Lake Water Samples Research Articles

Multi-core–shell nanoboxes comprising polydopamine-derived C coated NiCo@C and FeCo@C nanohybrid for enhanced electrochemical quantification of nitrofurantoin

The development of a high-performance electrochemical sensing platform for monitoring nitrofurantoin (NFT) levels in various real samples plays an important role in the research community worldwide. To accomplish this objective, the crucial challenge is to construct sensing interfaces with outstanding electrocatalytic capabilities. In the present work, a highly efficient metal@carbon electrocatalyst with porous and multi-core–shell nanobox structure comprising polydopamine (PDA)-derived C coated NiCo@C and FeCo@C nanohybrid (named as NiCo@C/FeCo@C@C) was fabricated by simply pyrolyzing NiCo@FeCo Prussian blue analogues (PBA)@PDA. The carbonization of PDA into carbon shells protected the framework from collapsing during high-temperature pyrolysis process, thus enlarging the specific surface areas and porosity. The NiCo@C/FeCo@C@C composite attained an enhanced electrochemical capability, such as an outstanding electronic conductivity from the double carbon shell with porous structure, a large number of active sites and a high electrocatalytic activity from the metallic alloy nanoparticles, which exhibited a highly sensitive response to NFT. Under optimized experimental conditions, the established NiCo@C/FeCo@C@C electrochemical sensor displayed a wide linear range of 0.05–100 μM for NFT determination, coupled with a low detection limit of 14 nM. The practical feasibility of this sensor was also confirmed by the analysis of NFT in tablet and lake water samples with outstanding recovery rates. Moreover, the sustainability of the sensor was demonstrated through its prominent performance in high reproducibility, selectivity and long-term stability. This study thus introduces an innovative approach for the advance of highly efficient electrocatalysts in the area of electrochemical sensing.

Cobalt single-site molecular Catalyst-mediated electrochemical Hydrodechlorination for detoxification of halogenated Antibiotics: Performance, reaction pathway and mechanism

Electrocatalytic hydrodehalogenation (ECHD) offers a promising approach for detoxification of the halogenated antibiotics via hydrogenolysis of the C-X bonds (X = F, Cl or Br). Herein we demonstrated that the commercially-available cobalt phthalocyanine (CoPc) molecules with a high-loading of −[Co-N4]- moieties (Co wt%: 10.8 %) were exceptionally active for hydrogenolysis of the C-Cl bonds in florfenicol (FLO). It afforded an impressive mass activity of 6.2 gFLO h−1 g-1Co, a low Co leaching of 0.34 μg/L and a strong tolerance to interference from impurities in water, significantly surpassing reported Co/Fe/Ni-based particle and single-site counterparts. Mechanistic studies revealed that the ECHD on CoPc underwent a direct electron transfer manner rather than the atomic hydrogen (H*)-mediated indirect way, and the ECHD efficacy was affected by both the electron and proton transfer kinetics. The single-atom Co, with its d orbitals constituting the lowest unoccupied molecular orbitals of CoPc, served as the primary active site. It facilitated both electron and proton transfer, as well as the cleavage of the C-Cl bond but not the C-F bond. In a continuous-flow cell, the CoPc/C-driven ECHD reduced the antibacterial activity of a FLO-contaminated natural lake water sample by 90.8 % with an energy consumption of 0.19 kwh g-1FLO. This study highlighted great promise of the single-atom metal-bearing molecular catalyst toward the sustainable detoxification of halogenated antibiotics-contaminated water.

Green and Mild Fabrication of Magnetic Poly(trithiocyanuric acid) Polymers for Rapid and Selective Separation of Mercury(II) Ions in Aqueous Samples.

