Author’s Accepted Manuscript Green in-situ synthesized silver nanoparticles Embedded in bacterial cellulose nanopaper as a bionanocomposite plasmonic sensor Nahid Pourreza, Hamed Golmohammadi, Tina Naghdi, Hossein Yousefi

PII: DOI: Reference:

S0956-5663(15)30205-0 BIOS7777

To appear in: Biosensors and Bioelectronic Received date: 14 February 2015 Revised date: 5 June 2015 Accepted date: 17 June 2015 Cite this article as: Nahid Pourreza, Hamed Golmohammadi, Tina Naghdi and Hossein Yousefi, Green in-situ synthesized silver nanoparticles Embedded in bacterial cellulose nanopaper as a bionanocomposite plasmonic sensor, Biosensors and Bioelectronic, This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Green in-Situ synthesized silver nanoparticles embedded in bacterial cellulose nanopaper as a bionanocomposite plasmonic sensor Nahid Pourreza,*,a Hamed Golmohammadi,a Tina Naghdi,a and HosseinYousefib a


Department of Chemistry, College of Science, Shahid Chamran University, Ahvaz, Iran

Department of Wood Science and Engineering, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, 4913815739, Iran

Abstract Herein, we introduce a new strategy for green, in-situ generation of silver nanoparticles using flexible and transparent bacterial cellulose nanopapers. In this method, adsorbed silver ions on bacterial cellulose nanopaper are reduced by the hydroxyl groups of cellulose nanofibers, acting as the reducing agent producing a bionanocomposite “Embedded silver nanoparticles in transparent nanopaper” (ESNPs). The fabricated ESNPs were investigated and characterized by field emission scanning electron microscopy (FE-SEM), UV–visible spectroscopy (UV–vis), fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and energy-dispersive X-ray spectroscopy (EDX). The important parameters affecting the ESNPs were optimized during the fabrication of specimens. The resulting ESNPs were used as a novel and sensitive probe for the optical sensing of cyanide ion (CN-) and 2-mercaptobenzothiazole (MBT) in water samples with satisfactory results. The change in surface plasmon resonance absorption intensity of ESNPs was linearly proportional to the concentration in the range of 0.2 – 2.5 µg mL-1 and 2 – 110 µg mL-1 with a detection limit of 0.012 µg mL-1 and 1.37 µg mL-1 for CN- and MBT, respectively. Keywords: bionanocomposite; bacterial cellulose nanopaper; silver nanoparticle; optical sensor; cyanide; 2-mercaptobenzothiazole. *Corresponding author Email: [email protected]

Tel: +98 613 3331044

Fax: +98 613 333 7009

1. Introduction During the recent decades, nanomaterial has worldwide attracted more and more attention in the various fields of science. The reason for such raising interest is related to their many remarkable and fascinating characteristics (Sharifi et al., 2012; Batley et al., 2013). Despite the many advantages of nanomaterials, most of them possess toxicity problem and have high potential risks for human and environmental health (Sharifi et al., 2012; Batley et al., 2013; Hutchison, 2008; Marquis et al., 2009; Roy et al., 2013). In addition, most of the methods used to produce nanoparticles are not green (Roy et al., 2013; Dahl et al., 2007). Hence, with the development of nanotechnology a problem appears as to the relation between the beneficial properties and environmental toxicity of nanosystems (Hutchison, 2008; Harper et al., 2011). Because of this, in the past few years the use of renewable bionanomaterials and the development of green approaches for the synthesis of nanoparticles has gained worldwide attention (Dahl et al., 2007; Harper et al., 2011; Sharma et al., 2009; Abdul Khalil et al., 2014; Lavoine et al., 2012). Biodegradable nanoparticles can be generated practically using a variety of biomaterials such as polysaccharides, proteins and synthetic biodegradable polymers (Lavoine et al., 2012; Mahapatro and Singh, 2011; Dufresne et al., 2013). Polysaccharides nanomaterials such as nanocellulose, nanochitin and nanostarch are promising bio-based nanomaterials that have been intensively investigated (Dufresne et al., 2013). Cellulose nanofibers (CNFs) are obtained thorugh both top-down and bottom-up approaches. In the topdown approach, lignocellulosic resources such as wood and agricultural residues are purified/downsized to nanoscale. Instead of obtaining cellulose nanofibers by downsizing lignocellulose materials, bacterial cellulose nanofibers are produced through bottom-up approach by synthesizing cellulose and building up bundles of nanofibrils by some bacteria species, especially Acetobactor xylinus in aqueous culture media during a time period of days


