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Carbohydrate Polymers 165 (2017) 255–265

Contents lists available at ScienceDirect

Carbohydrate Polymers

journa l homepage: www.e lsev ier .com/ locate /carbpol

n-situ deposition of Cu2O micro-needles for biologically activeextiles and their release properties

ossam E. Emam a,∗, Hanan B. Ahmed b, Thomas Bechtold c

Pretreatment and Finishing of Cellulosic Fibers, Textile Research Division, National Research Centre, Scopus Affiliation ID 60014618, El Buhouth St., Dokki,airo, 12622, EgyptChemistry Department, Faculty of Science, Helwan University, Ain-Helwan, Cairo, 11795, EgyptResearch Institute of Textile Chemistry and Textile Physics, University of Innsbruck, Hoechsterstrasse 73, A-6850 Dornbirn, Austria1

r t i c l e i n f o

rticle history:eceived 21 December 2016eceived in revised form 9 February 2017ccepted 13 February 2017

eywords:u2O

a b s t r a c t

Metal/metal oxide containing fibres are gradually increasing in textile industrialization recently, owingto their high potential for application as antimicrobial textiles. In this study, the reducing properties ofcellulose were applied to synthesize cuprous oxide in-situ. The direct formation of Cu2O on viscose fabricswas achieved via quite simple technique in two subsequent steps: alkalization and sorption. Cu contentsin fabrics before and after rinsing ranged between 45.2–86.4 mmol/kg and 18.1–67.7 mmol/kg, respec-tively. Uniform micro-needles of Cu2O were obtained with regular size and dimensions of 1.60 ± 0.20 �m

elluloseiscoseeleasentimicrobialurability

in length and 0.13 ± 0.03 �m in width. Release of Cu1+/2+ ions from selected samples was studied in water,physiological fluid and artificial sweat. Copper containing fabrics exhibited a percent of 96.8–97.8% and85.5–89.0% for reduction in microbial viability, which was tested for S. aureus (as gram positive bacteria),E. coli (as gram-negative bacteria) and C. albicans and A. niger (as fungal species), respectively after 24 hcontact time.

© 2017 Elsevier Ltd. All rights reserved.

. Introduction

According to United States environmental protection agencyUSEPA), copper exhibits lower toxicity in comparison to manyther heavy metals (IRIS, 2007). This makes copper preferableor use in different applications e.g. as disinfectant, water puri-er, antifungal or antibacterial agent, algaecide and medicines

Block, 2001; Cooney, 1995; Gawande et al., 2016; Hubacher,ara-Ricalde, Taylor, Guerra-Infante, & Guzmán-Rodríguez, 2001;rajciová, Melník, Havránek, Forgácsová, & Mikus, 2014; Mallickt al., 2012; Reza, Ilmiawati, & Matsuoka, 2016). Nowadays the usef metal containing textiles is a progressively growing area dueo their opportunities to be widely applicable in various purposes.lthough in textile industrialization, silver has large-scaled appli-ations (Angelova, Rangelova, Dineva, Georgieva, & Müller, 2014;

ivec et al., 2014; Pivec & Stana-Kleinschek, 2012; Wu et al., 2014),ut the usage of copper and copper compounds in textiles is morereferable, due to various factors, such like: 1) A low sensitivity

∗ Corresponding author.E-mail address: hossamelemam@yahoo.com (H.E. Emam).

1 Member of EPNOE—European Polysaccharide Network of Excellence, www.pnoe.eu.

ttp://dx.doi.org/10.1016/j.carbpol.2017.02.044144-8617/© 2017 Elsevier Ltd. All rights reserved.

for human tissues and skin towards copper and copper containingfibres as reported in numerous literatures (Borkow & Gabbay, 2004;Hostynek & Maibach, 2004). 2) Detailed studies about the effectsof Cu-containing intrauterine devices on women health, indicatedthat, low concentrations of copper could be expressed to be safe forhumans (Bilian, 2002; Hubacher et al., 2001; Mallick et al., 2012).3) Cu0 and copper ions exhibit antimicrobial properties (Borkow &Gabbay, 2004, 2009). 4) Compared to Ag and Au which belong to thesame subgroup in the periodic table, the cost of Cu is substantiallylower (Iarikov, Demian, Rubin, Alexander, & Nambiar, 2012).

Therefore, different natural and synthetic fibres treated by cop-per and copper salts are reported to be applicable in variouspurposes (Cárdenas, Meléndrez, & Cancino, 2009; Cioffi et al., 2005;Gasana et al., 2006; Grace, Chand, & Bajpai, 2009; Guo, Jiang, Yuen,& Ng, 2012; Han, Kim, & Oh, 2001; Jia, Dong, Zhou, & Zhang, 2014;Lu, Liang, & Xue, 2012; Mary, Bajpai, & Chand, 2009; Schwarzet al., 2012; Shim et al., 2002; Wei, Yu, Wu, & Hong, 2008). Tex-tiles for shielding of electromagnetic radiation have been preparedby plating of Cu on polyester fabrics through electroless deposi-tion (Han et al., 2001; Lu et al., 2012). Similarly, electrolytic copper

deposition was used for textile coloration (Guo et al., 2012). Elec-trically conductive textiles have been prepared by deposition of Cu(Gasana et al., 2006; Jia et al., 2014; Schwarz et al., 2012). The cat-alytic properties of Cu-nanoparticles and Cu-complexes also have

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een investigated on cellulose acetate (Shim et al., 2002). Medi-al textiles which exhibited antibacterial, antifungal and antiviralroperties have been obtained via treatment with copper in itsifferent forms (Cu, CuO, Cu2O) (Abramov et al., 2009; Borkow

Gabbay, 2004; Cárdenas et al., 2009; Cioffi et al., 2005; Emam,anian et al., 2014; Grace et al., 2009; Heliopoulos et al., 2013;

ramar et al., 2013; Mary et al., 2009; Turalija et al., 2015; Vainiot al., 2007; Wei et al., 2008).

