Synthesis of Novel Nickel Sulfide Submicrometer Hollow Spheres

Abstract

does not require an activation energy but it is certainly characterized by dissipation associated with the viscosity at the boundary between the crystalline domains and the amorphous matrix. A detailed description of this process goes well beyond the scope of this introductory communication.The recording speed of the holograms in our samples is of the order of tens of seconds, much slower than in the photorefractive composites with the smallest response times, [18,19] and this represents the main limit of our materials. Improvement in response time may require tighter control of the shape of the dispersed domains and of their surface dissipative properties. An increase in the holographic writing time was also observed as the AZPON content was lowered. This can be attributed to an increase in the surface/volume ratio of smaller domains, corresponding to an increased effect of the viscosity torques relative to the reorienting field torques. The stability towards further phase separation, corresponding to an increase in domain size beyond the limit of scattering in the visible, is relatively good, with little or no decrease of efficiency over a period of several months. An increase in the scattering is however observed after a 5±10 months period at room temperature, although the original performance is regained after a heating±cooling cycle during which phase separation is repeated. An improvement in the stability of the nanodispersions can, in principle, be obtained through well established techniques (vulcanization, reinforcement, etc.) of polymer stabilization. In summary, our data indicate that, at a given applied electric field, controlled phase separation can increase the orientational contribution to the dynamic range by orders of magnitude. As the improvement in performance that we describe here can in principle be obtained in most photoconductive composites, this method considerably broadens the range of potentially useful photorefractive materials for applications ranging from holographic storage to medical imaging. ExperimentalSamples consisted of thin amorphous films between two indium tin oxidecoated conducting glasses. They were obtained by mixing the required amounts of substances in chloroform and evaporating the solvent. Empty cells containing only glass spacers to control the thickness were prepared, placed on a hot plate, filled by capillary action, and cooled rapidly to room temperature. Alternatively, for solutions with higher viscosity, the hot melt was sandwiched between two hot glasses and then rapidly cooled.Light transmission was measured for a p-polarized laser beam at 633 nm, incident at a 60 angle with respect to the sample normal.Diffraction efficiency was measured by degenerate four-wave mixing experiments, carried out by overlapping two writing beams on a circular area of the sample with a 1 mm diameter. Writing beams had equal intensity and were s-polarized, with a power density of 0.4 W cm ±2, and the beam ratio was b = 1. The grating period was K = 3 lm in all cases. A reading bea...

Hollow Micro‐/Nanostructures: Synthesis and Applications

“…[178,179] After the silica shell is formed by the hydrolysis and condensation of TEOS, the liquid PDMS cores can be easily removed by solvent extraction. [180] In addition to sol-gel processes, many other synthetic approaches, such as hydrothermal methods [158] and g-irradiation, [181][182][183][184] have been employed in combination with emulsion templating to synthesize hollow particles of various crystalline materials, including metals, [185,186] oxides [187] and sulfides, [157,188,189] and inorganic/polymer composites. [183,184] Bao et al synthesized Ni hollow spheres (300-450 nm) using NiSO 4 and NaH 2 PO 2 as precursor and reducing agent respectively.…”

Deposition of Ni and Pd Sulfide Thin Films via Aerosol‐Assisted CVD

“…[20][21][22][23][24][25][26][27][28][29][30][31][32] There are, however, relatively few reports on the deposition of thin films of nickel and palladium chalcogenides. Films of nickel sulfide [33][34][35][36] have been deposited via solution growth techniques, and nickel [37][38] and palladium sulfide [37,39] have been deposited by both CVD, and non-CVD techniques. [40] Cheon et al [37] have reported deposition of stoichiometric NiS and PdS from both thermal and photochemical CVD routes using M(S 2 COCHMe 2 ) 2 , (M = Ni or Pd), and Nomura and Hayata studied the deposition of NiS 1.03 from Ni(S 2 CNEt 2 ) 2 on Si(111) substrates at 350-400°C by low-pressure metal-organic (LP-MO) CVD.…”

NiS Hollow Spheres for High‐Performance Supercapacitors and Non‐Enzymatic Glucose Sensors

“…Until now, despite the success in the preparation of NiS hollow structures, the synthesis of hollow structures of NiS by a simple route still remains as a significant challenge. [15,43,44] Herein, we provide a facile strategy to prepare hollow a-NiS and b-NiS spheres via the Kirkendall effect under different hydrothermal conditions. Unlike template-directed approaches, this route avoids complicated and tedious operational procedures for the removal of the templates.…”