AgNO3 Concentration Research Articles

Perturbation of fatty acid composition, pigments, and growth indices of Chlorella vulgaris in response to silver ions and nanoparticles: A new holistic understanding of hidden ecotoxicological aspect of pollutants

This study assesses and compares the influence of silver nanoparticles (AgNPs) and silver nitrate (AgNO3) on the fatty acid composition, pigments, and growth indices of Chlorella vulgaris. Toxicity testing was carried at the estimated and/or above predicted environmental concentrations of AgNPs and AgNO3. AgNO3 treatments impaired the population growth of C. vulgaris about 2–183 times more than the respective AgNPs ones. The pigments displayed a concentration-dependent decrease in response to both forms of silver; however, AgNO3 displayed higher severity to the pigments than AgNPs. In exposure to 10 μg L−1 AgNO3, the contents of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid, respectively, demonstrated a reduction of about 5, 3, 4, and 4 times when compared with the same respective concentration of AgNPs. Total amounts of saturated (∑SFA), monounsaturated (∑MUFA), and polyunsaturated (∑PUFA) fatty acids as well as the ratio of unsaturated to saturated ones (Unsat./Sat.) displayed somewhat similar-concentration responses. ∑SFA exhibited a hormesis response, and ∑MUFA, ∑PUFA, and Unsat./Sat. did a decreasing trend with increasing concentration of AgNPs and AgNO3. Myristoleic acid, nervonic acid, and eicosadienoic acid revealed the highest sensitivity. Pearson analysis illustrated the highest correlation among myristoleic acid, eicosenoic acid, and nervonic acid as well as among palmitic acid, stearic acid, palmitoleic acid, and oleic acid. Taken together, AgNPs and the released ions could disrupt physiological health state of microalgae through perturbation in the fatty acid composition (especially MUFAs and PUFAs) and other macromolecules. These types of bioperturbations could change the good health state of aquatic ecosystems.

Green synthesis of silver nanoparticles using Ocimum gratissimum leaf extract: characterization, antimicrobial activity and toxicity analysis

The present study reports the optimization of various parameters for green synthesis of silver nanoparticles using aqueous leaf extract of Ocimum gratissimum. The effects of various parameters such as concentration of AgNO3, ratio of AgNO3 to extract, pH and incubation time were studied in order to optimize the synthesis process. 5 mM AgNO3, 1:0.06 ratio of AgNO3 to O. gratissimum leaf extract, pH 9.0 and incubation of reaction mixtures for 24 h were found to be the optimum parameters for synthesis of silver nanoparticles (AgNPs). The synthesized AgNPs were characterized by UV–visible absorption spectroscopy, scanning electron microscopy and transmission electron microscopy. The nature of the reducing and capping agents in the leaf extract was determined using Fourier transform infrared spectrometer analysis. Furthermore, AgNPs showed higher antimicrobial activity against the Gram negative (Escherichia coli, Klebsiella pneumoniae) in comparison to the Gram positive bacteria (Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus). In addition to this, AgNP containing solution was subjected to toxicity analysis using seeds of Moong Bean (Vigna radiata). It was found that seeds treated with AgNP solutions showed better rates of germination and oxidative stress enzyme activity was at par with the control levels. This study demonstrates that O. gratissimum leaf extract can be used for production of AgNPs with potential antibacterial activity. Future research is warranted on the investigation of detailed mechanism of their antimicrobial activity, uptake and translocation in plants.

Physico-chemical, antimicrobial and anticancer properties of silver nanoparticles synthesised from organ-specific extracts of Bidens pilosa L.

