Green synthesis, characterization, photocatalytic, fluorescence and antimicrobial activities of Cochlospermum gossypium capped Ag2S nanoparticles

Silver sulphide nanoparticles (Ag2SNPs) synthesized using Phyllanthus emblica fruit extract for enhanced antibacterial and antioxidant properties

In this study, silver sulfide nanoparticles (Ag2SNP's) were successfully produced by using fruit extracts of Phyllanthus emblica. UV-vis, FTIR, XRD with SEM and EDX techniques were used for the synthesis process and for characterization of the resulting nanostructures. According to the findings, the fabricated nanostructure had a monoclinic crystal structure, measuring 44 nm in grain size, and its strain was 1.82 × 10-3. As revealed by SEM analysis, the synthesized nanostructure consists of irregular spherical and triangular shapes. The presence of silver (Ag) and sulfur (S) was also confirmed through EDX spectra. Furthermore, Ag2S nanoparticles were tested for their ability to effectively inhibit gram-positive and gram-negative bacterial growth. As a result of this study, it was clearly demonstrated that Ag2S nanoparticles possess powerful antibacterial properties, particularly when it came to inhibiting Escherichia coli growth. Ag2S nanoparticles had high total H2O2 and flavonoid concentrations and the greatest overall antioxidant activity, according to the evaluation of antioxidant activity of the samples. The results obtained from the P. emblica fruit extract were followed by those obtained from Ag2S nanoparticles were reported in detail. RESEARCH HIGHLIGHTS: Innovative Ag2SNP synthesis using Phyllanthus emblica fruit extract. SEM with EDX revealed a monoclinic crystal structure with a grain size of 44 nm and a strain of 1.82 × 10-3. Many of these applications are demonstrated by the potential of Ag2SNPs to treat and combat bacteria, particularly Escherichia coli. A peak at 653 cm-1 indicates the presence of primary sulfide aliphatic C-S extension vibrations. The abundant H2O2 and NO2 found in P. emblica nanocomposites make them potent antioxidants.

Efficient performance of InP and InP/ZnS quantum dots for photocatalytic degradation of toxic aquatic pollutants

In recent years, the growing concern over the presence of toxic aquatic pollutants has prompted intensive research into effective and environmentally friendly remediation methods. Photocatalysis using semiconductor quantum dots (QDs) has developed as a promising technology for pollutant degradation. Among various QD materials, indium phosphide (InP) and its hybrid with zinc sulfide (ZnS) have gained considerable attention due to their unique optical and photocatalytic properties. Herein, InP and InP/ZnS QDs were employed for the removal of dyes (crystal violet, and congo red), polyaromatic hydrocarbons (pyrene, naphthalene, and phenanthrene), and pesticides (deltamethrin) in the presence of visible light. The degradation efficiencies of crystal violet (CV) and congo red (CR) were 74.54% and 88.12% with InP, and 84.53% and 91.78% with InP/ZnS, respectively, within 50 min of reaction. The InP/ZnS showed efficient performance for the removal of polyaromatic hydrocarbons (PAHs). For example, the removal percentage for naphthalene, phenanthrene, and pyrene was 99.8%, 99.6%, and 88.97% after the photocatalytic reaction. However, the removal percentage of InP/ZnS for pesticide deltamethrin was 90.2% after 90 min light irradiation. Additionally, advanced characterization techniques including UV-visible spectrophotometer (UV-Vis), photoluminescence (PL), X-ray diffractometer (XRD), energy-dispersive spectrometer (EDS) elemental mapping, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) were used to analyze the crystal structure, morphology, and purity of the fabricated materials in detail. The particle size results obtained from TEM are in the range of 2.28-4.60 nm. Both materials (InP and InP/ZnS) exhibited a spherical morphology, displaying distinct lattice fringes. XRD results of InP depicted lattice planes (111), (220), and (311) in good agreement with cubic geometry. Furthermore, the addition of dopants was discovered to enhance the thermal stability of the fabricated material. In addition, QDs exhibited efficacy in the breakdown of PAHs. The analysis of their fragmentation suggests that the primary mechanism for PAHs degradation is the phthalic acid pathway.

