Facile colorimetric detection of Hg (II), photocatalytic and antibacterial efficiency based on silver-manganese disulfide/polyvinyl alcohol-chitosan nanocomposites

Sustainable chitosan-based materials as heterogeneous catalyst for application in wastewater treatment and water purification: An up-to-date review

Water pollution is one of serious environmental issues due to the rapid development of industrial and agricultural sectors, and clean water resources have been receiving increasing attention. Recently, more and more studies have witnessed significant development of catalysts (metal oxides, metal sulfides, metal-organic frameworks, zero-valent metal, etc.) for wastewater treatment and water purification. Sustainable and clean catalysts immobilized into chitosan-based materials (Cat@CSbMs) are considered one of the most appealing subclasses of functional materials due to their high catalytic activity, high adsorption capacities, non-toxicity and relative stability. This review provides a summary of various upgrading renewable Cat@CSbMs (such as cocatalyst, photocatalyst, and Fenton-like reagent, etc.). As for engineering applications, further researches of Cat@CSbMs should focus on treating complex wastewater containing both heavy metals and organic pollutants, as well as developing continuous flow treatment methods for industrial wastewater using Cat@CSbMs. In conclusion, this review abridges the gap between different approaches for upgrading renewable and clean Cat@CSbMs and their future applications. This will contribute to the development of cleaner and sustainable Cat@CSbMs for wastewater treatment and water purification.

Facile synthesis of magnetic intelligent sensors for the pH-sensitive controlled capture of Cr(vi)

In this work, intelligent pH-sensitive sensors (Fe3O4/RhB@PAM) for Cr(vi) detection were successfully synthesized based on polyacrylamide (PAM) and Rhodamine B (RhB) co-modified Fe3O4 nanocomposites. The characterization results indicated that the sensors had many favorable properties, including suitable size, stable crystal structure and excellent magnetic response performance (47.59 emu g-1). In addition, the fluorescence changes during the detection process indicated that Fe3O4/RhB@PAM were "ON-OFF" intelligent sensors. When the Fe3O4/RhB@PAM sensors were placed in acidic Cr(vi) solution (pH 4), PAM acted as a pH-responsive "gatekeeper" releasing RhB, and the fluorescence intensity of released RhB was weakened by the complexation of Cr(vi). Furthermore, the fluorescence changes of the magnetic sensors were remarkably specific for Cr(vi) even in the presence of other competitive cations, and the limit of detection (LOD) for Cr(vi) was lower (0.347 μM) than the value recommended by the World Health Organization (0.96 μM). All the results presented in this study showed that the Fe3O4/RhB@PAM sensors had significant potential for Cr(vi) detection in acidic environmental samples.

Silver oxide decorated urchin-like microporous organic polymer composites as versatile antibacterial organic coating materials

Microporous organic polymers (MOPs) and metal oxide hybrid composites are considered valuable coating materials because of their versatility derived from the synergistic combination of MOPs' inherent dispersibility and the distinctive properties of metal oxides. In this study, we present the synthesis of sea-urchin-like MOPs hybridised with silver oxide nanoparticles (Ag2O NPs) to fabricate antibacterial composites suitable for potential antibacterial coating applications. Ag2O NP-decorated urchin-like MOPs (Ag2O@UMOPs) were synthesised by employing a combination of two methods: a one-pot Lewis acid-base interaction-mediated self-assembly and a straightforward impregnation process. The as-prepared Ag2O@UMOPs demonstrated high antibacterial efficacy against both E. coli (G-) and S. aureus (G+). The antibacterial mechanism of Ag2O@UMOPs mainly involved the synergistic effects of accumulation of Ag2O@UMOPs, the release of Ag+ ions, and the generation of reactive oxygen species. The exceptional processability and biosafety of Ag2O@UMOPs make them ideal organic coating materials for convenient application on various substrates. These remarkable features of Ag2O@UMOPs provide an effective platform for potential antibacterial applications in biological sciences.