The removal and detection of highly toxic mercury(II) ions (Hg2+) in water used daily is essential for human health and monitoring environmental pollution. Efficient porous organic polymers (POPs) can provide a strong adsorption capacity toward heavy metal ions, although the complex synthetic process and inconvenient phase separation steps limit their application. Hence, a combination of POPs and magnetic nanomaterials was proposed and a new magnetic porous organic polymer adsorbent was fabricated by a green and mild redox reaction in the aqueous phase with trithiocyanuric acid (TA) and its sodium salts acting as reductive monomers and iodine acting as an oxidant. In the preparation steps, no additional harmful organic solvent is required and the byproducts of sodium iodine are generally considered to be non-toxic. The resulting magnetic poly(trithiocyanuric acid) polymers (MPTAPs) are highly porous, have large surface areas, are rich in sulfhydryl groups and show easy magnetic separation ability. The experimental results show that MPTAPs exhibit good adsorption affinity toward Hg2+ with high selectivity, rapid adsorption kinetics (10 min), a large adsorption capacity (211 mg g-1) and wide adsorption applicability under various pH environments (pH 2~8). Additionally, MPTAPs can be reused for up to 10 cycles, and the magnetic separation step of MPTAPs is fast and convenient, reducing energy consumption compared to centrifugation and filtration steps required for non-magnetic adsorbents. These results demonstrate the promising capability of MPTAPs as superior adsorbents for effective adsorption and separation of Hg2+. Based on this, the prepared MPTAPs were adopted as magnetic solid-phase extraction (MSPE) materials for isolation of trace Hg2+ from aqueous samples. Under optimized conditions, the extraction and quantification of trace Hg2+ in water samples were accomplished using inductively coupled plasma mass spectrometry (ICP-MS) detection after MSPE procedures. The proposed MPTAPs-based MSPE-ICP-MS method is efficient, rapid, sensitive and selective for the determination of trace Hg2+, and was successfully employed for the accurate analysis of trace Hg2+ in tap water, wastewater, lake water and river water samples.

One-step detection of nanoplastics in aquatic environments using a portable SERS chessboard substrate

Nanoplastics present a significant hazard to both the environment and human health. However, the development of rapid and sensitive analysis techniques for nanoplastics is limited by their small size, lack of specificity, and low concentrations. In this study, a surface-enhanced Raman scattering (SERS) chessboard substrate was introduced as a multi-channel platform for the pre-concentration and detection of nanoplastics, achieved by polydomain aggregating silver nanoparticles (PASN) on a hydrophilic and a punched hydrophobic PVDF combined filter membrane. Through a straightforward suction filtration process, nanoplastics were captured by the PASN gap in a single step for subsequent SERS detection, while excess moisture was promptly eliminated from the filter membrane. The PASN-based SERS chessboard substrate, benefiting from the enhanced electromagnetic (EM) field, effectively discriminated polystyrene (PS) nanoplastics ranging in size from 30 nm to 1000 nm. Furthermore, this substrate demonstrated favorable repeatability (RSD of 8.6 %), high sensitivity with a detection limit of 0.001 mg/mL for 100 nm of PS nanoplastics, and broad linear detection ranges spanning from 0.001 to 0.5 mg/mL (R2 = 0.9916). Additionally, the SERS chessboard substrate enabled quantitative analysis of nanoplastics spiked in tap and lake water samples. Notably, the entire pre-concentration and detection procedure required only 3 μL of sample and could be completed within 1 min. With the accessibility of portable detection instruments and the ability to prepare substrates on demand, the PASN-based SERS chessboard substrate is anticipated to facilitate the establishment of a comprehensive global nanoplastics map.

Construction of a ratiometric electrochemical sensor for Bisphenol A detection by coupling nonionic surfactant-decorated conductive carbon black with ferricyanide probe

In this work, a novel ratiometric electrochemical sensor for bisphenol A (BPA) detection was facilely constructed by coupling conductive carbon black (VXC-72R) with ferricyanide probe. The VXC-72R was decorated with nonionic surfactant Tween to enhance the sensitivity and coated on glassy carbon electrode (GCE), whereas K3[Fe(CN)6] was introduced into electrolyte solution as an internal reference probe to realize dual-signal outputs. The present ratiometric electrochemical sensor achieved a highly sensitive and selective detection of BPA in PBS solution (pH = 7.0), with a linear range of 0.08–40.0 μM and detection limit of 0.05 μM. Moreover, it has been successfully applied to the determination of BPA in real lake water and milk samples with the satisfactory recoveries rates of 94.8–102.3 %.

Biomass Carbon Dots as Fluorescent Probes for Fast and Highly Selective Detection of Fe3 + in Water Media.

