Antibacterial Properties Of Nanoparticles Research Articles

Evaluation of antimicrobial and antioxidant effects of silver nanoparticles synthesized with leaves of Lepidium draba L.

Nanoscience is a prominent scientific field with great potential and many novel and cost-effective applications. Numerous green and environmentally friendly synthesis methods have been introduced that use different plant extracts to produce silver, gold, copper, and iron antibacterial nanoparticles. Plant extracts contain rejuvenating compounds which, when exposed to metal salts (in this research, silver nitrate), facilitate their reduction to metal ions. In the present investigation, Lepidium draba was used as a regenerating factor. Silver nanoparticles (AgNPs) containing Azmak leaf extract were synthesized under optimal conditions including silver nitrate concentration, time, temperature, and pH. These nanoparticles were then evaluated for their characteristics using transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), and zeta potential analyses. Subsequently, the antibacterial properties of nanoparticles were assessed using the broth microdilution method. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) method was also employed to examine the antioxidant properties of synthesized nanoparticles. Structural analyses revealed the formation of spherical, stable, and pure AgNPs with a size of 20–35 nm. The synthesized AgNPs exhibited strong antibacterial activity against Gram-negative and Gram-positive bacteria. In addition, investigation of the antioxidant activity of the nanoparticles showed 89% inhibition at a concentration of 250 μg/mL. AgNPs synthesized using the Azmak leaf extract can be employed as low-cost and efficient nanoparticles for environmental and biomedical applications and their dual antimicrobial and antioxidant characteristics could potentially position them as candidates for treating infectious wound.

Biosynthesis Optimization of Antibacterial-Magnetic Iron Oxide Nanoparticles from Bacillus megaterium.

The occurrence of antibiotic resistance on common bacterial agents and the need to use new generations of antibiotics have led to the use of various strategies for production. Taking inspiration from nature, using bio-imitation patterns, in addition to the low cost of production, is advantageous and highly accurate. In this research, we were able to control the temperature, shake, and synthesis time of the synthesis conditions of Bacillus megaterium bacteria as a model for the synthesis of magnetic iron nanoparticles and optimize the ratio of reducing salt to bacterial regenerating agents as well as the concentration of salt to create iron oxide nanoparticles with more favorable properties and produced with more antibacterial properties. Bacterial growth was investigated by changing the incubation times of pre-culture and overnight culture in the range of the logarithmic phase. The synthesis time, salt ratio, and concentration were optimized to achieve the size, charge, colloidal stability, and magnetic and antibacterial properties of nanoparticles. The amount of the effective substance produced by the bacteria was selected by measuring the amount of the active substance synthesized using the free radical reduction (DPPH) method. With the help of DPPH, the duration of the synthesis was determined to be one week. Characterizations such as UV-vis spectroscopy, FTIR, FESEM, X-ray, and scattering optical dynamics were performed and showed that the nanoparticles synthesized with a salt concentration of 80mM and a bacterial suspension to salt ratio of 2:1 are smaller in size and have a light scattering index, a PDI index close to 0.1, and a greater amount of reducing salt used in the reaction during one week compared to other samples. Moreover, they had more antibacterial properties than the concentration of 100mM. As a result, better characteristics and more antibacterial properties than common antibiotics were created on E. coli and Bacillus cereus.

Biosynthesis of Zinc Nanoparticles From Actinobacterium Streptomyces Species and Their Biological Potential.