Modification of textiles with copper can be carried out throughwo main routes; deposition for Cu particles (oxides/metallic)Abramov et al., 2009; Barua, Das, Aidew, Buragohain, & Karak,013; Emam, Manian et al., 2014; Heliopoulos et al., 2013;otelnikova, Vainio, Pirkkalainen, & Serimaa, 2007; Perelshteint al., 2009; Turalija et al., 2015; Vainio et al., 2007) and sorption ofu ions (Chen et al., 2009; Emam, Manian, Siroká, & Bechtold, 2012;uang, Ou, Boving, Tyson, & Xing, 2009). Due to limitations in max-

mum copper content available by sorption of Cu ions (Emam et al.,012), the application of Cu particles based on oxide/metallic form

n textiles is described to be promising for textile functionaliza-ion and thus scientific interest increased recently (Abramov et al.,009; Emam, Manian et al., 2014; Heliopoulos et al., 2013; Turalijat al., 2015). Modification of cellulosic materials with cuprous oxidelready has been studied extensively (Abramov et al., 2009; Baruat al., 2013; Borkow & Gabbay, 2004; Emam, Manian et al., 2014;ia et al., 2014; Kotelnikova et al., 2007; Perelshtein et al., 2009;uralija et al., 2015; Vainio et al., 2007). Cuprous oxide may beeposited on cellulose through in-situ and ex-situ methods. In thex-situ method (indirect method), Cu(I)oxide is prepared in a firsttep and then loaded on the cellulose substrate (Abramov et al.,009; Turalija et al., 2015). However, in case of in-situ methoddirect methods) the Cu ions at first are inserted into the cel-ulose polymer matrix. In a second step the reduction to formhe insoluble Cu(I)oxide is initiated (Emam, Manian et al., 2014;otelnikova et al., 2007; Vainio et al., 2007). Copper uploadingould be controlled easily in case of the ex-situ technique. How-ver, incorporation of metal/metal oxides using in-situ techniqueas been reported to be advantageous with lower chemical con-umption and producing textiles with good fastness propertiesEmam, Mowafi, Mashaly, & Rehan, 2014; Emam, Saleh, Nagy, &ahran, 2015, 2016). Additionally, in case of in-situ techniques these of cross-linkers to bind the particulate material is not requiredTang et al., 2013; Tang et al., 2012). As a result, methods whichorm the active cuprous oxide in-situ by use of external reducinggents/chemicals are of high interest as basis for a clean productionechnique.

Under appropriate conditions cellulose exhibits reducing prop-rties due to the presence of hydroxyl and aldehyde groups (Emam

El-Bisi, 2014; Emam, Mowafi et al., 2014; Emam, Saleh et al.,015; Emam et al., 2016). This behaviour has been utilised to pre-are colloidal silver nanoparticles and for in-situ incorporationf nanosilver into cellulosic fibers/fabrics (Emam & El-Bisi, 2014;mam, Mowafi et al., 2014; Emam, Saleh et al., 2015; Emam et al.,016), carboxymethyl cellulose, starch, alginate, pectin, acacia andanthan, also have been used to synthesis nano-sized Ag0/Au0

articles from Ag1+/Au3+ ions solution (Ahmed, Abdel-Mohsen, &mam, 2016; Ahmed & Emam, 2016; Ahmed, Zahran, & Emam,016; El-Rafie, Ahmed, & Zahran, 2014; Emam & Ahmed, 2016;mam, El-Rafie, Ahmed, & Zahran, 2015; Emam & Zahran, 2015;ebeish, El-Rafie, Abdel-Mohdy, Abdel-Halim, & Emam, 2010;ahran, Ahmed, & El-Rafie, 2014a, 2014b). Similarly carbohydrateserve as active agents to reduced Cu2+ ions to Cu1+ to form Cu2OEmam, Manian et al., 2014; Ródio, Pereira, Tavares, & da Costa

erreira, 1999; Turalija et al., 2015). This reduction process wasromoted by elevated temperature and presence of alkali (El-Rafiet al., 2014; Emam & El-Bisi, 2014; Emam, Manian et al., 2014;mam, Mowafi et al., 2014; Emam, Saleh et al., 2015; Emam et al.,

lymers 165 (2017) 255–265

2016; Emam & Zahran, 2015; Ródio et al., 1999; Turalija et al., 2015;Zahran et al., 2014a, 2014b).

The present study focuses on direct deposition of Cu2O on vis-cose fabrics using a quite simple technique in two subsequentsteps which are alkalisation and sorption. Alkalization has beenused for enhancing the reducing power of cellulose, to achieve in-situ incorporation of cuprous oxide (Cu2O) into viscose fabrics. Toincorporate Cu2O into viscose fabrics, viscose fabrics were treatedwith a defined amount of alkali followed by impregnation in CuSO4solution of different concentration. Carboxylic group content wasdetermined using the methylene blue sorption and copper contenton Cu-fabrics was measured using atomic absorption spectroscopy(AAS). Colorimetric data and mechanical properties were recordedfor the treated fabrics as function of conditions applied in prepa-ration. Treated fabrics were characterized using scanning electronmicroscope (SEM), energy dispersive X-ray (EDX), X-ray diffrac-tion (XRD) and attenuated total reflection–fourier transformationinfrared spectroscopy (ATR-FTIR). Release properties of Cu2+ ionsfrom treated fabrics were studied in different liquid media suchas water, physiological model fluid and artificial sweat. Biologicalactivities of Cu-containing fabrics were tested quantitatively usingthe shaking flask test method with bacterial strains of Escherichiacoli and Staphylococcus aureus and fungal species of Candida albicansand Aspergillus niger.