In this study, a novel fluorescent probe for the rapid and highly selective detection of Fe3 + based on biomass carbon dots (b-CDs) was developed. The b-CDs were obtained via one-step hydrothermal synthesis by utilizing laurel fallen leaves. And the as-synthesized b-CDs were applied for sensing Fe3+ based on fluorescence (FL) quenching effect both in water and phosphate buffer solution (PBS) with a wide linear range from 1 µM to 300 µM, the detection limits (LODs) respectively to be 0.34 µM in water and 0.48 µM in PBS solution. The FL intensity of b-CDs was quenched fleetly within 1min after adding Fe3+. The sensing mechanism of the b-CDs + Fe3+ system can be attributed to the internal filtration effect (IFE) mechanism and the electron transfer (ET) between b-CDs and Fe3+ in water, and only the IFE mechanism in PBS solution based on multiple experimental evidences. Moreover, the as-proposed probe was successfully adopted for monitoring Fe3+ in lake water and tap water samples. This research shows some merits of economic, simplicity, green, high selectivity, and quick response for Fe3+ determination, and provides an approach for the water quality monitoring of Fe3+ and the effective utilization of waste biological materials.

Comprehensive characterization and resistome analysis of Antarctic Pseudomonas migulae strain CAS19.

Although traditionally considered pristine, Antarctica faces an increasing threat of antibiotic resistance due to human intervention. Here, we obtained a bacterial isolate, the CAS19 strain, from a lake water sample from Ardley Island, Antarctica and characterized it comprehensively. The CAS19 was a psychrotrophic and neutrophilic/alkalitolerant bacterium thriving at temperatures from 15 to 33°C and pH levels from 6.0 to 9.0. Besides the production of siderophore and indole acetic acid, it also exhibited proteolytic and lipolytic activities. It was identified as Pseudomonas migulae by multilocus (16S rRNA, gyrB, rpoB and rpoD) sequence analysis, and its genome was 6.5 Mbps in length, had 59% GC content, and contained 5,821 coding sequences. The CAS19 was resistant to several antibiotics, including trimethoprim, penicillin, vancomycin, and erythromycin, confirmed by RT-qPCR analysis, with a notable increase in dfr (63-fold), bla (461-fold), vanW (31.7-fold) and macA (24.7-fold) expressions upon antibiotic exposure. Additionally, CAS19 exhibited resistance to heavy metals with an order of Cr(III) = Cu(II) > Ni(II) > Zn(II) > Cd(II), and showed diesel fuel (5%) degradation capacity. Cold-related genes cspA_2 and cspD were overexpressed at 4 and 15°C, consistent with the cold adaptation mechanism. In conclusion, for the first time an Antarctic P. migulae isolate has been characterized in detail, uncovering a rich resistome repertoir that might be associated with anthropogenic disturbances.

Application of Fabric Phase Sorptive Extraction as a Green Method for the Analysis of 10 Anti-Diabetic Drugs in Environmental Water Samples

Due to the increased prevalence of diabetes, the consumption of anti-diabetic drugs for its treatment has likewise increased. Metformin is an anti-diabetic drug that is commonly prescribed for patients with type 2 diabetes and has been frequently detected in surface water and wastewaters, thus representing an emerging contaminant. Metformin can be prescribed in combination with other classes of anti-diabetic drugs; however, these drugs are not sufficiently investigated in environmental samples. Fabric phase sorptive extraction (FPSE) has emerged as a simple and green method for the extraction of analytes in environmental samples. In this study, FPSE coupled with a high-performance liquid chromatography diode array detector (HPLC-DAD) was employed for the simultaneous analysis of different classes of anti-diabetic drugs (metformin, dapagliflozin, liraglutide, pioglitazone, gliclazide, glimepiride, glargine, repaglinide, sitagliptin, and vildagliptin) in environmental water samples. Four different fabric membranes were synthesized but the microfiber glass filter coated with sol-gel polyethylene glycol (PEG 300) was observed to be the best FPSE membrane. The parameters affecting the FPSE process were optimized using a combination of one-factor-at-a-time processes and the design of experiments. The FPSE was evaluated as a green extraction method, based on green sample preparation criteria. The FPSE-HPLC-DAD method achieved acceptable validation results and was applied for the simultaneous analysis of anti-diabetic drugs in surface and wastewater samples. Glimepiride was detected below the quantification limit in both lake and river water samples. Dapagliflozin, liraglutide, and glimepiride were detected at 69.0 ± 1.0 μg·L−1, 71.9 ± 0.4 μg·L−1, and 93.9 ± 1.3 μg·L−1, respectively, in the city wastewater influent. Dapagliflozin and glimepiride were still detected below the quantification limit in city wastewater effluent. For the hospital wastewater influent, metformin and glimepiride were detected at 1158 ± 21 μg·L−1 and 28 ± 0.8 μg·L−1, respectively, while only metformin (392.6 ± 7.7 μg·L−1) was detected in hospital wastewater effluent.

