Investigation on the role of the molecular weight of polyvinyl pyrrolidone in the shape control of high-yield silver nanospheres and nanowires

Highly efficient hydrophobic nanocomposite in the decontamination of micropollutants and bacteria from aqueous wastes: A sustainable approach

Micro-pollutants (specifically antibiotics and personal care products) and potential bacterial contamination pose a severe threat to human health and marine life. The study derives indigenous novel fibrous hydrophobic nanocomposite, efficient in decontaminating the micro-pollutants (tetracycline (TC) and bisphenol A (BPA)) and potential pathogens (S. pyogenes and E. coli) from aqueous wastes. A facile method synthesizes the fibrous attapulgite (ATP)- poly(4-vinylpyridine-co-styrene) (PVP) framework decorated in situ with the Ag0 nanoparticles (ATP@PVP/Ag0). A greener method using the Artocarpus heterophyllus leaf extract derives the Ag0(NPs). Various analytical methods extensively characterize the materials. A comprehensive study that includes pH, concentration, background electrolytes, and ionic strength reveals the sorptive removal insights of TC and BPA utilizing the ATP@PVP solid. The elimination of tetracycline (TC) and bisphenol A (BPA) agrees well with the pseudo-second-order kinetics. The pH 3.07 and 6.06 favor removing TC and BPA with the capacity of 10.86 mg/g and 17.36 mg/g at 25 °C. The hydrogen bonding and hydrophobic interactions predominate the sorption mechanism, and the material shows remarkable stability and reusability in repeated sorption/desorption operations. Similarly, the natural water implications and flow-bed system show fair applicability of solid in decontaminating the TC and BPA in an aqueous medium. Further, the material ATP@PVP/Ag0 exhibits very high inhibition of potential pathogens S. pyogenes and E. coli and optimizes the solid dose and solution pH.

Role of polyvinylpyrrolidone in the polyol synthesis of platinum nanoparticles

In this work, platinum (Pt) nanoparticles (NPs) were prepared via the reduction of Pt salts in an ethylene glycol induced polyol process with an altered polyvinylpyrrolidone (PVP)/Pt molar ratio. With the systematic elucidation of the hydrodynamic size in a liquid; the solid-state size and morphology, crystal structure, surface chemical state and thermal decomposition behavior of the synthesized Pt NPs; as well as the reducing dynamic of Pt cations, the role of PVP in the polyol synthesis of Pt NPs is clarified for the first time. It was found that the amount of PVP does not affect the reducing dynamic of Pt cations, but the chemical state of PVP capped on Pt NPs and the resultant particle size significantly depend on the initial PVP/Pt molar ratio in the precursor solution. Dense-packed PVP via the chemisorption of carbonyl oxygen on the surface of Pt NPs occurs in the case of a higher PVP/Pt ratio, suppressing particle growth and resulting in smaller Pt NPs. On the contrary, the chemical structure of PVP is tuned by the cleavage of the N-C bond and results in the chemisorption of the N atom on the surface of Pt NPs, which promotes the production of larger Pt NPs when a lower PVP/Pt ratio is applied.

Fabrication of composite transparent conductive electrodes based on silver nanowires

Composite transparent conductive electrodes (C-TCEs) have recently been produced using low-cost techniques to keep up with the boom in the fabrication and development of optoelectronic devices. In this article, silver nanowires (AgNWs) were successfully synthesized by a simple hydrothermal method using different molecular weights MWs of poly (N-vinylpyrrolidone) (PVP). Graphene oxide (GO) was prepared using the modified Hummers' method and a reduction step was held on GO films to produce reduced GO (rGO). C-TCEs were fabricated by over-coating the AgNWs electrodes with rGO, or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate to improve the roughness, surface energy, and sheet resistance. The influence of using lower and higher MWs of PVP on the yield, shape, and size of AgNWs was investigated. The results showed that using lower MW of PVP had a great effect on the yield, morphology, and aspect ratio of AgNWs with diameter of 46 nm and average length 12 µm. The optical, morphological, topographical, and electrical properties of TCEs were studied. AgNWs/rGO composite electrode provided the lowest surface roughness and surface energy of 250 nm and 47.95 mN/m, respectively, with a relatively high transparency of 78.2% at 550 nm light wavelength, and a low sheet resistance of 27 Ω/□.

Facile Synthesis of Pd Nanosheets and Implications for Superior Catalytic Activity

As a member of the 2D materials family, 2D metal nanosheets (metallenes) have received increasing attention due to their intriguing properties distinct from those of graphene and other inorganic 2D nanosheets. However, the synthesis of metallenes is still challenging, owing to the lack of an efficient synthetic approach. Here we present a facile one-pot approach to the controlled synthesis of Pd nanosheets. A key feature of this process is a stepwise reaction using 2,4,6-trichlorophenyl formate (TCPF); TCPF emits carbon monoxide gas, which acts as both a reductant and a surface capping agent, promoting the anisotropic 2D growth of the Pd nanosheets. Photoemission spectroscopy revealed some peculiar features of the surface charge and valence band states due to suppressed electron transfer at the 2D surface. This surface state caused improved catalytic activity for the hydrogen evolution reaction compared to that of bulk Pd.

Novel Hybrid Silver-Silica Nanoparticles Synthesized by Modifications of the Sol-Gel Method and Their Theranostic Potential in Cancer

Cancer is one of the leading causes of death worldwide. Conventional therapies lack selectivity and suffer from toxicity and drug resistance, leading to metastasis. To overcome these limitations, a new category of nanomaterials exploiting the tumor characteristics has been developed in cancer nanotherapeutics. Among them, pH, metabolism, and the disrupted architecture of cells can be exploited for theranostic applications. Such nanomaterials can be inorganic nanoparticles with silver ones and gain high attention as diagnostic, therapeutic, and antibacterial compounds. Silver has been linked with triggering the death of cancer cells via DNA damage due to the production of reactive oxygen species (ROS) during photodynamic therapy. Thus, improvement of biocompatibility, modification with targeted agents, and drug conjugation promote the use of silver nanoparticles. In this work, we managed to synthesize hybrid Ag@SiO2 core-shell nanoparticles via a modified sol-gel method by tackling the known etching of silver caused by ammonia by employing different bases of the sol-gel reaction. The bases used in the synthetic route were diethylamine (DEA) and triethylamine (TEA) and were monitored with silver nanoparticles individually from the absorbance peak of silver in the UV-vis region, showing no etching of silver in contrast with ammonia, which is usually used in the sol-gel method. Furthermore, we synthesized biocompatible nanoparticles with anticancer and diagnostic properties toward breast cancer cells and glioblastoma cells. The nanoparticles were characterized both structurally and morphologically. Their biological evaluation suggests minor toxicity toward healthy cells and red blood cells (RBCs). Also, the diagnostic potential of the hybrid nanoparticles was exploited by optical fluorescence microscopy. Therefore, we strongly suggest the investigation of such nanostructures as a dual platform for the diagnosis and therapy of cancer.