Green synthesis of chitosan/glutamic acid/agarose/Ag nanocomposite hydrogel as a new platform for colorimetric detection of Cu ions and reduction of 4-nitrophenol

In this study, the green synthesis of chitosan/glutamic acid/agarose/Ag (Chi/GA/Aga/Ag) nanocomposite hydrogel was obtained via in situ reduction of Ag ions during the crosslinking process of chitosan-agarose double network hydrogels. The rich hydroxyl, carboxyl and amino groups in both agarose, chitosan, and glutamic acid can effectively control the growth, dispersion and immobilization of nearly spherical Ag nanoparticles (70 nm) in the Chi/GA/Aga/Ag composite hydrogel. Glutamic acids can act as the structure-directing agents to induce the formation of chitosan/glutamic acid hydrogel. The mechanical strength of the Chi/GA/Aga/Ag composite hydrogel can be enhanced by the introduction of chitosan-agarose double network hydrogels, which guarantees that it can be directly used as a visual test strip of the Cu ions with a lower detection limit of 1 μM and an active catalyst for the reduction of 4-nitrophenol within 18 min. The quantitative and semi-quantitative measurement of Cu ions can be carried out by UV-visible absorption spectroscopy and visual measurement, which provided a convenient, portable, and "naked-eye" solid-state detection methodology.

Synthesis of hydroxyethylcellulose phthalate-modified silver nanoparticles and their multifunctional applications as an efficient antibacterial, photocatalytic and mercury-selective sensing agent

Water contamination by several aquatic pollutants such as dyes, heavy metal ions and microbes is a prevalent concern to health and environment. Thus, developing facile, economical, and eco-friendly strategies to tackle this problem have become paramount. Hence, this study reports the synthesis of hydroxyethylcellulose phthalate-capped silver nanoparticles (HEC-PA@AgNPs) using a simple sunlight-assisted route. The multifunctional applications of the synthesized particles as an efficient nanoprobe for the selective sensing of Hg2+ as well as their photocatalytic and antimicrobial activities were demonstrated. HEC-PA@AgNPs were systematically characterized by various advanced analytical techniques such as FTIR, UV-Vis spectroscopy, X-ray diffraction (XRD), zeta potential (ZP) and dynamic light scattering (DLS). The successful functionalization of AgNPs with HEC-PA was manifested using FTIR. SEM and XRD revealed the formation of spherical AgNPs with a face centered cubic structure and a crystallite size of 14 nm. The particles demonstrated a hydrodynamic size of 40 nm with a good colloidal stability as evidenced from the ZP value of -35 mV, suggesting the effective role of the negatively charged HEC-PA capping agent in stabilizing the NPs. HEC-PA@AgNPs exhibited fast naked-eye colorimetric detection, high selectivity, and sensitivity to Hg2+ in spiked real water samples over a wide range of pH (3-9) and temperatures (298-328 K), achieving a detection limit of 119 nM. The presence of other diverse metal ions didn't affect the specificity of the particles toward Hg ions. Further, the sensing mechanism is based on a characteristic redox reaction between Hg2+ and AgNPs. Further, HEC-PA@AgNPs showcased a more noxious antimicrobial activity to gram-positive bacteria (B. subtilis and S. aureus) than gram-negative bacteria (E. coli). Besides, AgNPs exhibited high photocatalytic potential under sunlight irradiation with a degradation efficiency of 79 % for methylene blue dye in only 80 min following pseudo-1st order kinetics with a rate constant of 0.019 min-1. The photocatalyst exhibited good reusability after five recycling runs. These results render our approach promising multifunctional analytical probe for environmental and biomedical applications.

Synergistic activities of silver indium sulfide/nickel molybdenum sulfide nanostructures anchored on clay mineral for light-driven bactericidal performance, and detection of uric acid from gout patient serum

In this study, the hydrothermal method was used to synthesis of silver indium sulfide/nickel molybdenum sulfide (AgInS₂/NiMoS₄) nanostructure and decorated on Palygorskite (Plg) as an excellent carrier of antibacterial materials. The performance of the prepared AgInS₂/NiMoS₄/Plg composites was investigated for light-driven antibacterial process and detection of uric acid from biological samples. The result shows the highest antibacterial activity of the AgInS₂/NiMoS₄/Plg with the minimum inhibitory concentrations about 0.2-0.3 mg/mL. The prepared AgInS₂/NiMoS₄/Plg as sensor depicted enhanced peroxidase-like activity for detection of acid uric. The detection limit of acid uric by AgInS₂/NiMoS₄/Plg was about 26.1 nM. Therefore, the AgInS₂/NiMoS₄/Plg can be developed in the bactericidal process and sensing in complex biological systems.

