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Article

Antibacterial Activity of TiO2- and ZnO-Decorated with Silver Nanoparticles

by
Van Thang Nguyen
1,
Viet Tien Vu
1,
The Huu Nguyen
1,
Tuan Anh Nguyen
2,
Van Khanh Tran
3 and
Phuong Nguyen-Tri
4,*,†
1
Faculty of Chemical Technology, Hanoi University of Industry, BacTu Liem, Hanoi 100000, Vietnam
2
Institute for Tropical Technology, Vietnam Academy of Science and Technology, Hanoi 122100, Vietnam
3
Hanvet Pharmaceutical and Veterinary Materials JSC, Hungyen17000, Vietnam
4
Department of Chemistry, University of Montreal, Montreal, QC H3T 1J4, Canada
*
Author to whom correspondence should be addressed.
†
Département de chimie, biochimie et physique, Université du Québec à Trois-Rivières, Trois-Rivières, QC G8Z 4M3, Canada.
J. Compos. Sci. 2019, 3(2), 61; https://doi.org/10.3390/jcs3020061
Submission received: 23 May 2019 / Revised: 7 June 2019 / Accepted: 9 June 2019 / Published: 17 June 2019
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Abstract

:
This work emphasizes the use of the silver decorative method to enhance the antibacterial activity of TiO2 and ZnO nanoparticles. These silver-decorated nanoparticles (hybrid nanoparticles) were synthesized using sodium borohydride as a reducing agent, with the weight ratio of Ag precursors/oxide nanoparticles = 1:30. The morphology and optical properties of these hybrid nanoparticles were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD) patterns, and UV-Vis spectroscopy. The agar-well diffusion method was used to evaluate their antibacterial activity against both Staphylococcus aureus and Escherichia coli bacteria, with or without light irradiation. The TEM images indicated clearly that silver nanoparticles (AgNPs, 5–10 nm) were well deposited on the surface of nano-TiO2 particles (30–60 nm). In addition to this, bigger AgNPs (<20 nm) were dispersed on the surface of nano-ZnO particles (30–50 nm). XRD patterns confirmed the presence of AgNPs in both Ag-decorated TiO2 and Ag-decorated ZnO nanoparticles. UV-Vis spectra confirmed that the hybridization of Ag and oxide nanoparticles led to a shift in the absorption edge of oxide nanoparticles to the lower energy region (visible region). The antibacterial tests indicated that both oxide pure nanoparticles did not exhibit inhibitory effects against bacteria, with or without light irradiation. However, the presence of AgNPs in their hybrids, even at low content (<40 mg/mL), leads to a good antibacterial activity, and higher inhibition zones under light irradiation as compared to those in dark were observed.

1. Introduction

It was reported in literature that nanoparticles can attack bacteria through six main mechanisms [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]: (i) destruction of the cell wall and peptidoglycan layer; (ii) release of toxic ions; (iii) destruction of protons efflux bombs and modification of membrane charges; (iv) formation of reactive oxygen species (ROS) degrading cell wall; (v) reactive oxygen species (ROS) degrading DNA, RNA, and proteins; and (vi) low adenosine triphosphate (ATP) production. In the case of metallic oxide nanoparticles (such as NiO, Co3O4, ZnO, Fe2O3, Fe3O4, MgO, CuO, TiO2, and SiO2), ROS is the predominant antibacterial mechanism, especially for nano-ZnO and nano-TiO2. For noble metal nanoparticles, such as silver nanoparticles (AgNPs), they can attack effectively against both Gram-negative and Gram-positive bacteria [16,17,18,19] via all six abovementioned antimicrobial mechanisms [20,21,22]. Therefore, in this application, AgNPs can be used as the sole antimicrobial agent. AgNPs could also react with bacteria through the photocatalytic production of ROS in solution [23]. However, Ag+-free ions released from AgNPs are considered toxic not only to human cells but also to the environment. Loading (embedding/immobilizing) AgNPs into oxide matrices is a new approach due to its ability to control solubility and toxicity of AgNPs. Various metallic oxide matrices have been used for loading/hybridizing AgNPs, such SiO2, ZrO2, Al2O3, Fe3O4, and CuO [24].
In the case of ZnO and TiO2 nanoparticles, they can kill bacteria mainly through the ROS mechanism in the presence of UV light. The practical applications of these semiconducting oxide nanoparticles are limited due to the following two reasons: (i) wide band gap ~3.2 eV for nano-TiO2 [25] and 3.37 eV for nano-ZnO [26] and (ii) high recombination of photogenerated electron–hole pairs [27,28,29]. Thus, two main approaches have been tried to improve the photocatalytic properties of these nanoparticles: (1) diminution of the recombination for photogenerated electron–hole pairs and (2) enhancement of the visible light sensitivity [25]. The first pathway focused on the design of heterostructures (heterojunctions) for these semiconducting oxide nanoparticles [30,31,32,33,34]. The formation of the Schottky barriers at the interface of noble metals/semiconducting oxide nanoparticles could significantly enhance the segregation of charges and helps to reduce the charge recombination [35,36]. For this reason, under UV irradiation, Ag-doped TiO2 layers exhibited higher antibacterial activity against Pseudomonas aeruginosa bacteria compared to pure TiO2 layers [37]. It is reported that the sensibility of TiO2 with visible light could be significantly enhanced by doping with various elements [38,39].
Recently, the hybridization of noble metals (Au, Ag, Pd) and semiconducting oxides has become the most promising strategy to defeat the large band gap of semiconducting oxides [40,41,42,43,44]. The energy level alignment is combined by the heterojunction at the nanoscale in these nanoparticles. We have also recently published several books and articles on related topics [21,40,45,46].
In this study, the hybridization of AgNPs and ZnO/TiO2 nanoparticles is expected not only to simply combine properties of single components, but also to significantly enhance their antibacterial properties [46]. Thus, this work aimed to investigate the role of silver decoration in enhancing the antibacterial activity of ZnO and TiO2 nanoparticles against Staphylococcus aureus (ATCC 25923, Gram-positive) and Escherichia coli (Gram-negative, ATCC 25922).