One-pot synthesis of ultra-stable polyvinylpyrrolidone-modified MnO2 nanoparticles for efficient radiation protection

Radiobiological damage can be caused by radiation, and easy preparation of long-term stable radioprotectors is helpful for timely and efficient response to radiation emergencies. This study develops an ultra-stable radioprotector for rapid nuclear emergency with a simple preparing method. First of all, polyvinylpyrrolidone-modified MnO2 nanoparticles (PVP-MnO2 NPs) are obtained by one-pot synthesis with ultra-stability (remaining for at least three years) and multiple free radical scavenging activities. In the synthesis process, PVP acts as a reducing agent, a surfactant (soft template), and a steric stabilizer. PVP-MnO2 NPs can improve the survival rates of irradiated cells by effectively scavenging free radicals and protecting DNA from radiation damage. Besides, PVP-MnO2 NPs can also prevent peripheral blood cell and organ damage induced by radiation, and improve the survival rate of irradiated mice. Finally, PVP-MnO2 NPs are mainly metabolized by liver and kidney in mice, and basically excreted 72 h after administration. These results indicate that PVP-MnO2 NPs exhibit good biosafety and radioprotection activity, which is significant for the development of radioprotection agents.

Development of Biocompatible Ga2(HPO4)3 Nanoparticles as an Antimicrobial Agent with Improved Ga Resistance Development Profile against Pseudomonas aeruginosa

Ga(III) can mimic Fe(III) in the biological system due to its similarities in charge and ionic radius to those of Fe(III) and can exhibit antimicrobial activity by disrupting the acquisition and metabolism of Fe in bacterial cells. For example, Ga(NO3)3 has been proven to be effective in treating chronic lung infections by Pseudomonas aeruginosa (P. aeruginosa) in cystic fibrosis patients in a recent phase II clinical trial. However, Ga(NO3)3 is an ionic compound that can hydrolyze to form insoluble hydroxides at physiological pH, which not only reduces its bioavailability but also causes potential renal toxicity when it is used as a systemic drug. Although complexion with suitable chelating agents has offered a varying degree of success in alleviating the hydrolysis of Ga(III), the use of nanotechnology to deliver this metallic ion should constitute an ultimate solution to all the above-mentioned problems. Thus far, the development of Ga-based nanomaterials as metalloantibiotics is an underexploited area of research. We have developed two different synthetic routes for the preparation of biocompatible Ga2(HPO4)3 NPs and shown that both the PVP- or PEG-coated Ga2(HPO4)3 NPs exhibit potent antimicrobial activity against P. aeruginosa. More importantly, such polymer-coated NPs do not show any sign of Ga-resistant phenotype development after 30 passes, in sharp contrast to Ga(NO3)3, which can rapidly develop Ga-resistant phenotypes of P. aeruginosa, indicating the potential of using Ga2(HPO4)3 NPs a new antimicrobial agent in place of Ga(NO3)3.

Luminescent Hybrid BPA.DA-NVP@Eu2L3 Materials: In Situ Synthesis, Spectroscopic, Thermal, and Mechanical Characterization

A series of homogeneous hybrid BPA.DA-NVP@Eu2L3 materials were obtained through an in situ approach where the luminescent dopant was formed at the molecular level with different contents (0.1; 0.2; 0.5; 1; and 2% by weight). A Europium(III) complex (Eu2L3) with quinoline-2,4-dicarboxylic acid was applied as a luminescence additive while a polymer matrix consisted of a combination of bisphenol A diacrylate (BPA.DA) and N-vinylpyrrolidone (NVP) monomers. Synthesis steps and the final materials were monitored by NMR and Fourier transform infrared spectroscopy (FTIR). The emission, excitation spectra, lifetime, and quantum yield measurements were applied for the determination of the photophysical characteristics. The thermal and mechanical properties of the obtained materials were tested via thermal analysis methods (TG/DTG/DSC and TG-FTIR) in air and nitrogen atmospheres, dynamic mechanical analysis (DMA), and hardness and bending measurements. Generally, even a small addition of the metal complex component causes changes in the thermal, mechanical, and luminescent properties. Hybrid materials with a greater europium complex content are characterized by a lower stiffness and hardness while the heterogeneity and the flexibility of the samples increase. A very small amount of an Eu2L3 admixture (0.1% wt.) in a hybrid material causes an emission in the red spectral range and the luminescence intensity was reached for the BPA-DA-NVP@1%Eu2L3 material. These materials may be potentially used in chemical sensing, security systems, and protective coatings against UV.

Green Nanoformulations of Polyvinylpyrrolidone-Capped Metal Nanoparticles: A Study at the Hybrid Interface with Biomimetic Cell Membranes and In Vitro Cell Models

Noble metal nanoparticles (NP) with intrinsic antiangiogenic, antibacterial, and anti-inflammatory properties have great potential as potent chemotherapeutics, due to their unique features, including plasmonic properties for application in photothermal therapy, and their capability to slow down the migration/invasion speed of cancer cells and then suppress metastasis. In this work, gold (Au), silver (Ag), and palladium (Pd) NP were synthesized by a green redox chemistry method with the reduction of the metal salt precursor with glucose in the presence of polyvinylpyrrolidone (PVP) as stabilizing and capping agent. The physicochemical properties of the PVP-capped NP were investigated by UV-visible (UV-vis) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopies, dynamic light scattering (DLS), and atomic force microscopy (AFM), to scrutinize the optical features and the interface between the metal surface and the capping polymer, the hydrodynamic size, and the morphology, respectively. Biophysical studies with model cell membranes were carried out by using laser scanning confocal microscopy (LSM) with fluorescence recovery after photobleaching (FRAP) and fluorescence resonance energy transfer (FRET) techniques. To this purpose, artificial cell membranes of supported lipid bilayers (SLBs) made with 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC) dye-labeled with 7-nitro-2-1,3-benzoxadiazol-4-yl (NBD, FRET donor) and/or lissamine rhodamine B sulfonyl (Rh, FRET acceptor) were prepared. Proof-of-work in vitro cellular experiments were carried out with prostate cancer cells (PC-3 line) in terms of cytotoxicity, cell migration (wound scratch assay), NP cellular uptake, and cytoskeleton actin perturbation.