Hydrothermal Fabrication of Efficient Binary Pd/Ag2S Heterojunction Composites: Synthesis, Characterization, and Fluorometric Selective Sensing of Organophosphate Pesticides

Although many plasmonic nanosensors have been established for the detection of analytes, few of them are feasible for analyzing natural samples with very complex matrices because of insufficient method selectivity. To address this challenge, we propose an epitaxial and lattice-mismatch approach to the synthesis of a unique Pd/Ag2S nanostructure, which consists of a Pd segment with excellent plasmonic characteristics, and a highly stable Ag2S portion with minimum solubility product (Ksp(Ag2S) = 6.3 × 10- 50). Hence, Ag2S nanoparticles (NPs) and optimized (10.05 mmol/L) Pd/Ag2S composite were prepared using a hydrothermal method. The fabricated samples were characterized using different tools including UV-vis DRS, PL, powder XRD, TEM, and BET surface area measurements. Furthermore, the fluorometric sensing performance of the Ag2S and Pd/Ag2S samples was examined in the detection of organophosphate pesticides such as MLT, PRT, DZN, FNT, DCL, MCP, and CPS pesticides at room temperature. The quantitative detection of MLT, PRT, DZN, FNT, DCL, MCP, and CPS pesticides was achieved based on the Pd/Ag2S composite and organophosphate group-specific interaction. The optimized sensor exhibited a lower limit of detection (3.08 µM), excellent reproducibility, selectivity, and stability with an enhanced sensitivity of - 207.1 µA/µM cm2 (R2 = 0.98) in the range of 10 µM-100 µM for the detection of CPS pesticide. In addition, the fluorometric sensor has excellent selectivity, reproducibility, and stability, providing a feasible method for not only the detection of CPS pesticides but also other analytes in the future.

Highly selective CO2 sensing response of lanthanum oxide nanoparticle electrodes at ambient temperature

Lanthanum oxide nanoparticles (La₂O₃ NPs) are attractive rare earth metal oxides because of their applications in optical devices, catalysts, dielectric layers, and sensors. Herein, we report room temperature operative carbon dioxide gas sensing electrodes developed by a simple sonication assisted hydrothermal method. The physiochemical, morphological and gas-sensing properties of the prepared nanoparticles were studied systematically and their successful preparation was confirmed with the absence of impurities and high selectivity towards CO₂. The fabricated sensor showed a high sensitivity of 40% towards CO₂ at 50 ppm, and it can detect concentrations of up to 5 ppm with a quick response time of 6 s and recovery of 5 s. The electrode demonstrated long-term stability of 95% for 50 days when tested with an interval of 10 days. This simple and cost-effective method shows great potential for fabricating room temperature CO₂ gas sensors.

Luminescent Quantum Dots: Synthesis, Optical Properties, Bioimaging and Toxicity

Luminescent nanomaterials such as semiconductor nanocrystals (NCs) and quantum dots (QDs) attract much attention to optical detectors, LEDs, photovoltaics, displays, biosensing, and bioimaging. These materials include metal chalcogenide QDs and metal halide perovskite NCs. Since the introduction of cadmium chalcogenide QDs to biolabeling and bioimaging, various metal nanoparticles (NPs), atomically precise metal nanoclusters, carbon QDs, graphene QDs, silicon QDs, and other chalcogenide QDs have been infiltrating the nano-bio interface as imaging and therapeutic agents. Nanobioconjugates prepared from luminescent QDs form a new class of imaging probes for cellular and in vivo imaging with single-molecule, super-resolution, and 3D resolutions. Surface modified and bioconjugated core-only and core-shell QDs of metal chalcogenides (MX; M = Cd/Pb/Hg/Ag, and X = S/Se/Te,), binary metal chalcogenides (MInX₂; M = Cu/Ag, and X = S/Se/Te), indium compounds (InAs and InP), metal NPs (Ag, Au, and Pt), pure or mixed precision nanoclusters (Ag, Au, Pt), carbon nanomaterials (graphene QDs, graphene nanosheets, carbon NPs, and nanodiamond), silica NPs, silicon QDs, etc. have become prevalent in biosensing, bioimaging, and phototherapy. While heavy metal-based QDs are limited to in vitro bioanalysis or clinical testing due to their potential metal ion-induced toxicity, carbon (nanodiamond and graphene) and silicon QDs, gold and silica nanoparticles, and metal nanoclusters continue their in vivo voyage towards clinical imaging and therapeutic applications. This review summarizes the synthesis, chemical modifications, optical properties, and bioimaging applications of semiconductor QDs with particular references to metal chalcogenide QDs and bimetallic chalcogenide QDs. Also, this review highlights the toxicity and pharmacokinetics of QD bioconjugates.

