Plasma-assisted in-situ preparation of L-cystine functionalized silver nanoparticle: An intelligent multicolor nano-sensing of cadmium and paracetamol from environmental sample

L-cystine (L-cys) functionalized plasmonic silver nanomaterial (Ag NPs) was fabricated toward the selective and sensitive detection of paracetamol and cadmium. The prepared L-cys-Ag nanoparticles (NPs) were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD) and fourier transform infrared spectroscopy (FTIR) analyses. SEM imaging show that Ag NPs was decorated on the surface of L-cysteine 3D cubic nanosheet. L-cys-Ag NPs showed selective and sensitive detection towards paracetamol and cadmium. The interference study confirms that the presence of other metal ions didn't inhibit the detection of cadmium by L-cys-Ag NPs. The limit of detection of paracetamol and cadmium by L-cys-Ag NPs was calculated to be 1.2 and 2.82 nM respectively. In addition, the real sample detection of paracetamol on blood serum and urine, and cadmium on STP were performed and the recovery percentage was above 97%. Further, the real sample analysis was performed in tap and drinking water and the recovery percentage was more than 98%. The analytic logic gate on the multicolour detection of cadmium and paracetamol was performed for the semi-quantitative monitoring of paracetamol and cadmium by L-cys-Ag NPs. The developed L-cys-Ag NPs were found to be an effective tool for the monitoring of cadmium in environmental water bodies and paracetamol in blood and urine.

Sunlit photocatalytic degradation of organic pollutant by NiCr2O4/Bi2S3/Cr2S3 tracheid skeleton nanocomposite: Mechanism, pathway, reactive sites, genotoxicity and byproduct toxicity evaluation

In this study, 3D C₂S₃ (CS) and 2D Bi₂S₃ (BS) modified NiCr₂O₄ nanocomposite (NCO-BS-CS NCs) was prepared by sonochemical assisted co-precipitation method for the enhanced photocatalytic activity. Here, NCO-BS-CS NCs showed band gap energy of 2.23 eV and the PL intensity of NCO-BS-CS NCs was lower than NCO, BS, and CS NPs. Thus, the results indicate the fabricated NCO-BS-CS NCs enhance the charge segregation and lower in recombination rate. NCO-BS-CS NCs showed enhanced photodegradation of methyl orange (MO) (95%) and congo red (CR) (99.7%) respectively. The total organic compound (TOC) analysis shows the complete mineralization of about 91 and 98% for MO and CR respectively. Furthermore, the Fukui function was used for the prediction of reactive sites in the photodegradation pathway of MO and CR by NCs. ECOSAR program was done to determine the toxicity of the intermediate and the results conclude that the degraded product shows nontoxic to the environmental organism (fish, daphnia, and algae). Thus, the fabricated NCO-BS-CS NCs can be used for the remediation of toxic organic pollutants from the waste water by photocatalytic degradation.

Green synthesis of two-electron centre based ZnO/NiCo2S4 QDs-OVs using Punica granatum fruit peel extract for an exceptional visible light photocatalytic degradation of doxycycline and ciprofloxacin

Biosynthesis of nanomaterials using plant extract makes them attractive in the field of photocatalysis as they are environmental friendly. The current study focused on the biosynthesis of ZnO/NiCo₂S₄ QDs (NCs) using Punica granatum fruit peel extract as the reducing agent. The nanomaterials were characterized with XRD, FTIR, Raman, SEM, TEM, UV-vis DRS, BET, PL, EIS, and ESR analysis and were used for photocatalytic degradation of doxycycline (DOX) and ciprofloxacin (CIP). The bandgap of ZnO is 3.2 eV, and the decoration of NiCo₂S₄ QDs aids in narrowing the bandgap (2.8 eV), making the NCs visible light active. The fabricated NCs achieved 99 and 89% degradation of DOX and CIP respectively. The photocatalytic efficiency of ZnO/NiCo₂S₄ QDs was much higher compared to individual ZnO and NiCo₂S₄ QDs. The half-life period of DOX and CIP were evaluated to be 58 and 152 min respectively. The percentage of TOC removal in the photodegraded product of DOX and CIP was estimated to be 99 and 89% respectively, indicating the mineralization of the compounds. The enhanced photocatalytic efficiency of the NCs was attributed to the narrowed visible light active bandgap, synergistic charge transfer across the interface, and lower charge recombination. The intermediates formed during the photocatalytic degradation of DOX and CIP were analyzed using GC-MS/MS analysis, and the photodegradation pathway was elucidated. Also, the toxicity of the intermediates was computationally analyzed using ECOSAR software. The fabricated ZnO/NiCo₂S₄ QDs have excellent stability and reusability, confirmed by XRD and XPS analysis. The reusable efficiency of the NCs for the photocatalytic degradation of DOX and CIP were 98.93, and 99.4% respectively. Thus, the biologically fabricated NCs are shown to be an excellent photocatalyst and have wide applications in environmental remediation.