Rebuildable Silver Nanoparticles Employed as Seeds for Synthesis of Pure Silver Nanopillars with Hexagonal Cross-Sections under Room Temperature

Silver nanopillars with strong plasmonic effects are used for localized electromagnetic field enhancement and regulation and have wide potential applications in sensing, bioimaging, and surface-enhanced spectroscopy. Normally, the controlled synthesis of silver nanopillars is mainly achieved using heterometallic nanoparticles, including Au nanobipyramids and Pd decahedra, as seeds for inducing nanostructure growth. However, the seed materials are usually doped in silver nanopillar products. Herein, the synthesis of pure silver nanopillars with hexagonal cross-sections is achieved by employing rebuildable silver nanoparticles as seeds. An environmentally friendly, stable, and reproducible synthetic route for obtaining silver nanopillars is proposed using sodium dodecyl sulfate as the surface stabilizer. Furthermore, the seed particles induce the formation of regular structures at different temperatures, and, specifically, room temperature is beneficial for the growth of nanopillars. The availability of silver nanoparticle seeds using sodium alginate as a carrier at different temperatures was verified. A reproducible method was developed to synthesize pure silver nanopillars from silver nanoparticles at room temperature, which can provide a strategy for designing plasmonic nanostructures for chemical and biological applications.

Preliminary investigation on the impact of engineered PVP-capped and uncapped silver nanoparticles on Eudrilus eugeniae, a terrestrial ecosystem model

Recently, the production of silver nanoparticles and their commercial products has generated increased concern and caused a hazardous impact on the ecosystem. Therefore, the present study examines the toxic effect of chemically engineered silver nanoparticles (SNPs) and polyvinylpyrrolidone-capped silver nanoparticles (PVP-SNPs) on the earthworm Eudrilus eugeniae (E. eugeniae). The SNPs and PVP-SNPs were synthesized, and their characterization was determined by UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The toxicity of SNPs and PVP-SNPs was evaluated using E. eugeniae. The present result indicates that the lethal concentration (LC₅₀) of SNPs and PVP-SNPs were achieved at 22.66 and 43.27 μg/mL, respectively. The activity of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT) was increased in SNPs compared to PVP-SNPs. Importantly, we have noticed that the E. eugeniae can amputate its body segments after exposure to SNPs and PVP-SNPs. This exciting phenomenon is named "autotomy," which describes a specific feature of E. eugeniae to escape from the toxic contaminants and predators. Accordingly, we have suggested this unique behavior may facilitate to assess the toxic effect of SNPs and PVP-SNPs in E. eugeniae.

Virucidal PVP-Copper Salt Composites against Coronavirus Produced by Electrospinning and Electrospraying

Electrospinning technology was used to produced polyvinylpyrrolidone (PVP)-copper salt composites with structural differences, and their virucidal activity against coronavirus was investigated. The solutions were prepared with 20, 13.3, 10, and 6.6% w/v PVP containing 3, 1.0, 0.6, and 0.2% w/v Cu (II), respectively. The rheological properties and electrical conductivity contributing to the formation of the morphologies of the composite materials were observed by scanning electron microscopy (SEM). SEM images revealed the formation of electrospun PVP-copper salt ultrafine composite fibers (0.80 ± 0.35 µm) and electrosprayed PVP-copper salt composite microparticles (1.50 ± 0.70 µm). Energy-dispersive X-ray spectroscopy (EDS) evidenced the incorporation of copper into the produced composite materials. IR spectra confirmed the chemical composition and showed an interaction of Cu (II) ions with oxygen in the PVP resonant ring. Virucidal composite fibers inactivated 99.999% of coronavirus within 5 min of contact time, with moderate cytotoxicity to L929 cells, whereas the virucidal composite microparticles presented with a virucidal efficiency of 99.999% within 1440 min of exposure, with low cytotoxicity to L929 cells (mouse fibroblast). This produced virucidal composite materials have the potential to be applied in respirators, personal protective equipment, self-cleaning surfaces, and to fabric coat personal protective equipment against SARS-CoV-2, viral outbreaks, or pandemics.

Ag Nanoparticles for Biomedical Applications-Synthesis and Characterization-A Review

Silver nanoparticles have been intensively studied over a long period of time because they exhibit antibacterial properties in infection treatments, wound healing, or drug delivery systems. The advantages that silver nanoparticles offer regarding the functionalization confer prolonged stability and make them suitable for biomedical applications. Apart from functionalization, silver nanoparticles exhibit various shapes and sizes depending on the conditions used through their fabrications and depending on their final purpose. This paper presents a review of silver nanoparticles with respect to synthesis procedures, including the polluting green synthesis. Currently, the most commonly used characterization techniques required for nanoparticles investigation in antibacterial treatments are described briefly, since silver nanoparticles possess differences in their structure or morphology.

Silver nanowire loaded poly(ε-caprolactone) nanocomposite fibers as electroactive scaffolds for skeletal muscle regeneration

Volumetric muscle loss (VML) due to trauma and tumor removal operations affects millions of people every year. Although skeletal muscle has a natural repair mechanism, it cannot provide self-healing above a critical level of VML. In this study, nanocomposite aligned fiber scaffolds as support materials were developed for volumetric skeletal muscle regeneration. For this purpose, silver nanowire (Ag NW) loaded poly(ε-caprolactone) (PCL) nanocomposite fiber scaffolds (PCL-Ag NW) were prepared to mimic the aligned electroactive structure of skeletal muscle and provide topographic and conductive environment to modulate cellular behavior and orientation. A computer-aided rotational wet spinning (RWS) system was designed to produce high-yield fiber scaffolds. Nanocomposite fiber bundles with lengths of 50 cm were fabricated via this computer-aided RWS system. The morphological, chemical, thermal properties and biodegradation profiles of PCL and PCL-Ag NW nanocomposite fibers were characterized in detail. The proliferation behavior and morphology of C2C12 mouse myoblasts were investigated on PCL and PCL-Ag NW nanocomposite fibrous scaffolds with and without electrical stimulation. Significantly enhanced cell proliferation was observed on PCL-Ag NW nanocomposite fibers compared to neat PCL fibers with electrical stimulations of 1.5 V, 3 V and without electrical stimulation.

A sustainable, top-down mechanosynthesis of carbohydrate-functionalized silver nanoparticles

A method for the production of metal nanoparticles with a tribological process is proposed, aiming at minimising power consumption and risk factors related to unsafe unit operations.

The two-step electrosynthesis of nanocomposites of Ag, Au, and Pd nanoparticles with iron(ii) oxide-hydroxide

The two-step electrosynthesis of metal nanoparticle (MNP, M = Ag, Pd, and Au) nanocomposites with iron oxide-hydroxide FeO-xFe(OH)2 was investigated.