2. Experimental part

2.1. Chemicals and materials

Copper sulphate pentahydrate (CuSO4·5H2O, >99%), sodiumhydroxide (NaOH, 99%), sodium dihydrogenphosphate dihy-drate (NaH2PO4·2H2O, 98%) were obtained from Fluka, Buchs –Switzerland, sodium hydrogen carbonate (NaHCO3, 99%), sodiumcarbonate (Na2CO3, 99.5%), sodium chloride (NaCl, 98%), ammonia(NH3, 30%wt/wt) and nitric acid (HNO3, 55%wt/wt) were pur-chased from Merck, Darmstadt – Germany, DL-lactic acid sodiumsalt (C3H5O3Na, 50%wt/wt aqueous solution) were obtainedfrom AppliChem GmbH – Germany, disodium hydrogen phos-phate dihydrate (Na2HPO4·2H2O, 98%) from Riedel-de HaenAG – Germany, l-histidine mono-hydrochloride monohydrate(C6H9N3O2·HCl·H2O, ≥98.5%) from Aldrich – USA, urea (N2H4CO,98.5%) from Panreac PRS – Spain and calcium chloride (CaCl2, 99.5%)from Qualikems Fine Chemicals Pvt. Ltd. – India. All chemicals wereall used as received.

Plain-woven viscose fabrics (145 g/m2) de-sized and washedwith an average of 35 threads per cm over warp direction and 30threads per cm over weft direction were kindly provided by LenzingAG (Lenzing, Austria).

2.2. In-situ synthesis of Cu2O

In-situ synthesis of Cu2O into viscose fabrics was performed intwo consecutive steps; alkalization and sorption. Viscose as cellu-losic fabric was activated in alkalization step while in the sorptionstep; cuprous oxide was directly introduced into the fabrics. Foralkalization, specimens of fabrics with dimensions of 8.5 × 17 cm(ca. 2 g) were submerged at room temperature for 10 min in 200 mL0.1 M solution of different alkali: NaOH, NaHCO3, Na2CO3, NH3.Fabric samples then were taken out from solution, squeezed andpadded in a laboratory to remove excessive solution (Mathis HVFpadder, Switzerland; 1 bar nip pressure, roller speed 1 m/min).

In second step the alkalized fabrics were transferred into 200 mLof 1–10 mmol/L CuSO4 and treated with agitation for 2 h at 60 ◦C.Fabrics then were removed from the treatment bath and excessliquid was removed by padding (1 bar nip pressure, 1 m/min roller

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peed). After, removing of the treated fabrics, pH of solutions wasubsequently measured. The wet fabrics were dried and cured at50 ◦C for 5 min to initiate reduction of Cu-ions. The treated sam-les were divided into two pieces. The first part was characterisedithout further treatment, the second part was rinsed three times

n tap water for 10 min (liquor ratio 1:100) and dried at 70 ◦C.

.3. Copper contents

An exact mass of treated fabric near 0.2 g was extracted with0 mL of 15%wt/wt nitric acid for 2 h at 80 ± 3 ◦C. Concentrationsf Cu in the solutions were measured using high-resolution con-inuum source flame atomic absorption spectrometer (HR-CS AAS,ontrAA 300, Analytic Jena AG, Germany). Copper contents in fab-ics were calculated using Eq. (1). Calibration solutions in the rangef 0–10 mg/L were prepared from 1 g/L Cu standard solution.

uf = Cus

W(1 − MC/100)× V (1)

here, Cuf = copper content in fabrics (g/kg); Cus = copper concen-ration (g/L) in extracted solution; V = volume of extracted solution0.02 L); W = mass of dried treated fabrics (kg) and MC = moistureontent in dried treated fabrics (%)

.4. Carboxylic group contents

Carboxyl group content of viscose fabrics before and afteru treatment were measured using the methylene blue sorptionethod (Emam & Bechtold, 2015). The method can be summa-

ized as follows: 300 mg/L aqueous methylene blue, borate bufferolution with pH = 8.5 and 0.1 M HCl were separately prepared andamed as solutions A, B and C, respectively. Into a 50 mL vessel5 mL of solution A and solution B were added and a mass of 0.1 gf fabric sample was treated in the mixture for 20 h at room temper-ture. From solution mixture, a volume of 2.5 mL was transferrednto a 50 mL volumetric flask, a volume of 5 mL solution C was addednd the volume was completed to 50 mL with distilled water. Thebsorbance of the solutions was measured at �max of methylenelue (664.5 nm) using a double beam Spectrophotometer (6800V/Vis, d = 10 mm, Jenway – UK). Calibration solutions of methy-

ene blue at pH 8.5 were prepared in the range of 1–10 mg/L. Fromhe slope of the calibration curve the carboxylic group content wasalculated according to Eq. (2). For each sample, two repetitionsere performed and the average was calculated.

OOH = (C1-C2) × 0.00313W(1 − MC/100)

(2)

here, COOH is the carboxyl content of fabric (mmol/g),1 = concentration of methylene blue in the blank (sample without

abric) (mg/L), C2 = concentration of methylene blue in the samplesin presence of fabric) (mg/L), W = mass of viscose fabric samplesg) and MC is the moisture content (%), 0.00313 conversion factoro obtain result units of mmol/g

.5. Colorimetric data

The CIE Lab colour measurements (L*, a*, b*) for fabric samplesere determined using a spectrophotometer (KONICA MINOLTA

M 3610d, Japan) with pulsed xenon lamps, using 10◦ observer,65 illuminant, d/2 viewing geometry and measurement area of

mm. L* = Lightness, a* = red/green coordinate and b* is character-zed yellow/blue coordinate (AATCC, 2010a; Gulrajani, 2010). The

olour strength (K/S) both was measured in range of 360–740 nm.ata were recorded for each sample at four independent areasonsidering on both fabrics sides and the average values were con-idered.

lymers 165 (2017) 255–265 257

2.6. Mechanical properties

Mechanical properties including tensile strength and elongationat break were tested for viscose fabrics after Cu-treatment usingInstron IDN (model 2519–107, USA) according to ASTM methodD3822 (ASTM, 1972).

