No abstract

Defect chemistry in SnO2 is well established for resistive sensors but remains to be elusive for photoluminescence (PL) sensors. It demands a comprehensive understanding of the role of cationic and oxygen defects as well as the creation of abundant such defects to provide a selective PL signal. To accomplish it, SnO2 quantum dots (QDs ∼ 2.4 nm) are prepared without a capping agent along with other dimensions. Then, the relationship of defects with the blue-emission PL is unfolded by electron energy loss spectroscopy, lifetime measurements, X-ray absorption, and Raman spectroscopic measurements. The defects acting as Lewis acid sites are utilized for selective ammonia detection. Huge enhancements of the obscured blue luminescence at 2.77 and 2.96 eV from the SnO2 QDs are observed because of interaction with ammonia. The linear variation of PL intensities with analyte concentrations and the recovery of the sensor are elaborated with detection up to 5 ppm. The interplay of defects in SnO2 is further established theoretically for site-specific interactions with ammonia by density functional theory (DFT) calculations. Thus, the unique mechanism revealed for the superlative performance of the PL sensor with uncapped SnO2 QDs provides a novel platform for defect-engineering-based optoelectronic applications.

Pressure-induced phase transition studies in nanomaterials are important to comprehend thermodynamics at the nanoscale. Raman spectroscopic studies at high pressure in a diamond anvil cell were performed up to 40 GPa on rutile tetragonal phase of SnO 2 nanoparticles (NPs) of sizes ∼2, 4, and 25 nm to investigate their phase stability and phonon anharmonicity. In 25 nm NPs, evidence of phase transitions was observed at ∼11 and ∼24 GPa, 4 nm NPs indicated a cubic phase transition ∼21 GPa, and the 2.4 nm quasinanocrystals were found to stable up to 30 GPa. Raman spectra down to 90 K indicated that phonons of 2.4 nm NPs were more anharmonic. The analysis of total Raman intensity with increasing pressure suggested propagation of disorder from the surface to the central core of the NPs under pressure. Pressure-induced effects on 25, 4, and 2.4 nm NPs reduced their average diameters to 6.4 ± 2.6, 4.04 ± 1.36, and 3.85 ± 0.9 nm, respectively. Using Raman mode Gruneisen parameters γ j , the thermal expansion coefficient α of the 25, 4, and 2.4 nm SnO 2 NPs at 300 K was estimated as 1.674

No abstract

No abstract

No abstract

No abstract

Energy-efficient and environmentally benign photocatalyst with enormous reaction sites activated by similar wide spectrum of sunlight to treat an aqueous dye pollutant is of contemporary research interest. At the onset,...