Designing Highly Active S-g-C3N4/Te@NiS Ternary Nanocomposites for Antimicrobial Performance, Degradation of Organic Pollutants, and Their Kinetic Study

The current research is about the synthesis of pure nickel sulfide, a series of Te (0, 0.5, 1, 1.5, 2, and 3 wt.%)-doped NiS (Te@NiS) nanoparticles (NPs), and a series of S-g-C3N4 (10, 30, 50, 70, and 80 wt.%)/Te@NiS nanocomposites (NCs), fabricated through a hydrothermal route. XRD and FTIR spectroscopic techniques demonstrated the successful synthesis of NPs and NCs. SEM-EDX images confirmed the flakelike structure and elemental constituents of the fabricated materials. Tauc plots were drawn, to calculate the band gaps of the synthesized samples. Te doping resulted in a significant reduction in the band gap of the NiS NPs. The photocatalytic efficiency of the NPs and NCs was investigated against MB, under sunlight. The results obtained for the photocatalytic activity, showed that 1%Te@NiS nanoparticles have an excellent dye degradation capacity in sunlight. This was made even better by making a series of SGCN/1% Te@NiS nanocomposites with different amounts of S-g-C3N4. When compared to NiS, Te@NiS, SGCN, and 70%SGCN/1%Te@NiS, the 70%SGCN/1%Te@NiS NCs have excellent antifungal ability. The higher impact of SGCN/Te@NiS, may be due to its enhanced ability to disperse and interact with the membranes and intracellular proteins of fungi. The 70%SGCN/1%Te@NiS NCs showed excellent antibacterial and photocatalytic efficiency. Thus, the 70%SGCN/1%Te@NiS NCs might prove fruitful in antibacterial and photocatalytic applications.

Biogenic Synthesis of Carboxymethyl Cashew Gum Modified Gold Nanoparticles and its Sensitive and Selective Calorimetric Detection of Hg2+ Ions and Catalytic Reduction of Methyl Red

In the present study, we have successfully synthesized and characterized carboxy methyl cashew gum modified gold nanoparticles (CMCG-AuNPs) via a microwave-assisted method and used as a calorimetric probe for selective detection of Hg²⁺ ions as well as catalytic reduction of methyl red in an aqueous medium. The effect of different parameters including concentration and irradiation time on the formation of CMCG-AuNPs was also investigated. The presence of strong surface plasmon resonance (SPR) peak in the visible region indicated the formation of AuNPs. The characterization techniques were identified the interaction between the CMCG and AuNPs with estimation of size and morphology. The face centred cubic (FCC) crystal structure was identified by using XRD and supporting with SAED pattern. TEM images of CMCG-AuNPs were exhibited as polydispersed with spherical in shape and the average particle size was 12 ± 3 nm. The synthesized CMCG-AuNPs were utilized to sensing Hg²⁺ ions in an aqueous medium, the presence of Hg²⁺ ions selectively among other metal ions, the CMCG-AuNPs were aggregated by changing the color from wine red to purple blue accompanied by change in the position of SPR peak and intensity. It was observed as a strong linear relationship based on the change in intensity, the limit of detection was determined to be 0.277 nM. The catalytic activity was also examined for the reduction of methyl red (MR) in the presence of CMCG-AuNPs was completed within 12 min and followed pseudo-first order kinetics with a rate constant of 0.261 min^-1. From the obtained results, the synthesized CMCG-AuNPs were useful for detection of heavy metal ions as well as toxic pollutants degradation via a green method, and utilized sensing, environmental, and biomedical application in future.

