Nanostructured photocatalysts have always offered opportunities to solve issues concerned with the environmental challenges caused by rapid urbanization and industrialization. These materials, due to ...their tunable physicochemical characteristics, are capable of providing a clean and sustainable ecosystem to humanity. One of the current thriving research focuses of visible-light-driven photocatalysts is on the nanocomposites of titanium dioxide (TiO2) with carbon nanostructures, especially graphene. Coupling TiO2 with graphene has proven more active by photocatalysis than TiO2 alone. It is generally considered that graphene sheets act as an electron acceptor facilitating the transfer and separation of photogenerated electrons during TiO2 excitation, thereby reducing electron-hole recombination. This study briefly reviews the fundamental mechanism and interfacial charge-transfer dynamics in TiO2/graphene nanocomposites. Design strategies of various graphene-based hybrids are highlighted along with some specialized synthetic routes adopted to attain preferred properties. Importantly, the enhancing interfacial charge transfer of photogenerated e¯CB through the graphene layers by morphology orientation of TiO2, predominated exposure of their high energy crystal facets, defect engineering, enhancing catalytic sites in graphene, constructing dedicated architectures, tuning the nanomaterial dimensionality at the interface, and employing the synergism adopted through various modifications, are systematically compiled. Portraying the significance of these photocatalytic hybrids in environmental remediation, important applications including air and water purification, self-cleaning surfaces, H2 production, and CO2 reduction to desired fuels, are addressed.
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•Interfacial charge transfer mechanism in TiO2/graphene heterojunctions.•Specialized synthetic strategies for enhanced charge dynamics at the interface.•Facet and defect engineering in TiO2, functionalization in graphene, etc.•Photocatalytic degradation of pollutants and antimicrobial disinfection.•Solar fuel generation by photoreduction of H2O and CO2.
The recent advent of biodegradable materials has offered huge opportunity to transform healthcare technologies by enabling sensors that degrade naturally after use. The implantable electronic systems ...made from such materials eliminate the need for extraction or reoperation, minimize chronic inflammatory responses, and hence offer attractive propositions for future biomedical technology. The eco-friendly sensor systems developed from degradable materials could also help mitigate some of the major environmental issues by reducing the volume of electronic or medical waste produced and, in turn, the carbon footprint. With this background, herein we present a comprehensive overview of the structural and functional biodegradable materials that have been used for various biodegradable or bioresorbable electronic devices. The discussion focuses on the dissolution rates and degradation mechanisms of materials such as natural and synthetic polymers, organic or inorganic semiconductors, and hydrolyzable metals. The recent trend and examples of biodegradable or bioresorbable materials-based sensors for body monitoring, diagnostic, and medical therapeutic applications are also presented. Lastly, key technological challenges are discussed for clinical application of biodegradable sensors, particularly for implantable devices with wireless data and power transfer. Promising perspectives for the advancement of future generation of biodegradable sensor systems are also presented.
The photocatalytic water splitting technique is a promising alternative to produce hydrogen using a facile and proficient method. In the current Review, recent progress made in photocatalytic ...hydrogen evolution reaction (HER) using 2D nanomaterials (NMs) and composite heterostructures is described. The strong in-plane chemical bonds along with weak van der Waals interaction make these materials lucrative for surface-related applications. State-of-the-art protocols designed for the synthesis of 2D NMs is discussed in detail. The Review illustrates density functional theory (DFT)-based studies against the new set of 2D NMs, which also highlights the importance of structural defects and doping in the electronic structure. Additionally, the Review describes the influence of electronic, structural, and surface manipulation strategies. These impact the electronic structures, intrinsic conductivity, and finally output toward HER. Moreover, this Review also provides a fresh perspective on the prospects and challenges existing behind the application and fabrication strategies.
Absorbance spectra and photograph of MPA-GAA-Ag NPs with various organophosphorus pesticides (acephate, glyphosate, chlorpyriphos, quinalphos, dichlorovos and triazophos, 1mM).