2. Materials and Methods

2.1. Materials

TiO2 (rutile) and ZnO nanoparticles were purchased from Sigma Aldrich (Singapore), having a mean diameter of <100 nm and a specific surface area of 18 and 15–25 m2/g, respectively. AgNO3 and NaBH4 were provided by Sigma Aldrich (Pathumwan, Bangkok, Thailand).

2.2. Synthesis of Silver-Decorated Nanoparticles

Firstly, 0.2 g of TiO2 (or ZnO) nanoparticles was dispersed in 200 mL of distilled water under ultrasonication. AgNO3 solution (0.01 g in 20 mL water) was then slowly added into the prepared nano-TiO2 (or ZnO) solution under ultrasonication for 30 min. The mixing solution was then poured into the 500 mL three-necked pot. Then, NaBH4 solution (0.01 g in 30 mL water) was added dropwise (1 drop/s) to the 500 mL three-necked pot. The reaction temperature was kept at 4 °C, and reaction mixture was stirred mechanically for 60 min. The nanohybrids were then collected by centrifugation at high speed (10,000 rpm) for 5 min. The residual precursors and agents were then fully removed after several rounds of centrifugation by adding fresh distilled water.

2.3. Characterization

The morphology of the hybrid nanoparticles was investigated using a transmission electron microscopy (JEM1010, JEOL, Tokyo, Japan), operating at 80 kV. UV–Vis spectra were obtained using a CINTRA 40 spectrophotometer (Cintra, Austin, TX, USA) in absorbance mode with 2 nm slip width. To verify the possible phases that were present in the Ag-decorated oxide nanoparticles, the X-ray diffraction method was used a Siemens D5000 diffractor (Siemens/Bruker, Aubrey, TX, USA) with CuKα radiation at the scan rate of 0.015°·s−1).

2.4. Antibacterial Tests

The agar-well diffusion method was used to evaluate antibacterial activity against Gram-positive (Staphylococcus aureus—ATCC 25923) and Gram-negative (Escherichia coli—ATCC 25922) bacteria. Nutrient agar plates were inoculated in brain heart infusion (BHI) broth using 100 µL of 106 CFU bacterial suspensions. Wells (8 mm diameter) were then punched in the inoculated plates using a sterile plastic rod. These wells were then filled with 50 µL of solution containing nanoparticles, at various concentrations, such as 8, 16, and 40 mg/mL. Control wells were filled with 50 µL of distilled water. These plates were the incubated at 37 °C for 18 h (with or without light irradiation). After this period, the antibacterial activities of these nanoparticles were evaluated by measuring the inhibition zone diameter around the wells (100 µm resolution; Model: Haloes Caliper—Zone Reader, IUL, Barcelone, Spain).
For the light irradiation test, LED (cold white, 1500 mcd, 3V DC) bulbs (two bulbs) were used with an illumination intensity of 300 lux. These cold white LEDs were designed by mixing blue (450–470 nm) and yellow (560–590 nm) lights that could be perceived by the naked eye as white color [46].