Recent advances in metal sulfide nanoparticle-added bionanocomposite films for food packaging applications

Metal sulfide nanoparticles have recently attracted much attention due to their unique physical and functional properties. Metal sulfide nanoparticles used as optoelectronic and biomedical materials in the past decades are promising for making functional nanocomposite films due to their low toxicity and strong antibacterial activity. Recently, copper sulfide and zinc sulfide nanomaterials have been used to produce food packaging films for active packaging. Metal sulfide nanoparticles added as nanofillers are attracting attention in packaging applications due to their excellent potential to improve mechanical, barrier properties, and antibacterial activity. This review covers the fabrication process and important applications of metal sulfide nanoparticles. The development of metal sulfides reinforcing mainly copper sulfide and zinc sulfide nanomaterials as multifunctional nanofillers in bio-based films for active packaging applications has been comprehensively reviewed. As the recognition of metal sulfide nanoparticles as a functional filler increases, the development and application potential of active packaging films using them is expected to increase.

Design, Synthesis, Characterization, Catalytic, Fluorometric Sensing, Antimicrobial and Antioxidant Activities of Schiff Base Ligand Capped AgNPs

In recent days, the usage of biological and non-biological pollutants increased which poses a significant threat to environmental and biological systems. Therefore, the present aim is to develop effective methods to treat such pollutants by using highly stable and small-sized Schiff base ligand capped silver nanoparticles (AgNPs) with a face-centered cubic (fcc) crystalline structure and the size range is 5-10 nm. The potent role of the resulting synthesized AgNPs was found to be on multiple platforms such as catalyst, sensor, antioxidant, and antimicrobial disinfectant. The synthesized AgNPs were characterized through UV-vis spectroscopy, PL, FTIR, XRD, SEM, and TEM. The FTIR spectrum of AgNPs exhibited the interacted functional groups of Schiff base and size was estimated by XRD and TEM. AgNPs were able to catalytically degrade approximately 95% of methylene blue (MB), rhodamine B (RhB), and eosin Y (EY) dyes within 80 min of reaction time using NaBH₄. The fluorometric sensor studies of synthesized AgNPs showed selective sensing of the potentially hazardous Fe²⁺ ion in water. As an antimicrobial agent, the AgNPs are effective against both Gram-positive and Gram-negative bacteria; as well as fungi, with the zones of clearance as approximately compatible with standard drugs. The AgNPs displayed a greater ability to scavenge free radicals, especially DPPH when compared with AgNPs and ascorbic acid. Thus, the results of this study validate the triple role of AgNPs derived via a simple synthesis as a catalyst, sensor, antioxidant, and antimicrobial agent for effective environmental remediation.

Multifunctional nanocarrier with self-catalytic production of nitric oxide for photothermal and gas-combined therapy of tumor

Single treatment often faces the problem that it cannot completely eradicate tumor and inhibit the tumor metastasis. In order to overcome this shortcoming, multi-modal tumor treatment has attracted widespread attention. In the present article, based on ascorbyl palmitate (PA) and l-arginine (l-Arg), a multifunctional nanocarrier is designed for synergetic treatment of tumor with photothermal and nitric oxide (NO) gas therapy. Firstly, PA and l-Arg were self-assembled to form novel functional micelles, PL, with high biosafety using electrostatic interaction and hydrogen bonding. The functional micelles could self-catalyze to produce NO at the tumor site. Then, Ag₂S quantum dots having fluorescence imaging and photothermal properties were encapsulated to obtain the nanocarrier, A@PL. The results show that A@PL had a hydrated size of around 78 nm and presented good stability within 30 d. Moreover, in vitro studies indicate that it was efficient with regards to NO self-generating capacity, whereas the photothermal conversion efficiency was as high as 34% under near-infrared light irradiation. The cytotoxicity results show that, when the concentration of A@PL was as high as 2 mM, the survival rate of 3 T3 cells was still 78.23%, proving that the probe has good safety characteristics. Fluorescence imaging results show that its maximum enrichment can be achieved at the tumor site after tail vein injection for 3 h, and out of the body after 24 h, indicating good internal circulation. The in vivo studies show that the rate of inhibition of tumor using the nanocarrier was as high as 98%, and almost overcame the problem of tumor recurrence caused by single treatment, thus presenting a significant tumor treatment effect. This new multifunctional nanocarrier with self-catalytic production of NO provides a new idea for the efficient treatment of tumors.

