Promising performance of chemically exfoliated Zr-doped MoS2 nanosheets for catalytic and antibacterial applications

Emerging trends and future challenges of advanced 2D nanomaterials for combating bacterial resistance

The number of multi-drug-resistant bacteria has increased over the last few decades, which has caused a detrimental impact on public health worldwide. In resolving antibiotic resistance development among different bacterial communities, new antimicrobial agents and nanoparticle-based strategies need to be designed foreseeing the slow discovery of new functioning antibiotics. Advanced research studies have revealed the significant disinfection potential of two-dimensional nanomaterials (2D NMs) to be severed as effective antibacterial agents due to their unique physicochemical properties. This review covers the current research progress of 2D NMs-based antibacterial strategies based on an inclusive explanation of 2D NMs' impact as antibacterial agents, including a detailed introduction to each possible well-known antibacterial mechanism. The impact of the physicochemical properties of 2D NMs on their antibacterial activities has been deliberated while explaining the toxic effects of 2D NMs and discussing their biomedical significance, dysbiosis, and cellular nanotoxicity. Adding to the challenges, we also discussed the major issues regarding the current quality and availability of nanotoxicity data. However, smart advancements are required to fabricate biocompatible 2D antibacterial NMs and exploit their potential to combat bacterial resistance clinically.

Tailoring functional two-dimensional nanohybrids: A comprehensive approach for enhancing photocatalytic remediation

Photocatalysis is gaining prominence as a viable alternative to conventional biohazard treatment technologies. Two-dimensional (2D) nanomaterials have become crucial for fabricating novel photocatalysts due to their nanosheet architectures, large surface areas, and remarkable physicochemical properties. Furthermore, a variety of applications are possible with 2D nanomaterials, either in combination with other functional nanoparticles or by utilizing their inherent properties. Henceforth, the review commences its exploration into the synthesis of these materials, delving into their inherent properties and assessing their biocompatibility. Subsequently, an overview of mechanisms involved in the photocatalytic degradation of pollutants and the processes related to antimicrobial action is presented. As an integral part of our review, we conduct a systematic analysis of existing challenges and various types of 2D nanohybrid materials tailored for applications in the photocatalytic degradation of contaminants and the inactivation of pathogens through photocatalysis. This investigation will aid to contribute to the formulation of decision-making criteria and design principles for the next generation of 2D nanohybrid materials. Additionally, it is crucial to emphasize that further research is imperative for advancing our understanding of 2D nanohybrid materials.

Role of transition metals in coinage metal nanoclusters for the remediation of toxic dyes in aqueous systems

A difficult issue in chemistry and materials science is to create metal compounds with well-defined components. Metal nanoclusters, particularly those of coinage groups (Cu, Ag, and Au), have received considerable research interest in recent years owing to the availability of atomic-level precision via joint experimental and theoretical methods, thus revealing the mechanisms in diverse nano-catalysts and functional materials. The textile sector significantly contributes to wastewater containing pollutants such as dyes and chemical substances. Textile and fabric manufacturing account for about 7 × 105 tons of wastewater annually. Approximately one thousand tons of dyes used in textile processing and finishing has been recorded as being discharged into natural streams and water bodies. Owing to the widespread environmental concerns, research has been conducted to develop absorbents that are capable of removing contaminants and heavy metals from water bodies using low-cost technology. Considering this idea, we reviewed coinage metal nanoclusters for azo and cationic dye degradation. Fluorometric and colorimetric techniques are used for dye degradation using coinage metal nanoclusters. Few reports are available on dye degradation using silver nanoclusters; and some of them are discussed in detailed herein to demonstrate the synergistic effect of gold and silver in dye degradation. Mostly, the Rhodamine B dye is degraded using coinage metals. Silver nanoclusters take less time for degradation than gold and copper nanoclusters. Mostly, H2O2 is used for degradation in gold nanoclusters. Still, all coinage metal nanoclusters have been used for the degradation due to suitable HOMO-LUMO gap, and the adsorption of a dye onto the surface of the catalyst results in the exchange of electrons and holes, which leads to the oxidation and reduction of the adsorbed dye molecule. Compared to other coinage metal nanoclusters, Ag/g-C3N4 nanoclusters displayed an excellent degradation rate constant with the dye Rhodamine B (0.0332 min-1). The behavior of doping transition metals in coinage metal nanoclusters is also reviewed herein. In addition, we discuss the mechanistic grounds for degradation, the fate of metal nanoclusters, anti-bacterial activity of nanoclusters, toxicity of dyes, and sensing of dyes.

Recent advances of modification effect in Co3O4-based catalyst towards highly efficient photocatalysis

Tricobalt tetroxide (Co3O4) has been developed as a promising photocatalyst material for various applications. Several reports have been published on the self-modification of Co3O4 to achieve optimal photocatalytic performance. The pristine Co3O4 alone is inadequate for photocatalysis due to the rapid recombination process of photogenerated (PG) charge carriers. The modification of Co3O4 can be extended through the introduction of doping elements, incorporation of supporting materials, surface functionalization, metal loading, and combination with other photocatalysts. The addition of doping elements and support materials may enhance the photocatalysis process, although these modifications have a slight effect on decreasing the recombination process of PG charge carriers. On the other hand, combining Co3O4 with other semiconductors results in a different PG charge carrier mechanism, leading to a decrease in the recombination process and an increase in photocatalytic activity. Therefore, this work discusses recent modifications of Co3O4 and their effects on its photocatalytic performance. Additionally, the modification effects, such as enhanced surface area, generation of oxygen vacancies, tuning the band gap, and formation of heterojunctions, are reviewed to demonstrate the feasibility of separating PG charge carriers. Finally, the formation and mechanism of these modification effects are also reviewed based on theoretical and experimental approaches to validate their formation and the transfer process of charge carriers.

