A bond-order–bond-length–bond-strength (bond-OLS) correlation mechanism is presented for consistent insight into the origin of the shape-and-size dependence of a nanosolid, aiming to provide guidelines for designing nanomaterials with desired functions. It is proposed that the coordination number imperfection of an atom at a surface causes the remaining bonds of the lower-coordinated surface atom to relax spontaneously; as such, the bond energy rises (in absolute value). The bond energy rise contributes not only to the cohesive energy (ECoh) of the surface atom but also to the energy density in the relaxed region. ECoh relates to thermodynamic properties such as self-assembly, phase transition and thermal stability of a nanosolid. The binding energy density rise is responsible for the changes of the system Hamiltonian and related properties, such as the bandgap, core-level shift, phonon frequency and the dielectrics of a nanosolid of which the surface curvature and the portion of surface atoms vary with particle size. The bond-OLS premise, involving no assumptions or freely adjustable parameters, has led to consistency between predictions and experimental observations of a number of outstanding properties of nanosolids.

Amorphous silicon nitride films of different composition deposited at room temperature by pulsed glow discharge plasma immersion ion implantation and depositionIt is shown that bond contraction and nonbonding lone-pair interaction dominate at nitride surfaces. The maximum elastic recovery of a nitride surface was found to be 100% under a relatively lower nanoindentation load (Ͻ1.0 mN) and the hardness of the surface was found to be 100% higher than the bulk value. It is interpreted that the spontaneous bond contraction, estimated at 12%-14%, strengthens the binding energy and hence the hardness and Young's modulus at the surface. The lone-pair weak interaction claims the responsibility for ͑i͒ the high elastic recovery, ͑ii͒ the lower Raman frequencies of vibration, and ͑iii͒ the existence of critical loads for slide friction or lone-pair broken.

Figure 5. a,b) Density of state distributions of CdS (a) and CdS-P (b). c) Room-temperature time-resolved photoluminescence (TRPL) decay curves of samples in acetone. d) Schematic energy levels and variations in the Fermi levels of CdS and CdS-P. a-d) Reproduced with permission. [120] Copyright 2017, Wiley-VCH. e-g) Potential energy diagram of photocatalytic water splitting with corresponding depictions of transition-state structures on pristine ZnS and ZnS with vacancy defects. h) Proposed mechanism of M-ZnS with rich surface vacancy defects. e-h) Reproduced with permission. [121] Copyright 2021, American Chemical Society. i) Potentiostatic curves of samples. j) Digital images of as-prepared samples taken at different visible-light irradiation times. k,l) Potential barrier of an O 2 molecule (k) and an H 2 O molecule (l) through defective graphene. i-l) Reproduced with permission. [116]

A simple solid-phase method was developed for synthesis of high-quality boehmite nanorods by steam-assisted wet-gel conversion process. γ-Al2O3 nanorods with clear-cut edge have been successfully obtained by thermal treatment of boehmite nanorods at 600 °C for 5 h. The nanorods of boehmite and γ-Al2O3 were characterized by X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscope (FESEM) with energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and high-resolution tranmission electron microscopy (HRTEM) with selected area electron diffraction (SAED) spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), magic-angle spinning (MAS) 27Al nuclear magnetic resonance (NMR), and thermogravimetric and differential thermal analysis (TGA-DTA). The growth of boehmite was found to be greatly affected by the conditions used for precipitation of Al(NO3)3 with NH4OH aqueous solution. When precipitation was conducted under pH 5.0 or pH 7.0, nanorods of boehmite with lengths in the range of 100−400 nm and uniform diameters (20−30 nm) were obtained by steaming the solid wet gel at 200 °C for 48 h, whereas irregular boehmite particles were obtained from the wet gel precipitated under alkaline condition (pH 10.0). The directed crystallization of boehmite nanorods was attributed to the preferential growth along the longitudinal axis under supersaturated hydrothermal condition with the assistance of steam. The 1D nanostructure of boehmite was well preserved after being converted to γ-Al2O3 without sintering among the highly dispersed nanorods. This approach allows us to fabricate high-quality nanorods of boehmite and γ-Al2O3 with controlled size and morphology using cost-effective solid-phase chemical methods at a large scale.

A novel, facile, and highly enantioselective Brønsted acid-catalyzed alpha-hydroxylation of beta-dicarbonyl compounds with up to 99:1 er using nitroso compounds as the oxygen source has been developed. The results disclosed herein considerably extend the substrate scope for the alpha-aminoxylation, allowing expeditious, straightforward, and efficient access to valuable alpha-hydroxy-beta-dicarbonyl compounds with the highest levels of enantiocontrol.