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...•Molecular assembly of 3-mercaptopropinonic acid and guanidine acetic acid on Ag NPs.•The prepared Ag NPs were characterized by UV–vis, FT-IR, DLS and TEM.•MPS-GAA-Ag NPs act as a probe for sensing of triazophos via hydrogen bonding.•Other chemical species did not interfere in the assay of triazophos.•This probe provides simple platform for the visual read-out of triazophos in real samples.
In this work, a novel colorimetric nanosensor was developed for the selective detection of triazophos in environmental water and food samples using bifunctionalized silver nanoparticles (Ag NPs) as a probe. The Ag NPs were bifunctionalized with 3-mercaptopropinonic acid (MPA) and guanidineacetic acid (GAA) and used as a colorimetric probe for the selective sensing of triazophos via hydrogen bonding. The addition of triazophos into the bifunctionalized Ag NPs solution triggers the aggregation of bifunctionalized Ag NPs, inducing a color change from yellow to dark orange, which yields a red-shift in the surface plasmon resonance (SPR) peak of GAA-MPA-Au NPs. Results showed that the absorbance ratio (A550/A400) was linear with the logarithm of triazophos concentration in the range of 0.5–500μM and the detection limit (3σ) obtained by UV–visible spectra were 0.10 and 0.08μM using Tris-HCl pH 5.0 and sodium acetate pH 10.0 with addition of NaCl (0.4mM). The sensitivity of method was improved ∼85-fold using 0.4mM of NaCl as an ionic strength. This method was successfully applied to detect triazophos in water (tap, canal and river) and food (rice and apple) samples.
Surface contamination by microbes is a major public health concern. A damp environment is one of potential sources for microbe proliferation. Smart photocatalytic coatings on building surfaces using ...semiconductors like titania (TiO2) can effectively curb this growing threat. Metal-doped titania in anatase phase has been proven as a promising candidate for energy and environmental applications. In this present work, the antimicrobial efficacy of copper (Cu)-doped TiO2 (Cu-TiO2) was evaluated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) under visible light irradiation. Doping of a minute fraction of Cu (0.5 mol %) in TiO2 was carried out via sol-gel technique. Cu-TiO2 further calcined at various temperatures (in the range of 500–700 °C) to evaluate the thermal stability of TiO2 anatase phase. The physico-chemical properties of the samples were characterized through X-ray diffraction (XRD), Raman spectroscopy, X-ray photo-electron spectroscopy (XPS) and UV–visible spectroscopy techniques. XRD results revealed that the anatase phase of TiO2 was maintained well, up to 650 °C, by the Cu dopant. UV–vis results suggested that the visible light absorption property of Cu-TiO2 was enhanced and the band gap is reduced to 2.8 eV. Density functional theory (DFT) studies emphasize the introduction of Cu+ and Cu2+ ions by replacing Ti4+ ions in the TiO2 lattice, creating oxygen vacancies. These further promoted the photocatalytic efficiency. A significantly high bacterial inactivation (99.9999%) was attained in 30 min of visible light irradiation by Cu-TiO2.
On‐board sources of energy are critically needed for autonomous robots to work in unstructured environments for extended periods. Thus far, the power requirement of robots has been met through ...lead‐acid and Li‐ion batteries and energy harvesters. However, except for a few advances such as light weight, shape, and size, the batteries used in robotics have remained unchanged for several decades, even if the research advances in energy storage have led to devices with flexible form factors. Besides being slow at adopting new energy technologies, robotics also appears to have settled with the idea of centralized energy, as evident from the battery backpack designs of several humanoids. This is in contrast with the biological world, where energy sources are distributed all over the body. Although several attempts have been made to imitate the distributed tactile skin, the energy distribution has strangely not caught attention. With distributed energy, a robotic platform can benefit in terms of increased energy density, lesser design complexities, improved body dynamics, and operational reliability. By focusing on the distributed energy, this first comprehensive review presents the benefits of bioinspired distributed energy in robotics and various energy‐storage and energy‐harvesting technologies that are available or are tuned to attain the same.
The on‐board sources of energy are critical for autonomous robots. The biological systems‐type distributed energy architecture helps improve the energy density, and this can be enabled by advances in energy technology including flexible and stretchable energy storage and harvesting. Further, multifunctional energy devices add new dimension to the distributed energy architecture of robots.