Using biologically synthesized TiO2 nanoparticles as potential remedy against multiple drug resistant Staphylococcus aureus of bovine mastitis

Presently, there is considerable emphasis on biological synthesis of nanoparticles containing bioactive reducing compounds with an aim to mitigate the harmful effects of pollutants. The approach under study is simple and ideal for the production of durable antimicrobial nanomaterials by novel single-step green synthesis of TiO2 metal oxide nanostructures using ginger and garlic crude aqueous extracts with bactericidal and catalytic activity. A variety of experimental techniques were used to characterize the synthesized nanomaterials. As demonstrated using x-ray diffraction and ultra-violet visible spectroscopy, the produced nanoparticles exhibited high absorption at 318 nm with size varying between 23.38 nm for ginger and 58.64 nm for garlic in biologically-reduced TiO2. At increasing concentrations (500, 1000 µg/50 µl), nanoparticles reduced with garlic exhibited enhanced bactericidal efficacy against multiple drug-resistant S. aureus and effectively decomposed toxic methylene blue (MB) dye. In conclusion, biologically-reduced TiO2 nanoparticles may prove an effective tool in the fight against microbial illnesses and drug resistance.

Antimicrobial and anti-viral effects of selenium nanoparticles and selenoprotein based strategies: COVID-19 and beyond

Deficiency of selenium (Se) has been described in a significant number of COVID-19 patients having a higher incidence of mortality, which makes it a pertinent issue to be addressed clinically for effective management of the COVID-19 pandemic. Se nanoparticles (SeNPs) provide a unique option for managing the havoc caused by the COVID-19 pandemic. SeNPs possess promising anti-inflammatory and anti-fibrotic effects by virtue of their nuclear factor kappa-light-chain-stimulator of activated B cells (NFκB), mitogen-activated protein kinase (MAPKs), and transforming growth factor-beta (TGF-β) modulatory activity. In addition, SeNPs possess remarkable immunomodulatory effects, making them a suitable option for supplementation with a much lower risk of toxicity compared to their elemental counterpart. Further, SeNPs have been shown to curtail viral and microbial infections, thus, making it a novel means to halt viral growth. In addition, it can be administered in the form of aerosol spray, direct injection, or infused thin-film transdermal patches to reduce the spread of this highly contagious viral infection. Moreover, a considerable decrease in the expression of selenoprotein along with enhanced expression of IL-6 in COVID-19 suggests a potential association among selenoprotein expression and COVID-19. In this review, we highlight the unique antimicrobial and antiviral properties of SeNPs and the immunomodulatory potential of selenoproteins. We provide the rationale behind their potentially interesting properties and further exploration in the context of microbial and viral infections. Further, the importance of selenoproteins and their role in maintaining a successful immune response along with their association to Se status is summarized.

Acid protease functionalized novel silver nanoparticles (APTs-AgNPs): A new approach towards photocatalytic and biological applications

Herein, we described for the first time, an efficient biogenic synthesis of APTs-AgNPs using acid protease from Melilotus indicus leaf extract. The acid protease (APTs) has an essential role in the stabilization, reduction, and capping of APTs-AgNPs. The crystalline nature, size, and surface morphology of APTs-AgNPs were examined using different techniques such as XRD, UV, FTIR, SEM, EDS, HRTEM, and DLS analysis. The generated APTs-AgNPs demonstrated notable performance as dual functionality (photocatalyst and antibacterial disinfection). By destroying 91 % of methylene blue (MB) in <90 min of exposure, APTs-AgNPs demonstrated remarkable photocatalytic activity. APTs-AgNPs also showed remarkable stability as a photocatalyst after five test cycles. Furthermore, the APTs-AgNPs was found to be a potent antibacterial agent with inhibition zones of 30(±0.5 mm), 27(±0.4 mm), 16(±0.1 mm), and 19(±0.7 mm) against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, respectively, under both light and dark conditions. Furthermore, APTs-AgNPs effectively scavenged 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, demonstrating their potent antioxidant activity. The outcomes of this study thus demonstrates the dual functionality of APTs-AgNPs produced using the biogenic approach method as a photocatalyst and an antibacterial agent for effective microbial and environmental control.

Electronic sensitization enhanced p-type ammonia gas sensing of zinc doped MoS2/RGO composites

Zinc (Zn) doping induced synergetic effects of defects engineering and heterojunction in Molybdenum disulphide/Reduced graphene oxide (MoS₂/RGO) effectively enhances the p-type Volatile organic compounds (VOC) gas sensing traits and helps in tailoring the over dependence on noble metals for surface sensitization. Through this work, we have successfully prepared Zn doped MoS₂ grafted on RGO employing an in-situ hydrothermal method. Optimal doping concentration of Zn dopants in the MoS₂ lattice triggered more active sites on the basal plane of MoS₂ with the aid of defects promoted by the zinc dopants. Effective intercalation of RGO further boost up the exposed surface area of Zn doped MoS₂ for further interaction of ammonia gas molecules. Besides, smaller crystallite size brought out by 5% Zn dopants aids in efficient charge transfer across the heterojunctions that further amplifies the ammonia sensing traits with a peak response of 32.40% along with a response time of 21.3 s and recovery time of 44.90 s. The as prepared ammonia gas sensor exhibited excellent selectivity and repeatability. The obtained results reveal that transition metal doping into the host lattice proves to be a promising approach for VOC sensing characteristics of p-type gas sensors and gives insight about the importance of dopants and defects for the development of highly efficient gas sensors in the future.

Experimental and theoretical study of catalytic dye degradation and bactericidal potential of multiple phase Bi and MoS2 doped SnO2 quantum dots†

In the present study, different concentrations (1 and 3%) of Bi were incorporated into a fixed amount of molybdenum disulfide (MoS₂) and SnO₂ quantum dots (QDs) by co-precipitation technique. This research aimed to increase the efficacy of dye degradation and bactericidal behavior of SnO₂. The high recombination rate of SnO₂ can be decreased upon doping with two-dimensional materials (MoS₂ nanosheets) and Bi metal. These binary dopants-based SnO₂ showed a significant role in methylene blue (MB) dye degradation in various pH media and antimicrobial potential as more active sites are provided by nanostructured MoS₂ and Bi³⁺ is responsible for producing a variety of different oxygen vacancies within SnO₂. The prepared QDs were described via morphology, optical characteristics, elemental composition, functional group, phase formation, crystallinity, and d-spacing. In contrast, antimicrobial activity was checked at high and low dosages against Escherichia coli (E. coli) and the inhibition zone was calculated utilizing a Vernier caliper. Furthermore, prepared samples have expressed substantial antimicrobial effects against E. coli. To further explore the interactions between the MB and Bi/MoS₂–SnO₂ composite, we modeled and calculated the MB adsorption using density functional theory and the Heyd–Scuseria–Ernzerhof hybrid (HSE06) approach. There is a relatively strong interaction between the MB molecule and Bi/MoS₂–SnO₂ composite.

