Room-temperature irradiation route to synthesize a large-scale single-crystalline ZnO hexangular prism

A large-scale single-crystalline ZnO hexangular prism was successfully synthesized through a simple gamma-irradiation method at room temperature and under ambient pressure. The product of a ZnO hexangular prism with a rim of 230 +/- 10 nm and a length up to 8.5 microm was well monodisperse and showed a very strong and broad green light emission at around 577 nm. A possible formation process was also proposed.     

A simple method to synthesize triangular silver nanoparticles by light irradiation

We describe a simple method to synthesize triangular silver nanoparticles by photoreducing the silver ions by citrate. A noteworthy difference of the present method as compared with the previous photo-induced methods is that good shape control over the nanoparticles can be realized in the absence of soft templates or polymer directing agents. The formation process of the silver nanoparticles was investigated by UV-vis spectroscopy and transmission electron microscopy (TEM). It was found that the concentration of reactant plays important role in the morphology control of produced silver nanoparticles. As one of the applications of these nanoparticles, they were used as surface-enhanced Raman scattering substrates and 1,4-bis[2-(4-pyridyl)ethenyl]-benzene (BVPP) was used as a Raman probe to evaluate the enhancement ability of the triangular silver nanoparticles.     

Surface Diels-Alder reactions as an effective method to synthesize functional carbon materials

The post-synthesis chemical modification of various porous carbon materials with unsaturated organic compounds is reported. By this method, amine, alcohol, carboxylate, and sulfonic acid functional groups can be easily incorporated into the materials. Different carbonaceous materials with surface areas ranging from 240 to 1500?m(2)g(-1) and pore sizes between 3.0 and 7.0?nm have been studied. The resulting materials were analyzed by elemental analysis, nitrogen sorption, FTIR spectroscopy, zeta-potential measurements, thermogravimetric analysis, photoelectron spectroscopy, and small-angle X-ray scattering. These analyses indicated that the degree of functionalization is dependent on the nature of the dienophile (reactivity, steric hindrance) and the porosity of the carbon material. As possible applications, the functionalized carbonaceous materials were studied as catalysts in the Knoevenagel reaction and as adsorbents for Pb(2+) from aqueous solution.     

A novel transesterification system to rapidly synthesize cellulose aliphatic esters

Cellulose aliphatic esters (CEs) are important cellulose derivatives that have been widely used in many fields such as plastics, textiles, membranes, etc. However, in traditional methods, long pretreatment and reaction times limit the manufacture of CEs and their widespread application. Herein, a very efficient method for the preparation of CEs in a heterogeneous system was developed. This method involved the transesterification of cellulose with vinyl esters (from C4 to C14) in dimethylsulfoxide under the catalysis of aqueous NaOH. For better understanding of this new reaction system, factors such as the water content, amount of catalyst, reaction temperature and molar ratio of vinyl acetate to the anhydroglucose unit were explored. Results obtained from FT-IR, ¹H and ¹³C NMR spectroscopies confirmed that CEs could be synthesized at 100 °C within 5 min. High water content or excessive amounts of NaOH were detrimental to the synthesis of CEs. Results from small-angle X-ray diffraction showed that the interplanar spacings of these CEs showed an increasing trend with the length of the aliphatic chain. Thermogravimetric analysis and derivative thermogravimetric analysis showed that CEs had higher thermal stability than cellulose. This work provides a new and highly efficient method to synthesize various CEs.     

An efficient and eco-friendly protocol to synthesize calix[4]pyrroles

A facile, highly efficient and eco-friendly protocol for the synthesis of calix[4]pyrroles in excellent yields is reported. Instead of tedious column chromatography, simple recrystallization techniques were employed for compound purification yielding better results and leading to multi gram scale synthesis.     