up to two weeks, which usually resulted in a continuous sheet of cellulose nanofibers (Yousefi et al., 2013; Soykeabkaew et al., 2009). The CNF produced by bacterial synthesis possesses higher mechanical properties, purity and crystallinity than that of produced from lignocellulose resources. Nanopaper is defined as a sheet made completely of CNFs such as bacterial CNFs. Most of its characteristics including physical and mechanical properties have been reported to be superior to those of ordinary papers (Yousefi et al., 2013; Soykeabkaew et al., 2009). For example, bacterial cellulose nanopaper made from bacterial CNFs is highly transparent material, possesses very high mechanical properties, high oxygen barrier quality and low coefficients of thermal expansion (Yousefi et al., 2013; Soykeabkaew et al., 2009; Ifuku et al., 2009;). In addition, nanopapers have environmental sustainability, biodegradability and renewability, simplified end-of-life disposal, high functionalizing and favorable electrical and optical properties. Because of these promising properties, nanopapers are considered to be a multi-performance material, which have found numerous applications in biomedicine, biomaterials engineering, optical, magnetic and electronics, polymer nanocomposites, membranes and additive for food and cosmetic (Li et al., 2013; Chun et al., 2011; Zhang et al., 2010). Nowadays, there is a raising attempt for the development and fabrication of biobased composite materials (Soykeabkaew et al., 2009; John and Thomas, 2008; Pinto et al., 2012; Abdul Khalil et al., 2012). The interesting aforementioned properties of nanopapers or CNFs have also indicate that they are promising candidates for the functionalization and fabrication of composites (Leung et al., 2013; Nypelo et al., 2012). Various types of nanoparticles such as Fe3O4 (Li et al., 2013), titanium oxide (Gutierrez et al., 2013; Sun et al., 2010; Wesarg et al., 2012), gold (Zhang et al., 2010; Wang et al., 2011; Dong and Hinestroza, 2009), silver (Dong et al., 2013; Nogi et al., 2013; Hu et al., 2013; Dıez et al., 2011), Cobalt (Pinto et al.,


2012), Platinum (Dong and Hinestroza, 2009), Palladium (Dong and Hinestroza, 2009), vanadium oxide (Gutierrez et al., 2013), CdS (Li et al., 2009; Yang et al., 2011), carbon dot (Junka et al., 2014) and carbon nanotubes (Abdul Khalil et al., 2012) have been used for the fabrication of CNF based organic/inorganic hybrid nanocomposites. Among the nanomaterials, silver nanoparticles (AgNPs) have attracted researchers attention because of the outstanding chemical and physical properties, such as size and shape depending optical, electrical, biological and magnetic properties (Dıez et al., 2011; Pandey et al., 2012). The unique size-dependent optical properties of AgNPs has lead to their applications as sensing agents in localized surface plasmon resonance (LSPR) and fluorescence for the detection of many chemical and biological compounds (Vilela et al., 2012). The immobilization of AgNPs in transparent platforms is a key stage towards the development of chemical and biological sensors. AgNPs also have an intensive tendency to aggregate; therefore AgNPs need to be immobilized on suitable supports to prevent any undesirable aggregation (Ifuku et al., 2009; Azetsu et al., 2011). However, some of the processes for embedding nanoparticles within CNFs are complicated and time consuming and requires modification of CNFs, linking molecules or reducing agents. On the other hand, in many cases, inorganic nanoparticles and CNFs are separately synthesized, and then they are both mixed together. The transparency of the nanopapers makes them very suitable to be utilized as a substrate in optical sensors for embedding or immobilization of optical sensing compounds such as AgNPs. 2-mercaptobenzothiazole (MBT) is greatly used as a corrosion inhibitor agent in metal processing, as a vulcanization accelerator and antioxidant in the processing of rubber products and as a preservative, fungicide, bactericide and antifreeze agent in various industrial processes. MBT is also known as a poorly biodegradable pollutant that has potentially mutagenic, carcinogenic and allergenic influences on humans and can easily enter into the


