Shengli Zuo

Water-soluble multicolored fluorescent CdTe quantum dots: Synthesis and application for fingerprint developing

Multicolored water-soluble fluorescent CdTe quantum dots (QDs) have been synthesized by using Te, NaBH(4), and CdCl(2) as precursors and several mercapto-based compounds as modifiers. The effects of ratio of the precursor, type of modifier, refluxing time and initial pH value of the reaction on fluorescence intensity of CdTe QDs have been studied. XRD, HRTEM and fluorescence spectra were employed to characterize these samples. It is found that CdTe QDs with a crystalline size of 3-4nm are homogeneously embedded in the organic matrix. The maximum fluorescence emission peaks of CdTe QDs solutions shifted from 525nm to 591nm according to the refluxing time. The fingerprint details on the surface of smooth objects were clearly developed with CdTe QDs solution under irradiation of UV lights.

Solvothermal-induced phase transition and visible photocatalytic activity of nitrogen-doped titania

Nitrogen-doped titania nanoparticles consisting of pure anatase, pure rutile and bicrystallites (anatase+rutile and anatase+brookite) have been prepared in TiCl(3)-HMT (hexamethylene tetramine)-alcohol solution under solvothermal process. The effect of the solvent type and amount of HMT as pH adjuster on the phase composition of titania and its visible photocatalytic activity for degradation to MO (methyl orange) was investigated. It is found that anatase gradually transferred to rutile with increase of carbon chain using methanol, ethanol, 1-propanol and 1-butanol as solvent. The pure anatase formed at the pH value of 1-2, while bicrystalline titania (anatase+rutile and anatase+brookite) at that of 7-10 in the presence of methanol. The bicrystalline (anatase+brookite) titania have the best visible photocatalytic activity among all the samples. The -(NO) and -(NH) dopants with an N (1s) binding energy of 400 eV may have positive effects on the visible light photocatalytic activity.

Preparation of MCM-41 incorporated with lacunary Keggin polyoxometalate and its catalytic performance in esterification

The ordered mesoporous MCM-41 materials incorporated with lacunary polyoxometalate were prepared via an original direct synthesis method. As the control, the samples with similar lacunary polyoxometalate loadings were also prepared by impregnation of MCM-41. The prepared samples were characterized by XRF, XRD, FT-IR, Raman spectra, HRTEM, SEM, N(2) adsorption isotherm, TG-DTA, and NH(3)-TPD technology. The results show that the lacunary polyoxometalate is better dispersed in the direct synthesized samples than in the impregnated samples, and its structure remains intact after formation of the materials. The catalytic performance of the materials was tested using the esterification of n-butanol with acetic acid. The direct synthesized samples display excellent catalytic performance and reusability, which is superior to the impregnated samples. Under the optimized conditions, the conversion of n-butanol is 89.7%, and the selectivity of butyl acetate is nearly 100%.

Preparation of mesoporous ferrisilicate with high content of framework iron by pH-modification method and its catalytic performance

The mesoporous ferrisilicates (MFS) with high iron content were synthesized by pH-modification method, and the iron content could be up to 10.5 wt.% (Si/Fe=8). The pH was kept less than 2 at pre-hydrothermal synthesis step and was adjusted to 11 during hydrothermal step. The samples were characterized by XRD, HRTEM, N(2)-sorption, XRF, FTIR, DRUV-vis, Fe K-edge EXAFS, EPR, and DSC. The results suggested that the MFS materials were ordered 2D hexagonal mesophase of MCM-41, and the iron atoms were tetrahedral coordinated in the silica framework. This material could efficiently catalyze the hydroxylation of phenol in water medium using H(2)O(2) as an oxidant, and the phenol conversion could be up to 52% under the optimal experimental conditions.

Application of mercaptosuccinic acid capped CdTe quantum dots for latent fingermark development

The aqueous synthesis of mercaptosuccinic acid (MSA) capped CdTe quantum dots (QDs) solution for quickly and sensitively developing latent fingermarks is described. The rapid growth mechanism of CdTe/MSA QDs, which depends on the molecule structure of MSA, is briefly discussed and compared with that of thioglycolic acid (TGA) and mercaptopropionic acid (MPA) capped CdTe QDs. Development of latent fingermarks with the synthesized CdTe/MSA QDs was faster and the ridge details were clearer compared with CdTe/TGA QDs. In addition, latent fingermarks developed with CdTe/MSA QDs showed less background and better contrast than that of gentian violet or rhodamine 6G. Latent fingermarks could be well developed on black tape, scotch tape, tinfoil, aluminum alloy, stainless steel as well as on the adhesive side of yellow tape, even when the latter were aged up to seven days. As immersion time greatly reduced to 10 s by using CdTe/MSA QDs, a preliminary result of latent fingermark development by spraying was presented also.