There is an increasing commercial demand for nanoparticles synthesis by green as opposed to chemical methods, given the toxicity and contamination risks associated with the latter. This study compared the physico-chemical, antimicrobial and anticancer activities of silver nanoparticles (AgNPs) synthesised using organ-specific plant extracts in Bidens pilosa. Leaf, stem and root extracts were used as the reducing agent with varying concentrations of AgNO3 (1 mM and 2 mM, respectively). The synthesised AgNPs were subsequently characterised by UV–vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FT-IR). UV–vis spectroscopy showed a surface plasmon resonance peak for the synthesised AgNPs at 410 nm using all organ extracts. TEM studies indicated that nanoparticles ranged from 1.00 to 62.01 nm, with an average particle size of 17.00 nm. Average particle size was larger at the higher AgNO3 concentration. The FTIR analysis confirmed the presence of carbonyl groups, proteins and aldehydes on nanoparticles produced using all extract types. The leaf extract derived nanoparticles displayed maximum percentage cell death (76.0 ± 4.5%) against bacteria and superior antifungal activity (94.8 ± 0.5%) at 200 μg/ml. Leaf extract derived NPs also displayed maximum anticancer potency (38.1 ± 2.3%). The differential bioactivities of NPs across the three organ extracts investigated here suggests that comparative studies on plant organ-specific synthesised NPs can help us maximize the antimicrobial and anticancer benefits of plant-derived NPs.

The morphology control on the preparation of silver nanotriangles

A seed-mediated growth method was commonly applied to prepare one-dimension nanomaterials. However, some associated particles were unavoidable in the formation of target nanoparticles. Herein, we reported a modified method to prepare silver nanotriangles with higher uniform shape and particle size. The size and morphology of the formed nanoparticles could be controlled by regulating reaction conditions. The results showed that cetyl trimethyl ammonium bromide (CTAB) concentration and seed concentration were related with both the morphology and the particle size. The NaOH concentration, AgNO3 concentration, and the mole ratio of Vc/Ag+ mainly affected the particle size of the formed nanotriangles. The formation of silver nanotriangles may be due to the selective stacking of the new tiny nanoparticles and the oriented growth of silver seed crystals. The oxidizing action of Br−/O2 existing in the CTAB system should be responsible for the final morphology of truncated triangular silver nanoplates.

Size and morphology controlled synthesis of the silver (П) oxide particles

In this study, the experimental parameters for synthesis of silver (П) oxide (AgO) particles were controlled to achieve various particle sizes with different morphology. The AgO particles were synthesised by alkaline oxidation in the presence of potassium persulfate (K2S2O8). Characterisation of AgO particles was performed by X-ray diffraction, Fourier-transform infrared spectroscopy, and field emission scanning electron microscopy (FE-SEM) techniques. The analysis of FE-SEM images with Digimizer image analysis software indicated that the AgO particles were in micro and nanosize ranged from 50 to 150 nm in thickness and 0.58 to 1 µm in length. Also, pebble, slice, and flake morphologies were observed by controlling the experimental conditions. The general factorial design method was applied to investigate the effect of variable factors suchas the concentration of AgNO3 (CAg+), the concentration of K2S2O8 (CS2O8 2−), and the mole ratio of AgNO3 to K2S2O8 (RAg+/S2O8 2−), whereas the particle size was the response to be analysed. Based on the results of the analysis of variance, the model was significant. Investigations indicated that the interaction between CAg+ and RAg+/S2O8 2− has a significant effect on the AgO particle size. Validation of the results showed that residual and desirability values are 2.2% and 0.935, respectively.

The effect of silver nitrate on micropropagation of Moringa oleifera Lam. an important vegetable crop of tropics with substantial nutritional value.

An improved micropropagation protocol facilitating continuous multiplication of elite germplasm of Moringa oleifera has been developed. Initial culture of nodal explant in MS medium supplemented with 2.5µM BA resulted in the formation of 12.5 shoots per explant with high frequency of leaf fall (84.3%). To confirm whether the leaf fall is due to accumulation of ethylene in the culture vessel, effect of ethylene releasing agent CEPA in the medium was tested. In order to reduce leaf fall and improve multiplication, varying concentration of anti-ethylene agent, AgNO3 was incorporated in the medium. Addition of 2.5μM AgNO3 in combination with 2.5μM BA produced maximum number of shoots (17.6) including shoots originated from the base of the explant and shoots from the axillary buds of the primary shoots, where significant reduction in leaf fall (20.6%) was noticed. This enabled sustained multiplication of M. oleifera through continuous subculture without adversely affecting shoot number or shoot quality in terms of shoot length. Microshoots obtained from fourth subculture onwards were used for ex vitro rooting and found that by treating 50µM NAA for 30s, maximum numbers of microshoots (83.3%) were rooted. Rooted plants were acclimatized, survived and were successfully transferred to field. Genetic fidelity analysis using 10 ISSR primers revealed more than 95% monomorphic bands among plants raised in MS medium containing low concentration (2.5µM) of AgNO3 and BA (2.5µM). The addition of AgNO3 in the medium sustained in vitro growth and effectively prevented leaf fall compared to control, thus demonstrating efficient micropropagation of M. oleifera.