Fabrication of mesoporous Sm-Nd2O3/Thymine doped gC3N4 nanocomposite for the adsorption and photodegradation of ciprofloxacin under visible light

The ciprofloxacin (CIP) antibiotic was degraded using Sm-Nd2O3 decorated Thymine doped gC3N4 (Sm-Nd2O3/T-gC3N4) nanocomposite under visible light irradiation. The oxygen-containing component like thymine doped in the gC3N4 significantly improves the active sites of the catalyst and its ability to absorb light, which highly influences the adsorption and photocatalytic activity. The chemical and morphological analysis of the nanocomposite were studied utilizing the XRD, FTIR, HRSEM, HRTEM, EDAX, UV-DRS, XPS, BET, and PL. The photocatalytic activity was investigated under several factors such as pH, initial concentration of CIP, catalyst dosage, inorganic anions, and real lake water sample, to optimize and enhance the photocatalytic efficiency of Sm-Nd2O3/T-gC3N4 nanocomposite, as a result, the degradation efficiency achieved to 99.65 % within 120 min with the rate constant of 0.0472 min−1. The Z-scheme mechanism of the Sm-Nd2O3/T-gC3N4 photocatalyst was proposed based on the Mott-Schottky and trapping experiments. Further, the degradation pathway of CIP was postulated based on the intermediates, identified by the LC-MS analysis

Present Understanding of Biodiversity of Anoxygenic Phototrophic Bacteria in the Relic Lake Mogilnoe (Kildin Island, Murmansk oblast, Russia)

The relic Lake Mogilnoe, separated from the Barents Sea by a sand and pebble dam, is located in the high Arctic on the Kildin island (Murmansk region). This lake is a classic example of a meromictic basin of marine origin. The data obtained during the 2018 expedition showed changes in the hydrochemical regime of the lake that have occurred over the past 20 years. Sulfide concentration in the monimolimnion of the lake was as high as 140 mg/L. A tendency for salinization of the surface waters to 7 g/L has been noted. The Lake Mogilnoe is characterized by a discrepancy between the halocline and thermocline levels. The chemocline zone in the lake is below the halocline level. In a narrow oxygen-containing layer between 3 and 7.5 m, aerobic microflora of the marine type and marine fauna were present. The bacterial plate was formed at the boundary of the sulfide layer at ~8 m and mainly consisted of green sulfur bacteria (GSB). Brown-colored GSB species containing bacteriochlorophyll e were predominant. The previously formed concept of anaerobic phototrophic bacteria (APB) biodiversity based on morphological characteristics was modified using metagenomic data obtained by analyzing DNA from two samples of lake water in the chemocline zone, and was also supplemented by identifying new GSB species. Molecular diagnostic data confirmed the absolute dominance of the brackish species of GSB Chlorobium phaeovibrioides. This is the first on isolation and identification of brown- and green-colored Prosthecochloris aestuarii morphotypes from Lake Mogilnoe and identified, as well as of bacteriochlorophyll c-containing Prosthecochloris sp. The taxonomic position of Pelodyction phaem, which was constantly present in the Lake Mogilnoe, is discussed in detail. Despite the partial isolation of the ecosystem of Lake Mogilnoe from the Barents Sea, the main properties of the dominant GSB species of GSB and Prosthecochloris aestuarii turned out to be similar to those of the phylotypes living in lakes on the White Sea coast of the, which remained connected with the Barents Sea.

