Mechanochemical Pretreated Mn+1AXn (MAX) Phase to Synthesize 2D-Ti3C2Tx MXene Sheets for High-Performance Supercapacitors.

Two-dimensional (2D) MXenes sheet-like micro-structures have attracted attention as an effective electrochemical energy storage material due to their efficient electrolyte/cation interfacial charge transports inside the 2D sheets which results in ultrahigh rate capability and high volumetric capacitance. In this article, Ti3C2Tx MXene is prepared by a combination of ball milling and chemical etching from Ti3AlC2 powder. The effects of ball milling and etching duration on the physiochemical properties are also explored, as well as the electrochemical performance of as-prepared Ti3C2 MXene. The electrochemical performances of 6 h mechanochemically treated and 12 h chemically etched MXene (BM-12H) exhibit an electric double layer capacitance behavior with an enhanced specific capacitance of 146.3 F g-1 compared to 24 and 48 h treated samples. Moreover, 5000-cycle stability tested sample's (BM-12H) charge/discharge show increased specific capacitance due to the termination of the -OH group, intercalation of K+ ion and transformation to TiO2/Ti3C2 hybrid structure in a 3 M KOH electrolyte. Interestingly, a symmetric supercapacitor (SSC) device fabricated in a 1 M LiPF6 electrolyte in order to extend the voltage window up to 3 V shows a pseudocapacitance behavior due to Li on interaction/de-intercalation. In addition, the SSC shows an excellent energy and power density of 138.33 W h kg-1 and 1500 W kg-1, respectively. The ball milling pre-treated MXene exhibited an excellent performance and stability due to the increased interlayer distance between the MXene sheets and intercalation and deintercalation of Li+ ions.

Electrocatalytic Oxygen Reduction Reaction of Graphene Oxide and Metal-Free Graphene in an Alkaline Medium.

Graphene is a well-known two-dimensional material with a large surface area and is used for numerous applications in a variety of fields. Metal-free carbon materials such as graphene-based materials are widely used as an electrocatalyst for oxygen reduction reactions (ORRs). Recently, more attention has been paid to developing metal-free graphenes doped with heteroatoms such as N, S, and P as efficient electrocatalysts for ORR. In contrast, we found our prepared graphene from graphene oxide (GO) by the pyrolysis method under a nitrogen atmosphere at 900 °C has shown better ORR activity in aqueous 0.1 M potassium hydroxide solution electrolyte as compared with the electrocatalytic activity of pristine GO. At first, we prepared various graphene by pyrolysis of 50 mg and 100 mg of GO in one to three alumina boats and pyrolyzed the samples under a N2 atmosphere at 900 °C. The prepared samples are named G50-1B to 3B and G100-1B and G100-2B. The prepared GO and graphenes were also analyzed under various characterization techniques to confirm their morphology and structural integrity. The obtained results suggest that the ORR electrocatalytic activity of graphene may differ based on the pyrolysis conditions. We found that G100-1B (Eonset, E1/2, JL, and n values of 0.843, 0.774, 4.558, and 3.76) and G100-2B (Eonset, E1/2, and JL values of 0.837, 0.737, 4.544, and 3.41) displayed better electrocatalytic ORR activity, as did Pt/C electrode (Eonset, E1/2, and JL values of 0.965, 0.864, 5.222, and 3.71, respectively). These results display the wide use of the prepared graphene for ORR and also can be used for fuel cell and metal-air battery applications.

Djurleite Copper Sulfide-Coupled Cobalt Sulfide Interface for a Stable and Efficient Electrocatalyst.