Silver‐plated polyamide fabrics with high electromagnetic shielding effectiveness performance prepared by in situ reduction of polydopamine and chemical silvering

ABSTRACTIn this article, the silver‐plated polyamide fabrics (SPPAFs) with high electroconductibility and shielding effectiveness were fabricated by using in situ reduction of polydopamine and chemical silvering. The effects of SPPAFs dopamine (C8H11O2N) and silver nitrate (AgNO3) concentration on surface resistivity and electromagnetic interference shielding effectiveness were studied. The results showed that the surface resistivity of SPPAFs can reach a minimum value of 0.06 ± 0.014 Ω cm−1, when C8H11O2N concentration is 4 g L−1 and the AgNO3 concentration is 120 g L−1. The shielding effectiveness of SPPAFs in the wide frequency range of 10–3000 MHz increases with the increase in the concentration of AgNO3, and increases first and stabilizes afterward with increasing C8H11O2N concentration. When the concentration of C8H11O2N and AgNO3 is 3 and 120 g L−1, respectively, mean shielding effectiveness values in the low‐, medium‐, and high‐frequency bands are 71.3, 73.8, and 76.1 dB, respectively. Moreover, the mean shielding effectiveness values is 83.79 dB in the frequency range of 1.2–2.3 GHz. The dominant shielding mechanism of SPPAFs is the reflected electromagnetic waves and the absorption shielding effectiveness is less than 2 dB. The average electromagnetic shielding values of SPPAFs are above 67 dB after 16 weeks of storage, when C8H11O2N concentration is 4 g L−1 and the AgNO3 concentration is 80 and 100 g L−1. The prepared SPPAFs show promising applications in military textiles and smart wearable clothing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48227.

Biogenic synthesis and antibacterial activity of controlled silver nanoparticles using an extract of Gongronema Latifolium

Biogenic synthesis of silver nanoparticles (AgNPs) was conducted via an aqueous extract of fresh leaf of Gongronema Latifolium (FLGL) an herbaceous flowering plant as a fuel agent. The effects of different AgNO3 concentration with the fixed volume of FLGL on the properties of the formulated AgNPs were investigated. Also, the antibacterial activity AgNPs formed was observed through the solid agar plates supplemented with different concentrations of nano-sized AgNPs on Gram-negative (Coliform, Escherichia coli), and Gram-positive (Staphylococcus Aurea) bacterial strain. We observed from the various characterizations of AgNPs that the variation in the concentration of AgNO3 coupled with the incubation period played a major role in controlling the particle sizes and dispersions. The UV–visible confirmed the formation of AgNPs with the surface Plasmon resonance (SPR) peak value at 430 nm in the visible region showing the type as well as the nature of the particles in the colloidal solution. The Fourier transform infrared spectroscopy revealed the functional groups liable for the biogenic process of AgNPs. The X-ray diffraction pattern shows a single-phase crystalline structures in size range of 9–31 nm for the three concentrations. The Scanning and transmission electron microscopies results indicate the spherical shape of the formed AgNPs with proper coating from the bioactive compounds and a diameter of 19 nm for the highest concentration. The energy-dispersive X-ray spectroscopy analysis shows a strong signal for silver. It is noteworthy that the colloidal solutions obtained show effective therapeutic ability of the AgNPs against the bacterial strains using FLGL as a reducing agent for the first time. A bactericidal was observed through the inhibitory zone, against the bacterial strains, with a higher activity above Ciprofloxacin (the positive control). Hence, the biocompatible, nontoxicity and eco-friendly formulated AgNPs is auspicious and efficient as a therapeutic tool for antibacterial activities against human pathogens.