In the present study, different concentrations (1 and 3%) of Bi were incorporated into a fixed amount of molybdenum disulfide and SnO₂ quantum dots by co-precipitation technique. This research aimed to increase the efficacy of dye degradation and bactericidal behavior of SnO₂.

Facile Synthesis of Barium-Doped Cadmium Sulfide Quantum Dots for the Treatment of Polluted Water: Experimental and Computational Investigations

In this study, cadmium sulfide (CdS) quantum dots (QDs) and barium (Ba) (3 and 6 wt %)-doped CdS QDs were synthesized via a hydrothermal technique. The basic purpose of this work is to degrade methylene blue (MB) dye and evaluate density functional theory (DFT). The synthesized samples were characterized through X-ray powder diffraction (XRD), selected area electron diffraction (SAED), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HR-TEM), UV-vis spectrophotometer, PL, and density functional theory (DFT). The XRD (structural analysis) confirmed that the hexagonal crystal structure and crystallinity increased upon doping. Selected area electron diffraction (SAED) analysis confirmed the polycrystalline nature of the prepared QDs. The functional groups have been investigated using FTIR analysis. The surface and structural morphologies of the synthesized specimen have been investigated by applying TEM and FE-SEM, and it was found to exhibit the topology of QDs. In addition, optical characteristics have been investigated via UV-vis absorption spectroscopy, which exhibited a bathochromic shift (red shift) as a consequence of the reduction of the band-gap energy upon doping from 2.56 to 2.38 eV. PL analysis was used to observe the electron-hole recombination rate. Moreover, the electronic and optical properties of Ba-doped CdS were further explored using density functional theory. Pristine and Ba-doped QDs exhibit sufficient catalytic activity (CA) against the MB dye in all media as 62.59, 70.15, and 72.74% in neutral, basic, and acidic solutions, respectively.

Photocatalytic and antibacterial activity of graphene oxide/cellulose-doped TiO2 quantum dots: in silico molecular docking studies

Graphene oxide (GO) and cellulose nanocrystal (CNC)-doped TiO₂ quantum dots (QDs) were effectively synthesized by employing the co-precipitation method for the degradation of dyes and antimicrobial applications. A series of characterizations, i.e., XRD, FTIR, UV-visible spectroscopy, EDS, FE-SEM, and HR-TEM, was used to characterize the prepared samples. A reduction in PL intensity was observed, while the band gap energy (E _g) decreased from 3.22 to 2.96 eV upon the incorporation of GO/CNC in TiO₂. In the Raman spectra, the D and G bands were detected, indicating the presence of graphene oxide in the composites. Upon doping, the crystallinity of TiO₂ increased. HR-TEM was employed to estimate the interlayer d-spacing of the nanocomposites, which matched well with the XRD data. The photocatalytic potential of the prepared samples was tested against methylene blue, methylene violet, and ciprofloxacin (MB:MV:CF) when exposed to visible light for a certain period. The antibacterial activity of GO/CNC/TiO₂ QDs against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria in vitro was tested to determine their potential for medicinal applications. The molecular docking investigations of CNC-TiO₂ and GO/CNC-doped TiO₂ against DNA gyrase and FabI from E. coli and S. aureus were found to be consistent with the results of the in vitro bactericidal activity test. We believe that the prepared nanocomposites will be highly efficient for wastewater treatment and antimicrobial activities.

Synthesis of ZrO2:Dy3+ Nanoparticles: Photoluminescent, Photocatalytic, and Electrochemical Sensor Studies

Solution combustion was employed to create a series of ZrO2:Dy3+ (1-11 mol percent) nanoparticles (NPs) using oxalyl dihydrazide (ODH) as the fuel. ZrO2:Dy3+ NPs were subjected to calcination at about 700°C. ZrO2:Dy3+ NPs comprised of 1 to 11 mol% of Dy3+ were characterized by employing the X-ray diffraction (XRD), transmission electron microscopic (TEM), UV-visible, and X-ray photoelectron spectroscopic (XPS) techniques. The crystallite diameters of 1 to 11 mol% ZrO2:Dy3+ NPs were observed to range from 8.1 nm to 16.3 nm, exhibiting spherical shape. According to BET tests, the pore volume of ZrO2:Dy3+ NPs was determined to be 100.129 cm3/g. The mean pore diameter of ZrO2:Dy3+ NPs was determined to be 4.803 nm from the Barrett-Joyner-Halenda (BJH) plot. The photoluminescence and photocatalytic dye degradation properties of ZrO2:Dy3+ NPs were investigated. The acid red 88 (AR88) dye was applied to appraise the photocatalytic activities of the NPs under UV irradiation. ZrO2:Dy3+ NPs with 3 mol% Dy3+ exhibited improvised photocatalytic activity due to the operative departure of charge carriers. The electrochemical examination of ZrO2:Dy3+ NP modified carbon paste electrode in 0.1 N HCl demonstrated considerable redox potential output, as evidenced by cyclic voltammetric and amperometric measurements. The electrochemical sensor studies on ZrO2:Dy3+ NPs exhibited potentiality towards sensing of highly toxic metals like mercury and lead.