Transition metal sulfides (TMS) exhibit proliferated edge sites, facile electrode kinetics, and improved intrinsic electrical conductivity, which demand low potential requirements for total water splitting application. Here, we have propounded copper sulfide-coupled cobalt sulfide nanosheets grown on 3D nickel as an electrocatalyst for hydrogen (HER) and oxygen evolution (OER) reactions. The formation of djurleite copper sulfide with a Cu vacancy enables faster H+ ion transport and shows improved HER activity with a remarkably lower overpotential of 164 mV at 10 mA/cm2, whereas cobalt-incorporated copper sulfide undergoes cation exchange during synthesis and shows elevated OER activity with a lower overpotential of 240 mV at 10 mA/cm2 for the OER. Moreover, Cu2-xS/Co is said to have a hybrid CoS-CoS2 interface and provide Co2+ active sites on the surface and enable the fast adsorption of intermediate species (OH*, O*, and OOH*), which lowers the potential requirement. The copper vacancy and cation exchange with a hybrid CoS-CoS2 structure are helpful in supplying more surface reactive species and faster ion transport for the HER and OER, respectively. The full-cell electrolyzer requires a very low potential of 1.58 V to attain a current density of 10 mA/cm2, and it shows excellent stability for 50 h at 100 mA/cm2 as confirmed by the chronopotentiometry test.

Transition metal oxy/hydroxides functionalized flexible halloysite nanotubes for hydrogen evolution reaction.

The hierarchical halloysite nanotubes (HNT) have alumina containing positive Al-OH groups on its inner surface and silica-containing negative siloxane groups of Si-O-Si on its outer surface. The silicate laminate consists of silicon-oxygen at tetrahedral sites and aluminum-oxygen at octahedral sites. Since HNT has an abundant hydroxyl group on the surface with exceptional cation/anion exchange capacity, the surface-functionalized HNT could boost electrocatalytic activity. Hence, we have synthesized Ni, Co, and Cu metal oxy/hydroxides functionalized HNT by a facile hydrothermal method for HER. Among them, Co(OH)2@HNT on flexible carbon cloth displays an ultra-low overpotential of 65 mV at 10 mA cm-2 current density and Tafel slope of 181 mV dec-1 and also exhibited a larger exchange current density of 3.98 mA cm-2 in alkaline 1 M KOH electrolyte due to superior electrostatic affinity between OH- and Co2+. The electrolyzers with anion exchange membrane consisting of RuO2||Co(OH)2@HNT show remarkable stability of over 50 h at 10 mA cm-2 in alkaline electrolyte. The post stability sample retains the same surface oxidation state which confirms the robustness of the electrocatalyst. The reported results are far better than many of the transition metal oxides/chalcogenides electrocatalysts and hence it is expected that HNT could act as a potential alternative candidate to replace the benchmark platinum catalyst.

High-performance flexible transparent micro-supercapacitors from nanocomposite electrodes encapsulated with solution processed MoS2 nanosheets.

Two-dimensional molybdenum disulfide (MoS2) nanosheets have emerged as a promising material for transparent, flexible micro-supercapacitors, but their use in electrodes is hindered by their poor electrical conductivity and cycling stability because of restacking. In this paper, we report a novel electrode architecture to exploit electrochemical activity of MoS2 nanosheets. Electrochemically exfoliated MoS2 dispersion was spin coated on mesh-like silver networks encapsulated with a flexible conducting film exhibiting a pseudocapacitive behavior. MoS2 nanosheets were electrochemically active over the whole electrode surface and the conductive layer provided a pathway to transport electrons between the MoS2 and the electrolyte. As the result, the composite electrode achieved a large areal capacitance (89.44 mF cm-2 at 6 mA cm-2) and high energy and power densities (12.42 µWh cm-2 and P = 6043 µW cm-2 at 6 mA cm-2) in a symmetric cell configuration with 3 M KOH solution while exhibiting a high optical transmittance of ~80%. Because the system was stable against mechanical bending and charge/discharge cycles, a flexible micro-supercapacitor that can power electronics at different bending states was realized.

Enhancing ORR/OER active sites through lattice distortion of Fe-enriched FeNi3 intermetallic nanoparticles doped N-doped carbon for high-performance rechargeable Zn-air battery.