environment. Till now, many studies have been developed for the determination of MBT because of its manifold usages and toxic nature, but no attempts have been made to MBT sensing using AgNPs (Parham and Khoshnam, 2013; Jing et al., 2013). On the other hand, the importance of cyanide (CN-) sensing in the environmental samples has been clearly known, because it is one of the exceedingly toxic and hazardous ions that recognized to humankind even at low concentration. Cyanide has applications in many industries such as mining, metallurgy, metal plating, petrochemical plants, coke-processing, jewelry and plastic manufacturing owing to its excellent properties. It is naturally produced by microorganisms and naturally exists in many foods. The annual product of CN- has been estimated to be 1.4 million tons in the world. It is frequently released into the aquatic environments and could be found in surface and underground waters and wastewaters (Ghanavati et al., 2014; Xu et al., 2010). In the current work, AgNPs were in-situ generated within transparent bacterial cellulose nanopaper via direct chemical reduction of adsorbed silver ions onto the bacterial CNFs of nanopaper by hydroxyl groups, without adding any external linking, stabilizing or reducing agents. The result of this process is the fabrication of novel bionanocomposite “embedded silver nanoparticle in transparent nanopaper (ESNPs)”. In order to fabricate the ESNPs with high and efficient performance as an optical sensor, the affecting parameters including pH of solution, AgNO3 concentration, AgNO3/nanopaper mass ratio, temperature and reaction duration on the optical properties of ESNP were investigated. Finally, the applicability of ESNPs as an optical sensor was investigated in the presence of the different amounts of CNand MBT by monitoring the changes in LSPR spectra of ESNPs by UV–vis spectrophotometer. Here, the high affinity of thiol groups of MBT and CN- toward the AgNPs and consequently the changes in the size, LSPR property and color of ESNPs are the sensing strategy for CN- and MBT using ESNPs. To the best of our knowledge, this is the first study


that cellulose nanopaper based nanocomposite has been utilized as an optical sensor for the determination chemical compound.

2. Experiments 2.1. Apparatus The UV–vis absorption spectra and absorbance measurements were performed by GBC UV–visible spectrophotometer (Cintra 101, Australia) by placing the ESNPs in a 1 cm glass cells over the wavelength range of 350-700 nm. FE-SEM images were obtained with a field emission scanning electron microscope (FE-SEM, JSM- 6700F; JEOL, Tokyo, Japan) at an accelerating voltage of 2 kV. Energy-dispersive X-ray spectroscopic (EDX) analysis was acquired with the EDX detector connected with FE-SEM (FE-SEM, Zeiss; ΣIGMA series, Jena,









thermogravimetric analyzers (Perkin Elmer model Pyris 1 TGA, USA) at a scan rate of 10 °C /min under nitrogen atmosphere.

2.2. Reagents and materials All chemicals were of analytical grade and double distilled water was used throughout. Silver nitrate solution (0.1% w/v) was prepared by dissolving 0.1 g of silver nitrate (Merck, Germany) in water and diluting to 100 mL in a volumetric flask. A 1000 µg mL-1 stock solution of MBT was prepared by dissolving 0.1 g of 2-mercaptobenzothiazole (Merck) in water, followed by diluting to 100 mL in a volumetric flask. A 1000 µg mL-1 stock solution of CN- was prepared by dissolving 0.251 g of potassium cyanide (Merck) in water, followed by diluting to 100 mL in a volumetric flask. Wet form of bacterial cellulose nanopaper (350 mm long, 250 mm width and 3 mm thickness) containing 1 wt% solid content/99% dionized water were kindly supplied from Nano Novin Polymer Co., Iran.