2.7. Scanning electron microscopy (SEM)

The morphological structure of fabrics surface was detected byhigh resolution electron microscopy. Fabric samples were mountedon copper coated carbon tape and then placed in the electron micro-scope (SEM Quanta FEG 250 with field emission gun, FEI Company –Netherlands). The elemental analysis of the fabric surface was per-formed using energy dispersive X-ray spectroscopy (EDX) analysis(EDAX AMETEK analyzer).

2.8. X-ray diffraction (XRD)

For measuring of X-ray diffraction (XRD) patterns for viscosefabrics before and after Cu treatments, fabric was subjected to XRDwith Philips X’Pert MPD diffractometer (from) equipped with thegraphite monochromatized (Cu K� radiation, � = 1.5406 Å) in 2�angles ranging from 5◦ to 50◦ with a step size of 0.05◦ and scanningrate 1 s.

2.9. Attenuated total reflection–fourier transformation infraredspectroscopy

Viscose fabrics before and after Cu treatment were investigatedby attenuated total reflection–fourier transformation infraredspectroscopy (ATR-FTIR; JASCO FT/IR – 4700 spectroscopy, JASCOAnalytical Instruments, Easton, USA). Spectra were recorded in thewavelength range of 4000–400 cm−1 with 1.0 cm−1 interval using32 repetitious scans, scanning speed of 2 mm/sec and 4 cm−1 thespectra resolution. The data were processed with baseline correc-tion and by 25 points smoothing.

2.10. Release properties

Release of Cu2+ ions from Cu-treated fabrics was investigated indifferent media including water, physiological fluid (PF) and artifi-cial sweat (AS) (fastness, 2013; Grace et al., 2009; Kulthong, Srisung,Boonpavanitchakul, Kangwansupamonkon, & Maniratanachote,2010; Mary et al., 2009). Physiological fluid contained 142 mmol/Lsodium chloride and 2.5 mmol/L calcium chloride which performsthe representative ion concentration in human body fluid accord-ing to British Pharmacopia (Karnick, 1994). Artificial sweat wasprepared with four different formulations according to AATCC TestMethod 15-2002, ISO105-E04-2008E and BS EN1811-1999, in pHrange of 4.3–8.0. Artificial sweat solutions of AATCC and ISO con-tained 0.025% and 0.05% (wt/v) of l-histidine and 1.0% and 0.50%(wt/v) of sodium chloride respectively. According the EN artificialsweat solution included only 1.08% (wt/v) of sodium chloride. Lac-tic acid and urea were used to adjust pH of solutions to be 4.3 forthe AATCC method, 5.5 and 8 for the ISO tests and 6.5 for the ENmethod.

A sample with weight of 0.2 g was submerged into 50 mL ofleaching solution for 24 h. In case of water and PF, solutions wereleft at room temperature, while AS solutions were incubated at37 ◦C. After defined leaching time of 1, 4, 8 and 24 h, samplesof the leaching solution were withdrawn and acidified with 5%

nitric acid. Copper concentration then was measured using flameatomic absorption spectrophotometer (Agilent 200 series AA sys-tems, 240FS AA, Agilent technologies, USA) attached with atomizerof GTA 120 graphite tube. The amount of Cu determined in the

2 ate Polymers 165 (2017) 255–265

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xtracts then was related to the dry weight of the fabrics to deter-ine the amount of copper released.

.11. Biological activity

Biological activities of Cu-viscose fabrics were tested quantita-ively against different microbes including bacteria and fungi, usinghe shaking flask test method according to the AATCC test method00–2004 (AATCC, 2010c). In these tests, two different strains ofacteria were used namely, Escherichia coli ATCC- 25922 as gramegative bacteria and Staphylococcus aureus ATCC 47077 as gramositive bacteria. Two different types of fungi were also tested ;andida albicans ATCC 10231 as yeast and Aspergillus niger ATCC6888 as filamentous fungi.

Briefly, microbial suspensions of (ca. 2.5 × 108 CFU/mL) for. coli, (ca. 1.5 × 108 CFU/mL) for S. aureus, (ca. 1.0 × 107 CFU/mL) for. albicans and (ca. 0.5 × 107 CFU/mL) for A. niger were all prepared

n KH2PO4 buffer solution with pH 7.2. A mass of 0.1 g fabric wasmmersed in 20 mL of microbial suspension at 25 ◦C and then wasigorously shaken for consecutive intervals of 2, 4 and 24 h. Afterach time interval, a volume of 1 mL of the microbial suspensionas collected, plated on nutrient agar and incubated at 37 ◦C for

acteria and at 30 ◦C for fungi. The microbial colonies were countedfter 24 h and the microbial activities of fabrics was estimated byhe reduction in viability of colonies by using Eq. (3).

% = B-AB

× 100 (3)

here R% is the reduction in viability of microbial colonies, A ishe number of viable microbial colonies on the agar plate fromreated fabrics, and B is the number of viable microbial coloniesrom control experiments

.12. Wash fastness

Wash fastness of selected specimens for Cu-viscose fabrics waserformed via consecutive washing process using home laundryashing method (AATCC, 2010b) which can be described briefly as

ollows: in one liter washing liquor, 2 g of Na2CO3 and 2 mL of com-ercial household laundry detergent was dissolved. At 60 ± 3 ◦C,

abrics were soaked in liquor using 1:50 material to liquor ratio for5 min with stirring. Fabrics were gently squeezed, rinsed with tapater and then dried in oven at 70 ± 5 ◦C. The process was repeated

times. Copper contents after washing were measured for thextracted solution using flame atomic absorption spectrophotome-er (Agilent 200 series AA systems, 240FS AA, Agilent technologies,SA) conducted to GTA 120 graphite tube atomizer.