Low-cost, high-activity, non-precious metal electrocatalysts are needed to enhance the bifunctional oxygen activities of rechargeable Zn-Air batteries. In this study, a Fe-enriched FeNi3 inter-metallic nanoparticle/nitrogen-doped carbon (Fe-enriched-FeNi3/NC) electrocatalyst was designed and prepared using a facile method based on plasma engineering. The excess Fe-ions in the Fe-enriched FeNi3 nanoparticles led to a high degree of lattice distortion that produced abundant oxygen-active sites. The electrocatalyst exhibited excellent oxygen evolution reaction (OER) activity as well as favorable oxygen reduction reaction (ORR) activity in an alkaline electrolyte. In addition, the electrocatalyst revealed a lower potential difference (ΔE = 0.80 V vs. RHE) in a bifunctional oxygen reaction compared to that of the benchmark 20 wt% Pt/C + Ir/C (ΔE = 0.84 V vs. RHE), and most of the reported FeNi3 alloy-doped carbon catalysts. Based on DFT calculations, the lattice distortion in Fe-enriched-FeNi3/NC promoted a higher density of active electrons around the Fermi level. Owing to its great bifunctional oxygen activities, Fe-enriched FeNi3/NC was applied as an ORR/OER catalyst in the air cathode in a homemade zinc-air battery and exhibited an excellent discharge-charge voltage gap (0.89 V), peak power density (89 mW/cm2), and high specific capacity of 734 mAh/g at 20 mA/cm2, which outperformed the benchmark 20 wt% Pt/C + Ir/C electrocatalyst. In summary, this research provides a novel strategy to enhance the OER/ORR activities of transition metal-based alloys through lattice distortion defects. In addition, it provides a new pathway for achieving noble metal-free air cathode materials for the next generation Zn-air battery.

Electrodeposited Trimetallic NiFeW Hydroxide Electrocatalysts for Efficient Water Oxidation.

Tungsten-doped Ni-Fe hydroxides fabricated on a three-dimensional nickel foam through cathodic electrodeposition are proposed as effective oxygen evolution reaction (OER) catalysts for alkaline water oxidation. Incorporating an adequate amount of W into Ni-Fe hydroxides modulates the electronic structure by changing the local environment of Ni and Fe and create oxygen vacancies, resulting in abundant active sites for the OER. The optimized electrocatalyst, with a substantial number of catalytic sites, is found to outperform the well-established 20 wt% Ir/C electrocatalyst. The catalyst only requires small overpotentials of 224 mV and 251 mV to generate current densities of 10 mA cm-2 and 50 mA cm-2 , respectively, at an extremely low Tafel slope. Surface study after long-term chronopotentiometry (ca. 30 h) reveals that the tungsten dopant undergoes reduction to stabilize the Ni and Fe active sites for predominant water oxidation. This research provides new insight to apply optimum amounts of tungsten doping to enable more significant electronic coupling within Ni-Fe for the chemisorption of hydroxy and oxygen intermediates and greatly improved OER activity.

Extracellular DNA (eDNA): Neglected and Potential Sources of Antibiotic Resistant Genes (ARGs) in the Aquatic Environments.

Over the past decades, the rising antibiotic resistance bacteria (ARB) are continuing to emerge as a global threat due to potential public health risk. Rapidly evolving antibiotic resistance and its persistence in the environment, have underpinned the need for more studies to identify the possible sources and limit the spread. In this context, not commonly studied and a neglected genetic material called extracellular DNA (eDNA) is gaining increased attention as it can be one of the significant drivers for transmission of extracellular ARGS (eARGs) via horizontal gene transfer (HGT) to competent environmental bacteria and diverse sources of antibiotic-resistance genes (ARGs) in the environment. Consequently, this review highlights the studies that address the environmental occurrence of eDNA and encoding eARGs and its impact on the environmental resistome. In this review, we also brief the recent dedicated technological advancements that are accelerating extraction of eDNA and the efficiency of treatment technologies in reducing eDNA that focuses on environmental antibiotic resistance and potential ecological health risk.