2.3. Fabrication of ESNPs A typical procedure for fabrication of ESNPs was depicted as follows: Five pieces (1 cm × 2 cm) of nanopapers were cut from the as-received wet bacterial cellulose nanopaper and added to 20 mL double distilled water with pH 12 in a conical flask. Then, this mixture was stirred and heated at 65 °C for 15 min using heating magnetic stirrer. Afterwards, 5 mL of silver nitrate (0.1% w/v) was added dropwise to mixture (about 30 drops/minute) under the same conditions of temperature and continuous stirring. Following that, the contents were kept under continuous stirring at 65 °C for 2 h. The fabrication of ESNPs was preliminarily confirmed by color changing of nanopaper from colorless to yellow and then yellow to amber as the reaction time increases, which indicates the reduction of silver ions to silver nanoparticles. Then, the contents were cooled at room temperature and fabricated ESNPs were separated from the solution. On the other hand, two filter papers were cut (5 cm × 5 cm) and placed onto two glass plates (5 cm × 5 cm with 6 mm thickness). The wet ESNPs were sandwiched between above set-up and the assembly was pressed using four spring-type binder clips for 30 min to remove the excess water, untreated silver cations and physically trapped AgNPs. The fabricated ESNPs were then separated from the filter papers and rinsed several times with double distilled water to ensure that any possible oxidized AgNPs were completely removed from the ESNPs surface. The ESNPs were then stored in a brown bottle at 4°C. It was also found that the fabricated ESNPs are stable for more than 4 months.

3. Results and discussion Herein, an optical plasmonic chemosensor was fabricated via in-situ embedding of AgNPs within transparent bacterial CNFs and was utilized for optical sensing of CN- and MBT. The AgNPs have been embedded in some optical transparent materials such as functionalized silicate sol gel network film (Maduraiveer and Ramaraj, 2013), ZnO, Al2O3, SiNx, and SiOx


substrates to produce the optical sensors for analytes detection (Schmidl et al., 2015). Reports are currently available for embedding of AgNPs within microcrystalline cellulose (Vivekanandhan et al. 2012), TEMPO-mediated oxidized bacterial cellulose (Feng et al. 2014), and bacterial cellulose (Maneerung et al. 2008, Fortunati et al. 2012) for biomedical applications such as antimicrobial wound dressings. However, some of the optical transparent substrates or reducing agents used for embedding of AgNPs to fabricate the optical sensors are not green. To obtain highly transparent, non-agglomerated, reproducible and homogeneous ESNPs, which are necessary for a high-quality optical sensor, the size, amount and uniform distribution of embedded AgNPs in the scaffold of CNFs is important. Therefore in the preparation of ESNPs, the effects of parameters such as pH of solution, AgNO3 concentration, AgNO3/nanopaper mass ratio, temperature and reaction duration on the transparency of ESNPs were investigated.

3.1. Characterization of fabricated ESNPs A known method for green synthesis of metal nanoparticles such as gold, platinum and copper nanoparticles and specially AgNPs is the use of reducing agents baring hydroxyl groups for chemical reduction of metal ions to metal nanoparticles (Pinto et al., 2012; Siqueira et al., 2010; Dong et al., 2013). CNFs have a high density of OH reactive groups on the nanofiber surfaces that can be functionalized and make large chemical modification possible (Siqueira et al., 2010; Missoum et al., 2013). In this work, the penetrated silver ions into nanopaper are reduced to metallic silver atoms by hydroxyl groups of nanopaper as chemical reducing agents. This phenomenon results the in-situ fabrication and embedding of AgNPs within nanopaper. Figure 1A shows a schematic presentation for the fabrication process used in this study and Figure 1B is demonstrating the transparency of dried films of bare nanopaper and fabricated ESNP. As can be seen in this figure the color of transparent


ESNPs is amber, which is attributed to the presence of AgNPs. Figure 2 shows the typical FESEM micrographs of bare nanopaper (A) and as-synthesized ESNPs (B). The presence of AgNPs is obviously revealed by comparing these two micrographs. White spots in Figure 2B reveal the fabrication of AgNPs with the diameter size range 10-50 nm on the nanopapers. The evidence for the fabrication of ESNPs was EDX analysis. Figures 3A, 3B show the EDX spectra of the samples imaged by FE-SEM. The obvious signal peaks of Ag observed in Figure 3 B, also confirms the presence of AgNPs. Another evidence for the fabrication of ESNPs was TGA analysis. The TGA curves for bare nanopaper and fabricated ESNP over the temperature range from 25 to 700 °C given in Figure S1 indicate the completely weight loss occurs below 700 °C for bare nanopaper whereas the weight loss close to 93% is observed for fabricated ESNPs at the same temperature. This difference in decomposition (7%) also confirms the synthesis of AgNPs in the nanopaper network.

