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Graphitic carbon nitride (g-C3N4)-based materials are attracting attention for their unique properties, such as low-cost, chemical stability, facile synthesis, adjustable electronic structure, and optical properties. These facilitate the use of g-C3N4 to design better photocatalytic and sensing materials. Environmental pollution by hazardous gases and volatile organic compounds (VOCs) can be monitored and controlled using eco-friendly g-C3N4- photocatalysts. Firstly, this review introduces the structure, optical and electronic properties of C3N4 and C3N4 assisted materials, followed by various synthesis strategies. In continuation, binary and ternary nanocomposites of C3N4 with metal oxides, sulfides, noble metals, and graphene are elaborated. g-C3N4/metal oxide composites exhibited better charge separation that leads to enhancement in photocatalytic properties. g-C3N4/noble metal composites possess higher photocatalytic activities due to the surface plasmon effects of metals. Ternary composites by the presence of dual heterojunctions improve properties of g-C3N4 for enhanced photocatalytic application. In the later part, we have summarised the application of g-C3N4 and its assisted materials for sensing toxic gases and VOCs and decontaminating NOx and VOCs by photocatalysis. Composites of g-C3N4 with metal and metal oxide give comparatively better results. This review is expected to bring a new sketch for developing g-C3N4-based photocatalysts and sensors with practical applications.

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Wound healing is an extremely intricate process involving various potential factors that can contribute towards delayed healing, one of them being bacterial colonization. The current research addresses this issue through the development of herbal antimicrobial films that can be stripped off easily, formed using an essential oil component thymol, biopolymer chitosan, and herbal plant Aloe vera. In comparison to the conventionally used nanoemulsions, thymol encapsulated in chitosan-Aloe vera (CA) film exhibited high encapsulation efficiency (95.3 %) with alleviated physical stability, as established using a high zeta potential value. The pronounced loss of crystallinity, validated using X-ray diffractometry, combined with the results obtained from Infrared and Fluorescence spectroscopic analysis, confirmed the encapsulation of thymol in CA matrix through hydrophobic interactions. This encapsulation increases the spaces between biopolymer chains facilitating greater intrusion of water, conducive for preventing the possibility of bacterial infection. Antimicrobial activity was tested against various pathogenic microbes such as Bacillus, Staphylococcus, Escherichia, Pseudomonas, Klebsiella and Candida. Results showed potential antimicrobial activity in the prepared films. Release test was also run at 25 °C suggesting a two-step biphasic release mechanism. The encapsulated thymol had higher biological activity, as assessed by antioxidant DPPH assay, likely due to improved dispersibility.

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The aim of the present study was to design a unique bioelectrode for the quantitative analysis of a potential cancer biomarker, platelet-derived growth factor-BB (PDGF-BB), which can be used for the early detection of cancer. We report the fabrication of succinic acid-capped selenomolybdate polyoxometalate nanodots, POM (SA), decorated antimonene hybrid film on glassy carbon as a suitable bioelectrode. Antimonene nanosheets, synthesized by the chemical exfoliation of antimony provided a large surface area for the symmetric dispersal of POM (SA) nanodots, resulting in site-specific covalent immobilization of the aptamer, PDGF-BB. A comprehensive electrochemical immunosensing investigation was performed on the electrode for sensing of a target antigen, Ag-PDGF-BB. The sensitivity, selectivity, and reproducibility of the bioelectrode were investigated using a best-fit equivalent circuit model that fitted the impedance response. The bioelectrode showed a linear impedimetric response in a broad range for Ag-PDGF-BB (10 pM to 100 nM in pH 7.4 PB) with a limit of detection of 3.5 pM and sensitivity of 80 Ω cm2 per decade. The response sensitivity of the POM(SA)/antimonene hybrid based bioelectrode toward PDGF-BB was approximately ∼1.8-fold higher than that of the POM(SA) only modified bioelectrode. The dissociation constant of immunoreaction between the aptamer-functionalized bioelectrode and target Ag-PDGF-BB was 76 nM, indicating a high binding affinity between the aptamer PDGF-BB and target Ag-PDGF-BB on the electrode surface.