3. Results and Discussions

3.1. Characterization of Prepared Ag/TiO2 and Ag/ZnO Nanoparticles

Figure 1 shows the electron microscopy images of AgNP-decorated nano-TiO2 particles. As can be seen in this figure, AgNPs (black particles, 5–10 nm) were well dispersed on the surface of nano-TiO2 particles (30–60 nm). The bigger nanoparticles are assigned to nano-TiO2 and the smaller ones are AgNPs, as described in the literature [21]. It is worth noting that the synthesis process of hybrid nanoparticles was optimized to obtain the reported sizes of the hybrid nanoparticles.
TEM images of AgNP-decorated nano-ZnO particles are shown in Figure 2. As shown in this figure, AgNPs (black spots <20 nm) were alternatively deposited and linked to nano-ZnO nanoparticles (30–50 nm). The presence of AgNPs is proven by a sharp peak, located at 410 nm in the UV-vis spectra for these Ag/ZnO nanohybrids. For a comparative study, the size of AgNPs deposited on the surface of TiO2 nanoparticles was smaller than that on the surface of ZnO nanoparticles.
Figure 3 presents the XRD patterns of TiO2 and Ag/TiO2 nanoparticles. Figure 3a shows that the rutile phases of TiO2 exhibit several diffraction peaks, and the reflections at at (110), (101), (111), and (211) appear as the most intense, which is in line with the literature [47]. In the case of Ag/TiO2 in Figure 3b, the intense peak at 38° refers to a (111) reflection of metallic Ag [48]. Due to low concentration (as compared to TiO2 nanoparticles), other peaks of Ag are dominated by TiO2 phases.
Figure 4 shows the XRD patterns of ZnO and Ag/ZnO nanoparticles. For the pure ZnO nanoparticles, all characteristics of the X-rau diffraction for ZnO are observed, especially the 100, 103, and 202 plans. In the case of ZnO-decorated with metallic Ag, some new peaks assigned to the (111), (200), (220), and (311) reflections are observed at high intensity [48,49]. This helps to confirm the presence of successful synthesis of these nanomaterials.
Figure 5 shows the UV-visible spectra of aqueous solutions containing AgNPs, TiO2, and Ag/TiO2 nanoparticles. In the case of AgNPs (~10 nm of diameter), a broad band around 398 nm is believed to be present due to the surface plasmon resonance (SPR peak) of AgNPs [50]. The absorption band for pure TiO2 nanoparticles was observed in the UV region (at 360 nm), whereas it was shifted to the visible region for Ag-decorated TiO2 nanoparticles. These results are in line with those reported in the literature for Ag-doped TiO2 nanomaterials [51,52]. Figure 6 shows the UV-visible spectra for nano-ZnO- and nano-TiO2-decorated with AgNPs (dispersed in water). This figure shows a broad band at the 410 nm band, indicating the presence of AgNPs on the surface of the nano-ZnO particles.

