Aqueous Solution Of AgNO3 Research Articles

Optical Study of Desmodium Elegan Mediated Silver Nanoparticles Using Tauc’s Equation

Green synthesis of metallic nanoparticles is more eco-friendly, simpler, and nontoxic as compared to chemical synthesis. Due to their thermal stability and good electrical conduction silver nanoparticles have significant importance these days. In the present work, the stable silver nanoparticles were prepared from the aqueous solution of AgNO3 by green synthesis technique in which the Desmodium elegan plant extract was used as a reducing and capping agent to convert Ag+ to Ag0. A UV-visible spectrometer is used in the range of 200 nm to 800 nm with a scanning speed of 200 nm per minute, the absorption band is found at a 450 nm peak that indicates the synthesis of silver nanoparticles. The particle size of the nanoparticles was in the range of 11 nm to 70 nm with an average of 45 nm and a spherical shape. Further confirmation of nano size, scanning electron microscopy (SEM) was also utilized for the size distribution and shape of the synthesized nanoparticles. The synthesized nanoparticles SEM studies show irregular spherical morphology with polydispersed trend and the average particle size was found at 45 nm. The absorption band for the synthesized sample was found at 450 nm peak. The bandgap energy was 2.84 eV estimated by Tauc’s equation. This indicates that the synthesized nanoparticles electrically lie in the range of semiconductors and can be used as a biosensor. This synthesis technique is a nontoxic technique so these particles may be used for water treatment.

Preparation of Antimicrobial Agents: From Interpolyelectrolyte Complexes to Silver-Containing Metal–Polymer Complexes and Nanocomposites

In order to control pathogenic microorganisms, three polymer compositions were prepared and tested. First, a water-soluble positively charged polycomplex was synthesized via the electrostatic binding of anionic polyacrylic acid to an excess of polyethylenimine to enhance the biocidal activity of the polycation. Second, an aqueous solution of AgNO3 was added to the polycomplex, thus forming a ternary polycation-polyanion-Ag1+ complex with an additional antimicrobial effect. Third, the resulting ternary complex was subjected to UV irradiation, which ensured the conversion of Ag1+ ions into Ag nanoparticles ranging in size mainly from 10 to 20 nm. Aqueous solutions of the polymer compositions were added to suspensions of the Gram-positive bacteria S. aureus and the Gram-negative bacteria P. aeruginosa, with the following main results: (a) Upon the addition of the binary polycomplex, 30% or more of the cells survived after 20 h. (b) The ternary complex killed S. aureus bacteria but was ineffective against P. aeruginosa bacteria. (c) When the ternary complex with Ag nanoparticles was added, the percentage of surviving cells of both types did not exceed 0.03%. The obtained results are valuable for the development of antibacterial formulations.

Use of geopolymers as tunable and sustained silver ion release mediums

Silver was incorporated up to 3.4% (w/w) into the geopolymer structure via precipitation as Ag2O by dispersing the geopolymer powder in an aqueous solution of AgNO3. The precipitates were mainly located in the fine pores within the nanoparticles of the geopolymer network. The fine pores enabled the formation of very fine precipitates, mainly between 2 and 5 nm. The silver-incorporated geopolymer was found to have a sustained Ag+ release that can be tuned down by a thermal treatment, e.g., calcination. The Ag+ release amount could be reduced by about 30-fold after calcination at 850 °C. Calcination reduces the specific surface area, causes shrinkage, and makes the geopolymer structure less pervious. The size of the precipitates remains stable even up to 1050 °C, despite a large amount of sintering-related shrinkage. These results suggest that geopolymers could be a tunable Ag+ source for various antibacterial applications.

Conductive Nanosheets Fabricated from Au Nanoparticles on Aqueous Metal Solutions under UV Irradiation.