.13. Statistical analysis

All data reported in the present work were an average of ateast three independent measurements except for mechanical test,elease properties and carboxyl content, which were calculatedrom double measurements. The standard deviations are given inhe tables and included as error bars in figures.

. Results and discussion

.1. Metal contents and release in rinsing

Copper contents on viscose fabrics before and after rinsingre given in Table 1. Depending on the experimental conditions

.g. alkali type and concentration used for activation, between5 mmol/kg and 85 mmol/kg copper were analysed in the sam-les. Sorption of copper onto cellulose could take a place throughomplexation by carboxylic groups presented, and thus, copper

Scheme 1. Reaction scheme for the formation of Cu-deposits on alkali activatedcellulose.

content is supposed to be correlated to the respective carboxylgroup content of the cellulose (Bechtold et al., 2013; Emam et al.,2012; Emam, Manian et al., 2014). Carboxyl content for untreatedviscose fabric was determined using the methylene blue methodwith 18.58 ± 2.52 mmol/kg (Emam & Bechtold, 2015). For all treatedsamples, copper contents exceeded the carboxyl content of vis-cose which indicates the formation of copper deposits/precipitates(Emam & Bechtold, 2015; Emam et al., 2012; Emam, Manian et al.,2014).

For a given type of alkali used in the activation step the coppercontent in the samples increased with the Cu2+ concentration usedin the deposition step as the amount of deposits increased. Acti-vation with ammonia solution led to the lowest content of copper.This can be explained due to the possible complexation betweenammonia and Cu2+.

The copper contents on the treated fabrics exceeded the resid-ual content in the surrounding solution, which can be explainedwith deposition of Cu(OH)2 and basic copper carbonate e.g.CuCO3·Cu(OH)2 which then thermally dehydrate to form CuO. Dur-ing the thermal processing at 150 ◦C Cu2O is formed by action ofreducing groups present in cellulose (Scheme 1) (Emam et al., 2012;Emam, Manian et al., 2014; Kumar, Dharani, Mariappan, & Anthony,2016).

As a result of the reductive processes an increase in carboxylicgroup content is observed in processed samples. Contents of car-boxylic groups increased from18.58 mmol/kg for untreated viscoseto 19.30–32.83 mmol/kg for processed Cu-fabrics (supplementarydata), the absolute values being dependent on alkali type and Cuions concentration applied. This enlargement in COOH content sup-ported the suggested interaction between Cu2+ and cellulose ofviscose as shown in Scheme 1. As a by-product of the reductionof Cu2+ to Cu1+, hydroxyl and aldehyde groups of cellulose will beoxidized to carboxylic groups thus an increase in COOH group isexpected to occur.

The release of deposited copper-oxide from the samples wastested in the experiments with rinsing in water. Cu content in fabricbefore and after rinsing both was measured and compared (Table 1).The rinsing step led to a substantial decrease in, Cu content duerelease of weakly bound deposits. Cu release was around 30% ofthe initial copper content.

As an exception, the highest release was observed for sampleswhich had been activated by use of NaOH. In case of sample 1, NaOHactivation led to a pH in the treatment solution of 10.41. At this pH,formation of Cu-hydroxide and deposition on the fabric is expectedto occur which then subsequently form CuO under elevated tem-peratures. Such deposits are expected to be removed easily byrinsing, which explains the observed value of 60% in experiment 1.This assumption also is confirmed by appearance of black precip-itates in the supernatant solution and black deposits on the fabricsurface. When lower pH values were established during the cop-per impregnation (samples 3–12) similar release of copper deposits

was observed during the rinsing with water.

According to the above mentioned and discussed data, it couldbe concluded that, Cu2O incorporation was carried out in twosequential steps; alkalization and reduction. Cellulose in viscose

H.E. Emam et al. / Carbohydrate Polymers 165 (2017) 255–265 259

Table 1Copper contents and release percent of copper from fabrics by rinsing.

Samples Alkali (0.1 M) CuSO4 (mM) pH of solutions Cu Content (mmol/kg) Release (%)

Before rinse After rinse

1 NaOH 1 10.41 45.21 ± 3.58 18.10 ± 4.07 59.972 5 5.04 66.33 ± 3.44 33.82 ± 2.84 49.013 10 4.65 77.63 ± 7.69 55.03 ± 5.41 29.11

4 NaHCO3 1 5.75 48.45 ± 1.25 36.01 ± 0.45 25.665 5 5.21 61.28 ± 2.42 35.45 ± 0.68 42.166 10 4.87 78.05 ± 1.55 53.81 ± 0.16 31.06

7 Na2CO3 1 6.21 48.94 ± 4.67 36.43 ± 5.85 25.568 5 5.37 58.43 ± 6.10 39.36 ± 5.14 32.659 10 5.13 86.41 ± 4.63 67.67 ± 3.33 21.69

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abric was firstly swollen and activated by impregnation with basicolutions (Emam, Mowafi et al., 2014). In the reduction step, thelkalized viscose fabric was immersed in copper sulphate solutionnd gently heated (60 ◦C). During this step initially two competitiveeactions can take place, which are complexation of copper ions byellulose and precipitation of Cu2+ as Cu(OH)2 by action of alkaliollowed by deposition on the viscose fabric. During the thermalreatment at 150 ◦C complexed Cu2+ deposited as Cu(OH)2 becomeeduced to Cu+ by action of cellulose reducing groups and cuprousxide is formed (Emam et al., 2012; Emam, Manian et al., 2014;umar et al., 2016).