Novel acid-catalyzed rearrangement of methanofullerenes bearing an alpha-ylidic ester to cyclopentanofullerenes: a vinyl cyclopropane-type ring expansion

A novel acid-catalyzed ring expansion of methanofullerenes bearing an alpha-ylidic ester has been investigated. Treatment of dialkyl acetylenedicarboxylate and tricycloalkylphosphine with C(60) led to the isolation of a methanofullerene ylide after passing the reaction mixtures through a basic alumina column. If the reaction mixture was passed through a silica gel column, a cyclopentanofullerene was isolated instead. These new cyclopentanofullerenes consisted of a fused cyclopentanone ring bearing an alpha-hydroxy ester and a phosphonium ylide and were confirmed by their NMR, mass, and X-ray diffraction data. The cyclopentanofullerenes were formed by the ring expansion of the corresponding methanofullerenes in the presence of silica gel. The ring expansion also proceeded by treating methanofullerene with acetic acid in chloroform. On the other hand, the methanofullerenes from RO(2)CCCCO(2)R, PAr(3), and C(60) were stable in silica gel. However, upon heating with acetic acid at 50 degrees C, they underwent ring expansion and dephosphination to give cyclopentenofullerenes. An implicit vinyl cyclopropane ring expansion mechanism was proposed to account for this novel acid-catalyzed rearrangement.     

A new convenient way to synthesize 1‐hydroxyphosphonates from heterocyclic aldehydes and ketones under microwave irradiation

A simple and efficient method has been developed for the synthesis of 1‐hydroxyphosphonates from heterocyclic aldehydes and ketones under solvent‐free conditions using microwave irradiation. Various phosphites have been used to find the influence of steric exclusion on the reaction. The products are readily obtained in satisfactory yields, on the solid support of MgO. The reactions are also induced by oil‐heat, and we find that the condition of microwave is better than oil‐heat with respect to reaction times and product yields. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:347–353, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20304     

一种合成反式-1,2-二苯乙烯的新方法

采用Grubbs's催化剂,以苯乙烯为原料,CH2Cl2为溶剂进行烯烃置换作用,合成出反式-1,2-二苯乙烯。为合成反式-1,2-二苯乙烯提供了一种实验简单、方法可靠的新方法。实验证明,用2(mol)%Grubbs's催化剂,在40℃,6h内反应产率可达70%。产物的结构由1^HNMR、MS等确定。     

Novel route to synthesize CuO nanoplatelets

A new synthesis route to obtain high-purity cupric oxide, CuO, using the hydrothermal reaction of copper sulfide and a NaOH solution in an oxygen atmosphere has been developed. The synthesized products showed nanoplatelet-like morphologies with rectangular cross-sections and dimensions at the nanometric scale. Variations in the oxygen partial pressure and synthesis temperature produced changes in size and shape, being found that the proliferation of nanoplatelet structures occurred at 200 °C and 30 bar.     

An improved pyrolysis route to synthesize carbon-coated CdS quantum dots with fluorescence enhancement effect

Well-dispersed carbon-coated CdS (CdS@C) quantum dots were successfully prepared via the improved pyrolysis of bis(1-dodecanethiol)-cadmium(II) under nitrogen atmosphere. This simple method effectively solved the sintered problem resulted from conventional pyrolysis process. The experimental results indicated that most of the as-prepared nanoparticles displayed well-defined core-shell structures. The CdS cores with diameter of ∼5 nm exhibited hexagonal crystal phase, the carbon shells with thickness of ∼2 nm acted as a good dispersion medium to prevent CdS particles from aggregation, and together with CdS effectively formed a monodisperse CdS@Carbon nanocomposite. This composite presented a remarkable fluorescence enhancement effect, which indicated that the prepared nanoparticles might be a promising photoresponsive material or biosensor. This improved pyrolysis method might also offer a facile way to prepare other carbon-coated semiconductor nanostructures.     