Highly transparent, conductive nanosheets are extremely attractive for advanced opto-electronic applications. Previously, we have demonstrated that transparent, conductive Au nanosheets can be prepared by UV irradiation of Au nanoparticle (AuNP) monolayers spread on water, which serves as the subphase. However, thick Au nanosheets cannot be fabricated because the method is not applicable to large Au NPs. Further, in order to fabricate nanosheets with different thicknesses and compositions, it is necessary to prepare the appropriate NPs. A strategy is needed to produce nanosheets with different thicknesses and compositions from a single type of metal NP monolayer. In this study, we show that this UV irradiation technique can easily be extended as a nanosheet modification method by using subphases containing metal ions. UV irradiation of 4.7 nm AuNP monolayers on 480 µM HAuCl4 solution increased the thickness of Au nanosheets from 3.5 nm to 36.5 nm, which improved conductivity, but reduced transparency. On the other hand, the use of aqueous AgNO3 and CH3COOAg solutions yielded Au-Ag hybrid nanosheets; however, their morphologies depended on the electrolytes used. In Au-Ag nanosheets prepared on aqueous 500 µM AgNO3, Au and Ag metals are homogeneously distributed throughout the nanosheet. On the other hand, in Au-Ag nanosheets prepared on aqueous 500 µM CH3COOAg, AuNPs still remained and these AuNPs were covered with a Ag nanosheet. Further, these Au-Ag hybrid nanosheets had high conductivity without reduced transparency. Therefore, this UV irradiation method, modified by adding metal ions, is quite effective at improving and diversifying properties of Au nanosheets.

Green Synthesis of Silver Nanoparticles Using the Cell-Free Supernatant of Haematococcus pluvialis Culture.

The green synthesis of silver nanoparticles (AgNPs) using the cell-free supernatant of a Haematococcus pluvialis culture (CFS) was implemented in the current study, under illumination conditions. The reduction of Ag+ to AgNPs by the CFS could be described by a pseudo-first-order kinetic equation at the temperature range tested. A high reaction rate during synthesis and stable AgNPs were obtained at 45 °C, while an alkaline pH (pH = 11.0) and a AgNO3 aqueous solution to CFS ratio of 90:10 (v/v) proved to be the most effective conditions in AgNPs synthesis. A metal precursor (AgNO3) at the concentration range tested (1-5 mM) was the limited reactant in the synthesis process. The synthesis of AgNPs was accomplished under static and agitated conditions. Continuous stirring enhanced the rate of reaction but induced aggregation at prolonged incubation times. Zeta potential and polydispersity index measurements indicated stable AgNPs and the majority of AgNPs formation occurred in the monodisperse phase. The X-ray diffraction (XRD) pattern revealed the face-centered cubic structure of the formed AgNPs, while TEM analysis revealed that the AgNPs were of a quasi-spherical shape with a size from 30 to 50 nm. The long-term stability of the AgNPs could be achieved in darkness and at 4 °C. In addition, the synthesized nanoparticles showed antibacterial activity against Escherichia coli.

Highly ordered TiO2 nanotube films photo-decorated with Ag nanoparticles as SERS platforms: Relationship between morphology and enhancement

In this work, we synthesized TiO2 nanotube films (TiO2-NTFs) photo-decorated with Ag nanoparticles for their application in Surface-Enhanced Raman Scattering. In situ growth of Ag nanoparticles was performed through the exposure of anodic TiO2-NTFs to UVC radiation following their pretreatment in an AgNO3 aqueous solution. High nanoparticle surface densities, with uniform coverage on the film surface, and controllable size, were prepared by regulating the UVC exposure time and AgNO3 concentration. Ag nanoparticles nucleation and growth also take place along the tubes, including at the bottoms. The evidence obtained also indicates that a high enough AgNO3 concentration inhibits the well-known water-assisted crystallization mechanism, typically promoted when TiO2-NTFs are exposed for prolonged times in aqueous media. The performance of the photo-decorated films in Surface-Enhanced Raman Scattering shows that the presence of Ag nanoparticles plays a key role, and both the nanoparticle surface density and size must be regulated to promote a large number of hot-spots.

