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Proposed mechanism of BiVO 4 /CN-QA. [Display omitted] • Quinolinic acid (QA) doped g-CN (CN-QA) was developed via facile thermal approach. • Different samples of BiVO 4 /CN-QA with high stability were prepared via hydrothermal method. • Remarkable enhanced photocatalytic H 2 and O 2 evolution was achieved using these catalysts via overall water splitting. • A dual synergetic mechanism on BiVO 4 /CN-QA has been proposed. The development of copolymerized carbon nitride (CN)-based photocatalysts may support advances in photocatalytic overall water splitting. However, the recombination of charge carriers is the main bottleneck that reduces its overall photocatalytic activity. To overcome this problem, the construction of heterojunction technology has emerged as an effective approach to reduce the charge carrier recombination, thereby improving charge separation and transport efficiency. In this work, an innovative heterojunction was prepared between Quinolinic acid (QA) modified CN (CN-QA x) and novel nanorod-shaped bismuth vanadate (BiVO 4) (BiVO 4 /CN-QA x) for overall water splitting through a simple in-situ solvent evaporation technique. The obtained results show that the synthesized samples have efficient and improved activities for releasing H 2 (862.1 μmol/h) and O 2 (31.58 μmol/h) under visible light irradiation. Furthermore, an exceptional apparent quantum yield (AQY) of 64.52 % has been recorded for BiVO 4 /CN-QA 7.0 at 420 nm, which might be due to the substantial isolation of photoinduced charge carriers. Therefore, this work opens up a new channel toward efficient CN-based photocatalysts in the sustainable energy production processes. [ABSTRACT FROM AUTHOR]

Photocatalytic mechanism proposed for PCN-BTD 008 copolymer sample for overall water splitting under the illumination. [Display omitted] • BTD integrated copolymer (PCN-BTD) via thermal process. • An incorporation of BTD is reinforced by DFT data. • Eight-time enhanced HER of PCN-BTD 008 (744.2 μmol/h) than pure PCN (88.2 μmol/h). • The OER, generates 0.2 μmol/h−1 and 1.6 μmol/h−1 for PCN, while PCN-BTD 008 yield 2.2 μmol/h−1 (visible) and 14.8 μmol/h−1 (non-visible) respectively. Well-organized water splitting semiconducting photocatalyst is an important concept, but stimulating aimed at decisive energy and environmental emergencies. In this context, visible light-based photocatalytic water splitting with low-dimensional semiconducting materials is proposed to produce sustainable energy. Here we optimized the sequential of organic electron-rich heterocyclic monomer namely benzothiadiazole (BTD) quenched within polymeric carbon nitride (PCN) semiconductor via copolymerization, thereby assembling a sanctum of donor-π-acceptor (D-π-A) photocatalysts. The selection of BTD is based on the benzene ring, which consequently anticipating a π cross-linker unit for hydrogen and oxygen evolution. A hydrogen evolution rates (HER) of 88.2 μmol/h for pristine PCN and 744.2 μmol/h for PCN-BTD 008 (eight times higher than pure PCN) are observed. Additionally, a remarkable apparent quantum yield (AQY) of about 58.6% at 420 nm has been observed for PCN-BTD 008. Likewise, the oxygen evolution rate (OER) data reflect the generation of 0.2 μmol/h1 (visible) and 1.6 μmol/h1 (non-visible) for pure PCN. Though, OER of PCN-BTD 008 is found to be 2.2 μmol/h1 (visible) and 14.8 μmol/h1 (non-visible), which are economically better than pure PCN. As such, the results show an important step toward modifying the design and explain a vital part of the D-π-A scheme at a balanced theme for fruitful photocatalysts intended for future demand. [ABSTRACT FROM AUTHOR]