Antimicrobial activity of silver sulfide quantum dots functionalized with highly conjugated Schiff bases in a one-step synthesis

In the present paper, low-dimensional Ag2S QDs were fabricated for the first time, with four different dithiocarbazate derivative Schiff bases (SB) as capping agents in a one-pot synthesis. These SB-capped Ag2S QDs were almost spherical with an average size range of 4.0 to 5.6 nm, which is slightly smaller than conventional thioglycolic acid (TGA)-capped Ag2S QDs. We demonstrate that the growth of Gram-positive bacteria (Bacillus subtillus and Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and a prevalent fungal pathogen (Candida albicans) are inhibited more when the bacterial and fungal cells were nurtured with the synthesized SB-Ag2S QDs, compared with TGA-Ag2S QDs or free unbound Schiff bases. The minimum inhibitory concentration (MIC) results confirmed that even low concentrations of SB-Ag2S QDs were able to inhibit bacterial (MIC 5-75 μg mL-1) and fungal growth (MIC 80-310 μg mL-1), and in some cases they performed better than streptomycin (8-25 μg mL-1). Lethality bioassay results confirmed that SB-Ag2S QDs were not toxic to brine shrimp (Artemia salina). The results show that capping agents are essential in the design of functional Ag2S QDs, and highlight that Schiff bases provide an excellent opportunity to optimize the biological activities of silver based QDs.

Synthesis, Properties and Bioimaging Applications of Silver-Based Quantum Dots

Ag-based quantum dots (QDs) are semiconductor nanomaterials with exclusive electrooptical properties ideally adaptable for various biotechnological, chemical, and medical applications. Silver-based semiconductor nanocrystals have developed rapidly over the past decades. They have become a promising luminescent functional material for in vivo and in vitro fluorescent studies due to their ability to emit at the near-infrared (NIR) wavelength. In this review, we discuss the basic features of Ag-based QDs, the current status of classic (chemical) and novel methods ("green" synthesis) used to produce these QDs. Additionally, the advantages of using such organisms as bacteria, actinomycetes, fungi, algae, and plants for silver-based QDs biosynthesis have been discussed. The application of silver-based QDs as fluorophores for bioimaging application due to their fluorescence intensity, high quantum yield, fluorescent stability, and resistance to photobleaching has also been reviewed.

Sustainability consolidation via employment of biomimetic ecomaterials with an accentuated photo-catalytic potential: emerging progressions

Environmental pollution produced due to direct and untreated release of toxic organic pollutants such as dyes from the textile industries is not only effect the human life but also contaminates the ecosystem through different transferal modes. Green nanomaterials synthesized by using biological reducing agents offer sustainable, economically viable, facile, rapid and eco-friendly approach with photocatalytic degradation efficiencies >90% for organic dyes over the other traditional technologies. Current review has for the first time comprehensively abridged the suitability of green nanoparticles over chemogenic nanoparticles, the remediative role of these biogenic nanoparticles with major emphasis on the recent progressions in the photocatalysis of different toxic dyes and pollutants. Unlike physicochemically processed nanoparticles, biogenic nanoparticles has profound contribution to the sustainable development goals due to their cleaner and economical synthesis in addition to their detoxifying role. Meticulous review of the publications are strongly suggestive of the adoptability of biogenic nanoparticles at an implementation scale for their auspicious remediative role in addition to facile fabrication, natural reducing agents based synthetic mode, toxicity free and sustainable nature. However, the studies are also indicative of the need for utilization of biogenic synthesis at practical scale to derive maximum sustainability and ecological benefits.