Polymer based nanocomposites: A strategic tool for detection of toxic pollutants in environmental matrices

A large fraction of population is suffering from waterborne diseases due to the contaminated drinking water. Both anthropogenic and natural sources are responsible for water contamination. Revolution in industrial and agriculture sectors along with a huge increase in human population has brought more amount of wastes like heavy metals, pesticides and antibiotics. These toxins are very harmful for human health, therefore, it is necessary to sense their presence in environment. Conventional strategies face various problems in detection and quantification of these pollutants such as expensive equipment and requirement of high maintenance with limited portability. Recently, nanostructured devices have been developed to detect environmental pollutants. Polymeric nanocomposites have been found robust, cost effective, highly efficient and accurate for sensing various environmental pollutants and this is due to their porous framework, multi-functionalities, redox properties, great conductivity, catalytic features, facile operation at room temperature and large surface area. Synergistic effects between polymeric matrix and nanomaterials are responsible for improved sensing features and environmental adaptability. This review focuses on the recent advancement in polymeric nanocomposites for sensing heavy metals, pesticides and antibiotics. The advantages, disadvantages, operating conditions and future perspectives of polymeric nanocomposites for sensing toxic pollutants have also been discussed.

Ultrasensitive detection of mercury(II) in aqueous solutions via the spontaneous precipitation of CsPbBr3 crystallites

Mercury(II) is one of the most toxic ions and has the lowest allowed concentration in water. Lowering the detection limits of Hg²⁺ based on fluorescence methods is challenging compared to the detection of other heavy metal ions. Co-precipitation of the CsPbBr₃ precursor and mercury ions in aqueous solutions was developed for the ultra-trace level detection of Hg²⁺. It was found that the formed CsPbBr₃ crystals with sizes in the range of nanometers to micrometers exhibited strong fluorescence in the solid state free of water, and the incorporation of Hg²⁺ in the crystals would cause fluorescence quenching. Therefore, the decrease in fluorescence intensity could be used to quantitatively detect Hg²⁺. A microwell array was designed by dispersing the sample solution with the perovskite probe and evaporating water for 3 min to form solid fluorescent crystals, leading to the incorporation of Hg²⁺ in the crystals. This evaporation-induced co-precipitation strategy successfully solved the problem of the instability of perovskite materials in water. The concentration of Hg²⁺ can be obtained according to the decrease in the fluorescence intensity, which is caused by the replacement of Pb²⁺ by Hg²⁺ in the crystals during the crystallization process. The CsPbBr₃ crystallites can be used to detect ultra-trace levels of Hg²⁺ simply and quickly, with a linear range of 5-100 nM and limit of detection (LOD) as low as 0.1 nM. More importantly, no organic molecules are required to prepare crystals since the micron-sized crystals have obvious fluorescence. This method demonstrates great promise in detecting low concentrations of Hg²⁺ in aqueous solutions.

Facile fabrication of ternary MWCNTs/ZnO/Chitosan nanocomposite for enhanced photocatalytic degradation of methylene blue and antibacterial activity