In today's world, antibiotic-resistant microorganisms are a major concern. There is solid evidence that metal nanoparticles (NPs) tend to have antimicrobial properties. The most effective substitute for antibiotic resistance is the incorporation of metal NPs.The antibacterial properties of NPs are currently being explored and shown to be successful.Zinc (Zn)NPsthat are biosynthesized frommarine Actinobacterium proved to be more biocompatible, bioactive, and affordable. Aim: This study aims to investigate the synthesis of ZnNPs from Actinobacterium Streptomyces species and their antimicrobial effects against gram-positive and gram-negative bacteria. The current study uses natural, considerably safer processes to synthesize ZnNPs from marine Actinobacteria with little to no negative side effects. It involves sample collection, identification, and isolation of Actinobacterium Streptomyces species. The isolated sample was air-dried, and extracts of ZnNPswere taken. Among the isolates from marine sediment, two Actinobacteria that generate bioactive secondary metabolites-Streptomyces species (MOSEL-ME28) and Rhodococcus rhodochrous (MOSEL-ME29)-were selected for extracellular synthesis of ZnNPs.The antimicrobial activity of the biosynthesized ZnNPs from marine Actinobacteria was analyzed againstStaphylococcus(MRSA), Klebsiella pneumoniae,and Streptococcus mutans. The results were statistically analyzed and graphs were created. ZnNPs obtained from Actinobacterium Streptomyces species exhibited antimicrobial effects against Staphylococcus (MRSA), Klebsiella, and Streptococcus mutans. At 280 nm wavelength, analysis of the UV spectrum showed anotable absorbance value of 1.8. The antibacterial efficacy against Staphylococcus MRSA, Klebsiella species, and Streptococcus mutans was assessed by measuring the zone of inhibition in diameter. The zones of inhibition were 8, 8, and 7 mm on the evaluation forStreptococcus mutans, S. aureus, and Klebsiella species, respectively, at a dose of 75 μg/mL. When the dosage was increased to 100 μg/mL, the inhibition zones were found to be 9.5, 9, and 7.5mm for the respective bacterial strains. ZnNPs are biosynthesized from marine Actinobacterium Streptomyces species in this research study. They have a significant antimicrobial activity against both gram-positive and negative bacteria. This indicates that ZnNPs have enormous antimicrobial potential and have an extensive spectrum of applications. However, clinical trials must be completed before it can be used safely on patients.

Nanoparticle surface stabilizing agents influence antibacterial action.

The antibacterial properties of nanoparticles are of particular interest because of their potential to serve as an alternative therapy to combat antimicrobial resistance. Metal nanoparticles such as silver and copper nanoparticles have been investigated for their antibacterial properties. Silver and copper nanoparticles were synthesized with the surface stabilizing agents cetyltrimethylammonium bromide (CTAB, to confer a positive surface charge) and polyvinyl pyrrolidone (PVP, to confer a neutral surface charge). Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and viable plate count assays were used to determine effective doses of silver and copper nanoparticles treatment against Escherichia coli, Staphylococcus aureus and Sphingobacterium multivorum. Results show that CTAB stabilized silver and copper nanoparticles were more effective antibacterial agents than PVP stabilized metal nanoparticles, with MIC values in a range of 0.003 μM to 0.25 μM for CTAB stabilized metal nanoparticles and 0.25 μM to 2 μM for PVP stabilized metal nanoparticles. The recorded MIC and MBC values of the surface stabilized metal nanoparticles show that they can serve as effective antibacterial agents at low doses.

Green synthesis of trimetallic oxide nanoparticles and their use as an efficient catalyst for the green synthesis of quinoline and spirooxindoles: Antibacterial, cytotoxicity and anti-colon cancer effects

The three-metallic oxide (Cu/Cr/Ni) nanoparticles were prepared using Echinops persicus plant extract via a simple, biocompatible, cost-effective, and non-toxic procedure, and their catalytic activity was evaluated over the synthesis of biologically active quinoline and spirooxindole derivatives. The synthesized nanoparticles were characterized by various analytical methods including UV–Vis, FTIR, EDX, XRD, FE-SEM, DLS, and TEM analyses. Effective parameters involved in the reactions were designed by Design-Expert 10.0.7 software. The Cu/Cr/Ni nanoparticles were used as an efficient catalyst for the preparation of quinolines and spirooxindoles under solvent-free conditions with good to excellent efficiencies. Furthermore, due to the rich phenolic content of Echinops persicus flower extract, the antibacterial properties of nanoparticles against E. coli, S. aureus, and B. cereus were studied by MIC as well as well diffusion methods. In addition, the cytotoxicity and anti-colon cancer activity of the nanoparticles was studied on human colon cancer (HT29) cells based on the MTT assay. The results and observations clearly showed that Cu/Cr/Ni NPs have noteworthy catalytic and antibacterial activity, completely superior to their corresponding single-metal nanoparticles.

One Step Production of Silver-Copper (AgCu) Nanoparticles

AgCu nanoparticles were prepared through hydrogen-reduction-assisted Ultrasonic Spray Pyrolysis (USP) and the Hydrogen Reduction (HR) method. The changes in the morphology and crystal structure of nanoparticles were studied using different concentrated precursors. The structure and morphology of the mixed crystalline particles were characterized through X-ray diffraction analysis (XRD), scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM) and Energy-dispersive X-ray spectroscopy (EDS). The average particle size decreased from 364 nm to 224 nm by reducing the initial solution concentration from 0.05 M to 0.4 M. These results indicate that the increase in concentration also increases the grain size. Antibacterial properties of nanoparticles against Escherichia coli were investigated. The obtained results indicate that produced particles show antibacterial activity (100%). The AgCu nanoparticles have the usage potential in different areas of the industry.