A Comparative Study on Physicochemical, Photocatalytic, and Biological Properties of Silver Nanoparticles Formed Using Extracts of Different Parts of Cudrania tricuspidata

Green-synthesized silver nanoparticles (SNPs) have great potential for biomedical applications, due to their distinctive optical, chemical, and catalytic properties. In this study, we aimed to develop green-synthesized SNPs from extracts of Cudrania tricuspidata (CT) roots (CTR), stems (CTS), leaves (CTL), and fruit (CTF) and to evaluate their physicochemical, photocatalytic, and biological properties. CTR, CTS, CTL, and CTF extracts were evaluated and compared for their total phenol and flavonoid content, reducing capacity, and antioxidant activity. The results revealed that CTR, CTS, CTL, and CTF extracts have high phenol and flavonoid content, as well as a powerful antioxidant and reducing capacity. CTR and CTS extracts showed the strongest effects. The results from UV-Vis spectra analysis, dynamic light scattering, high-resolution transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy showed the successful formation of CT-SNPs with surface morphology, crystallinity, reduction capacity, capsulation, and stabilization. Synthesized CT-SNPs successfully photocatalyzed methylene blue, methyl orange, rhodamine B, and Reactive Black 5 within 20 min. The CTR- and CTS-SNPs showed better antibacterial properties against different pathogenic microbes (Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Salmonella enteritidis) than the CTL- and CTF-SNPs. CTS- and CTR-SNPs showed the most effective cytotoxicity and antiapoptosis properties in human hepatocellular carcinoma cells (HepG2 and SK-Hep-1). CT-SNPs also seemed to be more biologically active than the CT extracts. The results of this study provide evidence of the establishment of CT extract SNPs and their physicochemical, photocatalytic, and biological properties.

Recent Advances in Metal Decorated Nanomaterials and Their Various Biological Applications: A Review

Nanoparticles (nanoparticles) have received much attention in biological application because of their unique physicochemical properties. The metal- and metal oxide-supported nanomaterials have shown significant therapeutic effect in medical science. The mechanisms related to the interaction of nanoparticles with animal and plant cells can be used to establish its significant role and to improve their activity in health and medical applications. Various attempts have been made to discuss the antibiotic resistance and antimicrobial activity of metal-supported nanoparticles. Despite all these developments, there is still a need to investigate their performance to overcome modern challenges. In this regard, the present review examines the role of various types of metal-supported nanomaterials in different areas such as antibacterial, antifungal, anticancer, and so on. Based on the significant ongoing research and applications, it is expected that metal-supported nanomaterials play an outstanding role not only in medical but also in other important areas.

New avenues of controlling microbial infections through anti-microbial and anti-biofilm potentials of green mono-and multi-metallic nanoparticles: A review

Nanoparticles synthesized through the green route deserve special mention because this green technology is not only energy-efficient and cost-effective but also amenable to the environment. Various biological resources have been used for the generation of these 'green nanoparticles'. Biological wastes have also been focused in this direction thereby promoting the value of waste. Reports indicate that green nanoparticles exhibit remarkable antimicrobial activitiesboth singly as well as in combination with standard antibiotics. The current phenomenon of multi-drug resistance has resulted due to indiscriminate administration of high-doses of antibiotics followed by significant toxicity. In the face of this emergence of drug-resistant microbesthe efficacy of green nanoparticles might prove greatly beneficial. Microbial biofilm is another hurdle in the effective treatment of diseases as the microorganismsbeing embedded in the meshwork of the biofilmevade the antimicrobial agents. Nanoparticles may act as a ray of hope on the face of this challenge tooas they not only destroy the biofilms but also lessen the doses of antibiotics requiredwhen administered in combination with the nanoparticles. It should be further noted that the resistance mechanisms exhibited by the microorganisms seem not that relevant for nanoparticles. The current review, to the best of our knowledgefocuses on the structures of these green nanoparticles along with their biomedical potentials. It is interesting to note how a variety of structures are generated by using resources like microbes or plants or plant products and how the structure affects their activities. This study might pave the way for further development in this arena and future work may be taken up in identifying the detailed mechanism by which 'green' synthesis empowers nanoparticles to kill pathogenic microbes.