Ex vivo antiacetylcholinesterase studies on silver nanoparticles synthesized using green approach

For the green fabrication of silver nanoparticles (AgNPs), scientists are favoring herbal sources to avoid the toxic effects of synthetic sources. Thus, in this study, the AgNPs were generated using the herbal extract of the whole plant Hippeastrum hybridum L. (HH) and 1 mM AgNO3 aqueous solution. These HH‐AgNPs were characterized via UV–Vis Spectroscopy, which showed a maximum absorbance of 1.61 at a 432 nm sharp peak; FT‐R analysis, which confirmed the functional groups in HH extract and their AgNPs; XRD analysis, which gives 4‐Bragg's reflections at 2θ and confirmed the HH‐AgNPs crystal structure with 13.3 nm average size; SEM analysis, which confirmed the irregular‐shaped morphology with 40 nm mean size; and EDX analysis, which confirmed the elemental composition and reported that Ag was present in 22.75%. After characterization, these AgNPs were tested as anti‐Alzheimer agents against acetylcholinesterase (AChE) in ex vivo activity using rat brain homogenate as a source of AChE enzyme. AChE showed 48 ± 0.03 and 42 ± 0.05% activity at 150 μg concentration of HH plant and HH‐AgNPs, respectively, with 145 ± 0.24 and 124.2 ± 0.14 μg IC50 concentration. According to enzyme kinetics results, the plant extract inhibits AChE in competitive mode (Km increased from 166.2% to 1,379.2% and Vmax not affected), while HH‐AgNPs showed the mixed mode of inhibition (Km increased from 0.029 to 0.048, and Vmax decreased from 9 to 5.4). KIapp and Vmaxiapp were also calculated (KIapp increased from 39 to 95.1 μg, and Vmaxiapp remained constant for the plant), while for HH‐AgNPs, both Kmaxipp and Vmaxiapp increased from 122.32 to 325 μg and 8.15 to 9.8 μg, respectively. The Km, Ki, and KI were also calculated and were found to be 0.017 mM (HH‐plant) and 0.2 mM (HH‐AgNPs); 98 μg (HH‐plant); and 129 μg (HH‐AgNPs), 53 μg (HH‐plant), and 179 μg (HH‐AgNPs), respectively. γKm (18 mM) was calculated for HH‐AgNPs, while for HH‐plant, it is not applicable. In conclusion, it could be said that HH‐plant plays a significant role in the generation of small‐size HH‐AgNPs. These AgNPs exhibited significant anti‐AChE potential as compared to HH‐plant extract and proved to be an herbal source for the treatment of AD.

Antimicrobial Properties of AgNP/TEMPO-Oxidized Cellulose Nanofiber/Chitosan Composite Fibers

This study successfully synthesized functionalized silver nanoparticle/TEMPO-oxidized cellulose nanofiber/chitosan (AgNP/TOCN/CS) composite fibers. First, the TOCN/CS composite fibers were prepared through the wet-spinning technique, yielding Ag/TOCN/CS composite fibers after immersion in a 5 mM AgNO3 aqueous solution for 3 h, followed by washing with 100 mL of deionized water five times. Second, upon heat treatment without adding other reducing agents, TOCN reduced the Ag+ in the Ag/TOCN/CS composite fibers to AgNP/TOCN/CS composite fibers on the surface of the CS fibers. The fiber color changed from white to yellow-orange when the temperature changed from 100 to 170 °C. In addition, the results suggest that the heat treatment at 130 °C for 20 min was the optimal heat treatment condition. Meanwhile, soaking the fibers in 50 mM ascorbic acid for 1 min is the best condition for ascorbic acid reduction. The antibacterial test results showed that the AgNP/TOCN/CS composite fibers formed via ascorbic acid reduction exhibited better antibacterial activity against both Escherichia coli and Bacillus subtilis than those produced via heat treatment. In summary, AgNPs formed on the fiber surface of AgNP/TOCN/CS composite fibers and showed antibacterial activity, confirming the successful addition of antibacterial properties to TOCN/CS composite fibers.

In situ tailoring of Ag-doped-TiO2/TPMP/cotton nanocomposite with UV-protective, self-sterilizing and flame-retardant performance for advanced technical textiles