Developing a cheap, stable and effective photocatalyst is necessary for remediation of persistent organic pollutants. To address this challenge, we proposed a unique interfacial engineering technique and proper bandgap matching strategy to synthesize MWCNTs/ZnO/Chitosan ternary nanocomposite for effective photocatalytic application. The features of the prepared samples were determined by FESEM, TEM, EDX, elemental mapping, AFM, FT-IR, XRD, UV–Vis spectroscopy and BET surface analysis. The obtained results showed successful fabrication of synthesized nanocomposites with enhanced surface area. Degradation effect of nanostructures on methylene blue (MB) and antibacterial activity against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis) pathogenic strains were investigated. The proposed photocatalytic mechanism illustrated the electron transfer facilitated by MWCNTs/ZnO/Chitosan structure which results in spatial separation of electron–hole pairs. Compared with ZnO and ZnO/Chitosan, the prepared MWCNTs/ZnO/Chitosan ternary nanocomposite showed high usage of UV illumination and superior separation of photogenerated electron–hole pairs. MWCNTs/ZnO/Chitosan illustrated 86.26% adsorption rate and outstanding increased photocatalytic activity on MB degradation efficiency of 98.76% after 20 min. Stability of photocatalyst reached from 98.76% initial decolorization to 85% at the fourth cycle. In addition, the ternary nanocomposite also exhibited remarkable bactericidal activity against gram-positive (S. aureus) and (B. subtilis) and gram-negative (E. coli) bacteria strains. Due to the obtained results, the prepared nanocomposite would be an efficient candidate photocatalyst with antibacterial properties.

Removal of sulfur dioxide by carbon impregnated with triethylenediamine, using indigenously developed pilot scale setup

In order to provide protection against extremely toxic gases, activated carbon (AC) adsorption has long been regarded to be a useful technology in terms of gas removal. AC without chemical impregnation has been considerably less effective than impregnated ACs. AC in present use was modified with an organic amine, i.e., triethylenediamine (TEDA) to enhance the physical and chemical properties of AC in order to remove specific poisonous gases. With the rising concern on environmental pollution, there has been an increased curiosity in ACs as the means for eliminating pollutants from environment. Purpose of this study was to assess the TEDA impregnated AC in terms of adsorption capability for simulant gas like SO₂. Analysis was done in a properly designed setup. By using the scheme reported here, significant adsorption of toxic gas was obtained. Maximum removal capability observed by AC-4 for SO₂ gas was 374 mg/g-C and its breakthrough time was 264 min. Breakthrough time and adsorption capacity of AC-4 was found to be 25 times and 10 times greater as compared to raw AC. Different characterization techniques were also used to study impregnated AC. It was found that chemical adsorption was the crucial means by which TEDA-impregnated AC removed the simulant gas. Langmuir model was best to represent equilibrium, and adsorption kinetics follow second-order model. The process was endothermic, favorable, and spontaneous.

Effect of magnetic field on the removal of copper from aqueous solution using activated carbon derived from rice husk

Adsorptive removal of copper by activated carbon derived from modified rice husk (ACRH) was studied in the presence and absence of magnetic field (MF). The ACRH was prepared from the normal rice husk treated by NaOH solution and subsequent pyrolysis at 450 °C in the absence of oxygen. The physicochemical properties of ACRH's were determined before and after the adsorption process to delineate the adsorption mechanism. The BET analysis confirmed that the fabricated ACRH has a specific surface area of 8.244 m²/g with a mesopore to micropore ratio of 0.974. It was observed that the micropore structure gradually replaced the mesopores, and the surface area of the micropore increased (from 0.9219 to 4.1764 m²/g), and the pore diameter was also decreased from 180.381 to 46.249 Å after pyrolysis. The CHNO/S test result reveals that the carbon content was increased from 42 to 67.8% in the ACRH after pyrolysis. The batch sorption studies were performed by varying the initial adsorbate concentration, temperature, agitation speed, pH, adsorbent dose and contact time for magnetic and non-magnetic conditions to analyze the effect of the magnetic field. The univariate studies show that the maximum experimental adsorption capacity was 4.522 mg/g and 3.855 mg/g, respectively, for these two conditions (representing the magnetic impact) at 25 °C with an adsorbent dose of 2 g/L and an agitation speed of 150 rpm. It was also observed that the removal efficiency was 94.55% and 77.96% (magnetic and non-magnetic condition) at pH 7 with a concentration of 10 mg/L in 2 h. The test result on the impact of exposure time on the magnetic field suggested that the magnetic memory influenced the removal efficiency; after 40 to 60 min, the maximum removal efficiency was achieved, around 80 to 90%. The pseudo-second-order kinetic model was best fitted with the experimental data with a rate constant as 0.1749 and 0.1006 g/mg/min for these two conditions. The Temkin model delineates the adsorption isotherm suggesting the heat generated during the adsorption process is linearly abate with the coverage of the surface area of the adsorbent. The thermodynamic model confirms that the copper adsorption is spontaneous (ΔG = - 3.91 kJ/mol and - 6.02 kJ/mol), wherein the negative enthalpy value (ΔH = - 36.74 kJ/mol and - 25.74 kJ/mol) suggested that the process is exothermic irrespective of magnetic interference. The significant enhancement of copper removal was observed by incorporating the magnetic field, showing an increase in sorption capacity by 17.48% and a reduction of reaction time by 88.12%.