3.2. Antibaterial Tests

3.2.1. TiO2 and Ag/TiO2 Nanoparticles

Figure 7 and Figure 8 present the photographs of antibacterial tests for nano-TiO2 and Ag/TiO2 NPs against S. aureus and E. coli bacteria, with and without light irradiation, respectively. Table 1 and Table 2 show their corresponding inhibition zones. Figure 7a,b indicates that in the dark, TiO2 NPs do not exhibit inhibitory effects to S. aureus bacteria (at concentrations of 10–40 mg/mL), whereas Ag-loaded TiO2 NPs show a significant antibacterial activity at a concentration of 40 mg/mL. It was reported that TiO2 nanoparticles are easy to attach to the cell membranes and accumulate [53,54,55]. In general, TiO2 nanoparticles can destroy the pathogenic bacteria by the ROS mechanism under UV light radiation. Since the emitted wavelengths of the white LED lights include peaks in the blue (450–470 nm) and yellow (560–590nm) areas, the inhibition zone of Ag-loaded TiO2 NPs (40 mg/mL) could be attributed to the content of AgNPs in the nanohybrids (e.g., ~1.3 mg/mL). It is worth noting that the concentration of TiO2 in nanohybrids is 30 times higher than that of AgNPs (from synthesis: the weight ratio of Ag precursors:TiO2 = 1:30). These nanoparticles exhibited an inhibition zone of 2 mm (in diameter) at the lower concentration of 16 mg/mL, indicating the contribution of TiO2 nanoparticles in these nanohybrids to their antibacterial activity (Table 1). At a concentration of 40 mg/mL, their inhibition zone is similar to that observed in the dark (4 mm in diameter), indicating the dominated contribution of AgNPs to the antibacterial activity.
Figure 7c,d shows that TiO2 NPs did not exhibit inhibitory effects to bacteria under light irradiation (at concentration of 8–40 mg/mL). It was reported that the doping TiO2 with noble metals shifted its absorption band to the visible region [40]. Without UV irradiation, pure TiO2 nanoparticles did not inhibit bacterial growth. However, Ag–TiO2 core–shell nanoparticles exhibited a good antibacterial activity against both E. coli and S. aureus bacteria without UV light [56,57]. Other authors have also reported that TiO2 nanoparticles with highly dispersed Ag clusters are entirely restricted the growth of the E. coli bacterial [58]. Barudin et al. [59] indicated that Ag–TiO2 nanoparticles exhibited superior antibacterial activity, as compared to pure TiO2 nanoparticles, even under visible light irradiation [59].
In this work, for E. coli bacteria, under light irradiation, Ag/TiO2 nanohybrids show a higher antibacterial activity than that in the dark. Table 2 shows that, in the dark, the inhibition zones of Ag/TiO2 nanohybrids increase with their concentration, due to the increase of AgNP concentration in the nanohybrids.

3.2.2. ZnO and Ag/ZnO Nanoparticles

It was reported in literature that ZnO has the inherent gain of broad antibacterial activities against virus, bacteria, fungus, and spores [60,61,62]. Stoimenov et al. [63] defined that ZnO nanoparticles attach on the bacterial surface due to electrostatic force of attraction. We expect that the hybridization of AgNPs with ZnO NPs may exhibit a superior antibacterial activity compared to their counterparts [45].
Figure 9 and Figure 10 show the photographs of an antibacterial test for nano-ZnO and Ag/ZnO NPs against S. aureus and E. coli bacteria, without and with light irradiation, respectively. Table 3 and Table 4 show their corresponding inhibition zones. Figure 9 and Figure 10 indicate that ZnO NPs did not exhibit inhibitory effects for both bacteria, with or without light irradiation (at concentrations of 10–40 mg/mL).
For Ag/ZnO nanohybrids, as shown in Table 3 and Table 4, light irradiation leads to an increase of the diameter of the inhibition zone for both S. aureus (at 8 mg/mL) and E. coli (at 8, 16, and 40 mg/mL) bacteria. Similarity, Ibanescu et al. [64] reported the antimicrobial property of Ag/ZnO nanocomposites against both E. coli and M. luteus bacteria. Their finding indicates that small amounts of silver could significantly enhance antimicrobial activity. The photocatalytic activity of Ag/ZnO nanocomposites could also contribute to enhancing antimicrobial activity. Nagaraju et al. [65] indicated an improvement of antimicrobial activity of Ag–ZnO NPs against both E. coli and S. aureus bacteria compared to pure materials. The inhibition zone could be observed at a concentration of 500 µg Ag–ZnO NPs. Wei et al. [66] also described the high antibacterial activity of Ag–ZnO hybrid nanofibers against E. coli and P. aeruginosa bacteria.
For the comparative study, under light irradiation at a low concentration (8 mg/mL), Ag/ZnO nanohybrids exhibit higher antibacterial activity against both two bacteria than Ag–Ag/TiO2 nanohybrids. One possible explanation is the better hybridization between Ag and ZnO nanoparticles, through the presence of the SPR peak in Ag/ZnO nanoparticles (Figure 6), whereas the SPR peak seems to disappear in the Ag/TiO2 nanoparticles (Figure 5).