Growth mechanism and microstructures of Cu2O/PVP spherulites

Cu₂O spherulites are solvothermaly fabricated by using Cu(NO₃)₂ as the starting material and polyvinylpyrrolidone (PVP) as a multifunctional growth agent. The specimens at different growth stages are investigated by using X-ray diffraction, electron microscopy, energy dispersive X-ray spectroscopy, soft X-ray emission spectroscopy and infrared spectroscopy. The formation mechanism of Cu₂O spherulites is proposed accordingly. Hierarchically, the spherulites are composed of needle-like submicron-rods lying along the radial orientations. The submicron-rods are constructed by piling up of small Cu₂O/PVP spheres. The embedded Cu₂O nanocrystallites can generate a dipolar field in each along the [100] direction. They deposit at the surface of a negatively charged PVP-containing spherical core, and self-oriented along the radial directions. Therefore, all the Cu₂O nanocrystallites would have their positively charged (100) facet facing to the core and their negatively charged (1̄00) facet turning towards to the spherulite surface, leading to a negatively charged surface of spherulites. Unlike randomly oriented nanocrystallites embedded in polymer microspheres, the spherulites would not undergo surface recrystallisation into a single crystal shell due to the restricted potential of local shift and rotation of the nanocrystallites by the Coulomb force from the core. This work provides new perspective towards the formation of spherulites and their structural properties.

Cu₂O/PVP spherulites are synthesised using Cu(NO₃)₂ as precursor, PVP as a reductant/capping-agent and DMF as the solvent. The interaction between dipoles of Cu₂O nanocrystals and a negatively charged core plays an important role in their formation.

Antimicrobial electrospun nanofiber mats of NaOH-hydrolyzed chitosan (HCS)/PVP/PVA incorporated with in-situ synthesized AgNPs: Fabrication, characterization, and antibacterial activity

This work aims to improve the electrospinability and antibacterial activity of chitosan (CS) - based nanofibers. Three approaches consisting of reducing molecular weight of CS by NaOH hydrolysis (HCS), blending with two carrying polymers (polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA)) and incorporating with in-situ synthesized silver nanoparticles (AgNPs) were integrated simultaneously for the first time to fabricate the HCS-AgNPs/PVP/PVA multicomponent nanofibers. The electrospinning parameters were optimized to obtain the smooth and uniform nanofibers without beads of both HCS/PVP/PVA and HCS-AgNPs/PVP/PVA systems. The presence of in-situ AgNPs in the multicomponent blends gives the better electrospinning performance and the lowest fiber diameter of 139 nm. In addition, the thermal properties, thermal stability and crystallinity index of both nanofibers also increased with increasing HCS or HCS-AgNPs fractions. Finally, the best antibacterial activity of HCS/PVP/PVA and HCS-AgNPs/PVP/PVA nanofibers against E. coli was found to be 74.4% and 99.9%, respectively. The significant enhancement in bactericidal activity of HCS-AgNPs/PVP/PVA nanofibers against E. coli is due to the synergistic properties of HCS/PVP/PVA blends and AgNPs. Both nanofiber mats displayed the excellent structural stability in moisture environment for at least 7 days. Therefore, the HCS-AgNPs/PVP/PVA nanofibers could be a potential material for applying in the medical purpose.

Self-Assembled Hierarchical Cu x O@C18H36O2 Nanoflakes for Superior Fenton-like Catalysis over a Wide Range of pH

A novel copper-based catalyst supported by a long-chain hydrocarbon stearic acid (Cu _x O@C₁₈H₃₆O₂) was synthesized by a hydrothermal method and double replacement reactions. The as-prepared catalyst is shown as self-assembled hierarchical nanoflakes with an average size of ∼22 nm and a specific surface area of 51.4 m² g^-1. The catalyst has a good performance on adsorption as well as Fenton-like catalytic degradation of Rhodamine B (RhB). The catalyst (10 mg/L) showed an excellent adsorption efficiency toward RhB (20 mg/L) for pH ranging from 5 to 13, with the highest adsorption rate (99%) exhibited at pH 13. The Fenton-like catalytic degradation reaction of RhB (20 mg/L) by Cu _x O@C₁₈H₃₆O₂ nanoflakes was effective over a wide range of pH of 3-11, and ^•OH radicals were generated via Cu₂O/H₂O₂ interactions in acidic conditions and CuO/H₂O₂ reactions in a neutral solution. The highest efficiency catalytic degradation of RhB (20 mg/L) was 99.2% under acidic conditions (pH = 3, H₂O₂ = 0.05 M), with an excellent reusability of 96% at the 6th cycle. The results demonstrated that the as-prepared Cu _x O@C₁₈H₃₆O₂ nanoflakes are an efficient candidate for wastewater treatment, with excellent adsorption capacity and superior Fenton-like catalytic efficiency and stability for RhB.

Fabrication of a Sensitive and Stable NiO Uric Acid Biosensor Using Ag Nanowires and Reduced Graphene Oxide

How to detect uric acid is an important issue. For the purpose of preparing a potentiometric uric acid biosensor, this research used nickel oxide (NiO) as the sensing film to deposit it onto the substrate by radio frequency sputtering, then modified it with reduced graphene oxide (rGO) and silver (Ag) nanowires. Reduced graphene oxide (rGO) not only has excellent electrical conductivity, but also can make the surface of the film have a larger surface area, while AgNWs have also been proven to improve catalytic activity; hence, these two materials were chosen as sensor modifiers. Finally, the stability and the various characteristics of the uric acid biosensor were investigated using a voltage–time (V–T) system. The results showed that the AgNW–uricase/rGO/NiO uric acid biosensor has average sensitivity with 4.66 mV/(mg/L). In addition, the sensor has good stability.

Activity of Povidone in Recent Biomedical Applications with Emphasis on Micro- and Nano Drug Delivery Systems

Due to the unwanted toxic properties of some drugs, new efficient methods of protection of the organisms against that toxicity are required. New materials are synthesized to effectively disseminate the active substance without affecting the healthy cells. Thus far, a number of polymers have been applied to build novel drug delivery systems. One of interesting polymers for this purpose is povidone, pVP. Contrary to other polymeric materials, the synthesis of povidone nanoparticles can take place under various condition, due to good solubility of this polymer in several organic and inorganic solvents. Moreover, povidone is known as nontoxic, non-carcinogenic, and temperature-insensitive substance. Its flexible design and the presence of various functional groups allow connection with the hydrophobic and hydrophilic drugs. It is worth noting, that pVP is regarded as an ecofriendly substance. Despite wide application of pVP in medicine, it was not often selected for the production of drug carriers. This review article is focused on recent reports on the role povidone can play in micro- and nano drug delivery systems. Advantages and possible threats resulting from the use of povidone are indicated. Moreover, popular biomedical aspects are discussed.