Cation intercalated one-dimensional manganese hydroxide nanorods and hierarchical mesoporous activated carbon nanosheets with ultrahigh capacitance retention asymmetric supercapacitors.

We have reported the electrochemical performance of K+ ion doped Mn(OH)4 and MnO2 nanorods as a positive electrode and a highly porous activated carbon nanosheet (AC) made from Prosopis Juliflora as negative electrode asymmetric supercapacitor (ASC) with high rate capability and capacity retention. The cation K+ doped Mn(OH)4 and MnO2 nanorods with large tunnel sizes allow the electrolyte to penetrate through a well-defined pathway and hence benefits from the intercalation pseudocapacitance and surface redox reactions. As a result, they exhibit good electrochemical performance in neutral aqueous electrolytes. More specifically, the K+-Mn(OH)4 nanorods exhibit higher capacitance values than K+-MnO2 nanorods due to the homogenous distribution of 1D nanorods and optimum amount of OH bonds. The fabricated K+-Mn(OH)4 symmetric electrochemical Pseudocapacitor shows very high energy density of 10.11 Wh/kg and high-power density of 51.04 W/kg over the range of 1.0 V in aqueous electrolyte. The energy density of AC||K+-Mn(OH)4 ASC is improved significantly compared to those of symmetric supercapacitors. The fabricated ASC exhibits a wide working voltage window (1.6 V), high power (143.37 W/kg) and energy densities (41.38 Wh/kg) at 0.2 A g-1, and excellent cycling behavior with 107.3% capacitance retention after 6000 cycles at 2 A g-1 indicating the promising practical applications in electrochemical supercapacitors.

Self-assembled 3D hierarchical MnCO3/NiFe layered double hydroxides as a superior electrocatalysts for the oxygen evolution reactions.

Developing cost-effective and efficient oxygen evolution reaction (OER) electrocatalyst is highly essential for energy-conversion technologies. A self-assembled NiFe-layered double hydroxide (LDH)@MnCO3 heterostructure prepared on Ni foam using a successive hydrothermal strategy shows notable catalytic activity toward the OER with a small overpotential of 275 mV to drive a geometrical current density of 10 mA cm-2 under alkaline conditions with remarkable stability for 15 h, outperforming IrO2/C electrocatalyst (350 mV@10 mA cm-2). The hierarchical NiFe-LDH@MnCO3 heterostructure possess more exposed active sites, enhanced conductivity and superior interfacial coupling effect makes them an ideal candidate for OER electrocatalyst.

Environmental Prevalence of Carbapenem Resistance Enterobacteriaceae (CRE) in a Tropical Ecosystem in India: Human Health Perspectives and Future Directives.

In the past few decades, infectious diseases have become increasingly challenging to treat, which is explained by the growing number of antibiotic-resistant bacteria. Notably, carbapenem-resistant Enterobacteriaceae (CRE) infections at global level attribute a vast, dangerous clinical threat. In most cases, there are enormous difficulties for CRE infection except a few last resort toxic drugs such as tigecycline and colistin (polymyxin E). Due to this, CRE has now been categorized as one among the three most dangerous multidrug resistance (MDR) pathogens by the US Centres for Disease Control and Prevention (CDC). Considering this, the study of the frequency of CRE infections and the characterization of CRE is an important area of research in clinical settings. However, MDR bacteria are not only present in hospitals but are spreading more and more into the environment, thereby increasing the risk of infection with resistant bacteria outside the hospital. In this context, developing countries are a global concern where environmental regulations are often insufficient. It seems likely that overcrowding, poor sanitation, socioeconomic status, and limited infrastructures contribute to the rapid spread of MDR bacteria, becoming their reservoirs in the environment. Thus, in this review, we present the occurrence of CRE and their resistance determinants in different environmental compartments in India.