Herein, we present a novel approach to the development of a multifunctional, UV-protective, photocatalytic, antimicrobial and flame-retardant nanocomposite fabric surface. Using a sol–gel/hydrothermal approach, a phosphorus-based flame-retardant 3-(trihydroxysilyl)propyl methylphosphonate (TPMP) in combination with Ag-doped TiO2 was applied to the surface of cotton fibers for the first time, using an aqueous AgNO3 solution as the dopant. The modified cotton fabrics were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS) and X-ray diffraction spectroscopy (XRD) to confirm the successful application of Ag-TiO2 and TPMP on the cotton fabric by analyzing the surface morphology, chemical composition, chemical bonding and crystal structure. The functional properties of the modified cotton fabric were determined by measuring the UV protection factor (UPF), burning behavior and thermo-oxidative stability, as well as antibacterial activity against Escherichia coli and Staphylococcus aureus. The results show the formation of a unique nanocomposite matrix of TPMP–polysiloxane on the surface of cotton fibers with well-distributed Ag-TiO2. The formation of TiO2/Ag2O particles on the surface of cellulose fibers was also confirmed. The synergism between all components of the nanocomposite resulted in excellent UV protection in the UVA and UVB region, with a UPF of 50+, self-sterilizing activity against both tested bacteria and enhanced thermo-oxidative stability. Therefore, the novel approach proposed herein is promising for the development of multifunctional, protective surfaces for advanced technical textiles.

Eco-Friendly Green Synthesis and Characterization of Silver Nanoparticles by Scutellaria multicaulis Leaf Extract and Its Biological Activities.

Scutellaria multicaulis is a medicinal plant indigenous to Iran, Afghanistan, and Pakistan. It has been widely used as a prominent herb in traditional medicine for thousands of years. This plant is reported to contain baicalein, wogonin, and chrysin flavonoids, which are a significant group of chemical ingredients which can cure different diseases, such as breast cancer. S. multicaulis leaf extract was used for the bioreduction of silver nanoparticles (SmL-Ag-NPs), and their phytochemical contents and antioxidant, antibacterial, anti-proliferative, and apoptotic activity were evaluated. Optimal physicochemical properties of SmL-Ag-NPs were obtained by mixing 5% of leaf extract and 2 mM of aqueous AgNO3 solution and confirmed by characterization studies including UV-visible spectrophotometry, Field Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive X-ray (EDX), Dynamic Light Scattering (DLS), zeta potential, Thermogravimetric analysis (TGA), Surface-enhanced Raman spectroscopy (SERS), X-ray crystallography (XRD), and Fourier transform infrared (FTIR) Spectroscopy. SmL-Ag-NPs exhibited a higher content of total phenol and total flavonoid and potential antioxidant activity. SmL-Ag-NPs also demonstrated dose-dependent cytotoxicity against MDA-MB231 cell multiplication with an IC50 value of 37.62 μg/mL through inducing cell apoptosis. Results show that SmL-Ag-NPs is effective at inhibiting the proliferation of MDA-MB231 cells compared to tamoxifen. This demonstrates that SmL-Ag-NPs could be a bio-friendly and safe strategy to develop new cancer therapies with a reduction in the adverse effects of chemotherapy in the near future.

Synthesis and enhanced biological activities of methyl 5-amino-β-resorcylate capped silver nanoparticles

The biomedical potential of silver nanoparticles loaded and conjugated with a drug exhibited diverse effects. Compared to free molecules, these nanoconjugates demonstrated enhanced biological activities, requiring a reduced quantity of the active ingredient for effectiveness. To achieve this, silver nanomaterials (AgMRA) with a size of 19 nm were prepared and modified with methyl-5-amino-β-resorcylate (MRA) through the reduction of an aqueous solution of AgNO3. The capping of AgMRA was analyzed using TEM, FT-IR, and UV–vis techniques. The stability of the silver nanomaterials (AgMRA) was investigated in relation to salt concentration, pH, and temperature. The resulting nanoconjugates were soluble in water, and their suspension remained stable at a salt concentration of 4 mol/L, pH range of 2–13, and elevated temperatures. Multiple biological activities, including enzyme inhibition, antioxidant effects, and antimicrobial properties, were identified for the silver nanomaterials (AgMRA) and compared to the pure MRA and commercially available drugs. The urease inhibition and antioxidant properties of AgMRA were comparable to or even superior to those of MRA and the standard drugs. Notably, the synthesized nanoconjugates contained 25% of silver nanomaterials conjugated with MRA by weight, allowing for a four-fold reduction in the required dose of MRA for achieving the desired biological activities.