Supramolecular Solvent Liquid Phase Microextraction of Voriconazole İn Pharmaceutical and Environmental Samples With High Performance Liquid Chromatography Detection

In this study, a new analytical method based on the supramolecular solvent liquid phase microextraction (Ss-LPME) and HPLC was developed for the analysis of voriconazole as an active drug in the class of antifungals with a wide spectrum of action at trace levels. Nano/micro sized supramolecular phase formed in 1-decanol, tetrahydrofuran and aqueous environment was used as extraction agent for separation and preconcentration of trace level of voriconazole. For the optimization of the Ss-LPME method, important analytical parameters such as the effect of sample solution pH, volume of 1-decanol, amount of THF, ultrasounic irridation time, centrifugation time and sample solution volume on the extraction efficiency were evaluated. Optimal conditions of the Ss-LPME; pH: 8, 1-decanol volume: 200 µL, THF volume: 300 µL, ultrasounic irridation time:10 min and centrifugation time: 8 min. For the developed Ss-LPME/HPLC procedure, the limit of detection (LOD), limit of quantification (LOQ) and enhancement factor (EF) were found 2.7 µg·L-1, 8.8 µg·L-1 and 36, respectively. The Ss-LPME/HPLC procedure was applied to waste water, lake water and drug samples. The fact that recovery values ranging from 100% to 108.5% were obtained for these real samples proved that this method can be used successfully in the matrix environments studied

Template-synthesizing hollow cubic CeO2/Co3O4 heterostructure as electrocatalysts for sensing hydrogen peroxide

H2O2 as an important intermediary is becoming more widely acknowledged, and interest in its detection has increased significantly. Herein, we developed a hollow cubic CeO2/Co3O4 heterostructure and further employed as non-enzymatic H2O2 detection sensor through a series of facile synthesis strategies using cobalt-based zeolitic imidazolate framework as a template. The synthesized CeO2/Co3O4 with huge cavity structure offers numerous electrocatalytic active sites for the target analyte, thus endowing its high sensitivity (60.5 μA. mM−1cm−2), excellent selectivity, broad detection range for H2O2 (10 μM -1 mM), and favorable working potential (-0.45 V). Not only that the CeO2/Co3O4 sensor achieved satisfactory recovery and accuracy in real lake-water samples.

A green procedure for the determination of bioavailable forms of aluminum in natural waters by electrothermal atomic absorption spectroscopy combined with microextraction technique.

Aluminum is a prevalent element in nature, but bioavailable forms of aluminum are toxic to plants, animals, and humans. The present study is dedicated to the development of an ecologically friendly, fast, simple, reliable, sensitive, and accurate improved procedure for the determination of subtrace concentrations of bioavailable forms of aluminum in natural waters. The procedure includes the separation and pre-concentration of bioavailable forms of aluminum using vortex-assisted liquid-liquid microextraction (VALLME) of ionic associates with salicylaldehyde 4-picolinhydrazone (SAPH) and sodium dodecyl sulfate (DDSNa) by isoamylacetate (200μl) and direct electrothermal atomic absorption spectroscopy (ETAAS). The SAPH reagent interacts only with water-soluble forms of aluminum. SAPH is used for the pre-concentration of bioavailable forms of aluminum as well as a chemical modifier; it increases the absorbance and the precision of the analytical signal of aluminum. The calibration curve shows the linear dependence in the range of 0.05-86μg⋅L-1 of the aluminum concentration (R2 = 0.992), with the limit of detection at 0.015μg⋅L-1 and the limit of quantification at 0.05μg⋅L-1. The accuracy of the proposed procedure for bioavailable forms of aluminum determination was verified on model solutions and against a reference method on natural samples of river and lake waters (RSD 3.2-5.2%, recovery 97.1-103.4%).

One stone, three birds: The enhanced electrocatalytic sensing for 4-nitrophenol derived from the triple-strategies regulated interface of Co-ZIF-L/NCS/CP

4-nitrophenol (4-NP) is one of the most toxic organic pollutants, which causes severe damages to organism and environment. The electrochemical analysis for 4-NP proceeded slowly due to the hard electrocatalytic reduction of 4-NP, the limited catalytic sites and poor stability of the electrodes. In this paper, by the “one stone with three birds” strategy, a series of three-phase interfaces n-Co-ZIF-L/NCS-X/CP were constructed for the enhanced electrocatalytic sensing for 4-NP. By the dual in-situ strategy, NiCo2S4 (NCS) was first electrodepositing on carbon paper (CP) and then Co-based metal-organic framework (Co-ZIF-L) was grown on the NiCo2S4, which not only introduced abundant metal active sites, but also improved the interfacial stability due to the strong bond interactions; By the dual-regulation strategy, the structures and composites of NiCo2S4 and Co-ZIF-L were precisely regulated. The heterogeneous structure of lamellar and nanoflower-like NiCo2S4, as well as the two-dimensional leaf-like Co-ZIF-L, made more catalytic sites be exposed and improved the electrocatalytic activity; The triple synergistic effect among Co-ZIF-L, NiCo2S4 and CP effectively optimized the electronic structure of the interfacial active sites and widen the electron transport channels, thus accelerated the electrochemical sensing process. In addition, the three-phase interface of 0.3-Co-ZIF-L/NCS-20/CP was successfully applied for 4-NP detection in the practical samples of lake water, seawater and industrial wastewater.