Enhanced Photocatalytic Degradation with Sustainable CaO Nanorods Doped with Ce and Cellulose Nanocrystals: In Silico Molecular Docking Studies

This research work intends to evaluate the photoactivity of calcium oxide (CaO) nanorods (NRs) doped with cellulose nanocrystals (CNCs) and cerium (Ce). CNC-doped CaO and Ce/CNC codoped CaO were synthesized via the sol-gel technique. Structural, optical, morphological, physiochemical, phase constitution, and functional group evaluations were performed. The photodegradation of the prepared nanostructures was analyzed by observing photodegradation of a mixture of methylene blue and ciprofloxacin dye under light irradiation. The photocatalytic activity of the dye was drastically enhanced upon codoping in CaO. For both Escherichia coli and Staphylococcus aureus, statistically significant inhibitory zones (p < 0.05) were achieved in the case of CNCs and pristine and codoped CaO. Furthermore, in silico molecular docking studies (MDS) were accomplished against DNA gyrase from nucleic acid biosynthesis and enoyl-[acyl-carrier-protein] reductase (FabI) from the fatty acid biosynthetic pathway to rationalize the possible mechanism behind these antibacterial activities.

Enhanced Bactericidal Action of rGO-ZnO Hybrids Prepared by the One-Pot Co-precipitation Approach

Metal-based antimicrobials have the potential to profile sustainable solutions to infection care and health. In this study, we report the synthesis of rGO-ZnO hybrid nanostructures by a simple co-precipitation approach with various mass ratios of GO, and their antimicrobial potential was assessed. The structural analysis confirms the presence of a hexagonal wurtzite structure with peak shifting in hybrid nanostructures and increases in crystallite size (11-24 nm). Raman spectra revealed GO doping in the D band (1350 cm^-1) and G band (1590 cm^-1). Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were performed to investigate the surface morphologies of the synthesized sediments, which showed a change in the morphology of ZnO from non-uniform spherical nanoparticles to a rod-like morphology of the prepared hybrid nanostructures. RAMAN spectra revealed that the retained functional groups on rGO planes were significant in anchoring ZnO to rGO. At lowest and maximum doses of ZnO, substantial bactericidal zones (p < 0.05) for S. aureus (1.55 and 1.95 mm) and E. coli (1.25 and 1.70 mm) were achieved accordingly. Additionally, the inhibition regions were 2.45-3.85 mm and 3.75-6.85 mm for S. aureus whereas (2.05-3.25 mm) and (2.95-3.90 mm) for E. coli at the lowest and maximum concentrations.

Dye degradation, antibacterial activity and molecular docking analysis of cellulose/polyvinylpyrrolidone-doped cadmium sulphide quantum dots

In present study, control sized cadmium sulphide (CdS) quantum dots (QDs) and cellulose nanocrystals grafted polyvinylpyrrolidone (CNC-g-PVP) doped CdS QDs were synthesized via co-precipitation. The suggested pathway is fruitful in throwing out organic pollutants like methylene blue (MB) from industrial water and bactericidal applications. A series of characterization techniques were used to determine the structural, optical and morphological qualities of prepared samples. The X-ray diffraction (XRD) pattern verified hexagonal structure with no significant change occurring in the spectrum upon doping (2, 4, and 6 %). The UV-vis spectrophotometer describes blueshift in absorption pattern, resulting in an increase in band gap energy (E_g) upon doping. Catalytic activity (CA) against MB in basic and neutral medium demonstrated remarkable results compared with the acidic medium. Furthermore, bactericidal potential of doped sample (6 %) exhibited the significantly higher inhibition zones of 5.25 mm and 4.05 mm against Staphylococcus aureus (S. aureus) or Gram-positive (G₊ve) and Escherichia coli (E. coli) or Gram-negative (G-ve), respectively. In silico predictions for these doped QDs were performed against selected enzyme targets (i.e. DNA gyrase and FabI) to unveil the mystery governing these bactericidal activities.

Highly Efficient Industrial Dye Degradation, Bactericidal Properties, and In Silico Molecular Docking Analysis of Ag/Cellulose-Doped CuO Nanostructures

In this research, CuO nanostructures doped with Ag and cellulose nanocrystals (CNC) were synthesized using a facile coprecipitation technique. In this work, we doped Ag into fixed quantities of CNC and CuO to improve the photocatalytic, catalytic, and antibacterial activity. It was noted that catalytic activity increased upon doping, which was attributed to the formation of nanorods and a pH effect, while the reverse trend was observed in photocatalytic activity. The addition of Ag and CNC dopants into CuO improved the bactericidal efficacy for S. aureus and E. coli. In addition, to obtain insight into the possible mechanism behind their biocidal effects, molecular docking studies were conducted against specific enzyme targets: namely, dihydrofolate reductase from E. coli and DNA gyrase from S. aureus. This study suggested that codoped CuO could be highly efficient in the cleaning of polluted water and antibacterial applications.

Cytotoxic and photocatalytic studies of hexagonal boron nitride nanotubes: a potential candidate for wastewater and air treatment

Boron nitride (BN) nanomaterials are rapidly being investigated for potential applications in biomedical sciences due to their exceptional physico-chemical characteristics. However, their safe use demands a thorough understanding of their possible environmental and toxicological effects. The cytotoxicity of boron nitride nanotubes (BNNTs) was explored to see if they could be used in living cell imaging. It was observed that the cytotoxicity of BNNTs is higher in cancer cells (65 and 80%) than in normal cell lines (40 and 60%) for 24 h and 48 h respectively. The influence of multiple experimental parameters such as pH, time, amount of catalyst, and initial dye concentration on percentage degradation efficiency was also examined for both catalyst and dye. The degradation effectiveness decreases (92 to 25%) as the original concentration of dye increases (5-50 ppm) due to a decrease in the availability of adsorption sites. Similarly, the degradation efficiency improves up to 90% as the concentration of catalyst increases (0.01-0.05 g) due to an increase in the adsorption sites. The influence of pH was also investigated, the highest degradation efficiency for MO dye was observed at pH 4. Our results show that lower concentrations of BNNTs can be employed in biomedical applications. Dye degradation properties of BNNTs suggest that it can be a potential candidate as a wastewater and air treatment material.