Phoenix dactylifera L. extract: antioxidant activity and its application for green biosynthesis of Ag nanoparticles as a recyclable nanocatalyst for 4-nitrophenol reduction

In this study, antioxidant activity as well as preparation of silver nanoparticles (Ag NPs) were investigated by spathe of Phoenix dactylifera L. extracts. Excellent antiradical activity was found for the methanolic extract. Also, catalytic activity of the bio-synthesized Ag NPs was evaluated in the presence of DPPH. Ag nanoparticles were bio-synthesized through an environmental friendly and cost-effective method using aqueous solution of P. dactylifera L. extract. The bio-synthesized Ag NPs were characterized by different techniques including Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and dynamic light scattering. Then, we focused on optimization of the reaction parameters including pH, AgNO3 concentration, interaction time, temperature and mixing ratio on the bio-synthesis of Ag NPs according to surface plasmon band for Ag NPs around λ = 425 nm. Finally, catalytic ability of the NPs was investigated toward reduction of 4-nitrophenol in the presence of NaBH4, as a model reaction, the results indicated excellent catalytic ability of the NPs for the reduction of 4-nitrophenol for short reaction time. The bio-synthesized Ag NPs demonstrated well recyclability toward 4-nitrophenol reduction without any significant reactivity loss. The recovered NPs were studied by some analytical and spectroscopic methods.

A green approach for silver nanoparticles preparation by cell-free extract from Trichoderma reesei fungi and their characterization

Silver nanoparticles (AgNPs) exhibit unique optical, photochemical, electronic, photoelectrochemical properties and they are non-toxic to the mammalian cells at low concentrations. The biosynthesis of AgNPs is a green alternative to chemical and physical methods. The use of fungi is more efficient compared to other bio-alternatives because of the possibility for easy cultivation on a large scale and simple biomass harvesting. Trichoderma reesei fungi produce extracellular enzymes that can reduce silver ions (Ag+) to AgNPs. The present study describes an extracellular biosynthesis of AgNPs from AgNO3 solution by using cell-free water extract (CFE) of T reesei PF biomass. The impact of the components of the medium where the T. reesei PF were cultivated, the amount of biomass used for obtaining the CFE, the initial concentration of AgNO3 solution and the time for Ag+ reduction to AgNPs have been studied. It has been found that for all studied cultivation media the amount of biotransformed Ag+ increases with time and with the initial concentration of AgNO3. The higher amount of extracted wet biomass (i.e. the higher concentration of extracted metabolites) leads to a higher biotransformation of Ag+ to Ago. Having in mind the quantitative data from the ICP analysis of isolated and washed AgNPs produced at various experimental conditions, it could be concluded that the optimum formation of AgNPs was achieved when T reesei fungi were cultivated in media containing 0.1% corn steep liquor, 10% biomass extracted to obtain CFE and 10 mM concentration of the AgNO3 precursor was used. The formation of AgNPs was proved by XPS and TEM analysis. The HRTEM micrographs confirmed Ag metallic nanoparticles in crystal phase. The TEM images showed initial formation of AgNPs clusters with size 1–4 nm that increase further up to 15–25 nm. The NPs were stabilized by capping effect of the biomolecules, as the FTIR spectroscopy revealed. The small size, the particles’ narrow size distribution, nontoxicity, stability and the negative zeta potential which could facilitate attachment of biologically active substances render the produced AgNPs into suitable carriers of such substances.

Citrate-assisted galvanic replacement for fabrication of homogeneous Ag nanosheets as high-performance SERS substrate

An effective and simple method for the fabrication of Ag nanosheets (NSs) was developed via citrate-assisted galvanic replacement at room temperature. The effects of reaction time, concentration of AgNO3 and citrate on the morphology and surface-enhanced Raman scattering (SERS) performance of Ag NSs were investigated systematically. The results indicated that citrate played a vital role on preparing uniform Ag NSs, because it could retard the reaction rate and control the direction of Ag growth. Furthermore, citrate was bound weakly toward Ag NSs and easily replaced by probe molecules, which opened a new avenue for the fabrication of clean SERS substrates. In addition, the Ag NSs substrate exhibited a high sensitivity in SERS detection and the analytical enhancement factor was up to 7.93 × 105 with the minimum detected concentration of R6G as low as 10−8 M. Moreover, the color mapping was relatively uniform and the relative standard deviation was below 15%, revealing that the SERS performance of Ag NSs substrate was highly reproducible. Consequently, we believe this citrate-directed galvanic replacement could regulate the morphology and produce clean and highly active SERS substrates, which would be potentially useful for its practical application.