Photocatalytic Activity of Nanosized Cadmium Sulfides Synthesized by Complex Compound Thermolysis

The nanosized cadmium sulfides (CdSs) containing different phase structures were synthesized via the complex compound thermolysis method using different molar ratio of thiourea to acetate cadmium (S/Cd) and characterized by XRD, TEM, UV-Vis, and IR spectra. The results of photocatalytic degradation of rhodamine B (RB) show that the activity order of CdS concerning the phase compositions is of cubic hexagonal cubic

A template induced method to synthesize nanoporous graphitic carbon nitride with enhanced photocatalytic activity under visible light

A template induced method was developed to synthesize nanoporous graphitic carbon nitride (npg-CN) by directly heating Triton X-100-modified-melamine sulfate. The effects of the added amount of Triton X-100 and heating temperature on the formation of npg-CN were investigated. The npg-CN samples were characterized by XRD, FT-IR, and elemental analysis; nitrogen adsorption isotherms, SEM and TEM images; and UV-vis DRS and photoluminescence spectra. The results showed that the npg-CN samples possessed a laver-like layered structure with a high surface area (50–135 m2 g−1). Meanwhile, compared to the bulk g-CN (synthesized by directly heating melamine), the npg-CN samples possessed stronger optical absorptions, narrower band gaps, and significantly reduced fluorescence intensity. The photocatalytic activity was investigated by degradation of Rhodamine B under visible light irradiation. As a result, the photodegradation rate of Rhodamine B dye on the npg-CN samples was greatly improved over that on bulk g-CN.

AgBr-Coupled TiO2: A Visible Heterostructured Photocatalyst for Degrading Dye Pollutants

A series of AgBr/TiO2 visible photocatalysts with heterojunction structure was synthesized using Ti(OC4H9)4, KBr, and AgNO3 as precursors. The phase composition, particle morphology and size, microstructures, and absorbance of these photocatalysts were characterized by X-ray diffraction, transmission electron microscope (TEM), high-resolution TEM, and UV-vis spectra. It was found that the coupled AgBr/TiO2 was an effective photocatalyst to degrade the methylene blue under visible light irradiation, compared with the other noncoupled photocatalysts of AgBr, AgBr/P25, and P25. The photocatalytic activities of AgBr/TiO2 increase first and then decrease with increasing the mass ratio of mAgNO3/mTiO2 and the photocatalyst with the mass ratio of 3.35 has the highest photocatalytic activity. The results showed that the coupled photocatalyst has the particle size of about 15 nm with homogeneous dispersion and has the strongest absorption in whole UV-vis light region (250∼800 nm) originated from the synergetic effect of heterostructured AgBr/TiO2. The coupled AgBr/TiO2 photocatalyst can keep stable photocatalytic activity after five-circle runs.

Preparation and catalytic performance of a novel highly dispersed bifunctional catalyst Pt@Fe-MCM-41

A novel highly dispersed bifunctional catalyst Pt@Fe-MCM-41 was prepared successfully by an in situ synthesis combined with selective reduction. The catalyst contained highly dispersed metal active components and acid carriers with a regular structure. The results showed that the uniformly sized platinum nanoparticles were highly dispersed and fixed in the inner surface of MCM-41 and the iron atoms were tetrahedrally coordinated and highly dispersed in the silica framework. The samples showed an excellent catalytic activity and selectivity for hydrocracking of residual oil, which proved that there existed an obvious promotion effect between the highly dispersed platinum active sites and the Fe-MCM-41 carrier.

Structure of flower-like hierarchical CdS QDs/Bi/Bi2WO6 heterojunction with enhanced photocatalytic activity

A flower-like hierarchical CdS QDs/Bi/Bi2WO6 heterojunction photocatalyst was synthesized via an in situ reduction and deposition process. The samples were systematically characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), nitrogen absorption–desorption isotherms, photoelectrochemical measurements and photoluminescence spectroscopy (PL). The results indicate that plasmonic Bi nanoparticles as the electron-conduction mediator with size of 10 nm promote charge transfer effectively between the CdS nanoparticles and Bi2WO6 nanosheets. The photocatalytic performance tests show that the CdS QDs/Bi/Bi2WO6 composite exhibits extraordinarily enhanced photocatalytic activity than pure Bi2WO6, Bi/Bi2WO6 and CdS QDs/Bi2WO6 for the photodegradation of Rhodamine B and formaldehyde. The superior photocatalytic performance of the CdS QDs/Bi/Bi2WO6 composite is attributed to its improved visible light absorption property by coupling CdS QDs with plasmonic Bi and also to the efficient charge transfer of the metallic Bi nanoparticles.