Exfoliation and Noncovalent Functionalization of Graphene Surface with Poly-N-Vinyl-2-Pyrrolidone by In Situ Polymerization

Heteroatom functionalization on a graphene surface can endow the physical and structural properties of graphene. Here, a one-step in situ polymerization method was used for the noncovalent functionalization of a graphene surface with poly-N-vinyl-2-pyrrolidone (PNVP) and the exfoliation of graphite into graphene sheets. The obtained graphene/poly-N-vinyl pyrrolidone (GPNVP) composite was thoroughly characterized. The surface morphology of GPNVP was observed using field emission scanning electron microscopy and high-resolution transmission electron microscopy. Raman spectroscopy and X-ray diffraction studies were carried out to check for the exfoliation of graphite into graphene sheets. Thermogravimetric analysis was performed to calculate the amount of PNVP on the graphene surface in the GPNVP composite. The successful formation of the GPNVP composite and functionalization of the graphene surface was confirmed by various studies. The cyclic voltammetry measurement at different scan rates (5–500 mV/s) and electrochemical impedance spectroscopy study of the GPNVP composite were performed in the typical three-electrode system. The GPNVP composite has excellent rate capability with the capacitive property. This study demonstrates the one-pot preparation of exfoliation and functionalization of a graphene surface with the heterocyclic polymer PNVP; the resulting GPNVP composite will be an ideal candidate for various electrochemical applications.

Bipolymeric Pectin Millibeads Doped with Functional Polymers as Matrices for the Controlled and Targeted Release of Mesalazine

Targeted drug delivery systems are a very convenient method of treating inflammatory bowel disease. The properties of pectin make this biopolymer a suitable drug carrier. These properties allow pectin to overcome the diverse environment of the digestive tract and deliver the drug to the large intestine. This investigation proposed bipolymeric formulations consisting of the natural polymer pectin and a synthetic polymer containing the drug 5-aminosalicylic acid. Pectin beads were prepared via ionotropic gelation involving the interaction between the hydrophilic gel and calcium ions. The obtained formulations consisted of natural polymer, 5-aminosalicylic acid (5-ASA) and one of the synthetic polymers, such as polyacrylic acid, polyvinylpyrrolidone, polyethylene glycol or aristoflex. The release of the drug was carried out employing a basket apparatus (USP 1). The acceptor fluid was pH = 7.4 buffer with added enzyme pectinase to reflect the colon environment. The amount of the released drug was determined using UV-Vis spectrophotometry at a wavelength of λ = 330 nm. The kinetics of the drug dissolution revealed that none of the employed models was appropriate to describe the release process. A kinetic analysis of the release profile during two release stages was carried out. The fastest drug release occurred during the first stage from a formulation containing pectin and polyethylene glycol. However, according to the applied kinetic models, the dissolution of 5-ASA was rather high in the formulation without the synthetic polymer during the second stage. Depending on the formulation, 68-77% of 5-ASA was released in an 8-hour time period. The FTIR and DSC results showed that there was no interaction between the drug and the polymers, but interactions between pectin and synthetic polymers were found.

Physicochemical Characterization of Polyvinyl Pyrrolidone: A Tale of Two Polyvinyl Pyrrolidones

Of several samples of polyvinyl pyrrolidone (PVP) used to coat and stabilize freshly manufactured aqueous dispersions of silver nanoparticles, one batch gave anomalous results: the dispersion maintained continued stability, even on extensive dilution. Our efforts to understand this desirable feature concluded that the generally used spectral method of PVP purity verification, Fourier transform infrared (FTIR) spectroscopy, was incapable of answering our inquiry. This led to the employment of several other methods, including X-ray photoelectron and nuclear magnetic resonance spectroscopies, which ultimately revealed several possible reasons for the dilution stability, including incomplete PVP hydrolysis during manufacture and the presence of hydroperoxide contaminants. It led, as well, to explanations for the shortcomings of FTIR spectroscopy as a verification method for PVP purity.

Influence of surfactant-tailored Mn-doped ZnO nanoparticles on ROS production and DNA damage induced in murine fibroblast cells

The present study concerns the in vitro oxidative stress responses of non-malignant murine cells exposed to surfactant-tailored ZnO nanoparticles (NPs) with distinct morphologies and different levels of manganese doping. Two series of Mn-doped ZnO NPs were obtained by coprecipitation synthesis method, in the presence of either polyvinylpyrrolidone (PVP) or sodium hexametaphosphate (SHMTP). The samples were investigated by powder X-ray Diffraction, Transmission Electron Microscopy, Fourier-Transform Infrared and Electron Paramagnetic Resonance spectroscopic methods, and N₂ adsorption-desorption analysis. The observed surfactant-dependent effects concerned: i) particle size and morphology; ii) Mn-doping level; iii) specific surface area and porosity. The relationship between the surfactant dependent characteristics of the Mn-doped ZnO NPs and their in vitro toxicity was assessed by studying the cell viability, intracellular reactive oxygen species (ROS) generation, and DNA fragmentation in NIH3T3 fibroblast cells. The results indicated a positive correlation between the specific surface area and the magnitude of the induced toxicological effects and suggested that Mn-doping exerted a protective effect on cells by diminishing the pro-oxidative action associated with the increase in the specific BET area. The obtained results support the possibility to modulate the in vitro toxicity of ZnO nanomaterials by surfactant-controlled Mn-doping.

Synthesis and catalytic evaluation of PVP-CeO2/rGO as a highly efficient and recyclable heterogeneous catalyst for multicomponent reactions in water

A highly efficient and eco-friendly route for the reduction of graphene oxide (GO) to reduced graphene oxide (rGO) was developed by using polyvinylpyrrolidone coated CeO₂ NPs (PVP-CeO₂) as a reducing and stabilizing agent. The resulting carbonaceous material, PVP-CeO₂/rGO, was well characterized with different spectroscopic techniques such as Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), elemental mapping, Transmission Electron Microscopy (TEM), Raman spectroscopy, powder X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray Photoelectron Spectroscopy (XPS), and Thermal Gravimetric (TG) analyses. The material exhibited high catalytic potential towards multicomponent reactions for the synthesis of biologically relevant benzodiazepine derivatives in aqueous media. The efficiency of the material for the desired reaction was shown in the form of an excellent product yield (96-98%) and a very short reaction time period (7-10 min). The use of water as solvent and recyclability of the catalyst made the present protocol acceptable from a green perspective.

A facile route to transfer Cu nanoparticles to organic medium for better stabilization and improved photocatalytic activity towards N-formylation reaction

Cu nanoparticles were prepared in an aqueous phase by means of a simple reduction-route using sodium borohydride as the reducing agent in the presence of ascorbic acid and polyvinylpyrrolidone (PVP). The hydrosol of the Cu nanoparticles deteriorated within a day. It compelled to initiate a scheme to stabilize the nanoparticles for a long period of time. Phase transfer to organic solvents using Benzyldimethylstearylammonium chloride (BDSAC) as a phase transfer agent was found to be an effective path in this respect. BDSAC performed the dual role of dragging the Cu nanoparticles from water to organic solvent and also acted as a capping agent along with PVP for better stabilization of Cu nanoparticles. The organosol of the Cu nanoparticles exhibited excellent stability and promising catalytic activity towards N-formylation reactions on a number of amine substrates in presence of visible green LED light. The yield and reusability of the catalyst were promising. All the samples were thoroughly characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive analysis of x-rays, x-ray photoelectron spectroscopy and thermo gravimetric analysis.