Gamma radiation-induced crosslinked composite membranes based on polyvinyl alcohol/chitosan/AgNO3/vitamin E for biomedical applications

Crosslinked hydrogel composite membranes based on polyvinyl alcohol (PVA) and chitosan-loaded AgNO3 and vitamin E were prepared using gamma irradiation. Chitosan has been used as antimicrobial blend materials to provide further biocompatibility for the prepared composite hydrogel membranes. The crosslinking reaction between PVA and chitosan owing to gamma irradiation was verified and characterized by FTIR analysis, while the morphology of hydrogel composite membranes was investigated by SEM. Important parameters affecting on hydrogel membranes formation, such as copolymer concentration, irradiation dose, AgNO3 concentration, plasticizer, and vitamin E of PVA/chitosan membranes were evaluated and discussed in details. In addition, the mechanical and thermal properties of hydrogel composite membranes were examined to evaluate the possibility of its application for wound dressings. The results revealed that the gelation (%) of hydrogel membranes increased dramatically with PVA composition, irradiation dose and glycerol content up to 20%; however, it decreased with AgNP incorporation due to the viscosity of copolymer composition is hyper-increased. The swelling ratio of composed hydrogel membranes decreased notably with increasing the radiation dose and incorporation of AgNP, due to reducing of the crosslinking degree of formed hydrogel membranes. PVA-Cs-Ag composed hydrogel membranes showed significant antimicrobial activity in particular against Streptococcus mutans due to the presence of AgNP in membranes, compared to other bacteria and fungi microbes. Thus, the PVA/chitosan/AgNO3-Vit.E hydrogel composite membranes showed satisfactory properties for use as wound dressing materials.

Response of green synthesized drug blended silver nanoparticles against periodontal disease triggering pathogenic microbiota

Objective : Evidences for microorganisms to predominate periodontal disease, alteration of human pathogen shifted microbiota by Erythrina fusca, and antimicrobial response potentiation by ecofriendly silver nanoparticles, intended present study to perform green synthesis of silver nanoparticles (AgNPs) and evaluate against periodontal disease triggering pathogenic microbiota. Material and Methods: Present study involved green synthesis of silver nanoparticles (AgNPs) using Erythrina fusca leaves aqueous extract (EFLAE), followed by optimization, characterization, stability, and evaluation of antimicrobial potential of biosynthetic AgNPs against periodontitis causing pathogenic human microflora (Pseudomonas aeruginosa, Escherichia coli, Streptococcus pyogenes and Staphylococcus aureus). Results: The AgNPs green synthesis success was based on brown coloration and surface plasmon resonance signal at 433 nm. UV-Visible spectrometry driven optimization determined 5 mM AgNO3 concentration, 1:9 EFLAE and AgNO3 volumetric ratio, pH 7, 60 °C temperature and 2 hours time as parametric requirements for AgNPs biosynthesis. Stability studies revealed signal appearance between 415-424 nm supporting AgNPs stability. Characterization studies recognized shifted and broadened FTIR bands of AgNPs revealing silver capping by biochemical-moieties of EFLAE; AgNPs size below 32 nm in FESEM micrograph; XRD signals at 38.95, 44.97, 64.92 and 78.97 representing 111, 200, 220 and 311 AgNPs silver cubic structure planes; and elemental silver 83.66%, carbon 11.87% and oxygen 4.47% in EDX spectrum. Optimized and characterized biogenic AgNPs when evaluated against periodontal disease causing pathogenic microflora using well diffusion method, exhibited maximum inhibitory zone (in mm) against B. cereus (13 and 18), followed by P. aeruginosa (11 and 19), E. coli (10 and 18) and S. pyogenes (9 and 15) in 50 and 100 µg/ml administered dose. Conclusion: Present study concludes that biogenic AgNPs synthesized using EFLAE possess high inhibition potential against periodontitis triggering pathogens (E. coli, B. cereus, S. pyogenes, and P. aeruginosa) of microbiota, and recommends EFLAE as potential source for AgNPs green synthesis.