Monomer-mediated growth of β-cyclodextrin-based microporous organic network as stationary phase for capillary electrochromatography.

CD-MONs (β-cyclodextrin-based microporous organic networks), derived from β-cyclodextrin, possess notable hydrophobic characteristics, a considerable specific surface area, and remarkable stability, rendering them highly advantageous in separation science. This research aimed to investigate the utility of CD-MONs in chromatography separation. Through a monomer-mediated technique, we fabricated an innovative CD-MON modified capillary column for application in open-tubular capillary electrochromatography (OT-CEC). The CD-MON-based stationary phase on the capillary's inner surface was analyzed using Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). We assessed the performance of the CD-MON modified capillary column for separation purposes. The microstructure and pronounced hydrophobicity of CD-MON contributed to enhanced selectivity and resolution in separating diverse hydrophobic analytes, such as alkylbenzenes, halogenated benzenes, parabens, and polycyclic aromatic hydrocarbons (PAHs). The maximum column efficiency achieved was 1.5 × 105 N/m. Additionally, the CD-MON modified capillary column demonstrated notably high column capacity, with a methylbenzene mass loading capacity of up to 197.9pmol, surpassing that of previously reported porous-material-based capillaries. Furthermore, this self-constructed column was effectively utilized for PAHs determination in actual environmental water samples, exhibiting spiked recoveries ranging from 93.2 to 107.9% in lake water samples. These findings underscore the potential of CD-MON as an effective stationary phase in separation science.

Fluorescence/colorimetric dual-signal sensor based on carbon dots and gold nanoparticles for visual quantification of Cr3.

A convenient and sensitive dual-signal visualization method is constructed for detection of trivalent chromium ions (Cr3+) based on fluorescent carbon dots (CDs) and glutathione-modified gold nanoparticles (GSH-Au NPs). The fluorescence of CDs can be quenched by GSH-Au NPs due to the inner filter effect. Cr3+ induces aggregation of GSH-Au NPs because of the coordination with GSH on the surface of Au NPs, leading to the red shift of surface plasmon resonance absorption of Au NPs that provides a "turn-on" fluorescence and colorimetric assay for Cr3+. The fluorescence/colorimetric dual signal detection shows high sensitivity for Cr3+ with wide detection linear ranges (0.5-70μM for fluorescence detection and 2-50μM for colorimetric detection) and low detection limits (0.31μM for fluorescence detection and 0.30μM for colorimetric detection). Besides, the method has high selectivity for Cr3+ and can be used for detection of Cr3+ in lake water and tap water samples, showing great potential for visual detection of environmental Cr3+.

Characterization and genomic analysis of PA-56 Pseudomonas phage from Istanbul, Turkey: Antibacterial and antibiofilm efficacy alone and with antibiotics

Phages are ubiquitous in freshwater, seawater, soil, the human body, and sewage water. They are potent biopharmaceuticals against antimicrobial-resistant bacteria and offer a promising alternative for treating infectious diseases. Also, combining phages with antibiotics enhances the antibiotics' efficacy. This study focused on two Pseudomonas aeruginosa phages isolated from lake and sewage water samples and one of them selected for further investigation. Isolated phages PA-56 and PA-18 infected 92 % and 86 % of the tested 25 clinical Pseudomonas aeruginosa strains, respectively. PA-56 with strong activity was chosen for detailed characterization, antimicrobial studies, and genome analysis. Combining PA-56 with ciprofloxacin or meropenem demonstrated phage-antibiotic synergism and increased antibiofilm efficacy. Genome analysis revealed a GC ratio of 54 % and a genome size of 42.761 bp, with no virulence or antibiotic resistance genes. Notably, PA-56 harboured the toxin-antitoxin protein, MazG. Overall, this study suggests that PA-56 holds promise for future applications in industry or medicine.