Preparation, Characterization, and Antibacterial Activity of Silver Nanoparticle-Decorated Ordered Mesoporous Carbon

In this study, Ordered Mesoporous Carbon (OMC) was prepared using resol as a carbon precursor and F127 as a soft template. Small-angle X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) images, and nitrogen adsorption and desorption isotherms revealed that OMC possessed ordered hexagonal mesostructures (p6m) with an ordered pore size of 3.2nm, a high specific surface area (SBET) of 539m2/g, and a large total pore volume (Vtotal) of 0.44cm3/g. Subsequently, silver nanoparticles synthesized from an aqueous AgNO3 solution using glucose as a reducing agent and starch as a stabilizing agent were decorated on OMC, producing Ag/OMC. XRD analysis revealed that the composite contained silver crystals. In addition, the content and size of silver nanoparticles in Ag/OMC were 0.71wt% (AAS) and around 25-50nm (TEM), respectively. Due to the surface cover of silver nanoparticles, SBET and Vtotal of Ag/OMC slightly decreased to 417m2/g and 0.38cm3/g, respectively. Both agar and broth dilution techniques were used to evaluate the antibacterial activity of the material against Staphylococcus aureus. Ag/OMC with a Minimum Inhibitory Concentration (MIC) of 25.0μg/mL is a potential candidate for use against Staphylococcus aureus.

Bio-Colloidal Silver Nanoparticles Prepared via Green Synthesis Using Sandoricum koetjape Peel Extract for Selective Colorimetry-Based Mercury Ions Detection

Hazardous waste from mercury is a critical problem that requires serious attention. Herein, we report bio-colloidal silver nanoparticles (AgNPs) synthesized via green synthesis route from AgNO3 aqueous solution and Sandoricum koetjape (SK) peel extract and demonstrate their sensitivity at detecting mercury ions (Hg2+) using colorimetry. AgNPs were synthesized by varying the volume ratio of AgNO3 solution to SK peel extract, namely AgNPs(4:1), AgNPs(3:2), AgNPs(1:1), AgNPs(2:3), and AgNPs(1:4). Bio-colloidal AgNPs were tested for their ability to detect toxic heavy metal mercury ion by adding different concentrations of Hg2+. All samples have successfully detected Hg2+ at varying levels of sensitivity. This investigation revealed that AgNPs(4:1) is the most sensitive colloid for detecting Hg2+ up to a concentration of 1 ppm.

Synthesis of Fe3O4-Ag core shell nanoparticles using Cinnamomum verum bark extract and removal of methyl orange from aqueous media

Green synthesis of Fe3O4-Ag core shell nanoparticles (CSNPs) was performed using Cinnamomum verum bark extract (CVBE) as the green solvent, reducing agent and capping agent. Aqueous solutions of AgNO3, FeCl3.6H20 and CH3COONa were used for the synthesis. The first formation of Fe3O4-Ag CSNPs was observed within 10 minutes of the reaction time. The result recorded from UV-Vis spectroscopy, Fourier Transform infrared spectroscopy (FTIR) and Energy dispersive spectroscopy (EDS) favours the biosynthesis and characterization of Fe3O4-Ag CSNPs. Scanning electron microscopy (SEM) reveals that the shape is nearly spherical and Transmission electron microscopy (TEM) confirms the shape as spherical and minimum size achieved is 19 nm. The capability of synthesised Fe3O4-Ag CSNPs for adsorption of methyl orange (MO) was tested in batches. It was observed that the process is pH dependent with maximum adsorption occurring at pH 6. The adsorption equilibrium was achieved after 120 min of contact time. The data observed was fitted one by one to three different isotherm models, viz., Langmuir, Freundlich and Temkin isotherm model to find the mode of adsorption. The process was best described by Langmuir isotherm. The adsorption kinetics was further analysed by using the pseudo-first-order, pseudo-second-order and the Weber-Morris diffusion model on adsorption data. The kinetic data of this adsorption obeyed pseudo-second-order rate equation.