A prominent dual heterojunction framed CuWO4/Bi2WO6/MnS ternary NCs for para-chlorophenol degradation, Cr(VI) reduction & toxicity studies

In account of environmental remediation, an ideal photocatalyst was fabricated for the effective treatment of water systems. Herein, dual heterojunctions framed CuWO₄/Bi₂WO₆/MnS nanocomposite (NCs) was synthesized via simple co-precipitation method followed by ultra-sonicated assisted route. The prepared NCs were investigated its photocatalytic degradation performance using para-chlorophenol (4-CP) and reduction of chromium VI (Cr (VI)) under visible light irradiation. The photocatalyst were characterized by various analytical techniques including XRD, HR-TEM, XPS, UV-vis DRS, FE-SEM, EIS, PL, ESR, Raman and N₂ adsorption and desorption studies. The excellent photodegradation of 4-CP was observed within 180 min by the NCs. Similarly, the Cr (VI) reduction was about 97% within 140 min. The effect of pH and influence of different dosage of NCs and 4-CP on the photodegradation efficiency was investigated. The reusability and stability of the NCs was examined over 6 consecutive runs where the XRD and XPS confirm the structural stability of the prepared NCs. The scavenging experiment were carried out to elucidate the mechanism and the active species involved were O^2-• and OH• radicals. The TOC analysis affirmed the complete mineralization of the prepared NCs. The ecotoxicity analysis was carried out to determine the toxicity effect of intermediates using ECOSAR software and the end product toxicity was also evaluated against E. coli and S. epidermis. The end product toxicity study also confirmed that the degraded product was less toxic compared to parent compound. Further, the genotoxicity study was done to understand the environmental impact using allium cepa and results confirms that there are no causes of cytotoxicity & genotoxicity by the prepared NCs. Therefore, the prepared NCs can be economical, efficient with excellent photocatalytic performance and environment friendly.

Sunlit expeditious visible light-mediated photo-fenton degradation of ciprofloxacin by exfoliation of NiCo2O4 and Zn0·3Fe2·7O4 over g-C3N4 matrix: A brief insight on degradation mechanism, degraded product toxicity, and genotoxic evaluation in Allium cepa

Pharmaceutical pollutant in the environmental water bodies has become a major concern, which causes adverse effect to aquatic entities. This study provides an incisive insight on the photocatalytic degradation of ciprofloxacin (CIP) and the development of rationally engineered g-C3N4-NiCo2O4-Zn0.3Fe2·7O4 nanocomposite for boosted photocatalytic performance under visible light irradiation. The g-C3N4-NiCo2O4-Zn0.3Fe2·7O4 nanocomposite was synthesized via ultrasonication-assisted hydrothermal method. The characterization of the as-prepared material was evaluated by XPS, SEM, HR-TEM, PL, FT-IR, EIS, ESR, XRD, BET, and UV-Vis DRS techniques. Furthermore, the effect of catalytic dosage, drug dosage, and pH changes was explored, where g-C3N4-NiCo2O4-Zn0.3Fe2·7O4-10% unveiled excellent visible light photo-Fenton degradation of 92% for CIP at 140 min. The hydroxyl radicals (OH.) served as the predominant radical species on the photodegradation of CIP, which was confirmed by performing a radical scavenging test. Furthermore, the degradation efficiency was determined by six consecutive cycle tests, where the nanomaterial exhibited excellent stability with 98.5% reusable efficiency. The degradation of CIP was further scrutinized by GC-MS analysis, where the degraded intermediate products and the possible pathway were elucidated. The degraded product toxicity was determined by ECOSAR program, where the degraded products haven't exhibited any considerable toxic effects. In addition, the genotoxicity of the nanomaterial was determined by treating them with root tips of A. cepa, where it was found to be non-toxic. Here, the prepared g-C3N4-NiCo2O4-Zn0.3Fe2·7O4 nanocomposite (CNZ NCs) shows eco-friendly and excellent photo-Fenton activity for environmental applications.