Phylogenetic insight of Nonribosomal peptide synthetases (NRPS) Adenylate domain in Antibacterial potential Streptomyces BDUSMP 02 isolated from Pitchavaram Mangrove.

Identification of gene clusters in Streptomyces holds promise for the discovery of regulatory pathways linked to bioactive metabolites. We isolated a broad-spectrum antibacterial potential Streptomyces sp BDUSMP 02 from mangrove sediment. We further found a distinct of phylogeny pattern for NRPS A-domain in the Streptomyces sp BDUSMP 02. The result suggests that Streptomyces sp BDUSMP 02 has the potential to produce a new type of antibacterial compounds belonging to NRPS type.

Extreme Environment Streptomyces: Potential Sources for New Antibacterial and Anticancer Drug Leads?

Antimicrobial resistance (AR) is recognized as one of the greatest threats to public health and in global concern. Consequently, the increased morbidity and mortality, which are associated with multidrug resistance bacteria, urgently require the discovery of novel and more efficient drugs. Conversely, cancer is a growing complex human disease that demands new drugs with no or fewer side effects. Most of the drugs currently used in the health care systems were of Streptomyces origin or their synthetic forms. Natural product researches from Streptomyces have been genuinely spectacular over the recent years from extreme environments. It is because of technical advances in isolation, fermentation, spectroscopy, and genomic studies which led to the efficient recovering of Streptomyces and their new chemical compounds with distinct activities. Expanding the use of the last line of antibiotics and demand for new drugs will continue to play an essential role for the potent Streptomyces from previously unexplored environmental sources. In this context, deep-sea, desert, cryo, and volcanic environments have proven to be a unique habitat of more extreme, and of their adaptation to extreme living, environments attribute to novel antibiotics. Extreme Streptomyces have been an excellent source of a new class of compounds which include alkaloids, angucycline, macrolide, and peptides. This review covers novel drug leads with antibacterial and cytotoxic activities isolated from deep-sea, desert, cryo, and volcanic environment Streptomyces from 2009 to 2019. The structure and chemical classes of the compounds, their relevant bioactivities, and the sources of organisms are presented.

Revealing the Self-Degradation Mechanisms in Methylammonium Lead Iodide Perovskites in Dark and Vacuum.

Organic-inorganic lead halide perovskite phases segregate (and their structures degrade) under illumination, exhibiting a poor stability with hysteresis and producing halide accumulation at the surface.In this work, we observed structural and interfacial dissociation in methylammonium lead iodide (CH3 NH3 PbI3 ) perovskites even under dark and vacuum conditions. Here, we investigate the origin and consequences of self-degradation in CH3 NH3 PbI3 perovskites stored in the dark under vacuum. Diffraction and photoelectron spectroscopic studies reveal the structural dissociation of perovskites into PbI2 , which further dissociates into metallic lead (Pb0 ) and I2- ions, collectively degrading the perovskite stability. Using TOF-SIMS analysis, AuI2- formation was directly observed, and it was found that an interplay between CH3 NH3+ , I3- , and mobile I- ions continuously regenerates more I2- ions, which diffuse to the surface even in the absence of light. Besides, halide diffusion causes a concentration gradient between Pb0 and I2- and creates other ionic traps (PbI2- , PbI- ) that segregate as clusters at the perovskite/gold interface. A shift of the onset of the absorption band edge towards shorter wavelengths was also observed by absorption spectroscopy, indicating the formation of defect species upon aging in the dark under vacuum.

Inhibition of Redox Behaviors in Hierarchically Structured Manganese Cobalt Phosphate Supercapacitor Performance by Surface Trivalent Cations.