Sol–Gel and Electrospinning Synthesis of Silica–Hydroxyapatite–Silver Nanofibers for SEIRAS and SERS

Surface-enhanced Raman spectroscopy (SERS) and Surface-enhanced infrared absorption spectroscopy (SEIRAS) are both novel techniques favored by the excitation of surface plasmons onto metal nanostructures. The light emitted from the metal surface couples with the vibrational transitions of molecules in proximity, enhancing its spectral response and leading to more sensitive and effective spectroscopic analysis. The absence of inexpensive and reproducible substrates is among the major impediments to the accurate implementation and optimal performance of the technique. The development of a low-cost active substrate based on silica–hydroxyapatite through sol–gel synthesis and electrospinning is addressed in the present study. Fibers of 512 ± 199 nm diameter were produced after sintering at 1150 °C on the electrospun mats. The fibers are fixed to an indium tin oxide (ITO) glass base for electrodeposition with 10 and 20 mM AgNO3 at 1.5 and 3.3 V at different time periods. Electrodeposition produced silver nanorods and nanocubes on the fibers. The SERS and SEIRAS activity of each one of the nine supports was tested using pyridine 1 nM, comparing it with the spectrum of pyridine 1 mM. An enhancement factor of 2.01 × 106 for the band at 3335 cm−1 was obtained during a SEIRAS essay for the support doped for 2 min at 3.3 V with 10 mM silver nitrate solution. The highest SERS enhancement factor was 3.46 × 108, for the band at 1567 cm−1 in the substrate doped for 5 min at 1.5 V with silver nitrate solution at 10 mM. After testing both samples with 10−4 M violet crystal solution, no SERS enhancement factor was found, but higher band resolution in the spectra was observed.

Effect of Graphene Oxide and Silver Nanoparticles Hybrid Composite on P. aeruginosa Strains with Acquired Resistance Genes

BACKGROUND

In the last decades, nosocomial infections caused by drug-resistant Pseudomonas aeruginosa became a common problem in healthcare facilities. Antibiotics are becoming less effective as new resistant strains appear. Therefore, the development of novel enhanced activity antibacterial agents becomes very significant. A combination of nanomaterials with different physical and chemical properties enables us to generate novel multi-functional derivatives. In this study, graphene oxide and polyvinylpyrrolidone-stabilized silver nanoparticles hybrid nanocomposite (GO-Ag HN) were synthesized. The relation between antibiotic resistance and GO-Ag HN potential toxicity to clinical P. aeruginosa strains, their antibiotic resistance, and molecular mechanisms were assessed.

METHODS

Chemical state, particle size distribution, and morphology of synthesized GO-Ag NH were investigated using spectroscopy and microscopy techniques (UV-Vis, FTIR, XPS, TEM, SEM, AFM). Broad-spectrum antibiotic resistance of P. aeruginosa strains was determined using E-test. Antibiotic resistance genes were identified using polymerase chain reaction (PCR).

RESULTS

In this study, the toxicity of the GO-Ag NH to the isolated clinical P. aeruginosa strains has been investigated. A high antibiotic resistance level (92%) was found among P. aeruginosa strains. The most prevalent antibiotic resistance gene among tested strains was the AMPC beta-lactamase gene (65.6%). UV-vis, FTIR, and XPS studies confirmed the formation of the silver nanoparticles on the GO nanosheets. The functionalization process occurred through the interaction between Ag nanoparticles, GO, and polyvinylpyrrolidone used for nanoparticle stabilization. SEM analysis revealed that GO nanosheets undergo partial fragmentation during hybrid nanocomposite preparation, which remarkably increases the number of sharp edges and their mediated cutting effect. TEM analysis showed that GO-Ag HN spherical Ag nanoparticles mainly 9-12 nm in size were irregularly precipitated on the GO nanosheet surface. A higher density of Ag NPs was observed in the sheets' wrinkles, corrugations, and sharp edges. This hybrid nanocomposite poses enhanced antibacterial activity against carbapenem-resistant P. aeruginosa strains through a possible synergy between toxicity mechanisms of GO nanosheets and Ag nanoparticles. With incubation time increasing up to 10 minutes, the survival of P. aeruginosa decreased significantly.

CONCLUSION

A graphene oxide and silver nanoparticles hybrid composite has been shown to be a promising material to control nosocomial infections caused by bacteria strains resistant to most antibiotics.

Effect of Cellulose Microfiber Silylation Procedures on the Properties and Antibacterial Activity of Polydimethylsiloxane

In this study, the liquid phase and vapor phase procedures for silylating cellulose microfibers by hexamethyldisilazane (HMDS) were compared in terms of efficiency. The influence of functionalization degree on the morphology of microfibers and their interaction with polydimethylsiloxane (PDMS) matrix has been investigated. The antibacterial properties of silylated cellulose microfibers hybridized with Ag nanoparticles, obtained by in situ chemical reduction, were also studied. Sample morphology investigations were carried out using spectroscopy and microscopy techniques (FTIR, XPS, TEM, SEM, EDS, XPS). Trimethylsilyl moieties appear on the surface of the cellulose microfibers after modification and improve the dispersibility of the microfibers, allowing strong interaction with the PDMS matrix and favoring its crosslinking density. Microfibers functionalized by the vapor phase of HMDS show smoother surfaces with higher concentrations of Si-containing groups, resulting in a more hydrophobic wetting behavior and a greater influence on the mechanical properties of the polymer. The silylated cellulose microfiber–Ag nanohybrid shows stronger antimicrobial activity towards Gram-positive and Gram-negative bacteria strains compared to that of the untreated hybrid. A PDMS composite loaded with this hybrid exhibits the ability to inhibit bacterial growth.

General synthesis of hierarchical sheet/plate-like M-BDC (M = Cu, Mn, Ni, and Zr) metal-organic frameworks for electrochemical non-enzymatic glucose sensing

Two-dimensional metal-organic frameworks (2D MOFs) are an attractive platform to develop new kinds of catalysts because of their structural tunability and large specific surface area that exposes numerous active sites. In this work, we report a general method to synthesize benzene dicarboxylic acid (BDC)-based MOFs with hierarchical 3D morphologies composed of 2D nanosheets or nanoplates. In our proposed strategy, acetonitrile helps solvate the metal ions in solution and affects the morphology, while polyvinylpyrrolidone (PVP) serves as a shape-control agent to assist in the nucleation and growth of MOF nanosheets. PVP also acts as a depletion agent to drive the assembly of the hierarchical sheet/plate-like M-BDC under solvothermal conditions. Further, we also demonstrate the flexibility of the proposed method using numerous coordinating metal ions (M = Cu, Mn, Ni, and Zr). The potential of these MOFs for electrochemical glucose sensing is examined using the hierarchical sheet-like Ni-BDC MOF as the optimum sample. It drives the electrocatalytic oxidation of glucose over a wide range (0.01 mM to 0.8 mM) with high sensitivity (635.9 μA mM-1 cm-2) in the absence of modification with carbon or the use of conductive substrates. It also demonstrates good selectivity with low limit of detection (LoD = 6.68 μM; signal/noise = 3), and fast response time (<5 s).