In-silico identification of lysine residue for α-Amylase immobilization on dialdehyde cellulose

Enzymes are the precious gift of nature to humans. The wise utilization of enzymes may reduce energy needs of humans and the Immobilization technique can help a lot in this regard. This aspect overcomes limitations of the enzymes, therefore providing an opportunity to explore enzymatic chemistry further. In the present context, it is quite cumbersome & costly to identify the amino acid of enzymes involved in the covalent mode of Immobilization. In the present study, molecular modeling techniques were used to do this difficult task. The present work used molecular modeling methods to extract information about the immobilization of α-Amylase (E.C.3.2.1.1) on Dialdehyde Cellulose. The Lysine residue is the most probable residue to interact with Dialdehyde Cellulose. In the present work, a total of 23 lysine residues were used to study covalent binding behavior with α-Amylase. It was found that if Lys¹⁴² is involved in binding with Dialdehyde Cellulose then binding affinity (-6.1 & -5.9 kcal mol^-1), as well as the involvement of amino acids of both free α-Amylase and Lys¹⁴² immobilized α-Amylase with the starch substrate, were found to be similar. The technique reported here is used for the identification of amino acid residue for the Immobilization of enzymes.

Efficient removal of Pb(II) using modified chitosan Schiff base@Fe/NiFe

A novel modified chitosan Schiff base@Fe₂O₃-NiFe₂O₄ (CsSB@Fe/NiFe) was prepared and characterized using FT-IR, XRD, SEM, EDX, TGA, DSC and VSM. FT-IR and XRD results confirm that the nanoparticles of Fe/NiFe distributed throughout the surface of CS-OH and successfully prepared CsSB@Fe/NiFe. SEM image shows that the Fe/NiFe nanoparticles were assembled in the surface and inside of CS-OH. Coercivity (H_c) of CsSB@Fe/NiFe is ≈ 110 Oe, indicated that it was kind of soft-magnetic materials with saturation magnetization (M_s) of 6.45 emu/g. In addition, CsSB@Fe/NiFe was further explored as an new sorbent for the removal of Pb(II) ion from aqueous solution and the influence of various important parameters such as solution pH, contact time, dosage of adsorbent and initial Pb(II) concentration were studied and optimized. Optimum conditions for Pb(II) removal were found to be pH 5, adsorbent dosage 0.05 g, initial Pb(II) concentration of 75 ppm and contact time of 120 min. The maximum Pb(II) removal percentage was found to be 97%. Also, CsSB@Fe/NiFe shows about 88% Pb(II) removal after five adsorption-desorption cycles. The results suggested that the sorption of Pb(II) onto CsSB@Fe/NiFe was feasible and spontaneous.

[OPy][BF4] Selective Extraction for Trace Hg2+ Detection by Electrochemistry: Enrichment, Release and Sensing