One-step high-yield preparation of nitrogen- and sulfur-codoped carbon dots with applications in chromium(vi) and ascorbic acid detection

In this research, a nitrogen- (N) and sulfur- (S) codoped carbon dot (CDs-IPM)-based sensor was synthesized using a single-step hydrothermal method. Specifically, microcrystalline cellulose (MCC) was the main raw material, which was extracted from banana pseudo-stem-based waste, while autonomous sulfonic acid-functionalized ionic liquid (SO₃H-IL) and polyethylene glycol 400 (PEG 400) acted as the N, S dopant, and surface modifier, respectively. Comprehensive spectroscopic characterization of the synthesized CDs-IPM revealed the introduction of S, N atoms in the matrix with existence of surface oxygenic functional groups. The CDs-IPM possessed enhanced photoluminescence (PL) intensity, synthetic yield, and PL quantum yield (PLQY). Additionally, electron transfer between the CDs-IPM, hexavalent chromium (Cr(vi)), and subsequent ascorbic acid (AA) succeeded in turning the fluorescence on and off. The detection limit was 17 nM for Cr(vi), while it was 103 nM for AA. Our study data can simplify the process of synthesis of CDs utilizing biodegradable starting materials. The probe reported in this study may serve as a valuable addition to the field of environment monitoring by virtue of its enhanced detection sensitivity, high selectivity, and stability.

A novel bio-based nitrogen- and sulfur-codoped carbon dot with enhanced synthetic yield and photoluminescence quantum yield for reversible detection of chromium (Cr)(vi) and ascorbic acid was fabricated by a one-pot hydrothermal method.

Copper Modified Titania Nanocomposites with a High Photocatalytic Inactivation of Escherichia coli

As everyone knows, bacterial infectious diseases are serious hazards to human health in the world. Despite performing many methods towards the bacterial pollution, containing many detection and sterilization techniques, there is still a lack of effective means. Herein, a novel copper modified titanium (Cu@TiO₂) nanocomposites were resoundingly synthesized via the well-known sol-gel process, which revealed a significant antibacterial activity under the illumination of sunlight. The XRD, Raman spectroscopy and TEM images showed that the Cu@TiO₂ nanocomposites with a globular shape are anatase phase, Moreover, low temperature physical adsorption test and UV- visible spectrum indicate Cu_0.01 @TiO₂ owns a supernal specific area (80 m²/g) and the high visible light absorbing ability. Furthermore, the novel Cu@TiO₂ nanocomposites showed an unprecedented photocatalytic capacity towards Escherichia Coli (E. coli) bacteria. In vitro, Cu@TiO₂ nanocomposites can kill almost 98.7% E. coli under 60 min simulated solar light irradiation than that of TiO ₂(31.3 %). This study suggests that the Cu@TiO₂ will be as a potential material for ameliorating antibiotic-resistant bacteria in food detection.

Low-dimensional nanomaterials for antibacterial applications

The excessive use of antibiotics has led to a rise in drug-resistant bacteria. These "superbugs" are continuously emerging and becoming increasingly harder to treat. As a result, new and effective treatment protocols that have minimal risks of generating drug-resistant bacteria are urgently required. Advanced nanomaterials are particularly promising due to their drug loading/releasing capabilities combined with their potential photodynamic/photothermal therapeutic properties. In this review, 0-dimensional, 1-dimensional, 2-dimensional, and 3-dimensional nanomaterial-based systems are comprehensively discussed for bacterial-based diagnostic and treatment applications. Since the use of these platforms as antibacterials is relatively new, this review will provide appropriate insight into their construction and applications. As such, we hope this review will inspire researchers to explore antibacterial-based nanomaterials with the aim of developing systems for clinical applications.

Nitrogen and Carbon Nitride-Doped TiO2 for Multiple Catalysis and Its Antimicrobial Activity

Nitrogen (N) and carbon nitride (C3N4)-doped TiO2 nanostructures were prepared using co-precipitation route. Fixed amount of N and various concentrations (0.1, 0.2, 0.3 wt%) of C3N4 were doped in TiO2 lattice. Through multiple techniques, structural, chemical, optical and morphological properties of samples were thoroughly investigated. XRD results verified anatase TiO2 presence along the substitutional doping of N, while higher degree of crystallinity as well as increased crystallite size were noticed after doping. HR-TEM study revealed formation of nanostructures incorporated on two dimensional (2D) C3N4 nanosheet surface. Elemental composition was checked out using EDS technique which confirmed the presence of dopant in product. Optical characteristics were evaluated with UV-vis spectroscopy which depicted representative redshift in absorption spectra resulted in a reduction in bandgap energy in N/C3N4-doped TiO2 samples. The formation of Ti-O-Ti bonds and different molecular vibrations were disclosed by FTIR. Trap sites and charge carrier's migration in the materials were evaluated with PL spectroscopy. Multiple catalytic activities (photo, sono and photo-sono) were undertaken to evaluate the dye degradation performance of prepared specimen against methylene blue and ciprofloxacin. Further, antimicrobial activity was analyzed against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria.

A review on bismuth oxyhalide based materials for photocatalysis

Photocatalytic solar energy transformation is the most encouraging solution to alleviate the environmental crisis and energy scarcity. Bismuth oxyhalide (BiOX) is an emerging class of materials that exhibits photocatalytic properties, such as resilient response to light, which causes enhanced energy conversion (solar energy) owing to their exceptional layered structure and attractive band structure. The present review presents a summary of results from the recent developments on the tuning and design of BiOX-based materials to improve the energy conversion. In particular, the preparation and tuning approaches that have the potential to enhance the photocatalytic behavior of BiOX and some other techniques, such as elemental doping, are addressed, which prevent the rapid recombination of charges, and formation of oxygen vacancies, facilitating an improvement in the photocatalytic reaction. Various frameworks are also presented, displaying the significance of BiOX-based nanocomposites. Finally, the main challenges and opportunities associated with the future progress of BiOX-based materials are presented. This review will provide an extended understanding and offer a preferred direction for the innovative design of BiOX-based materials for environmental and especially energy-based applications.