3.2. Influence of the pH on the fabrication of ESNPs The experiments were carried out to study the effect of the pH on the fabrication of ESNPs. The influence of pH on the UV-vis absorption spectra was investigated in the pH range of 6.0–13.0 to obtain an optimum pH for the fabrication of ESNPs, whereas the other experimental parameters kept constant. The pH was adjusted to the desired value by the addition of dilute NaOH to the test solutions using a pH meter. Broadened UV-vis absorption spectra with low absorbance values can be observed in the pH range of 6.0-8.5 in Figure 4, but by increasing the pH values to 9.0, broadening of spectra decreased and absorbance values increased and the color of ESNPs changed from light yellow to dark yellow, indicating the better conversion of silver ions to AgNPs. At pH 9.5, absorbance value reduced, but at pH values 9.5 to 11.5 there was no UV-vis peak due to darkening ESNPs, preventing light to pass


through. Under these conditions, the color of ESNPs changed to dark brown with an intensive decrease in transparency. A high transparent, amber color ESNPs with a sharp peak (λ=417 nm) and high absorbance value appeared at pH 12.0. According to above observations, the pH 12.0 was chosen as optimum pH value for the fabrication of ESNPs in this study. Murray et al. (2005) have reported that the Ag+ ions are unstable in alkaline conditions (pH > 10.4) and are converted to insoluble Ag2O particles .Nishimura et al. (2011) studied the effect of NaOH on the formation mechanism and kinetic rate of AgNPs synthesized using sodium acrylate as a reducing and capping agent. They found that the insoluble Ag2O particles are formed in alkaline solution that are converted to Ag+ species such as Ag(OH)x during heating which are reduced to Ag0 followed by nucleation to form AgNPs. The reduction of Ag+ and nucleation of AgNPs are both accelerated by increasing the NaOH concentration. The reduction rate constant of Ag(OH)x is much higher than AgNO3 even under the same conditions. Based on above discussion it is possible that at pH ranges of 10-12 produced insoluble Ag2O particles covers nanopaper sheets and prevent transmission of light while at high enough pH values (e.g at pH 12) Ag(OH)x is obtained which is readily converted to AgNPs with a higher rate than AgNO3 producing transparent ESNPs.

3.3. Influence of AgNO3 concentration and nanopaper / AgNO3 mass ratio on the fabrication of ESNPs In the current study, AgNO3 was selected as the source of silver ion (Ag+) for fabricating ESNPs. Hence, to appraise the AgNO3 concentration effect on the fabrication procedure, the experiments were carried out using different volumes of AgNO3 (0.1% w/v) from 0.5 to 10 mL. The results of this investigation revealed that when the AgNO3 volume of 5 mL was used the band broadening sharply decreased and the highest absorbance value was obtained. Therefore, the AgNO3 volume of 5 mL was selected as the optimum concentration of AgNO3


for further experiments. On the other hand, to obtain the optimum ratio of AgNO3/nanopaper, the experiments were carried out in the various mass ratio of AgNO3/nanopaper from 2 to 40. At the AgNO3/nanopaper mass ratio of (2:5), band broadening sharply decreased and the absorbance reached its highest value. Thus, the mass ratio (2:5) of AgNO3/nanopaper was used for further experiments. The mass ratio 2:5 of AgNO3/nanopaper is equal to 5 mL AgNO3 (0.1% w/v) to 20 pieces (1 cm × 2 cm) nanopaper. The LSPR absorption spectra of metal nanoparticles such as AgNPs depends on their structure, size, shape and environment and any change in this physical features results in drastic changes (wavelength shifting or decrease in absorption intensity) in optical absorption spectra of AgNPs. Hence, in this work the LSPR absorption spectra of AgNPs were utilized to check the homogeneity of fabricated ESNPs. The reproducibility of the experimental data for fabricated ESNPs of the same batch and/or different batches under optimized condition for AgNO3/nanopaper was below 5%.