Improved Photocatalytic O2 Evolution on a Sillén–Aurivillius Perovskite Oxychloride Bi6NbWO14Cl by Rh2O3 Additives and Surface Modifications

A Sillén–Aurivillius-type single-layered perovskite oxyhalide, Bi6NbWO14Cl, was recently reported as a stable and efficient O2-evolving photocatalyst for Z-scheme water splitting, even without any modifications. However, efforts have not yet been made to improve its photocatalytic activity. In this study, we synthesized a Bi6NbWO14Cl photocatalyst using Rh2O3 additives and modified its surface with Rh species to improve its photocatalytic activity. An appropriate amount of the Rh2O3 additive significantly enhanced the O2 evolution rate on Bi6NbWO14Cl from the aqueous AgNO3 solution, likely owing to enhanced charge transfer by the metallic Rh nanoparticles formed around the grain boundaries. In addition, surface modification with Rh species led to a further enhancement of the O2 evolution rate. The apparent quantum efficiency of the O2 evolution reached 11% at 420 nm, which is the best reported performance for oxyhalides prepared by solid-state reactions. These Rh species were characterized by X-ray absorption fine structure, X-ray photoelectron spectroscopy, and transmission electron microscopy, and their roles in the enhanced photocatalytic activities were discussed.

Characterization of silver nanoparticles (AgNPs) synthesized from Piper ornatum leaf extract and its activity against food borne pathogen Staphylococcus aureus

Abstract. Dewi FRP, Lim V, Rosyidah A, Fatimah, Wahyuningsih SPA, Zubaidah U. 2023. Characterization of silver nanoparticles (AgNPs) synthesized from Piper ornatumleaf extract and its activity against food borne pathogen Staphylococcus aureus. Biodiversitas 24: 1742-1748. Staphylococcus aureusis the most recurrent food borne pathogen that commonly resists antibiotics. Silver nanoparticles (AgNPs) have potential to solve bacterial multidrug resistance. This study aims to assess bactericidal activityof AgNPs against S. aureussynthesized from Piper ornatumleaf extract. Biosynthesis was performed by mixing P. ornatumextract with AgNO3aqueous solution and then incubating for 24 h at room temperature under dark condition. The formation of AgNPs was confirmed by changing optical color from light yellowish to dark brown with a peak of UV spectrum at ~500 nm. According to SEM imaging, AgNPs had spherical form whereas EDS analysis revealed strong signal at 3 kV indicating existence of silver element. Meanwhile, face-centered cubic structures of AgNPs were indicated by XRD analysis. FTIR analysis confirmed ketone, flouro, and amine as functional groups presented in extract were essential for the bioreduction of silver nitrate to silver nanoparticles. This study revealed that AgNPs have a potent bactericidal effect. In vitroevaluation using agar well-diffusion assay showed high inhibition zone of S. aureus (14.28±0.26) upon treating with 25 µg/m L AgNPs while MIC value was 5 µg/mL. However, antibiotic erythromycin and chloramphenicol respectively exhibited better inhibition zone and MIC value.

Photodeposition of Fe-Based Cocatalysts Capable of Effectively Promoting the Oxygen Evolution Activity of BaTaO2N

Activation of narrow bandgap photocatalysts is a prerequisite for the efficient production of renewable hydrogen from water using sunlight. Loading of dual cocatalysts intended to promote reduction and oxidation reactions by photodeposition is known to greatly enhance the water splitting activity of certain oxide photocatalysts. However, it is difficult to photodeposit oxygen evolution cocatalysts onto narrow bandgap oxynitride photocatalysts because the driving forces for the necessary oxidation reactions are weak. The present work demonstrates oxidative photodeposition of the Fe-based cocatalyst FeOx onto a Mg-doped BaTaO2N photocatalyst having an absorption edge wavelength of 620 nm. This modification enhances the oxygen evolution activity of the photocatalyst more effectively than conventional impregnation methods. The rapid removal of photoexcited electrons from the photocatalyst by a reduction cocatalyst (Pt) and an electron acceptor (molecular oxygen) are evidently necessary for the photodeposition of the FeOx cocatalyst. A Mg-doped BaTaO2N photocatalyst coloaded with Pt and FeOx exhibits an apparent quantum yield of 1.2% at 420 nm during the oxygen evolution reaction in an aqueous AgNO3 solution. This photodeposition procedure does not involve any heat treatment and so provides new opportunities for the design and construction of oxygen evolution sites on narrow-bandgap non-oxide photocatalysts that may be prone to thermal decomposition.