Antibacterial Properties of Nanoparticles in Dental Restorative Materials. A Systematic Review and Meta-Analysis.

Background and Objectives: Nanotechnology has become a significant area of research focused mainly on increasing the antibacterial and mechanical properties of dental materials. The aim of the present systematic review and meta-analysis was to examine and quantitatively analyze the current evidence for the addition of different nanoparticles into dental restorative materials, to determine whether their incorporation increases the antibacterial/antimicrobial properties of the materials. Materials and Methods: A literature search was performed in the Pubmed, Scopus, and Embase databases, up to December 2018, following PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines for systematic reviews and meta-analyses. Results: A total of 624 papers were identified in the initial search. After screening the texts and applying inclusion criteria, only 11 of these were selected for quantitative analysis. The incorporation of nanoparticles led to a significant increase (p-value < 0.01) in the antibacterial capacity of all the dental materials synthesized in comparison with control materials. Conclusions: The incorporation of nanoparticles into dental restorative materials was a favorable option; the antibacterial activity of nanoparticle-modified dental materials was significantly higher compared with the original unmodified materials, TiO2 nanoparticles providing the greatest benefits. However, the high heterogeneity among the articles reviewed points to the need for further research and the application of standardized research protocols.

Study on the photocatalytic and antibacterial properties of silver nanoparticles synthesized by a green approach

Silver nanoparticles (AgNPs) have potential applications in several fields, mainly when they are synthesized by a green method. In the present work, the photocatalytic and antibacterial properties of silver nanoparticles biosynthesized using aqueous extracts of a variety of Eriobotrya japonica were investigated. The effects on the nanoparticles characteristics of parameters such as extract volume, stability, and reaction temperature were studied. The structural characterization showed that the synthesized nanoparticles have spherical morphology mostly with a size range of 10–60 nm. The increase of biosynthesis reaction temperature leads to an increase in the AgNPs concentration. However, the size and size distribution increased, resulting in a bimodal distribution. Therefore, the best results were obtained at room temperature with 4 ml of plant extract. According to FTIR results, the reduction of Ag ions and the subsequent nanoparticles stabilization are attributed to phenolic compounds from leaves extract. The antibacterial properties of the nanoparticles were evaluated. The bacteria analyzed were E. coli, P. aeruginosa, and S. aureus. The results demonstrate the capacity of the nanoparticles to inhibit the growth of gram-negative and gram-positive bacteria. These antibacterial properties depend on the concentration of nanoparticles. Finally, the catalytic activity of silver nanoparticles was analyzed. The results showed the excellent properties of nanoparticles to degrade methylene blue and methyl orange. Moreover, the rate and efficiency of degradation depending on the nanoparticles concentration, obtaining the best results when the highest concentration (60 μg ml−1) was employed. Therefore, silver nanoparticles synthesized by green synthesis are an excellent candidate for antibacterial and catalytic applications.

Mechanism of Larvicidal Activity of Antimicrobial Silver Nanoparticles Synthesized Using Garcinia mangostana Bark Extract

In this present investigation, we used an inexpensive method for the synthesis of silver nanoparticles (AgNPs) using Garcinia mangostana bark. The phyto-assisted AgNPs further characterized using scanning electron microscope for morphology and the elemental composition was detected via energy dispersive X-ray analysis. The domain size was characterized with the help of X-ray diffraction and UV–Vis spectrophotometric analysis for surface plasmon resonance. The possible functional groups were identified with the help of Fourier transform infrared spectroscopy. Antibacterial properties of nanoparticles were evaluated against Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Bacillus cereus and Klebsiella pneumoniae, using agar well diffusion method. Ultimately, the mosquitocidal activity of silver nanoparticles was assessed in the laboratory against fourth instar larvae of Aedes aegypti with LC50 of 5.93 mg L−1 which shows the potential larvicidal effect. To find out the mode of action for larvicidal activity, Agarose gel electrophoresis was carried out. We hypothesize that the toxicity of AgNPs against dengue vectors may be attributed to the small size of these AgNPs, which allows passage through the insect cuticle and into individual cells where they interfere with molting and other physiological processes.