Double Z-Scheme ZnCo2O4/MnO2/FeS2 photocatalyst with enhanced photodegradation of organic compound: Insights into mechanisms, kinetics, pathway and toxicity studies

The present work highlights the preparation of double Z-scheme ZnCo2O4/MnO2/FeS2 nanocomposite (NCs) and investigated its photocatalytic activity against methyl orange (MO) dye degradation under visible light. An array of techniques was carried out to characterize the nanoparticles (NPs) in order to evaluate their morphological, structural, optical, and photocatalytic properties using FE-SEM, TEM, XRD, N2 adsorption and desorption studies, PL, UV-visible spectrophotometer, XPS, Raman, and UV-vis DRS analysis. The degradation efficiency of NCs was tested along with different parameter studies such as different pH, NCs concentration, dye concentration, reusability and structural stability. The NCs exhibited complete photodegradation of MO dye under visible light within 80 min at pH 4. The structural and compositional stability of the prepared NCs over 6 consecutive cycles was tested via XRD and XPS analysis. The results of active species trapping experiments showed that O2-• and OH• are responsible for the degradation of MO dye. The TOC analysis showed 95% of mineralization by the prepared NCs. The MO dye degradation pathway was determined using GC-MS/MS analysis and drafted all the intermediates involved. End product toxicity via seed germination and intermediate toxicity study using ECOSAR software results in less toxicity of end product compared to parent compound. Finally, the genotoxicity of the prepared NCs was evaluated using Allium cepa and showed its no causes of cytotoxicity & genotoxicity by the prepared NCs. ZnCo2O4/MnO2/FeS2 NCs exhibited its high photocatalytic activity and the toxicity studies confirms that there is no cause of any environmental impact.

Robust visible light active CoNiO2-BiFeO3-NiS ternary nanocomposite for photo-fenton degradation of rhodamine B and methyl orange: Kinetics, degradation pathway and toxicity assessment

Sustainable wastewater treatment is crucial to remediate the water pollutants through the development of highly efficient, low-cost and separation free photocatalyst. The aim of this study is to construct a novel CoNiO₂-BiFeO₃-NiS ternary nanocomposite (NCs) for the efficient degradation of organic pollutants by utilising visible light. The NCs was characterized by various physiochemical techniques, including HR-TEM, SEM, XPS, FT-IR, ESR, EIS, PL, UV-visible DRS, and N₂ adsorption and desorption analysis. The photocatalyst exhibits extraordinary degradation efficiency towards MO (99.8%) and RhB (97.8%). The intermediates were determined using GC-MS analysis and the degradation pathway was elucidated. The complete mineralization was further confirmed by TOC analysis. The CoNiO₂-BiFeO₃-NiS ternary NCs have shown excellent photostability, structural stability and reusability even after six cycles and it is confirmed by XRD and XPS analysis. The kinetic study reveals that the photodegradation of the dyes follows first order reaction. The influence of different pH, dye concentrations and NCs dosages were investigated. The intermediate toxicity was predicted by computational stimulation using ECOSAR software. The NCs shows promising potential for ecological safety which demonstrates its practical application in the treatment of waste water pollutants in large scale.

Photodegradation of 5-flurouracil, carvedilol, para-chlorophenol and methimazole with 3D MnWO4 nanoflower modified Ag2WO4 nanorods: A non-genotoxic nanomaterial for water treatment