.2. Colorimetric data and mechanical properties

The effect of the copper treatment on the appearance of theiscose fabrics was analysed through measurement of the CIE labolour coordinates. L*, a*, b* and overall colour strength (K/S) werell plotted against Cu content in fabric and presented in Fig. 1. Fromhese data, the following results can be summarised:

Black CuO deposit was formed at the lowest Cu2+ concentrationf 1 mM in NaOH (exp. 1), which thus led to the lowest lightness*. Deposition of Cu2O, viscose fabric led to some reddish shade.ncrease of Cu content was accompanied by decrease in b* valuesndicating a shift in the direction of the blue coordinate. Increase inopper content led only to minor changes in K/S values, which cane explained with the low concentrations of copper in the samples.

The mechanical properties of viscose fabrics were measuredfter Cu-treatment and were reported in Table 2. When alkali acti-ation was used, slight decrease in mechanical properties wasbserved after treatment at low Cu content. At high Cu con-ent, considerable reduction in elongation at break was recorded.n opposite, tensile strength was slightly changed which maye attributed to the role of copper in complexation that obvi-usly appeared at high copper content, thus resulting in possiblerosslinking between cellulose fibrils (Chattopadhyay & Patel,010). Crosslinking process is accompanied by decrease in fabriclongation which further confirmed the assumed role of Cu ions asross-linker between cellulosic fibrils.

.3. XRD, SEM images and EDX analysis

The influence of treatment on crystallinity of viscose fabricshich may affect the fabric properties and functionality was tested

y measuring XRD analysis. From XRD patterns in (Supplemen-

ary data), the original viscose fabric exhibits two intense peakst 2� = 20.3◦ and 21.6◦ which are assigned to [002] lattice planef cellulose II. In addition, weaker broad diffraction peaks at� = 11.9◦ and 16.6◦ are referred to [101] lattice planes of cellulose

45.76 ± 2.24 31.20 ± 3.57 31.8048.57 ± 0.07 30.50 ± 0.06 37.2255.74 ± 2.76 39.58 ± 3.52 29.00

II (Abdelhameed, Abdel-Gawad, Elshahat, & Emam, 2016; Ahmed& Emam, 2016; Emam & Bechtold, 2015). A similar XRD patternwas recorded for viscose after treatment (sample 12), confirmingthat the crystalline structure of viscose fabrics was not influencedby activation/deposition steps. Due to the low amount of Cu on thefabrics no additional diffraction peaks related to the copper contentwere detected by XRD.

Surface of untreated and treated viscose fabrics was examinedby electron microscopy (HRSEM) to study the morphology of thedeposits (Fig. 2). EDX analysis confirmed the presence of copper andalso a sulfur was detected. Deposited particles could be observedon viscose fabrics. The presence of these deposits confirmed thehypothesis that the carboxyl group content of the fibres was ofminor relevance for the formation of the deposits, which also isin agreement with the literature (Emam & Bechtold, 2015; Emam,Manian et al., 2014). The deposits are mainly Cu2O which had beenproduced by action of cellulose reducing groups during the thermalprocessing at 150 ◦C.

Uniformly shaped Cu2O was observed in micro dimensionand with homogenous size. The size of the Cu2O micronee-dles was calculated from the microscopic photos by using 4 pisoftware program. The dimensions of Cu2O needles were in aver-age 1.60 ± 0.20 �m in length and 0.13 ± 0.03 �m in width. Cu2Omicroneedles were clearly observed in Fig. 2i & j. By using ammo-nia (sample 12, Fig. 2g–h), the particles were well distributed on thefabric surface due to the complexation of Cu2+ in form of the copper-diamine complex, which then decomposes during the curing step.Sodium carbonate exhibited intensive deposits which accumulatedto form agglomerates. Cubic Cu2O microneedles were obtained byreaction of the Cu(II)-tartaric acid complex with glucose as reducingagent (Turalija et al., 2015).

3.4. ATR-FTIR spectra

ATR-FTIR spectra of untreated viscose and Cu-treated fabric(sample 12) are shown in Fig. 3. Pristine viscose shows three char-acteristic peaks at 1640 cm−1, 2885 cm−1 and 3310 cm−1. Thesepeaks are indicated to the C O vibration of carboxylic groups,stretching vibration of C H and O H in cellulose, respectively.The absorption at 1016 cm−1 is referred to C O stretchingof cellulose (Abdelhameed et al., 2016; Ahmed & Emam, 2016;Barkhordari, Yadollahi, & Namazi, 2014). The absorption peaksbetween 1300 cm−1 and 1366 cm−1 are corresponding to in planebending of C H, vibration of C C and C H, respectively (Emam &

Bechtold, 2015; Kavkler & Demsar, 2012).

Compared to the IR spectra of origin viscose, the wavenum-ber of the absorbances remained unchanged. Thus both the alkaliactivation and the thermal processing during the deposition step

260 H.E. Emam et al. / Carbohydrate Polymers 165 (2017) 255–265

a

b

Fig. 1. Effect of copper content on the a* and b* color data and K/S value of Cu-viscose fabrics.

Table 2Mechanical properties of Cu-viscose fabrics after rinsing.

Samples CuSO4 (mM) Cu Content (mmol/kg) Tensile strength (N/cm2) Elongation at break (%)

CV Blank 0 0.0 412.5 ± 6.2 21.1 ± 1.1

NaOH 1 18.10 ± 4.07 391.4 ± 5.5 18.3 ± 1.45 33.82 ± 2.84 399.2 ± 7.3 17.4 ± 1.610 55.03 ± 5.41 428.1 ± 7.7 15.3 ± 2.1

NaHCO3 1 36.01 ± 0.45 402.8 ± 6.4 17.2 ± 1.85 35.45 ± 0.68 395.7 ± 5.1 17.7 ± 1.510 53.81 ± 0.16 434.0 ± 9.8 15.8 ± 2.0

Na2CO3 1 36.43 ± 5.85 422.2 ± 4.8 17.7 ± 1.25 39.36 ± 5.14 428.6 ± 7.4 18.0 ± 1.110 67.67 ± 3.33 444.0 ± 10.2 15.4 ± 1.5

NH3 1 31.20 ± 3.57 401.2 ± 6.3 17.8 ± 0.95 30.50 ± 0.06 392.2 ± 7.0 17.5 ± 1.310 39.58 ± 3.52 421.1 ± 5.5 16.7 ± 1.4

H.E. Emam et al. / Carbohydrate Polymers 165 (2017) 255–265 261

F eatedC ) and

dfi

3a

iaitiispuaTad

wt

ig. 2. Scanning electron images for CV fabrics; (a, b) untreated CV, (d, e, f, g) CV truSO4 in NH3 (sample 12). EDX analysis pattern (c) untreated, (h) Cu-CV (sample 9

id not cause substantial chemical modification of the celluloseber.