3.4. Influence of temperature and reaction duration on the fabrication of ESNPs Temperature is an important factor in the generation of AgNPs. To understand the effect of temperature on the fabrication of ESNPs, the experiments were carried out in the temperature range of 30-90 °C. When the temperature increased from 30 °C to 65 °C, the color of fabricated ESNPs changed from light yellow to amber. Consequently, the band broadening decreased and the absorbance values of fabricated ESNPs increased and reached a maximum at 65 °C, as shown in Figure S2 by increasing the temperature above 65 °C, the color of the fabricated ESNPs darkened due to the oxidation of AgNPs at high temperatures and no UVvis peak was observed at this condition. According to the above investigations, 65 °C was chosen as the optimum temperature for the fabrication of ESNPs. The influence of reaction time on the procedure of fabrication in the time confine 15-180 min was also investigated. It was observed that as the reaction time was prolonged, the band


broadening quickly decreased and subsequently, the absorbance value increased until it eventually reached a plateau after 120 min due to completion of the synthesis of AgNPs. Reaction times above 120 min did not significantly affect the absorbance value, but little band broadening was observed. Therefore, the reaction time of 120 min was chosen for the fabrication procedure.

3.5. Lifetime and the stability of fabricated ESNPs The life time and the stability of devices are very important factors for their practical applications. AgNPs have an intensive tendency to aggregate; hence stabilizing agents are mostly applied to prevent this drawback property. But in this work, the immobilization of AgNPs in nanopapers inhibits their aggregation and obviates the need for stabilizing agents. The stability of the fabricated ESNPs was investigated by storing them in a sealed brown bottle at 4°C for four months and recording the corresponding UV-vis. It was found that no significant change in UV-vis spectra occurred during three months. This shows the long life time of the fabricated ESNPs for practical applications.

3.6. Application of fabricated ESNPs sensors for the optical measurement of MBT and CNIn order to examine the analytical applicability of fabricated ESNPs as optical sensors for the determination of chemical compounds, we investigated the effect of the different amounts of CN- and MBT as two important chemical compounds on the LSPR characteristics of the fabricated ESNPs. Here, we have developed a sensitive colorimetric approach for monitoring MBT and/or CN- based on the size-dependent optical property of ESNPs. The sensing strategy for the determination of CN- and MBT is based on the strong affinity characteristics of the CN- and


thiol groups of MBT towards the surface of the AgNPs. As can be shown in Figure S3 the strong LSPR absorption band was observed for ESNPs. But, in the presence of MBT the LSPR absorption band of ESNPs shifted to longer wavelength (red-shift). The resulting FESEM micrograph was represented in Figure 5A, showing decrease in the number and yet the size increasing of AgNPs after introduction of MBT. Therefore, by the gradual increase of the MBT concentration, the color of ESNPs changed to dark brown color and the intensity of the LSPR absorption band significantly decreased upon the addition of MBT concentration. The decrease in the intensity of LSPR absorption band was proportional to MBT concentration and was used as analytical signal for the MBT sensing. On the other hand, as can be seen in Figure S4, the strong LSPR absorption band was observed for ESNPs. But, in the presence of CN- a blue-shift of the LSPR absorption band in the UV–vis spectrum of ESNPs was seen by the addition of CN-. The resulting FE-SEM micrograph was shown in Figure 5B, that indicates size decreasing AgNPs after interaction with CN-. This behavior is apparently due to etching of AgNPs and it is plausible sensing strategy for the changes in the LSPR characteristics of ESNPs after introduction of CN-. Figure 4S, shows that the amber color of ESNPs fades and changes to light yellow color and the intensity of the LSPR absorption band is meaningfully decreased depending on the CNconcentration. The decrease in the intensity of LSPR absorption band of ESNPs is proportional to CN- concentration, which was applied as analytical signal for the CN- sensing.

3.7. Analytical performance of fabricated ESNPs for monitoring MBT and CNThe analytical characteristics for the determination of MBT and CN- using ESNPs was evaluated and are presented in Table 1.