The present study focused on the photocatalytic degradation of 5-Flurouracil (FU), carvedilol (Car), para-chlorophenol (PCP) and methimazole (Met) under visible light irradiation by MnWO₄/Ag₂WO₄ (MWO/AWO) nanohybrid. Here, MWO/AWO nanohybrid was characterized by XRD, TEM, EDS, XPS, ESR, EIS, BET and DRS. The band gap energy of the MWO/AWO nanohybrid was found to be 2.75 eV, which enables effective photocatalytic activity of nanohybrid under visible light. The photocatalytic degradation of various PhACs such as Fu, Car, PCP and Met was found to be 98.8, 100, 98 and 98.1% respectively. The degradation efficiency of the MWO/AWO nanohybrid on various PhACs was higher than the pure MWO and AWO nanoparticle. The effective formation of OH• and •O₂ by MWO/AWO nanohybrid played an important role in degradation of PhACs and it was determined by radical scavenging experiment. Further, the intermediates formed during the photocatalytic process were analyzed by GC-MS/MS to elucidate the photodegradation pathway and the results reveal the complete mineralization of the PhACs. The toxicity of the degraded product was performed against on Bacillus subtilis and Escherichia coli where it shows that the nanohybrid possesses high relative growth inhibition than AWO and MWO nanoparticles. In addition, the genotoxicity of the nanohybrid against Allium cepa was performed and it exhibited lower toxicity. The synthesized nanohybrid proves to be an excellent photocatalyst with good stability, reusability, eco-friendly, and cost-effective material for implementation in practical applications.

Designing novel MgFe2O4 coupled V2O5 nanorod for synergetic photodegradation of tetracycline with enhanced visible-light energy harvesting: Photoluminescence, kinetics, intrinsic mechanism and bactericidal effect

The present study focused on the enhancement of degradation of an important pharmaceutical pollutant, tetracycline with the help of nano photocatalyst under visible light irradiation. The study found that the synergetic effect of novel MgFe₂O₄-V₂O₅ enhanced the photocatalytic degradation of tetracycline. Here, the photocatalyst was synthesized by sonochemical technique. Scanning electron microscopy image indicates the coupling of MgFe₂O₄ nanocapsules on the surface of the V₂O₅ nanorod. The bandgap of MgFe₂O₄ (1.8 eV) and V₂O₅ (2.5 eV) was shifted to 2.32 eV in MgFe₂O₄-V₂O₅ to promote visible-light harvesting and it was depicted by the UV-visible DRS. XPS was used to identify the presence of chemical states with the existence of Mg 1s, Fe 2p, V 2p, and O 1s. The electrochemical impedance spectroscopy and photoluminescence spectra indicate the better separation of charge carriers owing to the formation of type II heterojunction formation. The tetracycline (25 mg/L) was degraded with MgFe₂O₄-V₂O₅ (150 mg/L) that exhibited 3.3 and 5 folds enhanced rates than its counterparts (MgFe₂O₄ and V₂O₅) owing to synergism. The possible intermediate formation and degradation pathway was determined based on GC/MS analysis. TOC analysis of end products indicated maximum mineralization of tetracycline. The MgFe₂O₄-V₂O₅ showed excellent recycling ability and reusability. The key photo-degradation of tetracycline was occurred by the generation of hydroxyl radicals. The MgFe₂O₄-V₂O₅ exhibited high antibacterial activity that ensures the dual functionality of the prepared nanocomposites (NCs). Therefore, the present study displays MgFe₂O₄ decorated V₂O₅ nanorod as an ideal candidate for environmental remediation.

Self-assembling of 3D layered flower architecture of BiOI modified MgCr2O4 nanosphere for wider spectrum visible-light photocatalytic degradation of rhodamine B and malachite green: Mechanism, pathway, reactive sites and toxicity prediction

In this study, 3D BiOI nanoparticle (BOI NPs) modified MgCr₂O₄ nanoparticle (MCO NPs) was fabricated by simple sonochemical and coprecipitation method for the enhanced photocatalytic activity. The morphological structure of the MgCr₂O₄-BiOI nanocomposite (MCO-BOI NCs) was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS), electron impedance spectroscopy (EIS) and photo luminescence (PL). The lower in the PL intensity and small arc in EIS for NCs shows the effective charge separation and lower in rate of recombination of charge carriers in NCs than the pure MCO and BOI NPs. The degradation efficiency of Rhodamine B (RhB) and malachite green (MG) by MCO-BOI NCs was found to be 99.5% and 98.2% receptivity. In addition, the photocatalytic degradation of RhB and MG was studied under various environmental parameters (different pH, varying the concentration of NCs and dyes) and response surface (RSM) plot was performed. The complete mineralization of RhB and MG by MCO-BOI NCs was determined by TOC. In addition, the photocatalytic degradation pathway was elucidated based on GC-MS results and Fukui function. In addition, the toxicity of intermediate formed during the degradation of RhB and MG was predicted by ECOSAR. The present work highlights the application of MCO-BOI NCs in environmental remediation for toxic pollutant removal.