Trace mercury ion (Hg2+) detection is important for environmental monitoring and water safety. In this work, we study the electrochemical strategy to detect trace Hg2+ based on the preconcentration of temperature-controlled N-octylpyridinium tetrafluoroborate ([OPy][BF4]) dispersive liquid-liquid microextraction. The [OPy][BF4] selectively extracted Hg2+ from aqueous solution by the adsorption of unsaturated N in [OPy][BF4], which increased the concentration of Hg2+ and decreased that of other interference ions. It was noted that the adsorption of [OPy][BF4] to Hg2+ was weakened by aqueous solution. Hence, after extraction, precipitated [OPy][BF4] was diluted by a buffer solution comprising a mixture of water and acetonitrile to release Hg2+ and the single was detected by electrochemistry. Water is proposed to release Hg2+ adsorbed by [OPy][BF4], and the acetonitrile serves as a co-solvent in buffer solution. Sensitivity and anti-inference ability of sensors were improved using the proposed method and Hg2+ releasing procedure. The detection limit (S/N = 3) of the sensor is 0.0315 μg/L with a linear range from 0.1 to 1 μg/L. And the sensor exhibits good recovery with an range from 106 % to 118%, which has great potential for trace Hg2+ determination.

Cellulose-deconstruction potential of nano-biocatalytic systems: A strategic drive from designing to sustainable applications of immobilized cellulases

Nanostructured materials along with an added value of polymers-based support carriers have gained high interest and considered ideal for enzyme immobilization. The recently emerged nanoscience interface in the form of nanostructured materials combined with immobilized-enzyme-based bio-catalysis has now become research and development frontiers in advance and applied bio-catalysis engineering. With the involvement of nanoscience, various polymers have been thoroughly developed and exploited to nanostructured engineer constructs as ideal support carriers/matrices. Such nanotechnologically engineered support carriers/matrix possesses unique structural, physicochemical, and functional attributes which equilibrate principal factors and strengthen the biocatalysts efficacy for multipurpose applications. In addition, nano-supported catalysts are potential alternatives that can outstrip several limitations of conventional biocatalysts, such as reduced catalytic efficacy and turnover, low mass transfer efficiency, instability during the reaction, and most importantly, partial, or complete inhibition/deactivation. In this context, engineering robust and highly efficient biocatalysts is an industrially relevant prerequisite. This review comprehensively covered various biopolymers and nanostructured materials, including silica, hybrid nanoflower, nanotubes or nanofibers, nanomembranes, graphene oxide nanoparticles, metal-oxide frameworks, and magnetic nanoparticles as robust matrices for cellulase immobilization. The work is further enriched by spotlighting applied and industrially relevant considerations of nano-immobilized cellulases. For instance, owing to the cellulose-deconstruction features of nano-immobilized cellulases, the applications like lignocellulosic biomass conversion into industrially useful products or biofuels, improved paper sheet density and pulp beat in paper and pulp industry, fruit juice clarification in food industry are evident examples of cellulases, thereof are discussed in this work.

Recent progress in green and biopolymer based photocatalysts for the abatement of aquatic pollutants

Enormous research studies on the abatement of anthropogenic aquatic pollutants including organic dyes, pesticides, cosmetics, antibiotics and inorganic species by using varieties of semiconductor photocatalysts have been reported in recent decades. Besides, many of these photocatalysts suffer in real applications owing to their high production cost and low stability. In many cases, the photocatalysts themselves are being considered as secondary pollutants. To eliminate these drawbacks, the green synthesized photocatalysts and the use of biopolymers as photocatalyst supports are considered in recent years. In this context, recent developments in green synthesized metals, metal oxides, other metal compounds, and carbon based photocatalysts in water purification are critically reviewed. Furthermore, the pivotal role of biopolymers including chitin, chitosan, cellulose, natural gum, hydroxyapatite, alginate in photocatalytic removal of aquatic pollutants is comprehensively reviewed. The presence of functional groups, electron trapping ability, biocompatibility, natural occurrence, and low production cost are the major reasons for using biopolymers in photocatalysis. Finally, the summary and conclusion are presented along with existing challenges in this research area.

