In this study, a systematic approach was applied to the hydrothermal synthesis of Zn 2 SnO 4 (ZTO) nanocrystals to gain insight into the fundamental factors controlling phase composition, particle size, crystal morphology and photocatalytic activity. The influence of various operating conditions, such as reaction temperature, alkaline concentration, duration time, and additive surfactants on the treatment process were investigated. By combining the results of X-ray diffraction (XRD), electron microscopy (SEM/TEM/ED/HRTEM), Raman and FT-IR spectroscopy, a complete structural and morphological characterization of the products was performed. The results indicated that the phase transformation probably evolved via a "dissolution-recrystallization" mechanism and accompanying the "Ostwald ripening" process. Furthermore, a correlation between the photocatalytic activity in the UV photodegradation of MB solutions and the particle properties was established.

Red-emitting carbon dots (CDs) have attracted tremendous attention due to their wide applications in areas including imaging, sensing, drug delivery, and cancer therapy. However, it is still highly challenging for red-emitting CDs to simultaneously achieve high quantum yields (QYs), nucleus targeting, and super-resolution fluorescence imaging (especially the stimulated emission depletion (STED) imaging). Here, it is found that the addition of varied metal ions during the hydrothermal treatment of p-phenylenediamine (pPDA) leads to the formation of fluorescent CDs with emission wavelengths up to 700 nm. Strikingly, although metal ions play a crucial role in the synthesis of CDs with varied QYs, they are absent in the formed CDs, that is, the obtained CDs are metal-free, and the metal ions play a role similar to a “catalyst” during the CD formation. Besides, using pPDA and nickel ions (Ni2+) as raw materials, we prepare Ni–pPCDs which have the highest QY and exhibit various excellent fluorescence properties including excitation-independent emission (at ∼605 nm), good photostability, polarity sensitivity, and ribonucleic acid responsiveness. In vitro and in vivo experiments demonstrate that Ni–pPCDs are highly biocompatible and can realize real-time, wash-free, and high-resolution imaging of cell nuclei and high-contrast imaging of tumor-bearing mice and zebrafish. In summary, the present work may hold great promise in the synthesis and applications of red emissive CDs.

It is shown that the nonlinear optical phenomenon known as second-harmonic generation can be used for label-free, time-resolved study of the transport of molecules through living cell membranes. The adsorption and transport of a 300-Da molecular-mass hydrophobic ion at the Escherichia coli membrane is observed. Remarkably, at low ion concentrations, the second-harmonic generation technique clearly exposes a multistep molecular transport process: Transport of the molecular ion across the outer and cytoplasmic membranes of the Gram-negative bacteria is recorded, in sequence, in time. Fitting of the data to a multiprocess kinematic model reveals that the transport of this hydrophobic ion through the outer membrane is much faster than through the cytoplasmic membrane, likely reflecting the effectiveness of ion transport porins. The observations illustrate an experimental means for studying the interactions of small molecules with cell membranes.

Nanocubic La2Sn2O7 photocatalysts with pyrochlore structure have been successfully synthesized by a one-pot hydrothermal method. The effects of alkaline concentration, reaction time, and hydrothermal temperature on the structures and morphologies of the resultant products were investigated. On the basis of characterization results from X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED), a possible growth mechanism of the nanocubes under the hydrothermal conditions was proposed. The absorption spectra of as-prepared cubic La2Sn2O7 photocatalyst were determined by UV−vis spectrometer. Photocatalytic experiments showed that the La2Sn2O7 samples not only had a high activity for degradation of methyl orange, but also had the activity for generating H2 with a rate of 39 μmol/h under ultraviolet light irradiation.

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Efficient water harvesting from vapor has attracted increasing attention in recent years owing to its potential to addressing the daunting water crisis. A fundamental challenge limiting the water collection efficiency...

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