Determination of the rod-wire transition length in colloidal indium phosphide quantum rods

Colloidal InP quantum rods (QRs) having controlled diameters and lengths are grown by the solution-liquid-solid method, from Bi nanoparticles in the presence of hexadecylamine and other conventional quantum dot surfactants. These quantum rods show band-edge photoluminescence after HF photochemical etching. Photoluminescence efficiency is further enhanced after the Bi tips are selectively removed from the QRs by oleic acid etching. The QRs are anisotropically 3D confined, the nature of which is compared to the corresponding isotropic 3D confinement in quantum dots and 2D confinement in quantum wires. The 3D-2D rod-wire transition length is experimentally determined to be 25 nm, which is about 2 times the bulk InP exciton Bohr radius (of approximately 11 nm).     

Reactions of indium phosphide cluster cations with ammonia and trimethylamine

Chemistry of indium phosphide clusters is studied using the powerful trapped ion cell techniques of Fourier transform ion cyclotron resonance (FTICR) mass spectrometry in conjunction with an external cluster source and ion guide. The external source is capable of generating a wide range of cluster ions which the ion guide loads with high efficiency into the FTICR cell. The differential pumping of the ion guide allows for operation of the FTICR at requisite low pressure conditions while extracting clusters generated in a high pressure environment. Highly selective reactions of indium phosphide clusters are observed with ammonia and trimethylamine. Of all the In_xP⁺_y cluster sizes and stoichiometries studied, only the indium dimer ion reacts exothermically with ammonia. Thermalized In⁺₂ reacts by indium ion transfer to ammonia. