Fabrication of carbon and silver nanomaterials incorporated hydroxyapatite nanocomposites: Enhanced biological and mechanical performances for biomedical applications.

Hydroxyapatite is widely utilized for different biomedical applications because of its outstanding biocompatibility and bioactivity. Cuttlefish bones, which are available aplenty, are both inexpensive and eco-friendly sources for calcium carbonate. In the present study, cuttlefish bones-derived HAp nanorods have been utilized to fabricate HAp nanocomposites incorporating 1, 3 and 5 wt% each of GO, MWCNTs, GONRs and Ag NPs. Characterization using such techniques as XRD, FTIR, HRSEM and EDS was performed to analyze the physicochemical properties of nanocomposites, and MTT assay, hemolysis, bioactivity and drug release to evaluate the biological properties. The XRD and HRSEM results reveal that crystallite and particle size increase with increasing wt% of carbon nanomaterials and Ag NPs. However, the addition of nanomaterials did not modify the shape of HAp. The MTT assay and hemolysis results suggest GONRs possess better biocompatibility than GO and CNTs due to their smooth edge structure. While adding carbon materials up to 3 wt% caused an increase in the hardness, adding up to 5 wt% of them caused a decrease in the hardness due to the agglomeration of the particles. Biocompatibility and Vicker's hardness studies show that adding carbon nanomaterials up to 3 wt% caused significant improvement in biocompatibility and mechanical properties. Antibacterial activity test was performed to analyze the ability to preclude the formation of biofilms. The results showed better activity for silver-incorporated nanocomposites in the presence of E. coli and S. aureus bacteria. Drug release studies were performed using lidocaine drug and the results showed nearly similar drug release profile for all the samples except HAg3. Finally, nanocomposite HRA3 could be a suitable candidate for biomedical applications since it shows better biological and mechanical properties than GO and MWCNTs nanocomposites.

Graphene Nanosheet-Wrapped Mesoporous La0.8Ce0.2Fe0.5Mn0.5O3 Perovskite Oxide Composite for Improved Oxygen Reaction Electro-Kinetics and Li-O2 Battery Application.

A novel design and synthesis methodology is the most important consideration in the development of a superior electrocatalyst for improving the kinetics of oxygen electrode reactions, such as the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in Li-O2 battery application. Herein, we demonstrate a glycine-assisted hydrothermal and probe sonication method for the synthesis of a mesoporous spherical La0.8Ce0.2Fe0.5Mn0.5O3 perovskite particle and embedded graphene nanosheet (LCFM(8255)-gly/GNS) composite and evaluate its bifunctional ORR/OER kinetics in Li-O2 battery application. The physicochemical characterization confirms that the as-formed LCFM(8255)-gly perovskite catalyst has a highly crystalline structure and mesoporous morphology with a large specific surface area. The LCFM(8255)-gly/GNS composite hybrid structure exhibits an improved onset potential and high current density toward ORR/OER in both aqueous and non-aqueous electrolytes. The LCFM(8255)-gly/GNS composite cathode (ca. 8475 mAh g-1) delivers a higher discharge capacity than the La0.5Ce0.5Fe0.5Mn0.5O3-gly/GNS cathode (ca. 5796 mAh g-1) in a Li-O2 battery at a current density of 100 mA g-1. Our results revealed that the composite's high electrochemical activity comes from the synergism of highly abundant oxygen vacancies and redox-active sites due to the Ce and Fe dopant in LaMnO3 and the excellent charge transfer characteristics of the graphene materials. The as-developed cathode catalyst performed appreciable cycle stability up to 55 cycles at a limited capacity of 1000 mAh g-1 based on conventional glass fiber separators.

Ultra-stable Mn1-xNixCO3 nano/sub-microspheres positive electrodes for high-performance solid-state asymmetric supercapacitors.

Long-term cycling performance of electrodes for application in supercapcitor has received large research interest in recent years. Ultra-stable Mn1-xNixCO3 (x-0, 0.20, 0.25 and 0.30) nano/sub-microspheres were synthesized via simple co-precipitation method and the Mn1-xNixCO3 was confirmed by XRD, FT-IR, XPS and their morphology was studied by SEM and TEM analysis. Among the various Mn1-xNixCO3 electrodes, the Mn0.75Ni0.25CO3 electrode exhibited the higher specific capacitance (364 F g-1 at 1 A g-1) with capacity retention of 96% after 7500 cycles at 5 A g-1. Moreover, the assembled solid-state asymmetric supercapacitor based on Mn0.75Ni0.25CO3//graphene nanosheets performed a high specific capacity of 46 F g-1 and energy density of 25 Wh kg-1 at a power density of 499 W kg-1 along with high capacity retention of 87.7% after 7500 cycles. The improved electrochemical performances are mainly owing to the intrinsic conductivity and electrochemical activity of MnCO3 after Mn1-xNixCO3 (x-0.20, 0.25 and 0.30) with appropriate Ni concentration. This study highlights the potentiality of the Mn0.75Ni0.25CO3//GNS asymmetric supercapacitor device for promising energy storage applications.