Chitosan Mediated Formation and Impregnation of Silver Nanoparticles on Viscose Fabric in Single Bath for Antibacterial Performance

Cellulosic materials being biodegradable are susceptible to bacterial attack. Present study was meant to develop an antibacterial viscose fabric via a clean, easy and reproducible approach. Silver nanoparticles (SNPs) were prepared using chitosan both as reducing and as well as stabilizing agent to promote green synthesis of SNPs. The prepared SNPs were characterized using dynamic light scattering and UV-visible (vis) absorption spectroscopy. The average size of SNPs was found to be 8.574 nm with respective zeta potential of +45.2 mV using AgNO3 concentration of 1 mM and chitosan as 1 % (w/v). Pre-treated viscose fabric was undergone an in situ treatment to impregnate SNPs on its surface under certain autoclave conditions. Scanning electron microscopy revealed the presence of SNPs on surface of treated viscose fabric in comparison with the untreated fabric. In addition, Fourier transform infrared and elemental analysis confirmed the presence of silver on the treated fabric. The textile properties of the viscose fabric samples like; tensile strength, wettability, antibacterial activity and whiteness were evaluated using the standard protocols. The developed treated viscose fabric showed good antibacterial properties against both Gram negative Escherichia coli and Gram-positive Staphylococcus aureus bacterial strains with fair textile characteristics. This is the first report on in situ fabrication and impregnation of SNPs using chitosan as both reducing and stabilizing agent on a regenerated cellulose fabric like viscose.

Multimode sensing of riboflavin via Ag@carbon dot conjugates

In this study, we propose a simple and versatile tri-modal (colorimetric, fluorometric, and electrochemical) means for detection of riboflavin using silver carbon dot (Ag@CD) nanoconjugates. Hydroxyl-rich carbon dot (CD) synthesized by microwave-assisted method using citric acid and PEG was used as reductant for Ag@CD formation. Effect of CD and AgNO3 concentration on Ag@CD synthesis was examined. Furthermore, we observed that the Ag@CD conjugates were capable of selectively detecting riboflavin. The sensing mechanism was based on aggregation of nanoconjugates as confirmed from scanning electron microscope micrographs. Red shifting of surface plasmon resonance peaks to around 550 nm concomitant with quenching and red shift of fluorescence peak was observed. Colorimetric assay showed a change in colour of assay mixture to red and detection limit of 2.5 µM was observed. In addition, electrochemical detection showed a high selectivity for riboflavin even in the presence of interfering analytes with a sensitivity of 1.56 µA/mM/cm2. This rationally designed tri-modal sensing platform offers simplicity of operation and faster detection which may be developed into a point-of-care diagnostic device.

Bio-synthesis of silver nanoparticles with antibacterial activity

Silver nanoparticles (Ag-NPs) have potential applications in life science, food chemistry, biomedicine, photocatalysis and cosmetics fields due to its unique optical, electrical and catalytic properties besides the strong antibacterial property. Apple pomace, a by-product of apple juice production, is ample and easily available. In the present study, this green raw material was used to biosynthesize Ag-NPs for the first time. The obtained silver nanoparticles were investigated by UV–vis, TEM, XRD, and FTIR, respectively. The results showed that the concentration of AgNO3 and the volume ratio of AgNO3 solution to apple pomace extract were the important factors affecting the synthesis of silver nanoparticles. When the concentration of AgNO3 was 10 mmol/L, the volume ratio of AgNO3 solution to the apple pomace extract of 4:1(ν/ν), Ag-NPs were quickly formed. They were stable with high degree of crystallinity. The particle sizes ranged between 10 and 20 nm and the conversation of silver ions was up to 99%. The bacteriostatic circle tests revealed that the biosynthesized Ag-NPs had a strong antibacterial activity against gram positive bacteria and gram negative bacteria. FTIR analysis demonstrated that some bio-molecules with groups of -NH2, -COOH and -OH were distributed on the surface of the newly synthesized Ag-NPs. During the synthesis of silver nanoparticles, there were not any poisonous reducers and stabilizers introduced.

