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The worldwide pollution of water bodies by potential contaminants such as heavy metals, dyes, and pesticides etc. have severely affected the entire eco-system due to their toxic mobility and tough degradation in water. Consequently, there is a requirement to develop cost-competitive and easily handleable sensing materials which can detect targets sensitively and with selectivity. Among the low-cost sensory materials, carbon dots (CDs) constitute an important class of carbon nanomaterial with unique photostability, electronic and fluorescent properties. This review is an effort to comprehend the recent improvements in the sensing applications of CDs with prominence on synthetic routes, the effect of various synthesis parameters on physical properties (quantum yield, size range), detection mechanisms, and detection parameters (limit of detection, interference etc.). Particularly, the scope and progress for the detection of potential water contaminants using CDs have been explored and a holistic view of mechanisms of their detection has been included. Holistic view of mechanisms for different types of signals generated by CDs. [ABSTRACT FROM AUTHOR]

Sunlight driven Mnn+-ZnO (n = 2, 4 and 7) nanohybrids were prepared via impregnation method using different metal precursors of variable oxidation state. Dynamic light scattering (DLS) spectra showed that the average hydrodynamic size decreased when precursor of higher Mn oxidation state was used. Moreover, the structural analysis revealed that Mn nanoparticles (5–10 nm, d = 0.13 nm) dispersed over ZnO support (20–30 nm, d = 0.39 nm) while KMnO4 was added for impregnation purpose. Interestingly, the co-catalyst (Mn) was loaded in + 2, +4 and + 7 oxidation state when MnSO4.H2O, MnO2 and KMnO4 respectively utilized for loading over ZnO surface, confirmed from X-ray photon spectroscopy. The potential of prepared nanocomposites were investigated for methylene blue (MB) degradation, an organic pollutant and it was observed that oxidation state of the co-catalyst largely influenced the photoactive-response of nanocomposites. Notably, Mn7+-ZnO degraded MB (98%) nearly 3.3 times higher as compared to bare ZnO and also higher than Mn4+-ZnO (91%) and Mn2+-ZnO (83%). The metal nanoparticles played a dual role in the photo-oxidative reaction by sensitizing the nanomaterial in the sunlight and suppressing the recombination rate of electrons-holes to enhance the reaction efficiency. [ABSTRACT FROM AUTHOR]

Non-Abelian discrete symmetry group S 3 × Z 3 has been used to construct quark mass matrices in the flavor basis. Interestingly, the case when M d is nondiagonal and M u is diagonal, is very much compatible with the presently refined data regarding the quark masses and mixing. However, the other case, when M u is nondiagonal and M d is diagonal, looks to be incompatible with the data. [ABSTRACT FROM AUTHOR]

In the present report, Ce3+ modified SnO2 compositions [Sn(1−y)CeyO2, for y = 0, 0.05, and y = 0.10, where y is wt.% of Ce3+] were synthesized via co-precipitation and their physicochemical properties were investigated. Crystal structure studies were carried out by using Rietveld refinement which confirmed high phase-purity and rutile-type tetragonal crystallinity with a P42/mnm space group (space group no. 136) for all samples. Fourier transform infrared (FTIR) spectroscopy depicted the antisymmetric vibrations of Sn-O-Sn and stretching vibration of Sn-O, which were confirmed by bends located at 636 cm−1, and 460 cm−1, respectively. All the compositions showed a strong hump at ~ 300 nm in the ultra-violet (UV) region and the peak shifts slightly towards the blue region with increasing Ce3+content. Transmission electron microscopy (TEM) micrographs depicted pseudospherical particles with an average particle diameter of 12.84 ± 0.17 nm, 15.55 ± 0.31 nm, and 16.52 ± 0.36 nm for y= 0, 0.05, and 0.10, respectively. High-resolution transmission electron microscopy (HRTEM) images confirmed tetragonal crystallinity for all the compositions. Dielectric studies illustrated that on increasing the concentration of Ce3+ in the host SnO2, the value of dielectric permittivity increased. The value of tanδ is maximum for pristine SnO2. The variation of ac conductivity was due to Maxwell–Wagner type interfacial polarization. For all the compositions, a sharp hump centered at ~ 407 nm was observed in the photoluminescence spectrum, which may be attributed to the presence of oxygen anion vacancies. [ABSTRACT FROM AUTHOR]