr. Mohd Kassin Abd Razak from the School of Chemical Sciences.

3. "Fundamentals of Electroplating" held between March and July 2004 for four groups of technicians from Dynacraft, Penang. The training course was coordinated by Assoc. Prof. Mohd Asri Mohd Nawi.

Conference

The Regional Conference for Young Chemists was held on 13 & 14 April 2004. The conference was jointed organized by the School of Chemical Sciences, the Penang State Government and the Malaysia lnstitute of Chemistry (Northern Branch). The event had received overwhelming response from regional chemistry researchers.

Visit by the External Examiner for the Analytical Section

The external examiner for the Analytical Section, Professor Littlejohn, from the University of Strathclyde, Glasgow, visited the School from 15 to 18 March, 2004.

Research Grants Awarded in 2004

1. "The Advanced FT-NMR in Academic & Research" on 29 & 30 Jun 2004. The speaker was Mr. Peter Sprender from Bruker SEA.

Type of Grant IRPA

FRGS

Short-term

Others, Intel,

Cape, SAGA


Number 10

14

4

6

Amount (RM)

452,700

1,051,213

32,137

1,075,050

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