[Display omitted] TiO 2 nanostructures have been one of the most explored metal oxides photocatalysts to apply for environmental remediation. However, its wide band gap results in the underutilization of sunlight for degradation of pollutants. In order to overcome this handicap, the synthesis of TiO 2 -based composite has brought extraordinary materials. In this study, we design and prepare TiO 2 /Nb 2 O 5 heterostructures with different molar ratios by using peroxotitanium and peroxoniobium complex as precursors in aqueous solution. The TiO 2 exists in the form of anatase while Nb 2 O 5 is amorphous in the composite, leading to a special crystalline TiO 2 /amorphous Nb 2 O 5 heterostructures. In particular, Nb element is also doped and Ti3+ ions are formed in the TiO 2 lattice, leading to a reduced band gap. The unique TiO 2 /0.25Nb 2 O 5 (Ti:Nb = 2:1) heterostructures can effectively suppress the recombination of photogenerated electrons and holes, and facilitate the charge transfer, resulting in the optimum photocatalytic performance. The nitrogen oxide removal efficiency by TiO 2 /0.25Nb 2 O 5 is 77.23% in visible light, which is 3.8-folds and 7.0-folds higher than pure TiO 2 and Nb 2 O 5. Photocatalytic degradation of acetaminophen by TiO 2 /0.25Nb 2 O 5 is 90.6% in visible light, which is approximately 2.5-folds higher than pure TiO 2 and Nb 2 O 5. [ABSTRACT FROM AUTHOR]

Abstract: We report here a simple and modified solvothermal synthesis of NiO nanoparticles by using nickel nitrate hexahydrate [Ni(NO3)2⋅6H2O], hexamethylenetetramine [C6H12N4], sodium hydroxide [NaOH] and ethanol [C2H5OH] as refluxing solvent. Nickel hydroxide [β-Ni(OH)2] nanostructures were first formed which were then calcined at 400°C to obtain nickel oxide (NiO) nanoparticles. The nano-powder was investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy and Brunauer–Emmett–Teller surface area studies. The size of the NiO nanoparticles was estimated by X-ray powder diffraction pattern, which was in close agreement with the particle size obtained by transmission electron microscopy analysis. Scanning electron microscopy studies revealed that the synthesized nickel oxide nanostructures showed various morphologies and the morphologies can be easily tailored by adjusting the pH value. The chemical structure information of the products was studied by Fourier transform infrared spectroscopy. Electronic spectra were used to clarify qualitatively the change in absorption band positions on changing the particle size of NiO. The values of the optical band gap of the NiO nanoparticles increases from 2.9 to 3.5eV as the particle size decreases and indicated a direct transition. The specific surface area of NiO nanoparticles was found to increase from 58.3 to 131.4m2/g with decrease in the particle size from 20nm to 5nm. It also exhibited excellent adsorption of Co(II) and Pb(II), demonstrating a promising application in waste water treatment. [Copyright &y& Elsevier]

The first-principles based DFT calculations were used to investigate the effect of transition metal (TM) doping on structural, electronic, optical and thermoelectric properties of Sn 1-x A x Se (A = Au and Ag). The PBE-GGA approximation is used to calculate ground state properties of TM doped SnSe. These compounds show the presence of type-II intermediate band (IB) at Fermi level. A considerable energy bandgap is present between IB and conduction band. Significant contributions from Ag/Au and Se-atom in valence bands of Sn 1-x A x Se (A = Au and Ag) are evident from presented DOS spectra. The calculated Fermi surfaces and Seebeck coefficient (S) confirms p-type nature of these semiconductors. From ε 2 (ω) spectra, it is evident that Sn 1-x A x Se (A = Au and Ag) absorbs maximum number of incident photons in infrared (at ∼0.5 eV) and visible (at ∼2.2 eV) regions. The calculated values of n (ω) are 2.27 and 2.58 for Sn 1-x Ag x Se and Sn 1-x Au x Se, respectively. We can confirm that Sn 1-x A x Se (A = Au and Ag) are promising candidates for energy applications (especially solar cells) based on their optoelectronic and thermoelectric properties. [Display omitted] • Electronic, optical and thermoelectric properties of Sn 1-x A x Se (A = Ag and Au) are investigated ab-initio. • Sn 1-x A x Se (A = Ag and Au) show type-II intermediate band in their band structures. • These compounds are p-type materials based on Fermi surface and Seebeck coefficient. • Optical spectra show major absorption peaks in visible region around 2.2 eV. • Among the considered compounds, Sn 1-x Au x Se shows the highest absorption. [ABSTRACT FROM AUTHOR]