Synthesis and application of CdS nanoparticles-decorated core-shell Ag@Ni nanohybrids for visible-light spectrophotometric assay of sulfide in aqueous sample

Novel Ag@Ni nanosphere decorated with CdS NPs (Ag@Ni-CdS NCs) was synthesized by one step chemical synthesis method. The fabricated NCs were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), fourier transfer infra-red spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), zeta sizer and particle size analyzer. TEM and XRD confirmed the Ag in core and Ni in shell for the effective formation of Ag@Ni core shell nanosphere. EDAX and XPS spectra of NCs confirms the formation of Ag@Ni-CdS NCs. Zeta potential and particle size of the NCs was found to be 29.5 ± 1.5 mV and 24 ± 1 nm respectively. The complete loss in the peak intensity of Ag@Ni-CdS NCs (localized surface plasmon resonance (LSPR)) at ∼410 nm in presence of S^2- ions was observed which indicates its selective detection towards S^2- ions. The sulfide ion sensing by Ag@Ni-CdS NCs was due to the successive oxidation of Ag results in the formulation of Ag²⁺ ions in the system, which causes the diminishing of LSPR band of NCs. The limit of detection (LOD) of S^2- ions by Ag@Ni-CdS NCs was calculated to be of 2.66 nM. The combination of CdS NPs with core-shell Ag@Ni nanosphere guides a promising strategy for S^2- ions detection from environmental polluted samples.

CuO loaded ZnS nanoflower entrapped on PVA-chitosan matrix for boosted visible light photocatalysis for tetracycline degradation and anti-bacterial application

Novel photocatalyst CuO loaded ZnS nanoflower supported on carbon frame work PVA/Chitosan was synthesized by co-precipitation and ultrasonic assisted method. The co-existence of ZnS and CuO and its crystallinity in nanohybrid was verified by XRD, SAED and HR-TEM analysis. The availability of defects in ZnS was identified by EPR. FTIR and TGA verified the presence of PVA and Chitosan. Defects mediated ZnS-CuO/PVA/chitosan heterojunction promote synergistic charge separation with type II interface. Zn-vacancy facilitates two-photon excitation that improves visible-light harvesting. The photocatalytic activity of ZnS-CuO/PVA/Chitosan was 94.7% which is higher when compared to ZnS (40%) and CuO (60%). The photocatalytic mechanism was elucidated using scavenger test and both ·O₂^- and ·OH were found to play key role in tetracycline degradation. In addition, ZnS-CuO/PVA/Chitosan demonstrated efficient anti-microbial effect against the both gram strains on comparing with individual ZnS and CuO. Thus, the multifunctional ZnS-CuO/PVA/Chitosan is promising for the photocatalytic degradation of tetracycline and as an antimicrobial agent.

Ag0 decorated Cr2S3 NPs embedded on PVP matrix: A colorimetric probe for selective and rapid detection of sulphide ions from environmental samples

Globally, the environmental pollution is one of the major issues causing toxicity towards human and aquatic life. We have developed a facile and innovative sensing approach for detection of sulphide ions (S^2-) present in the aqueous media using Ag⁰ decorated Cr₂S₃ NPs embedded on PVP matrix (Ag/Cr₂S₃-PVP). Based on the SPR phenomena, the detection of S^2- ions was established. The nanohybrid was characterized using various techniques such as UV-vis spectrophotometer, High-Resolution Transmission Electron Microscopy (HR-TEM), Thermal Gravimetric Analysis (TGA), X-ray diffraction analysis(XRD), Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The yellowish colour of Ag/Cr₂S₃-PVP nanohybrid turned to brown colour in presence of S^2- ions. The selectivity and sensitivity of the prepared probe was studied against the other interfering metal ions. In addition, the effect of different concentration of S^2- ions in the nanohybrid solution was investigated and the Limit of detection (LOD) was found to be 6.6 nM. The good linearity was found over the range of 10 nM to 100 μM with R² value of 0.981. The paper strip based probe was developed for rapid onsite monitoring of S^2- ions. The proposed method is found to be cost-effective, rapid, and simple. We have validated the practical applicability of the prepared probe for determining the concentration of S^2- ions in real water samples.