Bactericidal Efficiency of Silver Nanoparticles Synthesized from Annona squamosa

Nanotechnology is described as an emerging technology that not only holds promise for society, but also is capable of providing novel approaches to overcome our common problems. The present study focused on the synthesis of silver nanoparticles using the metabolites of Annona squamosa seeds. The biological reduction procedure proposed in this method was considered as better one compared to chemical mediated reduction methods. The advantages include nontoxic to the environment, less energy consuming and highly suitable for further biological applications. The seeds were separated from the fruit pulp, grinded into powder and dissolved in distilled water. The suspension was used as reducing agent and treated with silver nitrate at the concentration of 1[Formula: see text]mM. The reduction reaction was continuously monitored by UV-visible photo spectrometer. Further the samples were subjected to AFM, SEM and XRD analysis for the confirmation of their size, structure, agglomerations and the arrangements of crystals. Finally the antibacterial properties of nanoparticles were tested against clinically important pathogenic microorganisms using disc diffusion method and compared with the activities of standard antibiotics. The combinational effects of nanoparticles with commercial antibiotics also were tested by the same method.

ANTIBACTERIAL EFFECT OF TWO TYPES OF NANO PARTICLES INCORPORATED IN ZINC OXIDE BASED SEALERS ON ENTEROCOCCUS FAECALIS (IN VITRO STUDY)

INTRODUCTION: Antibacterial properties of nanoparticles have recently come into the spotlight in endodontic therapy.OBJECTIVES: Evaluation of the antimicrobial efficacy of zinc oxide based sealer incorporated with silver and zinc oxide nanoparticles compared with simple zinc oxide sealer against Enterococcus faecalis.MATERIALS AND METHODS: The study was conducted on 60 human extracted mandibular premolars. After instrumentation of all teeth and inoculation of root canals with Enterococcus faecalis, teeth were divided into three groups according to the type of the tested sealer, Group I: control group where teeth were obturated with unmodified zinc oxide based sealer. Group II: teeth were obturated using sealer modified with silver nanoparticles, Group III: teeth were obturated using sealer modified with zinc oxide nanoparticles. Each group was subdivided into two subgroups according to the timing of filling removal and culture sample. Subgroup A: filling removal and culture sample were taken after one week. Subgroup B: filling removal and culture sample were taken after three weeks. Colony counting technique was used , the number of colony forming unites method was counted to assess the effect against Enterococcus faecalis. Data were recorded, tabulated and statistically analyzed using Friedman test to compare the differences between the three groups.RESULTS: After three weeks from obturation, silver nanoparticles had a superior antibacterial effect and there was a significant difference between the three tested groups, but after one week of obturation there was no significant difference between the three tested groups.CONCLUSION: In three weeks samples after obturation silver nanoparticles had a superior antibacterial effect and there was a significant difference between the three tested groups, but after one week of obturation there was no significant difference between the three tested groups.

Spectral features and antibacterial properties of Cu-doped ZnO nanoparticles prepared by sol-gel method**Project supported by the Universiti Teknologi Malaysia (UTM) (Grant No. R. J1300000.7809.4F626). Dr. Samavati is thankful to RMC for postdoctoral grants.

Zn1−xCuxO (x = 0.00, 0.01, 0.03, and 0.05) nanoparticles are synthesized via the sol-gel technique using gelatin and nitrate precursors. The impact of copper concentration on the structural, optical, and antibacterial properties of these nanoparticles is demonstrated. Powder x-ray diffraction investigations have illustrated the organized Cu doping into ZnO nanoparticles up to Cu concentration of 5% (x = 0.05). However, the peak corresponding to CuO for x = 0.01 is not distinguishable. The images of field emission scanning electron microscopy demonstrate the existence of a nearly spherical shape with a size in the range of 30–52 nm. Doping Cu creates the Cu–O–Zn on the surface and results in a decrease in the crystallite size. Photoluminescence and absorption spectra display that doping Cu causes an increment in the energy band gap. The antibacterial activities of the nanoparticles are examined against Escherichia coli (Gram negative bacteria) cultures using optical density at 600 nm and a comparison of the size of inhibition zone diameter. It is found that both pure and doped ZnO nanoparticles indicate appropriate antibacterial activity which rises with Cu doping.