The stability and performance of supercapacitor devices are limited by the diffusion-controlled redox process occurring at materials' surfaces. Phosphate-based metal oxides could be effectively used as pseudocapacitors because of their polar nature. However, electrochemical energy storage applications of Mn-Co-based phosphate materials and their related kinetics studies have been rarely reported. In this work, we have reported a morphology-tuned Mn x Co3-x (PO4)2·8H2O (MCP) spinel compound synthesized by a one-step hydrothermal method. Detailed physical and chemical insights of the active material coated on the nickel substrate are examined by X-ray diffraction, field-emission scanning electron microscopy, field-emission transmission electron microscopy, and high-resolution X-ray photoelectron spectroscopy analyses. Physiochemical studies reveal that the well-defined redox behavior usually observed in Co2+/Ni2+ surface-terminated compounds is suppressed by reducing the divalent cation density with an increased Co3+ and Mn3+ surface states. A uniform and dense leaflike morphology observed in the MnCo2 phosphate compound with an increased surface area enhances the electrochemical energy storage performance. The high polar nature of P-O bonding formed at the surface leads to a higher rate of polarization and a very low relaxation time, resulting in a perfect square-shaped cyclic voltagram and triangular-shaped galvanostatic charge and discharge curve. We have achieved a highly pseudocapacitive MCP, and it can be used as a vital candidate in supercapacitor energy storage applications.

Influence of solvents in the preparation of cobalt sulfide for supercapacitors.

In this study, cobalt sulfide (CoS) electrodes are synthesized using various solvents such as water, ethanol and a combination of the two via a facile chemical bath deposition method on Ni foam. The crystalline nature, chemical states and surface morphology of the prepared CoS nanoparticles are characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transition electron microscopy. The electrochemical properties of CoS electrodes are also evaluated using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. When used as an electrode for a supercapacitor, CoS prepared with ethanol as a solvent exhibits a capacitance of 41.36 F g-1 at 1.5 A g-1, which is significantly better than that prepared using water and water/ethanol-based solvents (31.66 and 18.94 F g-1 at 1.5 A g-1, respectively). This superior capacitance is attributed to the ideal surface morphology of the solvent, which allows for easy diffusion of electrolyte ions into the inner region of the electrode. High electrical conduction enables a high rate capability. These results suggest that CoS nanoparticles are highly promising for energy storage applications as well as photocatalysis, electrocatalysis, water splitting and solar cells, among others. These results show that CoS is a promising positive electrode material for practical supercapacitors.

Phase transition kinetics and surface binding states of methylammonium lead iodide perovskite.

We have presented a detailed analysis of the phase transition kinetics and binding energy states of solution processed methylammonium lead iodide (MAPbI3) thin films prepared at ambient conditions and annealed at different elevated temperatures. It is the processing temperature and environmental conditions that predominantly control the crystal structure and surface morphology of MAPbI3 thin films. The structural transformation from tetragonal to cubic occurs at 60 °C with a 30 minute annealing time while the 10 minute annealed films posses a tetragonal crystal structure. The transformed phase is greatly intact even at the higher annealing temperature of 150 °C and after a time of 2 hours. The charge transfer interaction between the Pb 4f and I 3d oxidation states is quantified using XPS.

Occurrence of Antibiotic Resistance Genes and Bacterial Markers in a Tropical River Receiving Hospital and Urban Wastewaters.

The occurrence of emerging biological contaminants including antibiotic resistance genes (ARGs) and Faecal Indicator Bacteria (FIB) is still little investigated in developing countries under tropical conditions. In this study, the total bacterial load, the abundance of FIB (E. coli and Enterococcus spp. (ENT)), Pseudomonas spp. and ARGs (blaTEM, blaCTX-M, blaSHV, blaNDM and aadA) were quantified using quantitative PCR in the total DNA extracted from the sediments recovered from hospital outlet pipes (HOP) and the Cauvery River Basin (CRB), Tiruchirappalli, Tamil Nadu, India. The abundance of bacterial marker genes were 120, 104 and 89 fold higher for the E. coli, Enterococcus spp. and Pseudomonas spp., respectively at HOP when compared with CRB. The ARGs aadA and blaTEM were most frequently detected in higher concentration than other ARGs at all the sampling sites. The ARGs blaSHV and blaNDM were identified in CRB sediments contaminated by hospital and urban wastewaters. The ARGs abundance strongly correlated (r ≥ 0.36, p < 0.05, n = 45) with total bacterial load and E. coli in the sediments, indicating a common origin and extant source of contamination. Tropical aquatic ecosystems receiving wastewaters can act as reservoir of ARGs, which could potentially be transferred to susceptible bacterial pathogens at these sites.