Cellular biogenesis of metal nanoparticles by water velvet (Azolla pinnata): different fates of the uptake Fe3+ and Ni2+ to transform into nanoparticles

Plants can produce cellular metal nanoparticles (NPs) from the uptake of metal ions, but the mechanism remains unclear. This work reported the new insight into different fates of iron (Fe) and nickel (Ni) ions to transform into the metal NPs in Azolla pinnata roots. After exposing to ferric nitrate, nickel nitrate, and a combination of both for 12 h, the energy dispersive X-ray fluorescence analysis indicated the efficient uptakes of both metal ions in the roots and their transports into the shoots. Transmission electron microscope images revealed the accumulation of spherical FeNPs, but not NiNPs, near the cell wall and cell membrane, and inside vacuoles and multivesicular bodies in cortical and vascular cells at the root tips. The energy dispersive X-ray analysis suggested that the formation of metal NPs depended on the sufficient concentration of metal ions localized in the roots. FeNPs were identified to ɑ-Fe₂O₃ and Fe₃O₄ by selected area electron diffraction analysis. The formation of FeNPs might involve the increase of superoxide dismutase activity. This work is the first report about the cellular biogenesis of metal NPs in plant roots that likely depends on cellular metal content and involves the reducing activity of antioxidant enzymes.

Metal/metal oxide nanocomposites for bactericidal effect: A review

Many microbial species causing infectious disease all over the world became a social burden and creating threat among community. These microbes possess long lifetime, enhancing mortality and morbidity rate in affected organisms. In this condition, the treatment was ineffective and more chances of spreading of infection into other organisms. Hence, it is necessary to initiate infection control efforts and prevention activities against multidrug resistant microbes, to reduce the death rate of people. Seriously concerning towards this problem progress was shown in developing significant drugs with least side effects. Emergence of nanoparticles and its novelty showed effective role in targeting and destructing microbes well. Further, many research works have shown nanocomposites developed from nanoparticles coupled with other nanoparticles, polymers, carbon material acted as an exotic substance against microbes causing severe loss. However, metal and metal oxide nanocomposites have gained interest due to its small size and enhancing the surface contact with bacteria, producing damage to it. The bactericidal mechanism of metal and metal oxide nanocomposites involve in the production of reactive oxygen species which includes superoxide radical anions, hydrogen peroxide anions and hydrogen peroxide which interact with the cell wall of bacteria causing damage to the cell membrane in turn inhibiting the further growth of cell with leakage of internal cellular components, leading to death of bacteria. This review provides the detailed view on antibacterial activity of metal and metal oxide nanocomposite which possessed novelty due to its physiochemical changes.

Impact of Bi Doping into Boron Nitride Nanosheets on Electronic and Optical Properties Using Theoretical Calculations and Experiments

In the present work, boron nitride (BN) nanosheets were prepared through bulk BN liquid phase exfoliation while various wt. ratios (2.5, 5, 7.5 and 10) of bismuth (Bi) were incorporated as dopant using hydrothermal technique. Our findings exhibit that the optical investigation showed absorption spectra in near UV region. Density functional theory calculations indicate that Bi doping has led to various modifications in the electronic structures of BN nanosheet by inducing new localized gap states around the Fermi level. It was found that bandgap energy decrease with the increase of Bi dopant concentrations. Therefore, in analysis of the calculated absorption spectra, a redshift has been observed in the absorption edges, which is consistent with the experimental observation. Additionally, host and Bi-doped BN nanosheets were assessed for their catalytic and antibacterial potential. Catalytic activity of doped free and doped BN nanosheets was evaluated by assessing their performance in dye reduction/degradation process. Bactericidal activity of Bi-doped BN nanosheets resulted in enhanced efficiency measured at 0-33.8% and 43.4-60% against S. aureus and 0-38.8% and 50.5-85.8% against E. coli, respectively. Furthermore, In silico molecular docking predictions were in good agreement with in-vitro bactericidal activity. Bi-doped BN nanosheets showed good binding score against DHFR of E. coli (- 11.971 kcal/mol) and S. aureus (- 8.526 kcal/mol) while binding score for DNA gyrase from E. coli (- 6.782 kcal/mol) and S. aureus (- 7.819 kcal/mol) suggested these selected enzymes as possible target.

Silver decorated 2D nanosheets of GO and MoS2serve as nanocatalyst for water treatment and antimicrobial applications as ascertained with molecular docking evaluation

In this work, synthesis of graphene oxide (GO) and reduced graphene oxide (rGO) was realized through a modified Hummers route. Different concentrations (5 and 10 wt%) of Ag were doped in MoS₂and rGO using a hydrothermal technique. Synthesized Ag-MoS₂and Ag-rGO were evaluated through XRD that confirmed the hexagonal structure of MoS₂along with the transformation of GO to Ag-rGO as indicated by a shift in XRD peaks while Mo-O bonding and S=O functional groups were confirmed with FTIR. Morphological information of GO and formation of MoS₂nanopetals as well as interlayer spacing were verified through FESEM and HRTEM respectively. Raman analysis was employed to probe any evidence regarding defect densities of GO. Optical properties of GO, MoS₂, Ag-rGO, and Ag-MoS₂were visualized through UV-vis and PL spectroscopy. Prepared products were employed as nanocatalysts to purify industrial wastewater. Experimental results revealed that Ag-rGO and Ag-MoS₂showed 99% and 80% response in photocatalytic activity. Besides, the nanocatalyst (Ag-MoS₂and Ag-rGO) exhibited 6.05 mm inhibition zones againstS. aureusgram positive (G+) and 3.05 mm forE. coligram negative (G-) in antibacterial activity. To rationalize biocidal mechanism of Ag-doped MoS₂NPs and Ag-rGO,in silicomolecular docking study was employed for two enzymes i.e.β-lactamase and D-alanine-D-alanine ligase B (ddlB) from cell wall biosynthetic pathway and enoyl-[acylcarrier-protein] reductase (FabI) from fatty acid biosynthetic pathway belonging toS. aureus. The present study provides evidence for the development of cost-effective, environment friendly and viable candidate for photocatalytic and antimicrobial applications.

