Hydrothermal synthesis and size-enhanced chromaticity of Sr2ZnSi2O7:Eu3+ nanoparticles.

Red phosphor Sr2ZnSi2O7:Eu3+ nanoparticles with an average diameter of 20 nm were successfully synthesized via a low-temperature hydrothermal route in order to understand the underlying relationship between size and luminescent properties. The nanometer-sized particles result in a distinct improvement in chromaticity and a high quenching concentration. According to emission spectra, the relative intensity of the 5D0 --> 7F2 to 5D0 --> 7F1 transitions in nanometer-sized phosphors is higher than that of the corresponding bulk material. The better chromaticity results from the more distorted lattices and relatively lower crystal symmetry around the Eu3+ ions, which is ascribed to the large surface area due to the nanometer size of the phosphor. Moreover, the nanometer-sized Sr2ZnSi2O7:Eu3+ red phosphor exhibits a shorter fluorescent lifetime and a blue-shift in excitation spectra compared to that of its bulk counterpart. These results indicate that size-induced enhancement of luminescent properties is an efficient way to obtain red phosphors with better chromaticity.

Mn-doped zinc aluminate nanoparticles: hydrothermal synthesis, characterization, and photoluminescence properties.

A two-step synthesis method was developed to fabricate Mn-doped zinc aluminate (ZnAl2O4) nanoparticles, including the first step of ageing, and the second step of crystallization. The effects of preparation conditions, such as ageing temperature, crystallization time, and the pH on the Mn-doped ZnAl2O4 nanoparticles were systematically investigated. The photoluminescence (PL) properties of green phosphor Mn-doped ZnAl2O4 nanoparticles were also discussed. Compared with the bulk sample, the PL spectrum of Mn-doped ZnAl2O4 nanoparticles has distinct blue shift. This procedure provides a facile way for the synthesis of well-crystallized ZnAl2O4:Mn at low temperature.

Single-source approach to cubic FeS2 crystallites and their optical and electrochemical properties.

Cubic FeS2 crystallites have been synthesized via a single-source approach using iron diethyldithiocarbamate as precursor under hydrothermal conditions. The sample is characterized by XRD, IR, TEM, and FESEM. The optical properties of the as-prepared FeS2 reveal that there exists a red shift compared with that of bulk materials. Meanwhile, the electrochemical properties of FeS2 demonstrate that it delivers a large discharge capacity, which might find possible application as an electrode material in lithium cells. It is also found that the reaction temperature is of importance to the formation of cubic FeS2 crystallites.

A simple hydrothermal route to large-scale synthesis of uniform silver nanowires.

This paper describes the preparation of uniform silver nanowires by reducing freshly prepared silver chloride with glucose at 180 degrees C for 18 hours in the absence of any surfactants or polymers. Scanning electron microscopy studies indicated that the silver nanowires are about 100 nm in diameter and up to 500 microm in length. High-resolution transmission electron microscopy analyses showed that the silver nanowires grow perpendicularly to the Ag(200) plane. The silver nanowires are believed to grow through a solid-solution-solid process. Some influential factors on the growth of silver nanowires are also discussed.