.5. Release behaviour in different physiological fluids andrtificial sweat

The release of Cu from the different tested samples was stud-ed to characterize the durability of antimicrobial function and tossess potential human risk due to exposition to Cu released dur-ng application. Body fluids and sweat contain various componentshat can dissolve and complex copper ions and thus can withdrawt from textile surface, thus medium to test the copper releases of significant influence. The release of Cu from impregnatedamples was tested using five different media including water,hysiological fluid (PF) and artificial sweat with different pH val-es. Two representative samples were chosen: samples 9 (Na2CO3)nd 12 (NH3) with 67.7 mmol/kg and 39.6 mmol/kg respectively.he release properties of Cu into different mediums were studiedt different intervals time from 1 h to 24 h (Fig. 4, Supplementary

ata).

A gradual release of Cu ions from fabric surface was observedith time. More rapid release was observed at the beginning of

he experiments. Between 1.8–50% of the uploaded copper were

with 10 mmol/L CuSO4 in Na2CO3 (sample 9), (i, j, k, l) CV treated with 10 mmol/L(m) Cu-CV (sample 12).

released within the first hour of immersion, which increased to be4–80% for 24 h of extraction. The composition of the tested liquidsexhibited significant influence on the copper release.

The lowest release was recorded for water, as 4.0% and 6.2% ofcopper content was leached out from the fabric during 24 h. In arti-ficial sweat considerably higher release of copper was observed, inthe order of ISO recipes > AATCC recipe > EN recipe. Using the ENrecipe for artificial sweat at pH of 6.5, comparable low amounts ofcopper were released with 840 mg/kg fabric (33% loss). Artificialsweat solutions which exhibit more acidic or alkaline pH value e.g.ISO and AATCC recipes resulted in higher release of copper up to80% of the initial content (sample 12, Supplementary data). Physi-ological fluid (PF, pH 5.9) led to a removal of 51–57% of the initialcontent of copper during a time of 24 h.

The higher mobility of copper in presence of the AATCC andISO test solutions can be explained by the presence of l-Histidineas a component in the recipe for artificial sweat solutions. l-Histidine forms soluble complexes with copper ions which thusdissolve rapidly. The highest concentration of l-Histidine is used

in the ISO recipe, which supports the explanation. In the ENrecipe l-Histidine is replaced by urea which does not form sta-ble copper complexes, and lower copper release was observed. The

262 H.E. Emam et al. / Carbohydrate Polymers 165 (2017) 255–265

cose a

ca

ccM6c2

bstc

3

iafCb2s

iwob2ocwccwm

f

Fig. 3. FTIR for untreated vis

omparable low release of copper in PF supported this explanation,s this solution only contains CaCl2 and NaCl.

Comparable high amounts of 17–18 g/kg Cu were released fromopper loaded alginate-cotton fibers and copper loaded chitosan-otton fibers after immersion in distilled water (Grace et al., 2009;ary et al., 2009). Using PF resulted in higher release of up to

0 g/kg for copper-loaded cotton fibers, copper loaded alginate-otton fibers and copper loaded chitosan-cotton fibers (Grace et al.,009; Mary et al., 2009).

Much lower Cu release was detected in current work while noinder or cross-linker was used to bind copper deposits to the fibreurface. This can be explained by two factors: A lower copper con-ent already was uploaded on viscose fibres and weakly bondedopper deposits were removed during the rinsing step.

.6. Biological activity

Antimicrobial activity of samples was tested against gram pos-tive bacteria S. aureus, gram negative bacteria E. coli and fungi C.lbicans and A. niger using the shaking flask test method. Two dif-erent samples (No. 12 and 9, Table 1) were selected based on theiru content (39.6 and 67.7 mmol/kg). The reduction in viability ofacteria and fungi was studied as function of contact time up to4 h and tabulated in Table 3. Untreated viscose served as controlample (blank).

From the results given in Table 3, a distinct reduction in viabil-ty of all tested microorganisms (bacteria and fungi) was observed

ith increase of contact time. The higher reduction in viability wasbserved for the tested bacteria, when compared to the fungi. Foracteria, the reduction in viability increased from 48.0–54.0% after

h, to 85.0–89.8% after 4 h and then reached 96.8–97.8% after 24 hf contact time. Reduction in gram-positive bacteria was higherompared to gram-negative bacteria. While, the reduction in fungias enlarged from 32.2–38.4% to 85.5–89.0% after 2 h and 24 h of

ontact time, respectively. No significant correlation between Cuontent and reduction in bacterial/fungal viability was observed,

hich indicates that an amount of 39.6 mmol copper per kg of fibreaterial is sufficient to achieve the observed reduction in viability.

The durability of Cu-viscose fabrics against the action of dif-erent microbes was tested after 5 washings. Due to washing

nd Cu-viscose (sample 12).

process, Cu content was dramatically diminished by percentage of39.1–45.6% and reached 24.1 and 36.8 mmol/kg for sample 12 and9, respectively. Despite the lower Cu content on washed fabrics,antimicrobial results were acceptable and sample with Cu contentof 24.1 mmol/kg exhibited reduction of 73.3–74.2% and 51.7–54.0%in the case of tested bacterial and fungal colonies, respectively after24 h contact time.