Antibacterial Properties of Nanoparticles: A Comparative Review of Chemically Synthesized and Laser-Generated Particles

Antibacterial Properties of Nanoparticles: A Comparative Review of Chemically Synthesized and Laser-Generated Particles

Leucas aspera mediated multifunctional CeO2 nanoparticles: Structural, photoluminescent, photocatalytic and antibacterial properties

Spherical shaped cerium dioxide (CeO2) nanoparticles (NPs) were synthesized via bio mediated route using Leucas aspera (LA) leaf extract. The NPs were characterized by PXRD, SEM, UV–Visible techniques. Photoluminescence (PL), photocatalysis and antibacterial properties of NPs were studied. PXRD patterns and Rietveld analysis confirm cubic fluorite structure with space group Fm-3m. SEM results evident that morphology of the NPs was greatly influenced by the concentration of LA leaf extract in the reaction mixture. The band gap energy of the NPs was found to be in the range of 2.98–3.4eV. The photocatalytic activity of NPs was evaluated by decolorization of Rhodamine-B (RhB) under UVA and Sun light irradiation. CeO2 NPs show intense blue emission with CIE coordinates (0.14, 0.22) and average color coordinated temperature value ∼148,953K. Therefore the present NPs quite useful for cool LEDs. The superior photocatalytic activity was observed for CeO2 NPs with 20ml LA under both UVA and Sunlight irradiation. The enhanced photocatalytic activity and photoluminescent properties were attributed to defect induced band gap engineered CeO2 NPs. Further, CeO2 with 20ml LA exhibit significant antibacterial activity against Escherichia coli (EC) and Staphylococcus aureus (SA). These findings show great promise of CeO2 NPs as multifunctional material for various applications.

Mosquitocidal and antibacterial activity of green-synthesized silver nanoparticles from Aloe vera extracts: towards an effective tool against the malaria vector Anopheles stephensi?

Mosquitoes represent an important threat for lives of millions of people worldwide, acting as vectors for devastating pathogens, such as malaria, yellow fever, dengue, and West Nile. In addition, pathogens and parasites polluting water also constitute a severe plague for populations of developing countries. Here, we investigated the mosquitocidal and antibacterial properties of Aloe vera leaf extract and silver nanoparticles synthesized using A. vera extract. Mosquitocidal properties were assessed in laboratory against larvae (I-IV instar) and pupae of the malaria vector Anopheles stephensi. Green-synthesized silver nanoparticles were tested against An. stephensi also in field conditions. Antibacterial properties of nanoparticles were evaluated against Bacillus subtilis, Klebsiella pneumoniae, and Salmonella typhi using the agar disk diffusion and minimum inhibitory concentration protocol. The synthesized silver nanoparticles were characterized by UV-vis spectrum, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In laboratory conditions, the A. vera extract was toxic against An. stephensi larvae and pupae, even at low dosages. LC50 were 48.79 ppm (I instar), 59.09 ppm (II instar), 70.88 ppm (III instar), 83.58 ppm (IV instar), and 152.55 ppm (pupae). Green-synthesized silver nanoparticles were highly toxic against An. stephensi. LC50 were 3.825 ppm (I instar), 4.119 ppm (II instar), 4.982 ppm (III instar), 5.711 ppm (IV instar), and 6.113 ppm (pupae). In field conditions, the application of A. vera-synthesized silver nanoparticles (10 × LC50) leads to An. stephensi larval reduction of 74.5, 86.6, and 97.7%, after 24, 48, and 72 h, respectively. Nanoparticles also showed antibacterial properties, and the maximum concentration tested (150 mg/L) evoked an inhibition zone wider than 80 mm in all tested bacterium species. This study adds knowledge about the use of green synthesis of nanoparticles in medical entomology and parasitology, allowing us to propose A. vera-synthesized silver nanoparticles as effective candidates to develop newer and safer mosquitocidal control tools.

Antibacterial properties of silver nanoparticles synthesized using Pulicaria glutinosa plant extract as a green bioreductant.

The antibacterial properties of nanoparticles (NPs) can be significantly enhanced by increasing the wettability or solubility of NPs in aqueous medium. In this study, we investigated the effects of the stabilizing agent on the solubility of silver NPs and its subsequent effect on their antimicrobial activities. Silver NPs were prepared using an aqueous solution of Pulicaria glutinosa plant extract as bioreductant. The solution also acts as a capping ligand. During this study, the antimicrobial activities of silver NPs, as well as the plant extract alone, were tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Micrococcus luteus. Silver NPs were prepared with various concentrations of the plant extract to study its effect on antimicrobial activity. Interestingly, various concentrations of P. glutinosa extract did not show any effect on the growth of tested bacteria; however, a significant effect on the antimicrobial property of plant extract capped silver NPs (Ag-NPs-PE) was observed. For instance, the half maximal inhibitory concentration values were found to decrease (from 4% to 21%) with the increasing concentrations of plant extract used for the synthesis of Ag-NPs-PE. These results clearly indicate that the addition of P. glutinosa extracts enhances the solubility of Ag-NPs-PE and, hence, increases their toxicity against the tested microorganisms.