Tree gum-based renewable materials: Sustainable applications in nanotechnology, biomedical and environmental fields

The prospective uses of tree gum polysaccharides and their nanostructures in various aspects of food, water, energy, biotechnology, environment and medicine industries, have garnered a great deal of attention recently. In addition to extensive applications of tree gums in food, there are substantial non-food applications of these commercial gums, which have gained widespread attention due to their availability, structural diversity and remarkable properties as 'green' bio-based renewable materials. Tree gums are obtainable as natural polysaccharides from various tree genera possessing exceptional properties, including their renewable, biocompatible, biodegradable, and non-toxic nature and their ability to undergo easy chemical modifications. This review focuses on non-food applications of several important commercially available gums (arabic, karaya, tragacanth, ghatti and kondagogu) for the greener synthesis and stabilization of metal/metal oxide NPs, production of electrospun fibers, environmental bioremediation, bio-catalysis, biosensors, coordination complexes of metal-hydrogels, and for antimicrobial and biomedical applications. Furthermore, polysaccharides acquired from botanical, seaweed, animal, and microbial origins are briefly compared with the characteristics of tree gum exudates.

Photo-reduction of heavy metal ions and photo-disinfection of pathogenic bacteria under simulated solar light using photosensitized TiO2 nanofibers

We report the photosensitization of electrospun titania nanofibers, with a mean diameter of 195 nm, by low bandgap silver sulfide nanoparticles of 11-23 nm mean size with the aim of treating heavy metal ions and pathogenic bacteria simultaneously under simulated solar light irradiation. The 17 nm Ag2S/TiO2 nanofibers showed 90% photocatalytic reduction of Cr(vi) at pH of 3 with a pseudo-first order rate constant of 0.016 min-1 which is significantly better than the previously reported for Ag-Ag2S/TiO2 composite particles. The antibacterial capability of the Ag2S/TiO2 nanofibers was evaluated via photo-disinfection of the Gram-positive and Gram-negative bacterial strains. The smallest sized 11 nm Ag2S/TiO2 nanofiber showed the best bactericidal efficiency of 100% and 90.6% against Gram-negative E. coli and Gram-positive S. aureus after 1 h of irradiation, respectively, whereas, only 50% E. coli and 41% S. aureus were found to be inactivated in dark. Furthermore, a UV-O3 treatment of the 11 nm Ag2S/TiO2 nanofibers remarkably enhanced the antibacterial activity where 89% E. coli and 81% S. aureus were inactivated in just 10 min of the irradiation. Enhanced photocatalytic activity is attributed to the efficient charge separation and transfer and reduced electron-hole recombination induced by the effective heterojunction formation between TiO2 and the optimally sized Ag2S nanoparticles. The disinfection nature of the Ag2S nanoparticles, role of the generated hydroxyl species under irradiation, and the cell wall damage mechanism is also discussed. This study demonstrates the potential use of these multifunctional composite TiO2 nanofibers for water remediation.

Nanostructured silver sulfide: synthesis of various forms and their application

The results of experimental studies on nanostructured silver sulfide are analyzed and generalized. The influence of small particle size on nonstoichiometry of silver sulfide is discussed. Methods for the synthesis of various forms of nanostructured Ag2S including nanopowders, stable colloidal solutions, quantum dots, core – shell nanoparticles and heteronanostructures are described. The advantages and drawbacks of different synthetic procedures are analyzed. Main fields of application of nanostructured silver sulfide are considered.

The bibliography includes 184 references.

Ternary semiconductor ZnxAg1−xS nanocomposites for efficient photocatalytic degradation of organophosphorus pesticides

Some approaches have been carried out for the degradation of organophosphorus pesticides using simple metal oxide nanostructures. This paper reports a comparison of the photocatalytic activity of ZnS and Ag₂S with that of ternary semiconductor Zn_0.5Ag_0.5S nanocomposites without any surfactant for the degradation of the pesticides MLT, MCP, and CPS under UV light for environmental safety.