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Hexestrol is a non-steroidal estrogen which causes carcinogenic effects in animals. It is therefore important to develop sensitive and selective test methods for its early detection. Herein, we report the development of an electrochemical sensor to detect hexestrol in ultralow concentrations. In order to devise a simple and cost-effective hexestrol sensing electrode, attention is paid to the development of biomass-derived porous carbon (PCB) with large surface area and suitable porosity to immobilize ruthenium oxide nanoparticles (RuO2 NPs, 3-4 nm). The leftover Citrus limetta pulp is chosen as waste biomass since it has N and O based chemical species. Structural, morphological and compositional analysis of PCB and RuO2@PCB revealed well-dispersed RuO2 NPs over the PCB surface. High loading (5.27 at%) of Ru content is achieved due to the large surface area of PCB. Cyclic voltammetry, chronoamperometry and differential pulse voltammetry results suggest that the RuO2@PCB/ITO electrode is capable of detecting hexestrol concentration (in the range of 1 × 10-7-2 × 10-5 M). The practical application of hexestrol detection in milk samples demonstrates the recovery from 96.28 to 101%.

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In quest of a stable structure throughout redox reactions, an approach of B-site ordering (0D arrangement) of cations in double perovskites is adopted. Here, we report B-site cation ordering in double perovskite Sr2CoMoO6-δ (DP-SCM) that tends to a favorable rock salt structure (0D arrangement). The synergy of Co/Mo having good redox ability further facilitates high oxygen mobility. A high content of oxygen vacancy examined using XPS and EPR facilitates a high oxygen anion diffusion rate (2.03 × 10-11 cm2 s-1). Moreover, fast kinetics (ΔEP ≈ 0.013 V@ 1 mV s-1) of charge storage prohibits any phase transformation reflecting the excellent cycle life (125% retention up to 5000 cycles). Such fast kinetics is majorly furnished from anion intercalation with little involvement from double layer mechanism (Cdl ≈ 42.1 F g-1). DP-SCM achieves a resultant capacitance of 747 F g-1@ 1 A g-1 with a rate capability of 56% up to 10 A g-1. Motivated by outstanding performance of DP-SCM electrodes, a symmetric cell is assembled with a 1.4 V operating potential that delivers a high energy density of 64 Wh kg-1@855 W kg-1. This work on double perovskites suggests that the advance understanding of cation ordering and charge storage mechanism can provide a new direction to fabricate highly capacitive electrode materials.

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The metallic phase (1T) of molybdenum sulfide is critical, pertaining to its exceptional interlayer structure and metastability, but forms up with low content. Herein, 1T-phase-prominent vanadium-incorporated MoS2 (MVS) nanoroses were synthesized through a hydrothermal process. A significant increase in 1T content (50 %) occurred with the addition of vanadium, enhancing the prompt diffusion of lithium ions by two orders. More exposed electroactive basal planes increased the number of redox active sites to 84 %, suggesting an excellent charge storage of 451 F g-1 at 1 A g-1 . On assembling MVS with MnO2 to form an asymmetric cell (MnO2 ∥MVS), a high energy density (62.7 Wh kg-1 at 428 W kg-1 ) with a threefold increment from the MVS‖MVS symmetric cell (21.8 Wh kg-1 at 255 Wkg-1 ) was achieved. The asymmetric cell also exhibited a superior cycling stability with 98 % retention of its capacitance after 10 000 cycles.

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Ophiocordyceps sinensis, a high-altitude medicinal mushroom, is widely revered in traditional medicine for its antiproliferative, antihypercholesterolemic, energy enhancement, etc. properties. These properties are attributed to the presence of steroids, terpenoids, polyphenolics, glycosides, and glycoproteins in it. The current study presents characterization of three phenolic rich fractions (PRFs) separated from aqueous extract of O. sinensis using diethyl ether and ethyl acetate. These fractions possessed considerable antioxidant potential in terms of total phenolic content, total flavonoid content, ferric ion reducing power, and free radical scavenging efficiency. Chemical characterization of the PRFs was carried out using HPTLC and GC-MS. The diethyl ether and ethyl acetate fractions elucidated appreciable antibacterial activity against Salmonella typhi. The aqueous extract and residual phenolic fraction displayed protective effect on HEK 293 cell lines against hypoxia stress and also bestowed appreciative adaptogenic role against cold, hypoxia, and restraint stress in vivo, by decreasing levels of malondialdehyde and superoxide dismutase and incrementing reduced glutathione concentrations.