During the experiments, to study the copper release into aque-ous solution, a liquor ratio of 1 g material in 200 mL of liquid hadbeen used which is similar to the conditions applied in the antimi-crobial tests (1:250). Hence on basis of the release experiments,Cu-concentrations in the microbial growth solution can be esti-mated. Assuming a Cu release of 62% after 24 h, the estimatedmaximum concentration of Cu in the microbial solution is esti-mated with 0.12–0.21 mM. Thus, low Cu concentrations alreadyshowed good reduction in microbial viability, which is compa-rable to the minimal inhibitory concentration (MIC) reported forchitosan Cu-nanoparticles (Qi, Xu, Jiang, Hu, & Zou, 2004). In experi-ments with CuSO4, a MIC of 2 mM has been determined for S. aureuswhile E. coli required a higher concentration of 20 mM (Aarestrup& Hasman, 2004). For CuO nanoparticles a MIC has been deter-mined with ≈ 0.3 mM against E. coli and S. aureus (Azam et al.,2012). Uniform sized CuNPs with dimensions of 7–9 nm showedlow MIC of 0.06 mM, while a MIC of 2.2 mM had been determined forirregularly sized particles (6–16 nm) (Díaz-Visurraga et al., 2012;Ruparelia, Chatterjee, Duttagupta, & Mukherji, 2008). When theMIC values published in the literature for E. coli and S. aureus arecompared to the results of this work, high efficiency with regardto antibacterial properties at low Cu content has been achieved bythe presented method.

Cu loaded chitosan-cotton and alginate-cotton fibres exhibitedhigh Cu release and subsequently offered good antibacterial actionusing inhibition zone method (Grace et al., 2009; Mary et al., 2009).Cu impregnated lyocell fabric with 2.62–23.7 mmol/kg Cu hasshown to exhibit high reduction in bacterial viability after a shortcontact time of 6 h (Emam, Manian et al., 2014), where, 1 g of lyocell

fibre was shaken in 50 mL of culture medium which is assumed toestablish 0.05–0.47 mM Cu in the culture medium, which is com-parable to this work. On synthetic fibres use of pigment bindersimproved durability of the Cu2O coating (Turalija et al., 2015)

H.E. Emam et al. / Carbohydrate Polymers 165 (2017) 255–265 263

a

b

Fig. 4. Release of Cu from Cu-fabrics in different solutions; (a) sample 12 and (b) sample 9.

Table 3Biological activities of Cu-viscose fabrics.

Sample Cu content (mmol/kg) Time (h) Bacterial reduction (%) Fungal reduction (%)

S. aureus E. coli C. albicans A. niger

Blank 0.0 24 0.0 0.0 0.0 0.0Sample 12 Unwashed 39.6 ± 3.5 2 53.3 54.0 32.8 32.2

4 89.8 85.0 65.5 60.824 97.6 97.2 85.5 88.0

5 washings 24.1 ± 2.6 24 74.2 73.3 54.0 51.7

Sample 9 Unwashed 67.7 ± 3.3 2 56.6 48.0 38.4 36.4

hCca(i(A

5 washings 36.8 ± 3.7

owever, reduction in bacterial viability was only ≤48.2% after 6 h.opper-Cu2O NP-coated cellulose nanofibrils showed good antimi-robial activity against E. coli and S. aureus as bacterial speciesnd C. albican as fungal species using the inhibition zone methodBarua et al., 2013). In recent studies, in-situ incorporation of AgNPs

nto cellulosic fibres did not exhibit substantial antifungal activityEmam, Saleh et al., 2015) even at high concentration of 0.112 mMg in the fungal growth medium.

4 88.2 86.6 68.0 64.024 97.0 96.8 89.0 88.024 87.8 85.6 77.4 72.3

4. Conclusions

Alkali activation and sorption were used as two subsequentsteps for successfully incorporation of Cu2O into cellulose fabrics.The reducing properties of cellulose fabrics were used to initiate

in-situ deposition of Cu2O in viscose fabric. The reduction powerof cellulose was activated by using alkaline medium followed bythermal heating to 150 ◦C. A substantial increase in carboxylic

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64 H.E. Emam et al. / Carbohydr

roup content for treated fabric was observed, which indicates thenvolvement of cellulose into copper reduction. Using low concen-ration of Cu2+ (1 mM) and NaOH activation CuO deposits wereormed as black pigments. In the majority of experiments forma-ion of Cu2O led to a reddish shade of the treated samples. In SEM

icro-images, equally distributed micro-needles of Cu2O could bebserved. For selected samples, release properties of Cu ions fromiscose fabrics were studied in different release media includingater, physiological fluid and artificial sweat. The release of copper

n the surrounding environment also forms the basis for antimi-robial activity, which was tested in the shaking flask tests againstifferent strains from bacteria and fungi.

Compared to the application of Cu2O using traditional meth-ds, direct incorporation of Cu2O on cellulose fabrics using theeported method has significant advantages to produce biologicallyctive textile material against S. aureus (gram positive bacteria),. coli (gram negative bacteria) and C. albicans and A. niger (fungi).he technique is quite simple and effective, the consumption ofhemicals is comparably low, high antimicrobial activity can bechieved at comparable low Cu content and the technique can beransferred on existing textile machinery without substantial mod-fication. Application of this reported technique to other naturalbres would be important to investigate the fundamentals of theeactions involved into the in-situ incorporation of Cu2O furthernd to transfer the technique into industrial production scale.

ppendix A. Supplementary data

Supplementary data associated with this article can be found, inhe online version, at http://dx.doi.org/10.1016/j.carbpol.2017.02.44.

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