Photocatalytic degradation of synthetic food dye, sunset yellow FCF (FD&C yellow no. 6) by Ailanthus excelsa Roxb. possessing antioxidant and cytotoxic activity

The purpose of our work is to identify the bioactive compounds of bark and leaves extract from Ailanthus excelsa Roxb. and to explore its effectiveness against synthetic food dye. The presence of primary and secondary metabolites was confirmed by carrying out phytochemicals analysis. With the prior knowledge accessible on the indispensable secondary metabolites holding antioxidant and cytotoxicity activity, the quantitative screening of total phenolic and flavonoid content in methanolic and aqueous extract of bark and leaves from Ailanthus excelsa were done. Comparatively, a higher value of flavonoid (161±0.3μg/mg) and phenolic acid content (152.4±0.14μg/mg) was found in bark extract. By FTIR analysis, the characteristic peak was obtained at 1581.63 and 1598.99cm^-1 confirmed the presence of functional groups associated to flavonoids and other phenolic groups respectively. In bark extract, 81% of DPPH inhibition was observed when compared to ascorbic acid (standard) 92% of free radical scavenging activity. Bark extract from Ailanthus excelsa exhibited 71% cytotoxicity against HeLa cell line (cervical cancer). In examining the toxicity level of crude extracts with red blood cells (RBC), the bark extract was showed a very less (2.8%) haemolytic activity. They also showed maximum zone of inhibition in antibacterial activity i.e. 13±0.5mm against Escherichia coli culture. At a concentration of 10mg/mL of crude extract from A. excelsa, 55% degradation of sunset yellow dye was observed. It concludes that, the compounds present in the A. excelsa, especially the bark extract showed better photocatalytic, haemolytic, antioxidant, cytotoxicity and antibacterial activity when compared to leaves extract.

Nanomaterials made of non-toxic metallic sulfides: A systematic review of their potential biomedical applications

Metallic sulfides involve the chemical bonding of one or more sulfur atoms to a metal. Metallic sulfides are cheap, abundant semiconductor materials that can be used for several applications. However, an important and emerging use for non-toxic metallic sulfides in biomedical applications has arisen quickly in the medical field. In this systematic review, the available data from electronic databases were collected according to PRISMA alignments for systematic reviews. This review shows that these metallic sulfides could be promising for biomedical uses and applications. This systematic review is focused primarily on the following compounds: silver sulfide, copper sulfide, and iron sulfide. The aim of this review was to provide a quick reference on synthesis methods, biocompatibility, recent advances and perspectives, with remarks on future improvements. The toxicity of metallic sulfides depends directly on the cytotoxicity of their interactions with cells and tissues. Metallic sulfides have potential biomedical applications due to their antibacterial properties, uses in imaging and diagnostics, therapies such as photothermal therapy and chemotherapy in tumors and cancer cells, drug delivery and the fabrication of biosensors for the sensitive and selective detection of moieties, among others. Although current evidence about metallic sulfide NPs is promising, there are still several issues to be addressed before these NPs can be used in biomedicine. The current review is a brief but significant guide to metallic sulfides and their potential uses in the biomedical field.

Photobiologic-mediated fabrication of silver nanoparticles with antibacterial activity

We present the simple, eco-friendly synthesis of silver nanoparticles (AgNPs) using sunlight or green, red, blue, or white LED light together with Dryopteris crassirhizoma rhizome extract (DCRE) as the reducing and capping agent. The preliminary indication of AgNP production was a color change from yellowish green to brown after light exposure in the presence of DCRE. Optimization of parameters such as pH, inoculum dose, and metal ion concentration played an important role in achieving nanoparticle production in 30min. The spectroscopic and morphological properties of AgNPs were characterized using UV-Vis spectroscopy through the presence of a characteristic surface plasmon resonance (SPR) band for AgNPs, Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). The FT-IR results indicated that the phytochemical present in DCRE was the probable reducing/capping agent involved in the synthesis of AgNPs, and light radiation enhanced nanoparticle production. HR-TEM revealed that the AgNPs were almost spherical with an average size of 5-60nm under all light sources. XRD studies confirmed the face cubic center (fcc) unit cell structure of AgNPs. The synthesized AgNPs showed good antimicrobial activity against Bacillus cereus and Pseudomonas aeruginosa. This study will bring a new insight in ecofriendly production of metal nanoparticles.