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Enriched with oxygen vacancies, Mo-doped strontium cobaltite (SrCo0.9 Mo0.1 O3-δ , SCM) is synthesized as an oxygen anion-intercalated charge-storage material through the sol-gel method. The supplemented oxygen vacancies, good electrical conductivity, and high ion diffusion coefficient bestow the SCM electrode with excellent specific capacitance (1223.34 F g-1 ) and specific capacity (168.88 mAh g-1 ) at 1 A g-1 . The decisive constant (b-value) deduced for the charge storage mechanism (low scan-rate region) is nearly 0.8, indicating a highly capacitive process. In the high scan-rate region, however, the b-value is almost 0.5, and a linear pattern of charge (q) versus the inverse of the square root of the scan rate (v-1/2 ) is obtained. The results reveal O2- diffusion as the rate-limiting factor for charge storage. Furthermore, a hybrid cell (SCM∥LRGONR) is fabricated by using lacey, reduced graphene oxide nanoribbon (LRGONR) as the negative electrode, which exhibits a high energy density (74.8 Wh kg-1 at a power density of 734.5 W kg-1 ). With a charging time of only 20.7 s, the cell sustains a very high energy density (33 Wh kg-1 ) with a high power delivery rate (6600 W kg-1 ). The excellent cycling stability (165.1 % activated specific capacitance retention and 97.6 % of the maximum value attained) after 10 000 charge-discharge cycles, demonstrates SCM is a potential electrode material for supercapacitors.

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Tuberculosis is one of the most dreadful diseases caused by Mycobacterium tuberculosis with more than 9 million individuals suffering from it in 2014. Traditional methods of detection are not efficient enough for its quick and reliable detection; therefore, it is imperative to develop methods of its detection in the early stages. Consequently, we report a highly sensitive and selective biosensor for detection of Mycobacterium tuberculosis. In this work, gold nanoparticles (AuNPs, dia. ∼6 nm, 1.81 wt% loading) are immobilized over reduced graphene oxide nanoribbons (RGONRs). An ssDNA/Au/RGONR electrode is prepared by immobilizing Au nanoparticles followed by covalent modification of Au nanoparticles with 5'SH-ssDNA. As per the best knowledge of the authors, the target DNA of Mycobacterium tuberculosis is detected using a ssDNA/Au/RGONR bioelectrode by cyclic voltammetry and chronoamperometric methods for the first time. With high detection efficiency (0.1 fM), the ssDNA/Au/RGONR bioelectrode exhibited better signal amplification and electrochemical response as compared to bare Au and RGONR electrodes. Additionally, the ssDNA/Au/RGONR bioelectrode displayed good linear response to different concentrations of target M. tuberculosis DNA. The ssDNA/Au/RGONR has shown excellent specificity (92%) to Mycobacterium tuberculosis target DNA as compared with non-complementary DNA. The Au/RGONR matrix has the potential to be used as an immobilization platform for single-stranded probe DNAs of different diseases other than tuberculosis reported here.

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Various synthetic methods were employed on a single precursor to synthesize magnetic cobalt dithiocarbamate (Co(dtc-SB)) coordination polymer nanoparticles (MCP NPs) having different morphologies. When subjected to hydrothermal method, the precursor led to the formation of nanosheets (NSs) of MCP (100 x 80 nm), whereas the same precursor when set to slow diffusion precipitation, formed nanowires (NWs) with 30 nm diameter. Further, on micro-emulsion ultrasonication, uniform MCP nanocubes (NCs) -5 nm were obtained. MCP NPs are weakly ferromagnetic in nature with a narrow hysteresis loop opening. In addition, the magnetic properties of MCP NPs are shown to be highly dependent on size. Further, the antimicrobial activity of MCP NPs against various microbes was also shown to be highly size dependent. The biocompatible MCP NCs were found to have the lowest minimum inhibitory concentration (MIC) value of 6.25 µg/ml against S. aureus and K. pneumoneae, which demonstrate that NPs are equally effective against both gram positive and gram negative bacteria.