Accumulation of clinically relevant antibiotic-resistance genes, bacterial load, and metals in freshwater lake sediments in Central Europe.

Wastewater treatment plants (WWTP) receive the effluents from various sources (communities, industrial, and hospital effluents) and are recognized as reservoir for antibiotic-resistance genes (ARGs) that are associated with clinical pathogens. The aquatic environment is considered a hot-spot for horizontal gene transfer, and lake sediments offer the opportunity for reconstructing the pollution history and evaluating the impacts. In this context, variation with depth and time of the total bacterial load, the abundance of faecal indicator bacteria (FIB; E. coli and Enterococcus spp. (ENT)), Pseudomonas spp., and ARGs (blaTEM, blaSHV, blaCTX-M, blaNDM, and aadA) were quantified in sediment profiles of different parts of Lake Geneva using quantitative PCR. The abundance of bacterial marker genes was identified in sediments contaminated by WWTP following eutrophication of the lake. Additionally, ARGs, including the extended-spectrum ß-lactam- and aminoglycoside-resistance genes, were identified in the surface sediments. The ARG and FIB abundance strongly correlated (r ≥ 0.403, p < 0.05, n = 34) with organic matter and metal concentrations in the sediments, indicating a common and contemporary source of contamination. The contamination of sediments by untreated or partially treated effluent water can affect the quality of ecosystem. Therefore, the reduction of contaminants from the source is recommended for further improvement of water quality.

Hospital and urban effluent waters as a source of accumulation of toxic metals in the sediment receiving system of the Cauvery River, Tiruchirappalli, Tamil Nadu, India.

Hospital and urban effluents contain a variety of toxic and/or persistent substances in a wide range of concentrations, and most of these compounds belong to the group of emerging contaminants. The release of these substances into the aquatic ecosystem can lead to the pollution of water resources and may place aquatic organisms and human health at risk. Sediments receiving untreated and urban effluent waters from the city of Tiruchirappalli in the state of Tamil Nadu, India, are analyzed for potential environmental and human health risks. The sediment samples were collected from five hospital outlet pipes (HOP) and from the Cauvery River Basin (CRB) both of which receive untreated municipal effluent waters (Tiruchirappalli, Tamil Nadu, India). The samples were characterized for grain size, organic matter, toxic metals, and ecotoxicity. The results highlight the high concentration of toxic metals in HOP, reaching values (mg kg(-1)) of 1851 (Cr), 210 (Cu), 986 (Zn), 82 (Pb), and 17 (Hg). In contrast, the metal concentrations in sediments from CRB were lower than the values found in the HOP (except for Cu, Pb), with maximum values (mg kg(-1)) of 75 (Cr), 906 (Cu), 649 (Zn), 111 (Pb), and 0.99 (Hg). The metal concentrations in all sampling sites largely exceed the Sediment Quality Guidelines (SQGs) and the Probable Effect Concentration (PEC) for the Protection of Aquatic Life recommendation. The ecotoxicity test with ostracods exposed to the sediment samples presents a mortality rate ranging from 22 to 100 % (in sediments from HOP) and 18-87 % (in sediments from CRB). The results of this study show the variation of toxic metal levels as well as toxicity in sediment composition related to both the type of hospital and the sampling period. The method of elimination of hospital and urban effluents leads to the pollution of water resources and may place aquatic organisms and human health at risk.