Silver Nanorings Fabricated by Glycerol-Based Cosolvent Polyol Method

The urgent demand for transparent flexible electrodes applied in wide bandgap devices has promoted the development of new materials. Silver nanoring (AgNR), known as a special structure of silver nanowire (AgNW), exhibits attractive potential in the field of wearable electronics. In this work, an environmentally friendly glycerol-based cosolvent polyol method was investigated. The Taguchi design was utilized to ascertain the factors that affect the yield and ring diameter of AgNRs. Structural characterization showed that AgNR seeds grew at a certain angle during the early nucleation period. The results indicated that the yield and ring diameter of AgNRs were significantly affected by the ratio of cosolvent. Besides, the ring diameter of AgNRs was also tightly related to the concentration of polyvinylpyrrolidone (PVP). The difference of reducibility between glycerol, water, and ethylene glycol leads to the selective growth of (111) plane and is probably the main reason AgNRs are formed. As a result, AgNRs with a ring diameter range from 7.17 to 42.94 μm were synthesized, and the quantity was increased significantly under the optimal level of factors.

Synthesis of corrugated surface AgNWs and their applications in surface enhanced Raman spectroscopy

Among metals, AgNWs are considered to be excellent materials for use in surface enhancement Raman spectroscopic (SERS) sensing due to their superior electrical properties, strong electromagnetic field generation and strong enhancement intensity.

Capping Agent Effect on Pd-Supported Nanoparticles in the Hydrogenation of Furfural

The catalytic performance of a series of 1 wt % Pd/C catalysts prepared by the sol-immobilization method has been studied in the liquid-phase hydrogenation of furfural. The temperature range studied was 25–75 °C, keeping the H2 pressure constant at 5 bar. The effect of the catalyst preparation using different capping agents containing oxygen or nitrogen groups was assessed. Polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and poly (diallyldimethylammonium chloride) (PDDA) were chosen. The catalysts were characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The characterization data suggest that the different capping agents affected the initial activity of the catalysts by adjusting the available Pd surface sites, without producing a significant change in the Pd particle size. The different activity of the three catalysts followed the trend: PdPVA/C > PdPDDA/C > PdPVP/C. In terms of selectivity to furfuryl alcohol, the opposite trend has been observed: PdPVP/C > PdPDDA/C > PdPVA/C. The different reactivity has been ascribed to the different shielding effect of the three ligands used; they influence the adsorption of the reactant on Pd active sites.

Combining Experiments and Theoretical Modeling To Interrogate the Anisotropic Growth and Structure-Plasmonic Property Relationships of Gold Nanostars

We present a combined strategy of experiments and theoretical modeling for understanding the evolution of the morphology and plasmonic properties of gold nanostars (GNSs) in the seed-mediated synthesis by changing the poly(vinylpyrrolidone) (PVP) molecular weight, PVP concentration, and synthesis temperature. A dramatic change of the morphology of GNSs as a function of these synthesis parameters is observed that is related to variations of the plasmonic properties and thus surface-enhanced Raman spectroscopy (SERS) enhancement. We observe the favorable growth of anisotropic GNS structures with sharp protruding tips using PVP of low molecular weight and of rounded GNSs with short protruding tips using PVP of high molecular weight. The PVP concentration has less influence on the core size than on the tip length of GNSs. The high synthesis temperature causes the rounding of the GNS structure. Finite-difference time-domain (FDTD) simulations reveal a remarkable correlation of the GNS morphology with the plasmonic properties as well as the SERS enhancement. The maximum local electric field enhancement occurs at the apex of the sharp protruding tips of the GNSs. The weak plasmonic coupling is observed between the protruding tips of GNSs because of their large separation distance, and increasing the number of protruding tips beyond two only increases the extinction cross section without further red-shifting the plasmon peak. A resonance overlap of the plasmon band with the incident laser wavelength is responsible for the morphology-dependent plasmonic properties and SERS enhancement. The present work demonstrates that a mechanistic understanding of the structural evolution of GNSs along with their morphology-plasmonic property correlation can be achieved through the combination of experimental investigations and FDTD-based theoretical modeling.

The role of polyvinylpyrrolidone (PVP) as a capping and structure-directing agent in the formation of Pt nanocubes

In this work, we have investigated the specific role of PVP and Ag⁺ ions in the formation of platinum nanocubes (NCs) in polyol synthesis. Various characterization techniques such as transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to unravel the effects of PVP and Ag⁺ ion concentrations on the monodispersity and particle size of the obtained Pt NCs. Very interestingly, we have already fabricated Pt NCs with similar monodispersity and particle size using only 0.4 M PVP (absence of Ag⁺ ions). Furthermore, the dispersity of the Pt NCs strongly depends on the initial PVP concentration. This observation underscores the important role of PVP during the NC formation processes by controlling the relative growth rates along the <100> direction with respect to those of the <111>. Time-resolved experiments show that the formation and growth of Pt NCs are much faster in the absence of Ag⁺ ions than with Ag⁺ ions, which can be explained by the enhanced growth rate along the <100> direction or/and the suppression of the growth rate along the <111>. Electronic interactions between the chemisorbed pyrrolidone ring of the PVP and Pt surface are revealed from the XPS and FTIR data, showing a negative shift of the binding energy of N 1s and a red shift of the Pt-CO vibration band. From our experimental results, we propose extended formation and growth mechanisms based on PVP as the main structure-directing agent. Our model indicates that the aliphatic chains of PVP forming a multi-layer shell influence the mass transport of precursor ions to the initial Pt seed to control the growth rate of Pt NCs with exposed {100} planes. Altogether, we provide a simple, efficient and resource-friendly synthetic guideline for the preparation of nano-sized Pt NCs with high monodispersity and high purity.