Chitosan capped Ag/NiS nanocomposites: A novel colorimetric probe for detection of L-cysteine at nanomolar level and its anti-microbial activity

L-Cysteine (L-cys) plays very crucial role in biological systems. The study reports the colorimetric detection of L-cys at nanomolar level using chitosan capped Ag decorated NiS nanocomposite (chit-Ag/NiS NCs).The chemical reduction and co-precipitation methods were adopted to prepare chit-Ag/NiS NCs. The fabricated NCs was characterized by X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), FT-Raman, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The chit-Ag/NiS NCs particularly detect L-cys even in other amino acids presence. The chit-Ag/NiS NCs showed the surface charge of -26 ± 39.9 mV. The detection of L-cys was indicated by disappearance of yellowish-brown color of Chit-Ag/NiS NCs to colorless. A good linear correlation was found between absorbance vs logarithmic concentration of L-cys (1 μM to 1 nM) with R² value of 0.99. The chit-Ag/NiS NCs impregnated cotton swabs was prepared for real time detection of L-cys and the prepared probe was found to be highly selective and specific. The effect of pH, temperature and salinity influencing the L-cys detection was studied. Also, the antimicrobial activity of Chit-Ag/NiS NCs was investigated against gram negative (E. coli) and gram positive (B. subtilis) bacteria.

Synthesis and characterizations of hybrid PEG-Fe3O4 nanoparticles for the efficient adsorptive removal of dye and antibacterial, and antibiofilm applications

PURPOSE

Dyes are highly toxic coloured compounds in nature that are largely applied in paper, food, textile and printing industries. Here, the adsorption technique was performed to remove methyl orange (MO) dye from water by polyethylene glycol (PEG) modified iron oxide nanoparticles (Fe₃O₄ NPs).

METHODS

The method used for Fe₃O₄ NPs synthesis was chemical precipitation. The particles were analyzed by transmission electron microscope, magnetometer, BET analyzer, fourier-transform infrared spectroscopy, X-ray powder diffraction, zetasizer and particle size analyzer. The influence of pH (4.0 to 10.0), NaCl concentration (0.01 mM to 2 M), adsorbent dosage (1 to 10 mg), and the role of surface charge on adsorptive removal were investigated.

RESULTS

The NPs size, zeta potential and surface area was found to be 26 ± 1.26 nm, 33.12 ± 1.01 mV and 119 m²/g respectively. The adsorption of MO on Fe₃O₄ NPs agreed best to Freundlich model (R² = 0.965) when compared with Langmuir model (R² = 0.249). By comparing pseudo-first-order kinetic model (R² = 0.937), kinetic adsorption study was better followed by pseudo-second-order kinetic model (R² = 1). The adsorption rate decreased with increasing NaCl concentration. At pH 4, maximum adsorption was noted. The particles were also exhibited excellent antibacterial and antibiofilm activities. The ROS formation, lipid peroxidation and oxidative stress were increased with increase in NPs concentration. The NPs precoated slides exhibited more than 50% growth inhibition.

CONCLUSION

The investigation denotes the versatile applications of the prepared particles for removing the dye stuffs from industrial effluents and as antibacterial and antibiofilm agent.

Impact of bovine serum albumin - A protein corona on toxicity of ZnO NPs in environmental model systems of plant, bacteria, algae and crustaceans