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This article describes the synthesis and characterization of ZnO nanoring embedded graphene nanoribbons. Patterned holes (mesopore dia.) in graphene nanoribbons are chemically generated, leading to a high density of the edge planes. These planes carry negatively charged surface groups (like -COOH and -OH) and therefore anchor the metal ions in a cordial fashion forming a string of metal ions along the edge planes. These strings of imbibed metal ions precipitate as tiny ZnO nanorings over lacey graphene nanoribbons. The thus obtained graphene nanoribbon (GNR) based hierarchical ZnO mesoporous structures are three dimensionally accessible to the electrolyte and demonstrate high performance in capacitive energy storage. The ZnO/GNR nanocomposite electrode in an asymmetric supercapacitor device with lacey reduced graphene oxide nanoribbons (LRGONRs) as a negative electrode exhibits a 2.0 V potential window in the aqueous electrolyte and an ultra-short time constant (0.08 s). The wide potential window consequently increased the energy density from 6.8 Wh kg(-1) (ZnO/GNR symmetric) to 9.4 Wh kg(-1) (ZnO/GNR||LRGONR asymmetric). The relaxation time constant obtained for the asymmetric supercapacitor device was three orders of magnitude less compared to the ZnO (symmetric, 33 s) supercapacitor device. The high cycling stability of ZnO/GNR||LRGONR up to 96.7% capacitance retention, after 5000 GCD cycles at 2 mA cm(-2), paves the way to a high performance aqueous electrochemical supercapacitive energy storage.

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High performance lacey reduced graphene oxide nanoribbons (LRGONR) were chemically synthesized. Holes created during the LRGONR synthesis not only enhanced the electrolytic accessibility but destacked all the graphene layers through protrusion at edge planes and corrugation in individual graphene. LRGONR in a supercapacitor cell showed ultrahigh performance in terms of specific capacitance and capacity retention. Consistently in aqueous, nonaqueous, and ionic electrolytes, LRGONR symmetric supercapacitor exhibited exceptionally high energy/power density, typically 15.06 W h kg(-1)/807 W kg(-1) in aqueous at 1.7 A g(-1), 90 W h kg(-1)/2046.8 W kg(-1) in nonaqueous at 1.8 A g(-1), and 181.5 W h kg(-1)/2316.8 W kg(-1) in ionic electrolyte at ∼1.6 A g(-1).

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A novel graphene nanoribbon (GNR)/cobalt coordination polymer (MCPs) composite (MCPs@GNR) is prepared by in situ reduction of graphene oxide nanoribbon (GONR) with simultaneous growth of MCPs nanoparticles on its surface. The morphology and structure are investigated by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared spectroscopy, X-ray diffraction and Raman spectroscopy. Results indicate that MCPs nanoparticles having dia. ∼6 nm are successfully deposited on GNR to form a hybrid conducting network. Analysis of the performance of the MCPs@GNR composite shows high non-enzymatic electrocatalytic activity for H2O2 reduction with a low limit of detection ∼60 nM at S/N = 3. The fluorescence of MCPs provides an optical feature which is also applied here for the detection of H2O2. The fluorescence quenching of MCPs@GNR can be achieved by addition of H2O2 which shows linearity over a range of increasing concentration of 10 µM to 150 µM.

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Oxidative stress is a condition when the concentration of free radicals and reactive molecular species rise above certain level in living systems. This condition not only perturbs the normal physiology of the system but also has been implicated in many diseases in humans and other animals. Hydrogen peroxide (H2O2) is known to be involved in induction of oxidative stress and has also been linked to a variety of ailments such as inflammation, rheumatoid arthritis, diabetes, and cancer in humans. It is one of the more stable reactive molecular species present in living systems. Because of its stability and links with various diseases, sensing the level of H2O2 can be of great help in diagnosing these diseases, thereby easing disease management and amelioration. Nanoceria is a potent candidate in free radical scavenging as well as sensing because of its unique redox properties. These properties have been exploited, in the reported work, to sense and quantify peroxide levels. Nanoceria has been synthesized using different capping agents: Hexamethylene-tetra-amine (HMTA) and fructose. CeO2-HMTA show rhombohedral and cubic 6.4 nm particles whereas CeO2-fructose are found to be spherical with average particle diameter size 5.8 nm. CeO2-HMTA, due to the better exposure of the active (200) and (220) planes relative to (111) plane, exhibits superior electrocatalytic activity toward H2O2 reduction. Amperometric responses were measured by increasing H2O2 concentration. The authors observed a sensitivity of 21.13 and 9.6 µA cm(-2) mM(-1) for CeO2-HMTA and CeO2-fructose, respectively. The response time of 4.8 and 6.5 s was observed for CeO2-HMTA and CeO2-fructose, respectively. The limit of detection is as low as 0.6 and 2.0 µM at S/N ratio 3 for CeO2-HMTA and CeO2-fructose, respectively. Ceria-HMTA was further tested for its antioxidant activity in an animal cell line in vitro and the results confirmed its activity.