Doped carbon dots have attracted great attention from researchers across disciplines because of their unique characteristics, such as their low toxicity, physiochemical stability, photostability, and outstanding biocompatibility. Nitrogen is one of the most commonly used elements for doping because of its sizeable atomic radius, strong electronegativity, abundance, and availability of electrons. This distinguishes them from other atoms and allows them to perform distinctive roles in various applications. Here, we have reviewed the most current breakthroughs in nitrogen-doped CDs (N-CDs) for fluorescent sensor applications in the last five years. The first section of the article addresses several synthetic and sustainable ways of making N-CDs. Next, we briefly reviewed the fluorescent features of N-CDs and their sensing mechanism. Furthermore, we have thoroughly reviewed their fluorescent sensor applications as sensors for cations, anions, small molecules, enzymes, antibiotics, pathogens, explosives, and pesticides. Finally, we have discussed the N-CDs' potential future as primary research and how that may be used. We hope that this study will contribute to a better understanding of the principles of N-CDs and the sensory applications that they can serve. [Display omitted] • Extensive overview of fluorescence N-CDs for optical sensor applications. • The possible processes underlying the PL origins of N-CDs were outlined. • Discussed the effects of various dopants on the photophysical characteristics of CDs. • Use of N-CDs for detecting ions, small compounds, and pharmaceuticals was described. [ABSTRACT FROM AUTHOR]

CO 2 sequestration into coalbed seams is one of the practical routes for mitigating CO 2 emissions. The adsorption mechanisms of CO 2 onto Malaysian coals, however, are not yet investigated. In this research CO 2 adsorption isotherms were first performed on dry and wet Mukah-Balingian coal samples at temperatures ranging from 300 to 348 K and pressures up to 6 MPa using volumetric technique. The dry S1 coal showed the highest CO 2 adsorption capacity of 1.3 mmol g−1, at 300 K and 6 MPa among the other coal samples. The experimental results of CO 2 adsorption were investigated using adsorption isotherms, thermodynamics, and kinetic models. Nonlinear analysis has been employed to investigate the data of CO 2 adsorption onto coal samples via three parameter isotherm equilibrium models, namely Redlich Peterson, Koble Corrigan, Toth, Sips, and Hill, and four parameter equilibrium model, namely Jensen Seaton. The results of adsorption isotherm suggested that the Jensen Seaton model described the experimental data well. Gibb's free energy change values are negative, suggesting that CO 2 adsorption onto the coal occurred randomly. Enthalpy change values in the negative range established that CO 2 adsorption onto coal is an exothermic mechanism. Webber's pore-diffusion model, in particular, demonstrated that pore-diffusion was the main controlling stage in CO 2 adsorption onto coal matrix. The activation energy of the coals was calculated to be below −13 kJ mol−1, indicating that adsorption of CO 2 onto coals occurred through physisorption. The results demonstrate that CO 2 adsorption onto coal matrix is favorable, spontaneous, and the adsorbed CO 2 molecules accumulate more onto coal matrix. The observations of this investigation have significant implications for a more accurate measurement of CO 2 injection into Malaysian coalbed seams. • CO 2 adsorption was investigated onto dry and wet coals at 300–348 K and 6 MPa • CO 2 interacts with the coal surface at high pressure in presence of water molecules. • Enthalpy value change confirmed that CO 2 adsorption with coal is an exothermic process. • Jensen Seaton model showed CO 2 adsorption best compliance with the experimental data. • Webber's pore-diffusion model showed the pore-diffusion was the major controlling step. [ABSTRACT FROM AUTHOR]

Conversion and reducing agent (NaBH 4) effect on zero valent iron into Fe 3 O 4 nanoparticles with diverse molar ratios of reducing agent was produced through chemical reduction technique. The structural, optical, vibrational analyses were executed via XRD, UV–Vis, Raman, and FT-IR analysis. The crystallite size obtained were 35 nm, 27 nm, and 18 nm for Fe:NaBH 4 (1:1), Fe:NaBH 4 (1:2) and Fe:NaBH 4 (1:3). The morphology of the Fe:NaBH 4 (1:1) was not in good orientation with higher dimensions. As explored in Fe:NaBH 4 (1:2) and (1:3) samples, there is a proper growth of nanoneedles and nanosheets formation. This was due to the addition of reducing agent which greatly helped in enhancement of morphology. The prepared photocatalysts were tested to reduce Malachite Green (MG) under UV illumination. The pure dye solution obtained 57% efficiency after irradiation. Fe:NaBH 4 (1:3) photocatalyst achieved 97% efficiency on reducing pollutants. The rate constant values calculated was 0.007, 0.013, 0.02 and 0.03 min−1 for pure, Fe: NaBH 4 (1:1), Fe: NaBH 4 (1:2) and Fe: NaBH 4 (1:3) assisted MG samples. The as prepared photocatalyst is more potential one on removal of toxic pollutants from wastewater which is due to the better enhancement of nanoneedles and nanosheets oriented by the effect of reducing agent. The advantage of Fe 3 O 4 nanoparticles for wastewater is that the removal of these nanoparticles can be ease with magnetic separation methods. On considering the advantage of removing of photocatalyst and efficiency, this prepared product is suitable one for wastewater remediation process in future days. • The pure dye solution obtained 57% efficiency after irradiation. • Fe:NaBH 4 (1:3) photocatalyst achieved 97% efficiency on reducing pollutants. • The rate constant values calculated was 0.007, 0.013, 0.02 and 0.03 min−1. [ABSTRACT FROM AUTHOR]

