A construction strategy for ratiometric fluorescent nanosensors based on water soluble C-dots was developed, which could sense temperature (10-82 °C), pH values (lower than 6.0 or higher than 8.6) and Fe(3+) ions (>0.04 μM) by monitoring the intensity ratios of dual fluorescence bands (Ib/Ig) under 380 nm excitation. Ib/Ig decreased nearly linearly with increasing temperature from 10 to 82 °C. In the pH range from 8.6 to 6.0, the Ib/Ig was nearly constant at 0.75. Ib/Ig gradually decreased from 0.75 to 0.52 in the pH range from 6.0 to 1.9, and increased nearly linearly from 0.52 to 0.75 in the pH range from 1.9 to 1.0. The dual fluorescence behavior was reversible in the pH range from 1.0 to 8.6. As pH increased from 10.6 to 13.0, the green fluorescence band decreased continuously and blue shifted with a nearly linear increase in Ib/Ig from 0.75 to 2.15, while the green fluorescence band cannot be recovered by decreasing the pH value. Ib/Ig was ultrasensitive and selective in presence of Fe(3+) (>0.04 μM) in neutral aqueous environments. The two fluorescence bands of the C-dots were attributed to different surface states that may produce different fluorescent signal responses to external physical or chemical stimuli.

In this work, two Cu(II) complex compounds are designed and synthesized for applications as p-type dopants in solid-state perovskite solar cells (PSCs). Through the characterization of the optical and electrochemical properties, the complex Cu(bpcm) 2 is shown to be eligible for oxidization of the commonly used hole-transport material (HTM) Spiro-OMeTAD. The reason is the electron-withdrawing effect of the chloride groups on the ligands. When the complex was applied as p-type dopant in PSCs containing Spiro-OMeTAD as HTM, an efficiency as high as 18.5% was achieved. This is the first time a Cu(II) pyridine complex has been used as p-type dopant in PSCs.

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The interactions between bovine serum albumin (BSA) and gold nanoparticles (AuNPs), and the conformational changes of BSA induced by this interaction, were investigated by UV-visible absorption spectroscopy, fluorescence spectroscopy, and Fourier transform infrared in combination with attenuated total reflection spectroscopy (ATR-FTIR). The critical adsorption density for preventing AuNP aggregation in 0.1 mol/L phosphate buffered saline (pH 7.2) was 23 BSA molecules per gold particle or 3.8×1012 BSA molecules/cm 2 . BSA bound to the AuNPs with high affinity (binding constant K s =7.59×10 8 L/mol), and the intrinsic fluorescence of BSA was quenched by the AuNPs in accordance with the static quenching mechanism. Both fluorescence spectroscopy and ATR-FTIR showed that AuNPs induced conformational changes in BSA, which resulted in it becoming less compact and increased the polarity of the microenvironment around the tryptophan residue Trp-212.

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The effect of ultrasound washing with different frequencies including sweeping, fixed and combined fixed frequencies on Escherichia coli inactivation and selected physical and chemical qualities of Chinese cabbage were investigated. Colour, microstructure, total chlorophyll, total carotenes, total phenolic content, DPPH radical scavenging, hydroxyl radical scavenging and reducing power activities were measured using standard in vitro assays. In contrast with water washed samples, ultrasound washing with a fixed frequency of 40 kHz resulted in >3 log CFU/g reduction in E. coli counts, approximately 20% improvement in total phenolic content and over 32% increase in reducing power activity. There was, however, a marginal improvement in DPPH radical scavenging activity and a decrease in hydroxyl radical scavenging activity. Scanning electron micrographs revealed the presence of micro‐fractures and minute holes and dislodging of surface particles Ultrasound washing improved the perceptible visual colour (∆E) and the greenish appearance of the leaves. Practical applications Multi‐frequency power ultrasound washing of fresh produce is a recent application of varying frequencies in decontamination of fresh produce. The remarkable influence of ultrasonic frequency aside other operating parameters in the removal of contaminants on fruits and vegetable surfaces influenced this study. The results reported in this experimental study may be considered for application in the inactivation of microorganisms including E. coli and other Gram‐negative bacteria. This washing technique may also be used in combination with other studied physical or chemical preservation methods as a synergy to enhance microbial removal and quality characteristics of fresh produce in the food industry.