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A simple strategy for the detection and estimation of ascorbic acid (AA), using lanthanum oxide-reduced graphene oxide nanocomposite (LO/RGO) on indium tin oxide (ITO) substrate, is reported. LO/RGO displays high catalytic activity toward the oxidation of AA, and the synergism between lanthanum oxide and reduced graphene oxide was attributed to the successful and efficient detection. Detection mechanism and sensing efficacy of LO/RGO nanocomposite are investigated by electrochemical techniques. Chronoamperometric results under optimal conditions show a linear response range from 14 to 100 µM for AA detection. Commercially available vitamin C tablets were also analyzed using the proposed LO/RGO sensor, and the remarkable recovery percentage (97.64-99.7) shows the potential application in AA detection.

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Silk cocoon membrane (SCM) is an insect engineered structure. We studied the electrical properties of mulberry (Bombyx mori) and non-mulberry (Tussar, Antheraea mylitta) SCM. When dry, SCM behaves like an insulator. On absorbing moisture, it generates electrical current, which is modulated by temperature. The current flowing across the SCM is possibly ionic and protonic in nature. We exploited the electrical properties of SCM to develop simple energy harvesting devices, which could operate low power electronic systems. Based on our findings, we propose that the temperature and humidity dependent electrical properties of the SCM could find applications in battery technology, bio-sensor, humidity sensor, steam engines and waste heat management.

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In this work, we synthesized graphene oxide from silk cocoon embarking its new dimension as a magnetic fluorophore when compared with its present technical status, which at best is for extracting silk as a biomaterial for tissue engineering applications. We produced graphene oxide by pyrolysing the silk cocoon in an inert atmosphere. The collected raw carbon is oxidized by nitric acid that readily produces multilayer graphene oxide with nano carbon particulates. Structural properties of the graphene oxide were analyzed using scanning electron microscopy, transmission electron microscopy, Fourier transform infra-red spectroscopy, and Raman spectroscopy. The oxidized sample shows remarkable fluorescence, multi-photon imaging and magnetic properties. On increasing the excitation wavelength, the fluorescence emission intensity of the graphene oxide also increases and found maximum emission at 380 nm excitation wavelength. On studying the two photon absorption (TPA) property of aqueous graphene oxide using Z-scan technique, we found significant TPA activity at near infrared wavelength. In addition, the graphene oxide shows ferromagnetic behavior at room temperature. The observed fluorescence and magnetic property were attributed to the defects caused in the graphene oxide structure by introducing oxygen containing hydrophilic groups during the oxidation process. Previously silk cocoon has been used extensively in deriving silk-based tissue engineering materials and as gas filter. Here we show a novel application of silk cocoon by synthesizing graphene oxide based magnetic-fluorophore for bio-imaging applications.

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Cubic spinel Co3O4 nanoparticles with spherical (0D) and hexagonal platelet (2D) morphologies were synthesized using a simple solvothermal method by tuning the reaction time. XRD and HRTEM analyses revealed pure phase with growth of Co3O4 particles along [111] and [110] directions. UV-vis studies showed two clear optical absorption peaks corresponding to two optical band gaps in the range of 400-500 nm and 700-800 nm, respectively, related to the ligand to metal charge transfer events (O(2-) → Co(2+,3+)). Under the electrochemical study in two electrode assembly system (Co3O4/KOH/Co3O4) without adding any large area support or a conductive filler, the hexagonal platelet Co3O4 particles exhibited comparatively better characteristics with high specific capacitance (476 F g(-1)), energy density 42.3 Wh kg(-1) and power density 1.56 kW kg(-1) at current density of 0.5 Ag(-1), that suited for potential applications in supercapacitors. The observed better electrochemical properties of the nanoporous Co3O4 particles is attributed to the layered platelet structural arrangement of the hexagonal platelet and the presence of exceptionally high numbers of regularly ordered pores.