In this paper, we provide a comprehensive evaluation of graphitic carbon nitride (C
3
N
4
) powders derived from the four different precursors melamine, cyanamide, thiourea, and urea for the ...photocatalytic degradation of tetracycline (TC) antibiotic under sunlight irradiation. The powders were synthesized by employing the conventional thermal decomposition method. The synthesized powders were examined using different characterization tools for evaluating the photophysical properties. The degradation profile revealed that urea-derived C
3
N
4
showed the highest activity while melamine-derived C
3
N
4
showed the least activity. The TC degradation efficiency of the photocatalyst was found to be influenced more by the surface area values despite extended absorption by melamine in the visible light region. Stability tests on urea-derived C
3
N
4
and others were checked by four runs of TC degradation under sunlight irradiation. The synthesized C
3
N
4
powders also confirmed the dominance of urea-derived powders for cyclic stability.
Environmental remediation employing semiconducting materials offer a greener solution for pollution control. Herein, we report the development of high surface area porous architecture of C3N4 ...nanosheets by a simple aqueous spray drying process. g-C3N4 nanosheets obtained by the thermal decomposition of urea-thiourea mixture are spray granulated to microspheres using 2 wt% poly vinyl alcohol (PVA) as binder. The post granulation thermal oxidation treatment resulted in in situ doping of carbon leading to improved photophysical properties compared to pristine g-C3N4. The C3N4 granules with surface area values of 150 m2/g rendered repetitive adsorption of tetracycline antibiotic (∼75% in 60 min) and the extended absorption in the visible region facilitated complete photocatalytic degradation upon sunlight irradiation (>95% in 90 min). The delocalized π bonds generated after carbon doping and the macro-meso porous architecture created by the granulation process aided high adsorption capacity (70 mg/g). The photoregenerable, bifunctional materials herein obtained can thus be employed for the adsorption and subsequent degradation of harmful organic pollutants without any secondary remediation processes.
Materials combining the abilities of adsorption and photocatalysis provide a facile solution for pollutant disposal as secondary remediation processes are avoided. Herein, we report a simple strategy ...for the development of C3N4 anchored ZIF-8 microcrystals as sheathed architectures for the highly efficient adsorption and sunlight induced photocatalytic degradation of tetracycline from solution. An adsorption capacity as high as 420 mg g-1 of adsorbent was realized for a composition containing 60 : 40 wt% of C3N4 and ZIF. Subsequently, the adsorbed tetracycline was degraded to over 96% in 1 h of sunlight exposure. The effects of pH and adsorbate concentration are studied and valid adsorption and degradation kinetic models are arrived at. The bifunctional composite thus developed offers a photo-regenerable adsorbent for the effective removal of an emerging hazardous contaminant.
•Structural modifications in C3N4 for enhanced photophysical properties.•Antibiotic degradation kinetics and plausible path ways for mineralization.•Potential strategies to alleviate existing ...shortcomings for widespread application.
The uncontrolled and unethical release of pharmaceutical contaminants into aquatic sources have severe adversities, including the possible emergence of antimicrobial-resistant bacteria. Photocatalysis utilizing semiconductor heterostructures is a greener and sustainable option for the effective degradation of organic contaminants into relatively harmless by-products. Visible/sunlight active graphitic carbon nitride based photocatalysts have been explored for antibiotic degradation (Tetracycline, Doxycycline, Oxytetracycline, Sulfamethoxazole, Amoxicillin) owing to their excellent chemical/thermal stability, tunable photophysical properties and facile methods of synthesis. The properties were further enhanced by heterostructure formation with other compatible semiconductors, elemental/molecular doping and through the creation of hierarchically porous structures. Moreover, nanocomposite formation with high surface area porous frameworks induces adsorptive photocatalysis imparting bifunctionality and alleviating secondary remediation measures for regeneration of the catalysts. The review summarizes the efforts in developing C3N4 based systems for the effective degradation of various antibiotics. Finally, an outlook on essential improvements is forecasted.
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