Effects of the Template Composition and Coating on the Photoluminescence Properties of ZnS:Mn Nanoparticles

Mn-doped ZnS nanocrystals based on low dopant concentrations (0–2%) and coated with a shell of Zn(OH)2 have been prepared via soft template and precipitation reaction. The results indicate that the ZnS:Mn nanocrystal is cubic zinc blende structure and its diameter is 3.02 nm as demonstrated by XRD. Measured by TEM, the morphology of nanocrystals is a spherical shape, and their particle size (3–5 nm) is similar to that of XRD results. Photoluminescence spectra under ultraviolet region shows that the volume ratio of alcohol to water in the template has a great effect on the luminescence properties of ZnS:Mn particles. Compared with unpassivated ZnS:Mn nanocrystals, ZnS:Mn/Zn(OH)2 core/shell nanocrystal exhibits much improved luminescence and higher absolute quantum efficiency. Meanwhile, we simply explore the formation mechanism of ZnS:Mn nanocrystals in alcohol and water system and analyze the reason why alcohol and water cluster structures can affect the luminescent properties of nanoparticle

Metal Oxoclusters as Molecular Building Blocks for the Development of Nanostructured Inorganic\u2013Organic Hybrid Thin Films

Silica-based inorganic\u2013organic hybrid thin \ufb01lms embedding the organically modi\ufb01ed oxohafnium clusters (Hf4O2(OMc)12, OMc=OC(O)\u2013C(CH3)=CH2) were obtained by photo-activated free radical copolymerisation of the methacrylate groups of the cluster with those of the pre-hydrolysed (methacryloxypropyl)trimethoxysilane (MAPTMS, (CH2=C(CH3)C(O)O)(CH2)3Si(OCH3)3). By this route, a covalent anchoring of the cluster to the forming silica network was achieved. Samples characterized by two different Si=Hf compositions (18:1, 5:1) were prepared. The surface and in-depth composition of the thin \ufb01lms were investigated through Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). XPS depth pro\ufb01les performed on the thin layers evidenced a homogenous in depth distribution of the hafnium guest species within the whole silica \ufb01lms and sharp \ufb01lm-substrate interfaces. Broad band dielectric spectroscopy (BDS) measurements permitted to investigate the electric response of the obtained \ufb01lms in the frequency and temperature range of 40 Hz \u2013 1 MHz and 0\u2013160\ub0C

Search for [Formula presented] production in [Formula presented] annihilations at 4.03 GeV

A search is performed for the production of the (Formula presented) in (Formula presented) annihilation at a center-of-mass energy of 4.03 GeV using the BES detector operated at the Beijing Electron Positron Collider (BEPC). The kinematic features of the reconstructed (Formula presented) signal are consistent with its being produced only in association with an energetic photon resulting from initial state radiation (ISR). Limits are placed on (Formula presented) production from the decay of unknown charmonia or metastable hybrids that might be produced in (Formula presented) annihilations at 4.03 GeV. Under the assumption that the observed cross section for (Formula presented) production is due entirely to ISR, the partial width (Formula presented) of the (Formula presented) is measured to be (Formula presented). © 1998 The American Physical Society

Search for a vector glueball by a scan of the J/ψ resonance

The cross section for e e-→ρπ has been measured by the BES detector at BEPC at center-of-mass energies covering a 40 MeV interval spanning the J/ψresonance. The data are used to search for the vector gluonium state hypothesized by Brodsky, Lepage, and Tuan as an explanation of the ρπ puzzle in charmonium physics. The shape of the ρπ cross section is compatible with that of the total hadronic cross section. No distortions indicating the presence of a vector glueball are seen. © 1996 The American Physical Society.

Study of the hadronic decays of [formula presented] states

Hadronic decays of the P-wave spin-triplet charmonium states (Formula presented) are studied using a sample of (Formula presented) decays collected by the BES detector operating at the BEPC storage ring. Branching fractions for the decays (Formula presented) (Formula presented) (Formula presented) (Formula presented) (Formula presented) and (Formula presented) are measured for the first time, and those for (Formula presented) (Formula presented) (Formula presented) and (Formula presented) are measured with improved precision. In addition, we determine the masses of the (Formula presented) and (Formula presented) to be (Formula presented) and (Formula presented) © 1999 The American Physical Society

ψ(2S)→π+π-J/ψ decay distributions

Using a sample of 3.8 M ψ(2S) events accumulated with the BES detector, the process ψ(2S) →π+π-J/ψ is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D wave amplitude, as well as S wave. On the other hand, the J/ψ-(π+π-) relative angular momentum is consistent with being pure S wave. The decay distributions have been fit to heavy quarkonium models, including the Novikov-Shifman model. This model, which is written in terms of the parameter κ, predicts that D wave pions should be present. We determine κ=0.183 ±0.002±0.003 based on the joint mππ-cos θπ* distribution. The fraction of D wave amplitude as a function of mππ is found to decrease with increasing mππ, in agreement with the model. We have also fit the Mannel-Yan model, which is another model that allows D wave pions. ©2000 The American Physical Society