Bi2MoO6/MWCNTs-COOH/GCE electrochemical probe for ultrasensitively and selectively detecting antibiotic norfloxacin

Antibiotics have emerged as a class of contaminants of concern globally, raising widespread worry and unease, primarily because of their inappropriately use and endless migration in food chains. Electrochemical ultrasensitive and selective determination of norfloxacin (NOR) using bismuth-based bimetallic salt bismuth molybdate (Bi2MoO6) and carboxylated multi-walled carbon nanotube (MWCNTs-COOH) hybrid electrode as sensing platforms is presented hereby. The electrocatalytic ability of the electrodes was verified to be enhanced by the synergy effect of both Bi2MoO6 and MWCNTs-COOH using cyclic voltammetry and electrochemical impedance spectroscopy. Linear scan voltammetry was applied to detect NOR. The oxidation peak current was linearly correlated with NOR concentration of 0.03–10 μM and the low limit detection of the optimized method was 6.7 nM (S/N = 3). In addition, it was verified that Bi2MoO6/MWCNTs-COOH/GCE probe had good stability, reproducibility, repeatability and selectivity. The spiked recovery method for NOR in milk and lake water samples showed recoveries of 94.8 – 96.9% and 90.2 – 98.3%, respectively, which can be used to determine NOR in real samples with high sensitivity. The preparation of Bi2MoO6/MWCNTs-COOH/GCE provides a new prototype for probing NOR detection at nanomolar concentration and safeguarding antibiotic contamination in environmental and food chains.

Response surface methodology for the production of a filter membrane from the combination of sand, PET and salt as a pore-forming agent

Plastic waste is increasing every day due to urbanization, population growth and in turn, pollutes the environment. These wastes are considered to be a big problem due to their very low biodegradability and presence in large quantities. A large amount of plastic which is being brought by human activities is discarded or burned which leads to the contamination of the environment and air. Therefore, finding alternative methods of disposing of waste by using kind approaches is becoming a major research issue. In this research, polyethene terephthalate waste is used as a binder by burning and mixing with sand and sodium carbonate to investigate the possibility of producing composite material with a plastic sand filter and study the effect of sand, polyethene terephthalate waste and porogen with different design mix ratio on the properties of the product. An experimental design plan was adopted to formulate the materials. To fabricate this material, the melt moulding/particulate leaching technique was used, in which the components are mixed in their respective proportions, moulded, melted and afterwards leached to remove the porogen. We obtained an optimum of 31.0711% porosity for the optimum mixture containing proportions of 0.5, 0.25 and 0.25 plastic sand and porogen respectively. An improved melt/moulding particulate leaching technique was used to improve the permeability and reduce pore sizes of the optimum. This technique involved using a saturated solution of porogen instead of using the porogen in particulate form. The microbial cut-off efficacy of the material was evaluated, in which microbiological analyses were used to enumerate the number of microbes in a lake water sample before and after filtration through the porous material. The results of viable cell counting showed that the material eliminated 92.6% of the water microbes analysed.

In2O3 electrochemical transistors based on PtAu4/RGO nanocomposites functionalized gate for highly sensitive nitrite detection

Nitrite is commonly found in the environment, but its overuse and potential toxicity pose serious health risks. There is a strong need to develop robust and reliable methods for detecting nitrite. Herein, a novel In2O3 solution-gated electrochemical transistor (SGET) nitrite sensor was designed and fabricated for highly sensitive detection of nitrite. Different thicknesses of In2O3 thin films were prepared by sol–gel method, which were used as the channel of transistors and optimized through evaluating the electronic and electrochemical properties. To improve the catalytic oxidation of nitrite, PtAu4 nanoparticles modified reduced graphene oxide nanocomposites (PtAu4/RGO) were fabricated on the gate of transistors through electrodeposition approach. The developed sensor exhibited exceptional sensing performance in nitrite detection, which featured with low detection limit (0.1 nM nitrite) and ultra-wide linear range from 0.1 nM to 1 mM. The developed In2O3 SGET sensor displayed excellent stability and high resistance to common interfering ions, thereby demonstrating superior anti-interference performance. Nitrite in real samples of natural lake water has been accurately measured, suggesting that the designed sensor could act as an ideal transducer platform for highly sensitive and selective nitrite detection in food and environmental fields.