Zinc oxide nanoparticles (ZnO NPs) are widely applied in industrial, household and medical areas that lead to its discharge and accumulation in ecosystem. Here, the toxic effect of ZnO NPs in presence and absence of bovine serum albumin (BSA) was analyzed. The difference in toxicity of bare ZnO and BSA interacted ZnO was studied with different environmental models. P. aeruginosa and S. aureus were used as model bacterial systems. Toxicity against bacteria was determined by employing plate count method. C. pyrenoidsa was used as algal system for evaluating toxicity and it was determined by chlorophyll estimation assay. Daphnia sp. was chosen as crustacean system model. A. cepa root cells were chosen as plant model. ZnO NPs increased the ROS formation, lipid peroxidation and oxidative stress and it reduced in the presence of BSA. The cytotoxicity, chromosomal aberrations and micronuclei (MN) index of A. cepa were increased after ZnO NPs treatment. Same time the toxic effect was decreased in case of BSA coated ZnO NPs. The NPs toxic potential on the organisms decreased in the order of P. aeruginosa (LC₅₀-0.092 mg/L) > S. aureus (LC₅₀-0.33 mg/L) > Daphnia sp (LC₅₀-0.35 mg/L) > C. pyrenoidosa (LC₅₀-8.17 mg/L). LC₅₀ in presence of BSA was determined to be 18.45, 26.24, 17.27 and 53.97 mg/L for P. aeruginosa, S. aureus, Daphnia sp and C. pyrenoidosa respectively. Therefore, the report suggests that BSA stabilized ZnO NPs could be more amenable towards applications in biotechnology and bioengineering.

A potent multifunctional Ag/Co-polyvinylpyrrolidone nanocomposite for enhanced detection of Cr(III) from environmental samples and its photocatalytic and antibacterial applications

Trivalent chromium (Cr(III)) is considered to exhibit hormesis (bi-phasic dose-response) property, where low dose be beneficial and high dose shows toxic effect. The present work describe the development of a bimetallic Ag/Co-polyvinylpyrrolidone nanocomposite (Ag/Co-PVP NPs) probe to detect and quantify Cr(III) ions from aqueous samples. The hydrodynamic size and zeta potential of the particle was determined to be 29 ± 1.3 nm and -37.19 ± 2.4 mV respectively. The interaction of Cr(III) with Ag/Co-PVP probe showed drastic change in colour of NPs from dark brown to pale yellow, with corresponding blue shift, tapering width and increased peak intensity. The probe showed high specificity towards Cr(III) among the tested metal ions. A linearity was observed between various dilutions of Cr(III) ions (10 to 50 nM) and the absorbance of Ag/Co-PVP NPs at 428 nm with R² value of 0.998. The minimum detectable limit of Cr(III) was calculated to be 0.6 nM. The influence of salinity, temperature and pH on detection was studied. The probe was found to detect Cr(III) at acidic pH effectively. Competitive metal ions did not interfere the detection of Cr(III). The water sample collected from Noyyal river was taken to estimate Cr(III) by using the prepared probe to ensure practical applicability. The sample contains 9.3 nM of Cr(III) that was cross verified with AAS analysis. Hence, it is understood that the reported probe can be used to detect Cr(III) selectively with high accuracy from aqueous samples. In addition, the particles also exhibited excellent photocatalytic activity under visible light. Ag/Co-PVP nanocomposites exhibited excellent antibacterial activity against both gram +ve (B. subtilis) and gram -ve (E. coli) bacteria.

Highly selective and sensitive tool for the detection of Hg(II) using 3-(Trimethoxysilyl) propyl methacrylate functionalized Ag-Ce nanocomposite from real water sample

Mercury and its derivates cause distinct toxicity and it is detrimental to the ecosystem where the excessive concentration contributes towards the environmental pollutants. The current study reported a colorimetric method for the detection of Hg(II) ion with high specificity and selectivity using Ag-Ce nanocomposite (NC) functionalized by 3-(Trimethoxysilyl) propyl methacrylate. The synthesized Ag-Ce NC was characterized by using double beam UV-visible spectrophotometer, zeta sizer, EDS, TEM, FT-IR, XRD and particle size analyzer. The synthesized particle possessed an average particle size of 27 ± 1 nm and zeta potential of -39.32 ± 3 mV. The brownish yellow colored Ag-Ce NC changed to colorless in presence of Hg(II) where the colorimetric detection was extremely specific and superior towards Hg(II) ion on comparing the tests with other metal ions. An excellent linear correlation was observed between absorbance (395 nm) and Hg(II) concentrations (1 nM-10 μM) (R² = 0.988) with LOD of 0.03 nM. A cotton swab based probe was prepared for selective, elegant and low cost colorimetric method to detect Hg(II). The parametric study was performed for optimizing the suitable condition. The colorimetric probe developed by this study for Hg(II) detection using Ag-Ce NC shows excellent practical applicability.