3.8. Interference studies


To evaluate the selectivity of the developed assay, an analysis of a standard solution of CN(1 µg mL-1) and MBT (50 µg mL-1) were independently performed in the presence of some chemicals probably existing in the water samples. Any relative error equal or higher than ±5% from the analytical signal value was considered interference. The results presented in Table S1 and S2 show the selectivity of developed method for CN- and MBT, respectively. Citrate ion did not interfere even at 100 µg mL-1, hence it was utilized as a masking agent for 5 µg mL-1 of Cu2+, 5 µg mL-1 of Zn2+ and 10 µg mL-1 Fe3+ in MBT sensing.

3.9. Practical applications of fabricated ESNPs for analysis of MBT and CN- in water samples Additionally, practical applications of the fabricated ESNPs as optical sensors were successfully carried out for the determination of MBT and CN - values in various environmental and industrial water samples such as tap water and pond water. The quantification results of these assays are represented in Table S3 and S4. Three measurements were performed at each concentration. The recovery tests were performed by spiking known concentrations of the analytes to the samples. The obtained results revealed that recoveries are in the range of 97.4-105.0 for the determination procedures for both analytes and the matrices of the water samples did not have significant affect on the analysis procedure.

4. Conclusions We have successfully demonstrated a green and in-situ approach for the generation of the AgNPs using transparent cellulose nanopaper and embedding AgNPs within the naopaper at the same time. The nanopaper acts as an efficient nanoreactor for in-situ synthesis and embedding of AgNPs due to its active reducing groups and excellent physical and mechanical properties. The main advantages of the ESNPs fabrication method are as follows: First, there


was no need for the addition of external reducing and linking agents for the fabrication of ESNPs. Second, immobilization of AgNPs in nanopapers inhibits their aggregation and obviates the need for stabilizing agents. Important parameters affecting the fabrication of ESNPs were optimized. By combining the optical characteristics of AgNPs with transparency, flexibility,




friendly properties




bionanocamposite was fabricated that has high potential to be used as a portable, inexpensive, and green optical sensor for detection of chemical compounds. The work presented here shows the first application of fabricated ESNPs for chemical sensing and determination of CN- and MBT as two important target chemicals in various water samples with satisfactory results. Finally the present strategy for the in-situ generation of AgNPs within transparent bacterial cellulose nanopaper shows simple and green process resulting in a transparent bionanocomposite having a great potential for other optical sensing applications.

Acknowledgements The authors are sincerely grateful to Shahid Chamran University, Research Council for the financial support of this project (Grant 1393). The financial support of the Iranian Nanotechnology Initiative Council is greatly appreciated. Nano Novin Polymer Co. is also acknowledged for kindly providing bacterial cellulose nanopapers. Hamed Golmohammadi and Tina Naghdi contributed equally to this work.

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Linear range

2 - 110 µg mL-1

0.2 – 2.5 µg mL-1

Correlation coefficient (r)



*Linear regression equation



* FRelative standard deviation o r Limit of detection (S/N=3)



1.37 µg mL-1

0.012 µg mL-1

10 replicate measurements of 30 µg mL-1 of MBT and 1 µg mL-1 of CN-

Figure Captions Figure 1. A) Schematic representation for fabrication of ESNPs and B) A transparency demonstration of dried films of (left) fabricated ESNP and (right) bare nanopaper, on top of “Olympic symbol”. Figure 2. FE-SEM images of A) transparent nanopaper and B) ESNP. Figure 3. Energy-dispersive X-ray spectra of A) nanopaper and B) ESNPs. Figure 4. Influence of pH on the fabrication of ESNPs.


Figure 5. FE-SEM images of ESNPs A) in the presence of 100 µg mL-1 of MBT, B) in the presence of 2 µg mL-1 of CN-




Figure 1




Figure 2




Figure 3

Figure 4





Figure 5

Highlights  Green, in-situ generation of silver nanoparticles using bacterial cellulose nanopapers  Embedded silver nanoparticles in transparent nanopaper (ESNPs) were used as a chemosensor

 The fabricated ESNPs were characterized by spectroscopic techniques ESNPs were used as a novel probe for the optical sensing of cyanide and 2mercaptobenzothiazole


Green in-situ synthesized silver nanoparticles embedded in bacterial cellulose nanopaper as a bionanocomposite plasmonic sensor.

Herein, we introduce a new strategy for green, in-situ generation of silver nanoparticles using flexible and transparent bacterial cellulose nanopaper...
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