Herein we reported the effect of doping and addition of surfactant on SnO 2 nanostructures for enhanced photocatalytic activity. Pristine SnO 2 , Zn–SnO 2 and SDS-(Zn–SnO 2) was prepared via simple co-precipitation method and the product was annealed at 600 °C to obtain a clear phase. The structural, optical, vibrational, morphological characteristics of the synthesized SnO 2 , Zn–SnO 2 and SDS-(Zn–SnO 2) product were investigated. SnO 2 , Zn–SnO 2 and SDS-(Zn–SnO 2) possess crystallite size of 20 nm, 19 nm and 18 nm correspondingly with tetragonal structure and high purity. The metal oxygen vibrations were present in FT-IR spectra. The obtained bandgap energies of SnO 2 , Zn–SnO 2 and SDS-(Zn–SnO 2) were 3.58 eV, 3.51 eV and 2.81 eV due to the effect of dopant and surfactant. This narrowing of bandgap helped in the photocatalytic activity. The morphology of the pristine sample showed poor growth of nanostructures with high level of agglomeration which was effectively reduced for other two samples. Product photocatalytic action was tested beneath visible light of 300 W. SDS-(Zn–SnO 2) nanostructure efficiency showed 90% degradation of RhB dye which is 2.5 times higher than pristine sample. Narrow bandgap, crystallite size, better growth of nanostructures paved the way for SDS-(Zn–SnO 2) to degrade the toxic pollutant. The superior performance and individuality of SDS-(Zn–SnO 2) will makes it a potential competitor on reducing toxic pollutants from wastewater in future research. • SnO 2 , Zn–SnO 2 and SDS-(Zn–SnO 2) product were investigated. • Bandgap of SnO 2 , Zn–SnO 2 and SDS-(Zn–SnO 2) were 3.58, 3.51, 2.81 eV. • Narrowing bandgap helped in photocatalytic activity. • SDS-(Zn–SnO 2) efficiency showed 90% RhB degradation. • SDS-(Zn–SnO 2) explored 2.5 times higher than pristine sample. [ABSTRACT FROM AUTHOR]

Waste water remediation is the ongoing hot research topic that can reduce the water scarcity all over the world. By reducing the pollutants in the waste water drawn from industries and other sources will be more useful for domestic purposes. To reduce the rate of pollutants in water may also help in improving the aquatic environment and decreases other side effects. Efficient and cost effective catalysts were in search for both dye degradation and water remediation treatment applications. NiMoO 4 nanorods were prepared by employing co-precipitation method with different stirrer time (2 h, 4 h and 6 h). The formation of NiMoO 4 was substantiated employing X-ray diffractometer analysis (XRD). Vibrational and rotational property of the samples was analyzed by FT-IR spectra and Raman spectra. The optical property was further confirmed by UV–vis spectral studies. Morphological analysis studies revealed growth of nanorods with 6 h stirrer time. The photocatalytic behavior of the obtained product was carried out under both UV light (364 nm) and visible light irradiation. The samples subjected to visible light environment showed better efficiency on degrading the methylene blue (MB) dye. The efficiency obtained under UV irradiation were 20%, 31%, 33%, 41% and efficiency obtained in visible light irradiation were 27%, 42%, 46%, 55% with respect to bare methylene blue (MB), MB with NiMoO 4 (2 h), MB with NiMoO 4 (4 h), MB with NiMoO 4 (6 h) catalyst added. NiMoO 4 sample with 6 h stirrer time and fine nanorods growth will be the good candidate for future use. • UV irradiation efficiency were 20%, 31%, 33%, 41%. • Visible light irradiation efficiency were 27%, 42%, 46%, 55%. • NiMoO 4 with 6 h stirrer revealed good results. [ABSTRACT FROM AUTHOR]