4. Conclusions

This research is a continuous works focused on polymers and multifunctional composites [67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86]. The main findings of this work were as follows:
  • Silver-decorated oxide nanoparticles were successfully prepared using sodium borohydride as a reducing agent, with the weight ratio of Ag precursors:oxide nanoparticles = 1:30.
  • The TEM images indicated that AgNPs (5–10 nm) were deposited on the surface of nano-TiO2 particles (30–60 nm), whereas the bigger AgNPs (<20 nm) were dispersed on the surface of nano-ZnO particles (30–50 nm). XRD patterns confirmed the presence of AgNPs in both Ag-decorated TiO2 and Ag-decorated ZnO nanoparticles.
  • UV-vis spectra indicated that the hybridization of Ag and oxide nanoparticles led to a shift in the absorption edge of oxide nanoparticles to the lower energy region (visible region).
  • The antibacterial tests indicated that both oxide nanoparticles did not exhibit inhibitory against bacteria, with or without light irradiation. However, the presence of AgNPs in their hybrids (at a concentration <40 mg/mL) exhibited higher inhibition zones under light irradiation, as compared to that in dark. At a high concentration of 40 mg/mL, the antibacterial behavior of these nanohybrids under light irradiation is similar to that in dark, indicating the dominated contribution of AgNPs to the antibacterial activity of these nanohybrids (at this high concentration).
  • In the comparative study, under light irradiation at a low concentration (8 mg/mL), Ag/ZnO nanohybrids exhibited higher antibacterial activity against both bacteria than the Ag–Ag/TiO2 nanohybrids.

Author Contributions

Conceptualization and methodology, P.N.-T., T.A.N. and V.T.N.; synthesis of ZnO–AgNPs, V.T.V., V.K.T. and V.T.N.; Synthesis of TiO2–AgNPs, T.H.N. and V.K.T.; writing—original draft preparation, T.A.N.; writing—review and editing P.N.-T.; supervision, P.N.-T.

Funding

This work was financial supported by Natural Sciences and Engineering Research Council of Canada (NSERC).