Preparation of Nano-Ag-TiO2 Composites by Co-60 Gamma Irradiation to Enhance the Photocurrent of Dye-Sensitized Solar Cells

Nano-silver-titanium dioxide (Ag-TiO2) composites were prepared from commercial TiO2 (P25, Degussa) and silver nitrate (AgNO3) by gamma Co-60 irradiation method with various initial concentrations of AgNO3. The nano-AgTiO2 composites are utilized as the photoanode for dye-sensitized solar cells (DSCs). Under full sunlight illumination (1000 W/m2, AM 1.5), the efficiency of DSCs has improved significantly despite the Ag content of below 1%. The DSC—assembled with 0.75 Ag-TiO2 (0.75% Ag) photoanode—showed that the photocurrent was significantly enhanced from 8.1 mA.cm−2 to 9.5 mA.cm−2 compared to the DSCs using bared TiO2 photoanode. The unchanged open-circuit voltage resulted in the overall energy conversion efficiency to be increased by 25% from 3.75% to 4.86%. Electrochemical impedance spectroscopy (EIS) analysis showed that the charge transfer resistance is reduced when increasing Ag content, demonstrating that the charge transfer at TiO2/dye interface was enhanced in the presence of silver nanoparticles.

Synthesis of silver nanowires with controlled diameter and their conductive thin films

Silver nanowires (AgNWs) with high uniformity and controlled morphology were synthesized by employing silver nitrate as precursor and ethylene glycol as reducing agent and solvent. Polyvinyl pyrrolidone (PVP) was used as growth controlling agent and the synthetic process was carried out in salt free environment. The effect of reaction parameters like concentration of AgNO3 and the reaction temperature on the final morphology of AgNWs was studied. AgNWs obtained by changing different conditions were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM), selected area electron diffraction pattern (SAED), X-ray diffraction (XRD) and UV–Vis spectroscopy. Synthesized AgNWs were coated on polyethylene terephthalate substrate by spin coating method to make thin conductive flexible film. The silver nanowires film was found to have a sheet resistance of 6.82 Ω/sq.

Effect of MACE Parameters on Electrical and Optical Properties of ALD Passivated Black Silicon

Metal-assisted chemical etching (MACE) enables efficient texturing of diamond-wire sawn multicrystalline silicon wafers. However, the excellent optics are often sacrificed by polishing the surface to achieve better surface passivation with chemical-vapor-deposited (CVD) silicon nitride (SiN x ). In this paper, we show that a polishing step is not required when CVD SiN x is replaced with atomic-layer-deposited (ALD) aluminum oxide (Al2O3). Indeed, while polishing increases reflectance, it has in general only very modest effect on surface recombination velocity of ALD-passivated b-Si. Furthermore, since ALD Al2O3 is compatible with various surface morphologies due to its excellent conformality, the MACE parameters can be more freely adjusted. First, the concentration of silver nitrate (AgNO3) in AgNO3/H2O solution that is used to deposit Ag nanoparticles is shown to affect the final b-Si morphology. Instead of needle-shaped b-Si produced by 5 mmol/L AgNO3 concentration, two orders of magnitude lower AgNO3 concentration produces porous structures, which are more challenging to passivate. Additionally, we demonstrate that a separate Ag nanoparticle removal step in nitric acid (HNO3) is not a prerequisite for high carrier lifetime. Instead, Ag nanoparticles present during polishing in a HF/HNO3/H2O solution affect the final b-Si morphology by accelerating the etching of Si. The results demonstrate that no tradeoffs are necessary between optical and electrical properties of MACE b-Si when using ALD.

Mussel-inspired construction of multifunctional cotton fabric with superhydrophobicity, conductivity and antibacterial activity

Using a facile strategy to fabricate multifunctional cotton fabrics with superhydrophobicity, conductivity and antibacterial activity is an important and urgent issue in the development of natural fabrics. Herein, a new type of cotton fabric, denoted as Cot@PDA/Ag/NDM, has been fabricated utilizing mussel-inspired polydopamine (PDA) chemistry, followed by electroless Ag plating and n-dodecyl mercaptan (NDM) self-assembly. The influence of dopamine (DA) and AgNO3 concentration on the surface morphology and conductivity, as well as NDM treatment time on the surface wettability of the fabric is systematically investigated. Cot@PDA/Ag/NDM not only exhibits superhydrophobicity with water contact angle of 155.9 ± 1°, but also possesses excellent self-cleaning and antifouling properties. In addition, the fabric has a highly conductive surface with sheet resistance as low as 10.2 Ω cm, and shows outstanding mechanical properties and antibacterial activity against Escherichia coli and Staphylococcus aureus.