Graphene‐based Materials for Fighting Coronavirus Disease 2019: Challenges and Opportunities

The coronavirus disease 2019 (COVID‐19) caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is considered as serious global threat of this time and greatest challenge for recent days. Several approaches have been carried out in this direction to fight against COVID‐19. Among these, nanotechnology is one of the promising approach to face these challenges in the current situation. Recently, graphene‐based nanomaterials have been explored for COVID‐19 due to its unique physicochemical properties. This mini review provides a recent progress in graphene‐based nanomaterials and its applications for diagnosis, detection, decontamination, and protection against COVID‐19. Further, main challenges and perspective for fundamental design and development of technologies based on graphene‐based materials are discussed and suitable directions to improve these technologies are suggested. This article will provide timely knowledge and future direction about this wonder materials in various biological applications.

Algae-mediated route to biogenic cuprous oxide nanoparticles and spindle-like CaCO3: a comparative study, facile synthesis, and biological properties

Biocompatible syntheses of Cu2O nanoparticles are relatively low compared to some other reported metal oxides due to their low stability and requiring more carefully controlled synthetic conditions. In the present study, the efficiency of three brown algae (Cystoseira myrica, Sargassum latifolium and Padina australis) extracts collected from the Persian Gulf was evaluated in the biosynthesis of Cu2O nanoparticles. A fast and simplified synthesis of Cu2O nanoparticles with average size between 12 and 26 nm was successfully achieved through an eco-friendly method using the aqueous extracts of Sargassum latifolium and Cystoseira myrica. Whereas, under the same reaction conditions using Padina australis extract no Cu2O nanoparticles were produced, and unexpectedly, the results approved the formation of spindle shaped CaCO3 with average sizes of 1-2 μm in length and 300-500 nm in width. Structure, morphology and composition of the as-prepared products were characterized by XRD, FT-IR, UV-vis, TEM and FESEM analysis. This work confirms that the biomolecules present in algae have the ability to affect particle size, morphology, composition, and physicochemical properties of the synthesized particles. The Cu2O nanoparticles prepared in this study were stable and exhibited efficient antibacterial and anticancer activity. This biosynthesis technique can be valuable in environmental, biotechnological, pharmaceutical and medical applications.

Symbiotic composite composed of MoS2 and pelagic clay with enhanced disinfection efficiency

Molybdenum disulfide (MoS2) has attracted increasing attention as a promising photocatalyst. In addition to its application in photocatalytic hydrogen production and pollutant degradation, MoS2 is also used in water disinfection. However, its poor disinfection performance limits its practical utility. Herein, we prepared a symbiotic composite composed of MoS2 and pelagic clay (MoS2/PC) as a photocatalyst for water disinfection. The composite achieved a high disinfection rate of 99.95% to Escherichia coli (E. coli) under visible light illumination, which is significantly higher than that of bulk MoS2 (61.87%). Characterization shows that abundant hydroxyl groups in illite/montmorillonite (I/M) formed during hydrothermal synthesis of MoS2, which contributed to the enhanced disinfection activity. Those hydroxyl groups can attract photogenerated holes through electrostatic attraction, and facilitate the separation of photogenerated charge carriers, thereby enhancing the disinfection activity. Moreover, the good hydrophilicity of pelagic clay improves the dispersity of MoS2 in water, which is beneficial for its utility in aqueous solutions. In addition, the symbiotic structure restricts the growth and aggregation of MoS2 nanosheets and shortens the diffusion distance of charge carriers to the material surface, further reducing the recombination of electrons and holes. This study provides a way to improve the disinfection activity of MoS2 and also sheds light on high value-added utilization of pelagic clay.

Synthesis of biocompatible chitosan functionalized Ag decorated biocomposite for effective antibacterial and anticancer activity

The transition-metal dichalcogenides (TMDCs) like MoS₂ and WS₂ are a new and interesting class of materials and show considerable promise for use in a wide variety of fields, including nanomedicine for cancer. The eco-friendly, biodegradability, toxicity, and antimicrobial activity remain an open issue. Herein, we focused on the current demands of two dimensional (2D) TMDCs and produced high-quality, few-layered MoS₂ nanosheets. Noble metal Ag incorporated into the 2D-CS/MoS₂ NC by the liquid exfoliated process. The manufactured CS/MoS₂/Ag hybrid NC showed excellent antibacterial activity against two microorganisms such as Gram-positive (21, 27, and 33 mm) and Gram-negative bacteria (23, 30, and 39 mm). The CS/MoS_2/Ag hybrid NC was designed to have significant antibacterial activity against E.coli bacteria than S.aureus. Furthermore, the hybrid NC has a 74.18% cell inhibition against MCF-7 cancer cells. According to the literature relevant, it is the first extensive experimental analysis on the nano-bio interaction of 2D TMDCs nanomaterials in MCF-7 breast cancer cells.

Liquid-phase exfoliated MoS2 nanosheets doped with p-type transition metals: a comparative analysis of photocatalytic and antimicrobial potential combined with density functional theory

