In this paper, we present a new procedure for the rapid synthesis of luminescent ZnSe nanocrystals in aqueous phase by microwave irradiation with controllable temperature. The effects of microwave irradiation and experimental conditions on the synthesis of nanocrystals were investigated systematically. It was found that there were significant effects of pH value of reaction solutions, molar ratio of precursors, and heating time of microwave irradiation on the optical properties of the ZnSe nanocrystals. A series of nanocrystals with different size was prepared in 1 h, and the photoluminescence quantum yield reached up to 17% at the optimal reaction condition. The results of HRTEM and XRD showed that the as-prepared nanocrystals had high crystallinity. The characterizations of EDS spectra and elemental analysis showed that the sulfur content of nanocrystals increased with the growth of nanocrystals. We speculated that the structure of nanocrystals was an alloy ZnSe(S) shell on the surface of the ZnSe particles core. Furthermore, we found that the oxygen from air in the reaction vessel played an important role in the decomposition of the thiol group under microwave irradiation.

In this article, near-infrared (NIR) CdHgTe alloyed quantum dots (QDs) were directly synthesized in water by heating a mixed solution of CdCl 2 , Hg(ClO 4 ) 2 and NaHTe in the presence of thiol stabilizers. The CdHgTe QDs exhibit photoluminescence (PL) ranging from 600 to 830 nm that can be tuned by size and composition. The quantum yields (QYs) of QDs were about 20-50%, associated with their emission wavelength and composition. Compared to other reported NIR QDs such as CdTe/CdHgTe and InAs, the as-prepared CdHgTe alloyed QDs have much narrower emission spectra, and their full widths at half-maximum (fwhm) are only 60-80 nm. Characterization by HRTEM and XRD showed that the CdHgTe QDs have good monodispersity and a nice crystal structure. To improve the photostability and reduce the cytotoxity of the CdHgTe QDs, a CdS nanocrystal shell was added to the surface of the CdHgTe QD core. Furthermore, the CdHgTe/CdS core/shell QDs were successfully applied for the imaging of living animals. Our preliminary results illustrate that our synthesis procedure is very simple and inexpensive and that the as-prepared products CdHgTe/CdS core/shell QDs are water-soluble and photostable and will be an alternative probe in the imaging of living animals.

The flow theory of mechanism-based strain gradient (MSG) plasticity is established in this paper following the same multiscale, hierarchical framework for the deformation theory of MSG plasticity in order to connect with the Taylor model in dislocation mechanics. We have used the flow theory of MSG plasticity to study micro-indentation hardness experiments. The difference between deformation and flow theories is vanishingly small, and both agree well with experimental hardness data. We have also used the flow theory of MSG plasticity to investigate stress fields around a stationary mode-I crack tip as well as around a steady state, quasi-statically growing crack tip. At a distance to crack tip much larger than dislocation spacings such that continuum plasticity still applies, the stress level around a stationary crack tip in MSG plasticity is significantly higher than that in classical plasticity. The same conclusion is also established for a steady state, quasi-statically growing crack tip, though only the flow theory can be used because of unloading during crack propagation. This significant stress increase due to strain gradient effect provides a means to explain the experimentally observed cleavage fracture in ductile materials

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All‐inorganic perovskite nanocrystals (NCs) have attracted considerable attention due to their extensive photonic and optoelectronic properties. These NCs are shown to exhibit strong multiphoton absorption (MPA). However, studies on the MPA properties of perovskite NCs are only conducted on weakly confined perovskite cubic NCs, while the relevant influences of the geometry are never discussed. To the best of knowledge, this report describes the first comparison of the MPA properties of CsPbBr3 2D nanoplates (2D NPs) and cubic NCs. Based on the experimental results, it can be concluded that stronger quantum confinement effect of 2D NPs will strongly enhance their MPA with outstanding normalized‐volume two‐ and three‐photon absorption cross sections up to 1561 GM nm−3 and 7.2 × 10−78 cm6 s2 photon−2 nm−3, respectively. This work demonstrates that CsPbBr3 2D NPs are good candidates for exploring the influences of quantum confinement on MPA properties of perovskite NCs, which are also highly suitable for the applications of multiphoton imaging and nonlinear optoelectronics.