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. TEM images of Ag-loaded TiO2 nanoparticles at different magnifications showing the hybrid structure; (a) 40,000× and (b) 80,000×. Inserted images show the schematic illustration of hybrid nanoparticles. The red point represents Ag nanoparticles, and the blue support is nano-TiO2.
Figure 1. TEM images of Ag-loaded TiO2 nanoparticles at different magnifications showing the hybrid structure; (a) 40,000× and (b) 80,000×. Inserted images show the schematic illustration of hybrid nanoparticles. The red point represents Ag nanoparticles, and the blue support is nano-TiO2.
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Figure 2. TEM images of Ag-loaded ZnO nanoparticles at different magnifications: (a) 43,000× and (b) 195,000×.
Figure 2. TEM images of Ag-loaded ZnO nanoparticles at different magnifications: (a) 43,000× and (b) 195,000×.
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Figure 3. XRD patterns of (a) TiO2 nanoparticles and (b) Ag/TiO2 nanoparticles.
Figure 3. XRD patterns of (a) TiO2 nanoparticles and (b) Ag/TiO2 nanoparticles.
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Figure 4. XRD patterns of (a) ZnO nanoparticles and (b) Ag/ZnO nanoparticles.
Figure 4. XRD patterns of (a) ZnO nanoparticles and (b) Ag/ZnO nanoparticles.
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Figure 5. UV-Vis spectra of AgNPs, nano-TiO2, and AgNP-decorated nano-TiO2 particles (dispersed in water).
Figure 5. UV-Vis spectra of AgNPs, nano-TiO2, and AgNP-decorated nano-TiO2 particles (dispersed in water).
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Figure 6. UV-Vis spectra of AgNP-decorated nano-ZnO particles (dispersed in water).
Figure 6. UV-Vis spectra of AgNP-decorated nano-ZnO particles (dispersed in water).
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Figure 7. Photographs of antibacterial test against Staphylococcus aureus bacteria (agar-well diffusion method) for pure TiO2 and Ag-loaded TiO2 nanoparticles: (a) and (b): without light irradiation; (c) and (d): under light irradiation. Concentrations of AgNPs used are 8, 16, and 40 mg/mL.
Figure 7. Photographs of antibacterial test against Staphylococcus aureus bacteria (agar-well diffusion method) for pure TiO2 and Ag-loaded TiO2 nanoparticles: (a) and (b): without light irradiation; (c) and (d): under light irradiation. Concentrations of AgNPs used are 8, 16, and 40 mg/mL.
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Figure 8. Photographs of antibacterial test against Escherichia coli bacteria (agar-well diffusion method) for Ag-loaded TiO2 nanoparticles: (a) without light irradiation; (b) under light irradiation). Concentration of 8, 16, and 40 mg/mL.
Figure 8. Photographs of antibacterial test against Escherichia coli bacteria (agar-well diffusion method) for Ag-loaded TiO2 nanoparticles: (a) without light irradiation; (b) under light irradiation). Concentration of 8, 16, and 40 mg/mL.
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Figure 9. Photographs of antibacterial test against S. aureus bacteria (agar-well diffusion method) for pure ZnO nanoparticles ((a): without light irradiation; (b): under light irradiation) and Ag-loaded ZnO nanoparticles ((c): without light irradiation; (d): under light irradiation).
Figure 9. Photographs of antibacterial test against S. aureus bacteria (agar-well diffusion method) for pure ZnO nanoparticles ((a): without light irradiation; (b): under light irradiation) and Ag-loaded ZnO nanoparticles ((c): without light irradiation; (d): under light irradiation).
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Figure 10. Photographs of antibacterial test against E. coli bacteria (agar-well diffusion method) for ZnO nanoparticles ((a): without light irradiation; (b): under light irradiation) and Ag-loaded ZnO nanoparticles ((c): without light irradiation; (d): under light irradiation).
Figure 10. Photographs of antibacterial test against E. coli bacteria (agar-well diffusion method) for ZnO nanoparticles ((a): without light irradiation; (b): under light irradiation) and Ag-loaded ZnO nanoparticles ((c): without light irradiation; (d): under light irradiation).
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Table
Table 1. Antibacterial activity against S. aureus bacteria of TiO2 nanoparticles and Ag-loaded TiO2 nanoparticles.
Table 1. Antibacterial activity against S. aureus bacteria of TiO2 nanoparticles and Ag-loaded TiO2 nanoparticles.
Concentrations (mg/mL)Inhibition Zone (mm)
Without Light IrradiationUnder Light Irradiation
TiO2 NanoparticlesAg-Decorated TiO2 NanoparticlesTiO2 NanoparticlesAg-Decorated TiO2 Nanoparticles
80000
160002
400404
Table
Table 2. Antibacterial activity against E. coli bacteria of TiO2 nanoparticles and Ag-loaded TiO2 nanoparticles.
Table 2. Antibacterial activity against E. coli bacteria of TiO2 nanoparticles and Ag-loaded TiO2 nanoparticles.
Concentrations (mg/mL)Inhibition Zone (mm)
Without Light IrradiationUnder Light Irradiation
TiO2 NanoparticlesAg-Decorated TiO2 NanoparticlesTiO2 NanoparticlesAg-Decorated TiO2 Nanoparticles
80206
160608
400808
Table
Table 3. Antibacterial activity against S. aureus bacteria of ZnO nanoparticles and Ag-loaded ZnO nanoparticles.
Table 3. Antibacterial activity against S. aureus bacteria of ZnO nanoparticles and Ag-loaded ZnO nanoparticles.
Concentrations (mg/mL)Inhibition Zone (mm)
Without Light IrradiationWith Light Irradiation
ZnO NanoparticlesAg-Decorated ZnO NanoparticlesZnO nanoparticlesAg-Decorated ZnO Nanoparticles
80002
160202
400404
Table
Table 4. Antibacterial activity against E. coli bacteria of ZnO nanoparticles and Ag-loaded ZnO nanoparticles.
Table 4. Antibacterial activity against E. coli bacteria of ZnO nanoparticles and Ag-loaded ZnO nanoparticles.
Concentrations (mg/mL)Inhibition Zone (mm)
Without Light IrradiationWith Light Irradiation
ZnO NanoparticlesAg-Decorated ZnO NanoparticlesZnO NanoparticlesAg-Decorated ZnO Nanoparticles
80207
160408
400608

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Nguyen, V.T.; Vu, V.T.; Nguyen, T.H.; Nguyen, T.A.; Tran, V.K.; Nguyen-Tri, P. Antibacterial Activity of TiO2- and ZnO-Decorated with Silver Nanoparticles. J. Compos. Sci. 2019, 3, 61. https://doi.org/10.3390/jcs3020061

AMA Style

Nguyen VT, Vu VT, Nguyen TH, Nguyen TA, Tran VK, Nguyen-Tri P. Antibacterial Activity of TiO2- and ZnO-Decorated with Silver Nanoparticles. Journal of Composites Science. 2019; 3(2):61. https://doi.org/10.3390/jcs3020061

Chicago/Turabian Style

Nguyen, Van Thang, Viet Tien Vu, The Huu Nguyen, Tuan Anh Nguyen, Van Khanh Tran, and Phuong Nguyen-Tri. 2019. "Antibacterial Activity of TiO2- and ZnO-Decorated with Silver Nanoparticles" Journal of Composites Science 3, no. 2: 61. https://doi.org/10.3390/jcs3020061

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