Preparation of Sn/Fe nanoparticles for Cr (III) detection in presence of leucine, photocatalytic and antibacterial activities

In this project, Sn-Fe bimetallic nanoparticles were prepared by a facile method. The bimetallic nanoparticles of it could be well established by a field emission scanning electron microscope micrographs. Due to the excellent synergistic influence between Sn-Fe nanoparticles and leucine indicated a great performance for determination of Cr³⁺. The material was characterized using the XRD, DLS, and zetasizer for theevaluation of crystal structure and morphologyinformation.The potential and effective size of Sn-Fe NPs was -29.10 mV and 30 nm, respectively. Cr³⁺ ions interaction with the Sn-Fe NPs-leucine probe was carried out in 1 min as response time. The limit of detection of Sn-Fe NPs for Cr(III) colorimetric method was 0.25 nM. The prepared nanoparticles showed impressive photocatalysis efficiency for degradation of MO was about 95.1% in 35 min, thus the prepared nanoparticles may be developed for the detoxification of pollution. The prepared nanoparticles depicted effective antibacterial activity againstC. botulinum and, H. pylori bacteria.

Facile synthesis of gold-silver/copper sulfide nanoparticles for the selective/sensitive detection of chromium, photochemical and bactericidal application

In this project, bimetallic Au-Agnanoparticles/CuS nanoparticles were prepared via simple hydrothermal methods, which were used as highly efficient material for Cr (III) detection, photocatalytic, and biological process. The Au-Ag/CuS nanoparticles was studied via UV-visible spectroscopy, field-emission scanning electron microscopy, Dynamic light scattering, and X-ray diffraction. The zeta potential and effective size of Au-Ag/CuS nanoparticles was -32.1 mV and 25 nm respectively. The response time of Cr (III) ions interaction was 2 min. The lowest detection of Cr (III) by Au-Ag/CuS nanoparticles was 0.5 nM. The Au-Ag/CuS nano catalyst was applied to decomposition of drug under visible lamp irradiation. The photo degradation response of drug was 100.0% in 30 min irradiation. The particles exhibited excellent antibacterial activities.

Kinetic and thermodynamic studies of novel acid phosphates extracted from Cichorium intybus seedlings

Herein for the first time a novel acid phosphatase from the seedlings of Cichorium intybus was purified to homogeneity by using various chromatographic techniques (salt precipitation, ion exchange, size exclusion and affinity chromatography) and thermodynamically characterized. The molecular mass of purified enzyme (66 kDa) was determined by SDS-PAGE under denaturing and non-denaturing conditions and by gel-filtration confirmed as dimer of molecular mass 130 kDa. The Michaelis-Menten (Km) constant for -p-NPP (0.3 mM) and (7.6 μmol/min/mg) Vmax. The enzyme was competitively inhibited by phosphate, molybdate and vanadate. Phenyl phosphate, ɑ and β-glycero-phosphate and-p-NPP were found to be good substrate. When temperature increased from (55 °C to 75 °C), the deactivation rate constant (kd) was increased (0.1 to 4.6 min-1) and half- life was decreased from 630 min to 15 min. Various thermal denaturation parameters; change in enthalpy (ΔH°), change in entropy (ΔS°) and change in free energy (ΔG°) were found 121.93 KJ·mol-1, 72.45 KJ·mol-1 and 98.08 KJ·mol-1 respectively, confirming that acid phosphatase undergoes a significant process of unfolding during deactivation. The biochemical properties of acid phosphatase from C. intybus on the behalf of biological activity and its relationship to pH variations, thermal deactivation and kinetics parameters provide an insight into its novel features.

Synthesis and Characterization of Ru-MOFs on Microelectrode for Trace Mercury Detection

Mercury ions (Hg2+) pollution in the water environment can cause serious harm to human health. Trace Hg2+ detection is of vital importance for environmental monitoring. Herein, we report a novel design of Ru-MOFs modified gold microelectrode for Hg2+ determination. Ru-MOFs are synthesized directly by the cathodic method on gold microelectrode, with the covered area accurately controlled. Cathodic synthesized Ru-MOFs show good conductivity and are suitable to be used as the electrode surface material directly. The synergy of the pre-deposition process and the adsorption process of Ru-MOFs can effectively improves the performance of the sensor. The results show good linearity (R2 = 0.996) from 0.1 ppb to 5 ppb, with a high sensitivity of 0.583 μA ppb-1 mm-2. The limit of detection is found to be 0.08 ppb and the test process is within 6 min. Most importantly, the senor has a good anti-interference ability and the recoveries are satisfactory. This miniature electrochemical sensor has the potential for on-site detection of trace mercury in the field.