Glassy carbon electrodes modified with reduced graphene oxide-MoS2-poly (3, 4-ethylene dioxythiophene) nanocomposites for the non-enzymatic detection of nitrite in water and milk.

The detrimental effect of (NO2-) on environment, a sensitive and selective detection of nitrite (NO2-) ions with point-to-care device is need to be fabricated. Herein, we report the non-enzymatic nitrite sensor using a novel reduced graphene oxide/molybdenum disulfide/poly (3, 4-ethylene dioxythiophene) (rGO/MoS2/PEDOT) nanocomposite electrode. The rGO/MoS2/PEDOT nanocomposite was synthesized using facile and cost-effective hydrothermal and polymerization approaches. The characteristics of rGO-MoS2-PEDOT nanocomposite was investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analyses. The rGO-MoS2-PEDOT nanocomposite modified glassy carbon electrode (GCE) was directly used for electrocatalytic detection of nitrite ions present in the solution. TEM images show the PEDOT nanoparticles with an average size of 100-120 nm are uniformly covered on the outer face of rGO-MoS2 nanosheets. The interaction between the PEDOT and rGO-MoS2 is evidenced in the FTIR, XRD and XPS studies, and they produced synergistic effect, resulting enhanced electrocatalytic performance activity towards oxidation of nitrite. Under optimized conditions, the fabricated electrode exhibited remarkably good sensitivity (874.19 µA µM-1 cm-2), low detection limit (LOD) (0.059 µM, S/N = 3), wide linear range (0.001-1 mM) of nitrite with desirable selectivity, long-term stability and reproducibility. Furthermore, the practical feasibility of the fabricated sensor is validated by the successful detection of nitrite ion in some water and milk samples with excellent correlation. Thus, feasible easier synthesis method was adopted first time to fabricate rGO-MoS2-PEDOT nanocomposite nitrite sensor in the milk and water samples with enhanced selectivity, sensitivity and LOD.

Temperature-Controlled Synthesis of Li- and Mn-Rich Li1.2Mn0.54Ni0.13Co0.13O2 Hollow Nano/Sub-Microsphere Electrodes for High-Performance Lithium-Ion Battery.

The calcination temperature plays a significant role in the structural, textural, and energy-storage performance of metal oxide nanomaterials in Li-ion battery application. Here, we report the formation of well-crystallized homogeneously dispersed Li1.2Mn0.54Ni0.13Co0.13O2 hollow nano/sub-microsphere architectures through a simple cost-effective coprecipitation and chemical mixing route without surface modification for improving the efficiency of energy storage devices. The synthesized Li1.2Mn0.54Ni0.13Co0.13O2 hollow nano/sub-microsphere cathode materials are calcined at 800, 900, 950, and 1000 °C. Among them, Li1.2Mn0.54Ni0.13Co0.13O2 calcined at 950 °C exhibits a high discharge capacity (277 mAh g-1 at 0.1C rate) and excellent capacity retention (88%) after 50 cycles and also delivers an excellent discharge capacity of >172 mAh g-1 at 5C rate. Good electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2-950 is directly related to the optimized size of its primary particles (85 nm) (which constitute the spherical secondary particle, ∼720 nm) and homogeneous cation mixing. Higher calcination temperature (≥950 °C) leads to an increase of the primary particle size, poor cycling stability, and inferior rate capacity of Li1.2Mn0.54Ni0.13Co0.13O2 due to smashing of quasi-hollow spheres upon repeated lithium ion intercalations/deintercalations. Therefore, Li1.2Mn0.54Ni0.13Co0.13O2-950 is a promising electrode for the next-generation high-voltage and high-capacity Li-ion battery application.

Sensitive and selective non-enzymatic detection of glucose by monodispersed NiO @ S-doped hollow carbon sphere hybrid nanostructures.

Development of selective, sensitive and non-enzymatic sensor for glucose determination is highly important for the diagnosis and management of diabetes. Herein, we have reported the novel ultra sensitive and non-enzymatic sensor development by in-situ wraped NiO nanostructures (∼10-15 nm) on the sulfur-doped hollow carbon nanospheres (SDHCNSs) through hydrothermal-assisted process. The structural and morphological properties of the nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The prepared NiO@SDHCNSs was directly used as an electrochemical sensor for glucose determination, and its performance was evaluated by cyclic voltammetry and amperometric techniques. The fabricated non-enzymatic biosensor was exhibited remarkably good sensitivity (1697 µA mM-1cm-2), low detection limit (LOD) (52 nM), a wide linear range (up to 13 mM) of glucose with desirable selectivity, stability and reproducibility. Further, the constructed sensor has demonstrated an excellent anti-interference property in the presence of common interferences such as dopamine (DA), uric acid (UA) and ascorbic acid (AA). Most interestingly, the fabricated electrode is applicable for the practical analysis of glucose in the real blood serum and urine samples. The excellent electrochemical performances of NiO@SDHCNSs towards the oxidation of glucose are attributed to the increased electron transfer passage through unique hollow spherical morphology with increased redox couple of Ni(OH)2/NiOOH derived from NiO. Thus, the improved electrochemical performances of NiO@SDHCNSs can be adopted as a potential electrode for the real sample analysis.