MoS2 nanosheets were developed by undertaking the liquid-phase exfoliation of bulk counterparts. In order to enhance its photocatalytic properties, the host material was doped with p-type transition metals (i.e., Ag, Co, Bi, and Zr). The hydrothermal technique was used to produce samples doped with 7.5 wt% transition metals (TM). X-ray diffraction detected the existence of 2H-phase by mirroring its reflection at 2θ ∼ 14°, while the peak distribution revealed the degree of exfoliation in samples. Low PL intensities indicated a lower recombination of electron-hole pairs, as corroborated by a high degree of photocatalytic action. Raman analysis was undertaken to identify molecular vibrations. The A1g mode in Raman spectra consistently showed a blueshift in all samples and the E12g mode was only slightly affected, which is evidence of the p-type doping in the MoS2 nanosheets. In the XPS spectrum, two characteristic peaks of Mo 3d appeared at 229.87 and 233.03 eV assigned to Mo-3d5/2 and Mo-3d3/2, respectively. Furthermore, a microstructural examination with HR-TEM and FESEM divulged a thin-layered structure of MoS2 consisting of flat, gently curved or twisted nanosheets. Diverse morphologies were observed with a non-uniform distribution of the dopant. Photocatalytic action of the TM-doped products effectively degraded methylene blue (MB) concentrations of up to 94 percent (for Ag-MoS2). The synergistic effect of doped MoS2 nanosheets against S. aureus in comparison to E. coli bacteria was also evaluated. The efficacy % age improved from (0-31.7%) and (23.5-55.2%) against E. coli, and (0-34.2%) and (8.3-69.23%) against S. aureus. Moreover, results from first principles calculations indicate that substitutional doping of TM atoms is indeed advantageous. Theoretical calculations confirmed that doping with Ag, Co, Bi, and Zr leads to a decrease in the band gap to a certain degree, in which the conduction band edge shifts toward lower energy, while the valence band shifts closer to the high energy end. It can be concluded that Ag, Co, and Bi impurities can lead to beneficial p-type doping in MoS2 monolayered structures. With regards to doping with Zr, the acceptor levels are formed above the edge of the valence band, revealing an introduction of the p-type character.

Core–shell hybrid structured rGO decorated ZnO nanorods synthesized via a facile chemical route with photosensitive properties

Two-dimensional graphene-based nanocomposites have gained much attention due to their promising applications in electronic and optoelectronic devices.

Dye degradation performance, bactericidal behavior and molecular docking analysis of Cu-doped TiO2 nanoparticles

Copper-doped TiO2 was prepared with a sol-gel chemical method. Various concentrations (3, 6, and 9 wt%) of Cu dopant were employed. Several techniques were implemented to assess the structural, optical, morphological and chemical properties of the synthesized samples. Evaluation of elemental composition using SEM-EDS and XRF techniques showed the presence of dopant element in the prepared samples. XRD analysis confirmed the presence of anatase (TiO2) phase with interstitial doping. Incorporation of dopant was observed to enhance the crystallinity and increase the crystallite size of the synthesized products. SAED profiles revealed a high degree of crystallinity in the prepared specimens, which was also evident in the XRD spectra. Optical properties studied using UV-vis spectroscopy depicted a shift of the maximum absorption to the visible region (redshift) that signified a reduction in the band gap energy of Cu-doped TiO2 samples. Examination of morphological features with scanning and high-resolution transmission electron microscopes revealed the formation of spherical nanoparticles with a tendency to agglomerate with increasing dopant concentration. Molecular vibrations and the formation of Ti-O-Ti bonds were revealed through FTIR spectra. PL spectroscopy recorded the trapping efficiency and migration of charge carriers, which exhibited electron-hole recombination behavior. Doped nanostructures showed enhanced bactericidal performance and synergism against S. aureus and E. coli. In summary, Cu-doped TiO2 nanostructures were observed to impede bacteria effectively, which is deemed beneficial in overcoming ailments caused by pathogens such as microbial etiologies. Furthermore, molecular docking analysis was conducted to study the interaction of Cu-doped TiO2 nanoparticles with multiple proteins namely β-lactamase (binding score: -4.91 kcal mol-1), ddlB (binding score: -5.67 kcal mol-1) and FabI (binding score: -6.13 kcal mol-1) as possible targets with active site residues. Dye degradation/reduction of control and Cu-doped samples were studied through absorption spectroscopy. The obtained outcomes of the performed experiment indicated that the photocatalytic activity of Cu-TiO2 enhanced with increasing dopant concentration, which is thought to be due to a decreased rate of electron-hole pair recombination. Consequently, it is suggested that Cu-TiO2 can be exploited as an effective candidate for antibacterial and dye degradation applications.

Photocatalytic and bactericidal properties and molecular docking analysis of TiO2 nanoparticles conjugated with Zr for environmental remediation

Despite implementing several methodologies including a combination of physical, chemical and biological techniques, aquatic and microbial pollution remains a challenge to this day. Recently, nanomaterials have attracted considerable attention due to their extraordinary prospective for utilization toward environmental remediation. Among several probable candidates, TiO₂ stands out due to its potential for use in multifaceted applications. One way to improve the catalytic and antimicrobial potential of TiO₂ is to dope it with certain elements. In this study, Zr-doped TiO₂ was synthesized through a sol–gel chemical method using various dopant concentrations (2, 4, 6, and 8 wt%). Surface morphological, microstructural and elemental analysis was carried out using FESEM and HR-TEM along with EDS to confirm the formation of Zr–TiO₂. XRD spectra showed a linear shift of the (101) anatase peak to lower diffraction angles (from 25.4° to 25.08°) with increasing Zr⁴⁺ concentration. Functional groups were examined via FTIR, an ample absorption band appearing between 400 and 700 cm⁻¹ in the acquired spectrum was attributed to the vibration modes of the Ti–O–Ti linkage present within TiO₂ nanoparticles, which denotes the formation of TiO₂. Experimental results indicated that with increasing dopant concentrations, photocatalytic potential was enhanced significantly. In this respect, TiO₂ doped with 8 wt% Zr (sample 0.08 : 1) exhibited outstanding performance by realizing 98% elimination of synthetic MB in 100 minutes. This is thought to be due to a decreased rate of electron–hole pair recombination that transpires upon doping. Therefore, it is proposed that Zr-doped TiO₂ can be used as an effective photocatalyst material for various environmental and wastewater treatment applications. The good docking scores and binding confirmation of Zr-doped TiO₂ suggested doped nanoparticles as a potential inhibitor against selected targets of both E. coli and S. aureus. Hence, enzyme inhibition studies of Zr-doped TiO₂ NPs are suggested for further confirmation of these in silico predictions.

Despite implementing several methodologies including a combination of physical, chemical and biological techniques, aquatic and microbial pollution remains a challenge to this day.