Quantitative use of ultraviolet spectroscopy to calculate the effective irradiation dosage during weathering

The ultraviolet absorbance of a urethane coating showed typical yellowing that increased with exposure period. An effective dosage was calculated from the solar spectrum, the quantum yield for the degradation process and the ultraviolet absorption. Assuming a constant quantum yield, there is a clear acceleration of the absorption of damaging radiation because the ultraviolet absorption increases with exposure. This non-linear relationship offers possibilities on how to estimate a service lifetime. In addition, the yellowing can be analyzed as an “Urbach” tail which is usually attributed to structural disorder that introduces energy levels between the ground and excited electronic states.     

An improved Hummers method to synthesize graphene oxide using much less concentrated sulfuric acid

The production of graphene oxide with less acid is beneficial to reduce the costs and lower the impact on the environment, but it is still a great challenge. In this work, a relatively simple, safe method for synthesizing graphene oxide with much less acid (decrease ～40%) is proposed. With assistance of the heat absorbed from environment and reaction system, the temperature of reaction system of low acid can be well controlled. More interestingly, the graphite can be completely oxidized into graphite oxide by using much less acid, with lowering the production of high-concentration aqueous waste acid (> 1 mol/L, decrease ～40%). A series of characterizations show that the prepared graphene oxide has similar yield and functional groups compared with that of using the conventional method. This work provides a safe and environmentally friendly choice for the large-scale production of graphene oxide and its derivative materials.     

An effective enantioselective route to the platensimycin core

An efficient enantiocontrolled synthetic pathway to platensimycin has been developed.     

Copper-catalyzed domino coupling reaction: an efficient method to synthesize oxindoles

An efficient and novel procedure for a copper catalyzed domino coupling reaction has been developed, which afforded various oxindoles in good to excellent yields with tolerance of various substituents. In addition, this method could be applied to synthesize horsfiline and coerulescine in few steps with high total yields.     

The stability of ferrocenylmethyl derivatives: Further attempts to synthesize ferrocenylacetone

Attempts have been made to synthesize ferrocenylacetone by various routes. The reaction of ferrocene and chloroacetone in the presence of boron trifluoride etherate was investigated as a potential route but this gave 2,2-diferrocenylpropane and not ferrocenylacetone as reported in the literature. Several other attempts to synthesize ferrocenylacetone also failed and possible reasons for the instability of this and of other ferrocenylmethyl derivatives are discussed.     

A simple method to synthesize NiO fibers

Nickel oxide fibers with diameters 1-2 μm and lengths up to 100 μm were synthesized by a simple pyrolytic decomposition method in NaCl flux with NiSO₄ as precursor. X-Ray diffraction, X-ray photoelectron spectrum (XPS) and scanning electron microscopy (SEM) techniques were used to characterize these fibers. They have single-crystal structure, large aspect ratios and macroscopic quantity. Suitable precursor and molten NaCl environment are conjectured to be key factors in this method.     

A new way to synthesize ZnS nanoparticles

ZnS nanoparticles were prepared with normal ZnO and Na2S by solid-liquid chemical reaction under ultrasonic condition andcharacterized by XRD,TEM,SEM,IR and TG-DTG.The results showed that these particles were good crystal cubic zinc blendedwith average size of 50 nm,possess good IR transmittance in the range of 400-4000 cm and good thermal stability.     

Continuous system with microwave irradiation to obtain alkyl benzoates

In this study, a continuous linear alcohol derivatization is developed. Reaction of alcohol group (ROH) with benzoyl chloride (BC) is carried out in an on-line system with UV detection. All reaction conditions, as flow rate (FR), ROH/BC molar ratio, wavelength, temperature, microwave (MW) irradiation and reaction coil size (internal diameter and length) were optimized. 0.5 mL min⁻¹, 2.49 [BC]/[ROH], 230 nm, 60 °C or medium power (225 W) when MW irradiation was used and a reactor coil of 159 μL (0.5 mm × 810 mm) were the optimum conditions. The on-line system with microwave irradiation was more efficient than the one with a water bath heating. The developed system reduces analysis time consumption, reagent amounts and this system was used to evaluate the composition of commercial samples of alcohols polyethoxylated (surfactants).