Cytotoxicological evaluation of copper oxide nanoparticles on green algae, bacteria and crustacean systems

PURPOSE

Copper oxide (CuO) nanoparticles (NPs) have been utilized in several industries including textile, consumer products, medical, automobiles etc. The discharge of industrial effluents in environment increased the probability of CuO NPs contamination in the ecosystem.

METHODS

The present investigation used CuO NPs to determine the toxic effect on Lyngbya species, fresh water algae isolated from natural pond, bacterial species Pseudomonas aeruginosa and Staphylococcus aureus and a crustacean species Daphnia magna.

RESULTS

The NPs average diameter and zeta potential was estimated to be 45 ± 3 nm and 29 ± 1.78 mV respectively. The results showed that 0.1 µg/mL CuO NPs showed the growth inhibition of 47 ± 2% on Lyngbya sp. after 5 days of incubation. The CuO NPs also showed toxic effect to bacterial systems such as P. aeruginosa and S. aureus and crustacean system D. magna. Further, there was an increased lipid peroxidation and generation of reactive oxygen species (ROS) in algal cells observed up on NPs exposure. The exposure of NPs suppressed the antioxidant defense system. The amount of glutathione was reduced after the exposure of NPs.

CONCLUSION

The study suggested the role of ROS in toxicity of algal and bacterial systems. The present study pointed out the potent toxicity of CuO NPs to the organisms present in the aquatic environment.

Preparation of Ag-cellulose nanocomposite for the selective detection and quantification of mercury at nanomolar level and the evaluation of its photocatalytic performance

Mercury is a toxic heavy metal that reaches to the water bodies mainly by coal burning, mining and petrol refining. The study was focused to investigate the application of Ag-cellulose nanocomposite to detect and quantify mercury colorimetrically. The Ag-cellulose nanocomposite was characterized by X-ray diffraction, Transmission electron microscopy, Fourier transform infrared spectroscopy, UV-visible spectroscopy, particle size analyzer and zetasizer. The study identified that the presence of other metal ions did not interfere with the detection of Hg²⁺ ion by the probe. The prepared Ag-cellulose nanocomposite-phenylalanine conjugate incorporated paper strip showed an excellent result in Hg²⁺ detection. The Ag-cellulose nanocomposite was used to quantify the unknown concentration of mercury on real sample (environmental sample) and it was found to be highly accurate by confirming with atomic absorption spectrophotometric analysis. The Ag-cellulose nanocomposite showed effective detection at 45 °C, pH 9 and 0.1% of salinity. The Ag-cellulose nanocomposite showed efficient photocatalytic performance under visible light irradiation. The half-life period of MB by Ag-cellulose nanocomposite under visible light was determined to be 90 min. The study suggests the application of prepared probe in photocatalysis and the detection of Hg²⁺ from various environmental samples.

Rapid colorimetric detection of mercury using silver nanoparticles in the presence of methionine

Development of potential sensors is inevitable for the detection of environmental pollutants including toxins, organic pollutants and heavy metal which cause hazardous effect to human and other living organisms. The present study is to develop silver nanoparticle (Ag NPs) based sensor for the accurate, sensitive and selective colorimetric detection of Hg²⁺ ions from aqueous samples at nano molar level. The nanoparticles were synthesized chemically and it was stabilized by polyvinylpyrrolidone (PVP). The prepared particles were characterized by UV-visible spectroscopy, scanning electron microscopy (SEM), particle analysiser and Zetasizer. The UV-visible spectra of Ag NPs showed absorbance maximum at 392 nm. The average diameter of Ag NPs was determined to be 6 ± 0.9 nm by using particle analyzer. The zeta sizer analysis showed that the PVP stabilized Ag NPs possessed a zeta potential of -35.56 ± 3 mV. The Ag NPs-methionine conjugate showed the colour change from the brownish yellow colour to colourless when it was reacted with mercury. The Ag NPs conjugated methionine is sensitive to mercury and detects the mercury at nano molar level. The influence of other metal ion did not interfere with the detection and quantification of Hg²⁺. The detection of Hg²⁺ was also performed with paper strip and agarose gel method. The Ag NPs conjugate with methionine can applied for the detection of Hg²⁺ from various aqueous samples.