Janus metallic film with gold and silver luster by electroless deposition of silver using poly(dopamine acrylamide) thin film.

Films that exhibit different metallic luster on the front and back, called Janus metallic films, have broad applications ranging from design materials to optical devices. However, the fabrication of these films is often a complicated process involving multiple metal deposition steps, thermal annealing, and calcination. Herein, we report the simple preparation of a Janus metallic film by electroless deposition of silver on a poly(dopamine acrylamide) (pDOPAm) thin film. pDOPAm was successfully synthesized via the controlled reversible addition-fragmentation chain transfer polymerization of dopamine acrylamide without a protective group using dimethylformamide as the solvent. The synthesized pDOPAm was spin-coated onto a solid substrate, which was then immersed in an aqueous AgNO3 solution to achieve the electroless deposition of silver. Our preparation method will considerably simplify the fabrication of Janus metallic films, enabling their widespread application as decorative or authentication materials.

Nanoporous Ag-Decorated Ag7O8NO3 Micro-Pyramids for Sensitive Surface-Enhanced Raman Scattering Detection

Porous noble metal nanomaterials can be employed to construct sensitive surface-enhanced Raman scattering (SERS) substrates, because the plasmonic nanopores and nanogaps of the porous materials can provide a larger number of hotspots, and can also serve as containers of analyte molecules. However, the fabrication processes of nanoporous noble metal are generally complicated. Here, a facile method is presented to prepare nanoporous Ag nanoparticles-decorated Ag7O8NO3 micro-pyramids, which are fabricated through the chemical reduction of the electrodeposited Ag7O8NO3 micro-pyramids using NaBH4. The Ag7O8NO3 micro-pyramids are fabricated by electrodeposition by using a simple aqueous solution of AgNO3 as electrolyte. Then, porous Ag-decorated Ag7O8NO3 micro-pyramids are achieved by the chemical reduction of the surface of the electrodeposited Ag7O8NO3 micro-pyramids with NaBH4. The high-density nanopores and nanogaps of the fabricated nanoporous Ag can provide plenty of hot spots for Raman enhancement. Additionally, the nanopores have an effective capacity to trap and enrich analytes. Using rhodamine 6G (R6G) as a probe molecule, the SERS performance of the fabricated SERS substrate has been investigated. It is found that a limit of detection (LOD) ~1.0 × 10−15 M can be achieved for R6G. Then, the SERS substrates are employed to detect dye molecule (crystal violet) and pesticide (thiram), and their LODs are calculated down to 9.6 × 10−13 M and 1.3 × 10−15 M, respectively. The enhancement factor of the fabricated SERS substrate is estimated to be as high as 5.6 × 108. Therefore, the nanoporous Ag-decorated Ag7O8NO3 micro-pyramids have shown promising application in the sensitive SERS detection of organic molecules.

Remediation of Water Using a Nanofabricated Cellulose Membrane Embedded with Silver Nanoparticles.

The removal of pesticide pollution is imperative, because of their high environmental load and persistence, and their potential for bioaccumulation in, and toxicity to the environment. Most pesticides are found to be toxic even at trace levels. AgNPs can be effectively used for the adsorption of pesticides, and the incorporation of the AgNPs onto a support polymeric membrane enhances their effectiveness and reduces the potential unwanted consequences of intentionally adding free nanoparticles to the environment. Here, silver nanoparticles (AgNPs) were synthesized using a reliable, eco-friendly, and one-step "green" method, by reacting Mentha Piperita (mint) extract with AgNO3 aqueous solution at 60 °C in a microwave. The resulting high surface area nanoparticles are both economic and effective environmental remediation agents, playing a promising role in the elimination of aquatic pesticide pollution. Embedding the nanoparticles into a cellulose membrane at a low concentration (0.1 g) of AgNPs was shown to result in effectively adsorption of representative pesticides (Cypermethrin, Paraquat, and Cartap) within 60 min, while increasing the concentration of nanoparticles incorporated into the membrane further enhanced the removal of the exemplar pesticides from water. The high adsorption capacity makes the cellulose-AgNPs membrane an excellent substrate for the remediation of pesticide-polluted water.