Enhancing the physical stability and supersaturation generation of amorphous drug-polyelectrolyte nanoparticle complex via incorporation of crystallization inhibitor at the nanoparticle formation step: A case of HPMC versus PVP

Amorphous drug-polyelectrolyte nanoparticle complex (or nanoplex in short) has emerged as a highly attractive solubility enhancement strategy of poorly-soluble drugs attributed to its simple and highly efficient preparation. The existing nanoplex formulation, however, exhibits poor amorphous form stability during long-term storage for drugs with high crystallization propensity. Using ciprofloxacin (CIP) and sodium dextran sulfate (DXT) as the model drug-polyelectrolyte nanoplex, we investigated the feasibility of incorporating crystallization inhibiting agents, i.e. hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP), at the nanoplex formation step to improve the physical stability of the CIP nanoplex. The effects of the HPMC or PVP additions on the nanoplex's physical characteristics (i.e. size, zeta potential, CIP payload), CIP utilization rate, dissolution rate, and supersaturation generation were also examined. The results showed that the additions of HPMC or PVP increased the CIP nanoplex size (from 300 to 500 nm) and CIP utilization rate (from 65% to 90% w/w) with minimal impacts on the CIP payload (70-80% w/w). Their additions had opposite impacts on the nanoplex's colloidal stability due to surfactant nature of PVP. Significantly, unlike the CIP-DXT and CIP-DXT-PVP nanoplexes, the CIP-DXT-HPMC nanoplex remained amorphous after three-month accelerated storage, while also exhibited superior solubility enhancement (15-30% higher).

To what extent do polymeric stabilizers affect nanoparticles characteristics?

Colloidal synthesis of nanoparticles using polymeric stabilizers as a template of a structure directing agent provided a plethora of opportunities in fabricating nanoparticles (NPs) with controlled size, shape, composition and structural characteristics. To understand the complete potency of polymeric stabilizers during the synthesis of nanoparticles, the relationship between polymer characteristics such as structure, molecular weight and concentration and nanoparticles characteristics is discussed in depth. This review portrays the use of polymers to attain nanostructured materials via covalent and non-covalent approaches. These polymers can also serve as surfaces modifier as well as the growth regulators during the synthesis of nanomaterials. The effect provided by polymers that directs the formation of nanomaterials into desired forms is otherwise hard to achieve. We especially spotlight on the approaches for tuning the characteristic properties of nanoparticles via cautious choice of the polymer system with special focus to stimuli-responsive polymers. This review mainly focusses on answering the main challenging question; what is the ideal polymeric stabilizer system to obtain specific morphology, size and phase structure of nanoparticles? Such vital information will enable rational design of nanoparticles to meet specific needs for different applications.

Silver Nanowire-Modified Filter with Controllable Silver Ion Release for Point-of-Use Disinfection

Waterborne diseases related to unsafe water are still major threats to public health in some developing countries and rural areas. Providing affordable and safe drinking water globally remains a great challenge in the coming decades. In this study, we develop a high-throughput and conductive silver nanowire (AgNW)-modified composite filter via depositing thin and ultralong AgNWs on a macroporous substrate. An electrochemical filtration cell (EFC) equipped with the composite filter achieves controllable Ag⁺ release at a μg L^-1 level and superior bacterial inactivation performance (>6-log inactivation efficiency) with an operation voltage of only 1 V at a high flux of 100 m³ h^-1 m^-2. Under such operation conditions, each composite filter (effective area: 0.79 cm²) can treat at least 750 mL of the bacterial suspension (∼10⁷ CFU mL^-1 of Escherichia coli) with a low effluent Ag⁺ concentration below 50 μg L^-1 and almost negligible energy consumption of only ∼70 J m^-3.

Nozzle-free electrospinning of Polyvinylpyrrolidone/Poly(glycerol sebacate) fibrous scaffolds for skin tissue engineering applications

A novel composite for skin tissue engineering applications by use of blends of Poly(vinylpyrrolidone) (PVP) and Poly (glycerol sebacate) (PGS) was fabricated via the scalable nozzle-free electrospinning technique. The formed PVP:PGS blends were morphologically, thermochemically and mechanically characterized. The morphology of the developed fibers correlated to the blend ratio. The tensile modulus appeared to be affected by the concentration of PGS within the blends, with an apparent decrease in the elastic modulus of the electrospun mats and an exponential increase of the elongation at break. Ultraviolet (UV) crosslinking of the composite fibers significantly decreased the construct's wettability and stabilized the formed fiber mats, which was indicated by contact angle measurements. In vitro examination showed good viability and proliferation of human dermal fibroblast cells. The present findings provide valuable insights for tuning the elastic properties of electrospun material by incorporating this unique elastomer as a promising future candidate for skin substitute constructs.

Microstructure and Resistivity Analysis of Silver Nanoparticle-Based Crystalline Conductive Films Synthesized using PEG Surfactant

Silver nanoparticle-based crystalline conductive films were synthesized using a simple and environmentally friendly method centered on chemical reduction. A stoichiometric balance of three different molecular weights of polyethylene glycol (PEG) was used as a capping agent. Resistivity, and its correlation with temperature and the particle size of nanoparticle films, was probed. The silver nanoparticles were characterized using thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM). Further silver films deposited on a glass substrate were characterized by FESEM, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and resistivity measurements. Particle size distribution and room temperature electrical conductivity were also investigated. The high conductivity of sintered films suggested applications for the ink-jet printing of electronic circuitry on thermally sensitive substrates.

The Effect of Low Weight Percent Multiwalled Carbon Nanotubes on the Dielectric Properties of Non-Conducting Polymer/Ceramic Nanocomposites for Energy Storage Materials

Here in this study timing saving, easy and cost effective methods has been applied for fabricating the dielectric energy storage materials. Ceramic nanoparticles (FLZC’s) have been successfully synthesized by Sol-Gel method and its nanocomposites with non-conducting polymers (PVP, PVA, PEG, PEO) and multiwalled carbon nanotubes (MWCNT’s) by one-pot blending technique. Energy dispersive x-ray diffraction (EDX), x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA/DTA), AC impedance analyzer and dielectric properties were determined for all the samples. Dielectric properties showed good agreement with that of energy storage substances for electronic device fabrication. High dielectric constant was achieved when 0.5 wt% MWCNT’s was added to FLZC’s/MWCNT’s/Polymer nanocomposites. The stability and performance of the nanocomposites were dependent on the type of polymer used. These preparation materials can be employed in functional materials, such as high charge-storage capacitors, electrostriction for artificial muscles and smart skins etc.

Laser-Scribed Lossy Microstrip Lines for Radio Frequency Applications

Laser-direct writing has become an alternative method to fabricate flexible electronics, whereas the resistive nature of laser-scribed conductors may distort the radio-frequency characteristics of circuits for high-frequency applications. We demonstrate that the transmission characteristics of microstrip lines are insensitive to the resistance of laser-scripted conductors when the sheet resistance is not above 0.32 Ω/□. On the other hand, the transmission and reflection characteristics of the MS lines can be simply modified through the accommodation of the resistance of the conductors, because a laser can trigger the sintering and melting of laser produced silver nanostructures. This could provide an alternative way to fabricate radio frequency (RF) resistors and promote their applications to flexible radio-frequency devices and systems.

Influence of the average molar mass of poly(N-vinylpyrrolidone) on the dimensions and conductivity of silver nanowires

Improving the performance of Ag nanowire electrodes by adjusting the reaction conditions and the molar mass of PVP.