Structural and Biological Properties of CuO Nanoparticles Prepared Under Ultrasonic Irradiation

In this research, the structural, optical, and biological characteristics of sonochemically prepared CuO nanoparticles have been investigated using scanning electron microscope (SEM), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and antibacterial and anticancer test. The results show that nanoparticles have been formed in crystalline form with the average size of about 10–50 nm, which aggregated in the form of nanoclusters with average cluster size of about 50–200 nm. The copper oxide nanoparticles, after 48 h, show excellent antitumor activity against two kinds of cancer cells that are AGS (human gastric carcinoma) cells and HeLa (human cervix carcinoma) cells. The results are completely new and provide new views for using of the mentioned compound in chemotherapy. Antibacterial properties of nanoparticles also have been studied and were determined against the two gram-positive bacteria and also against the two gram-negative bacteria. Obtained results showed a strong antibacterial activity of CuO nanoparticles against gram-positive bacteria.

Preparation, Characterization and Antibacterial Properties of Silver-Chitosan Nanocomposites Using Different Molecular Weight Grades of Chitosan

Purpose : To study the effect of chitosan molecular weight on the physicochemical and antibacterial properties of silver-chitosan nanoparticles. Methods : A series of silver-chitosan nanoparticles of different sizes were produced using various molecular weight (MW) grades of chitosan by an aqueous chemical reduction method. The nanoparticles were characterized by ultraviolet-visible absorption spectroscopy (UV-Vis), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic light scattering (DLS) and laser Doppler electrophoresis (LDE). The antibacterial properties of the nanoparticles were also evaluated by agar diffusion method. Results : The size of the silver-chitosan nanoparticles, ranging from 21.9 to 175.3 nm, was influenced by chitosan MW as well as by other process conditions. Although, the nanoparticles were not stable in liquid form, they however showed good stability in the solid state due to their low zeta potential. SEM images indicate that the nanoparticles were spherical. The antibacterial activity of the nanoparticles against Staphylococcus aureus increased with decrease in particle size owing to increase in surface area. The smallest particle size (21.9 nm) was obtained by using high chitosan MW at 4 °C and a stirring speed of 800 rpm. Conclusion : Chitosan is an effective agent for the preparation of silver nanoparticles. The size of the nanoparticles can be modulated by varying both chitosan MW and process conditions such as temperature and stirring speed.

TiO&lt;SUB&gt;2&lt;/SUB&gt; Nanoparticles Co-Doped with Silver and Nitrogen for Antibacterial Application

We have prepared a series of TiO2 nanoparticles for antibacterial applications. These TiO2 nanoparticles were prepared by the hydrolysis precipitation method with Ti(OBu)4, silver nitrate and ammonia. Crystal structure, particle size, interfacial structure and UV-visible light response of the prepared nanoparticles were characterized by X-ray diffraction measurements (XRD), Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRs). The XRD spectra showed that all samples were anatase structure calcined at 450 degrees C for 3 hours. The Ag doping made the peak of diffraction wider. The results of TEM showed that the nanoparticles of TiO2, N-TiO2 and 1% Ag-N-TiO2 were all spherical in shape and well distributed with a mean size of 19.8 nm, 39.2 nm and 20.7 nm, respectively. N doping caused the nanoparticle size to increase, while, when the doped amount of Ag+ increased, the TiO2 particle size decreased. The FTIR revealed that Ag and N doping of TiO2 appeared to have strong absorption by -OH group and showed the characteristic absorption band of NH4+ and Ag. The UV-Vis-DRs indicated that the absorption band of Ag-N co-doped TiO2 had red shift and that the optical absorption response (between 400 nm and 700 nm) had obvious enhancement. The antibacterial properties of nanoparticles were investigated by agar diffusion method toward Escherichia coli and Bacillus subtilis. The results indicated that both Ag- and N-doped TiO2 could increase the antibacterial properties of TiO2 nanoparticles under fluorescent light irradiation. A 1% Ag-N-TiO2 had the highest antibacterial activity with a clear antibacterial circle of 33.0 mm toward Escherichia coli and 22.8 mm toward Bacillus subtilis after cultivation for 24 hours.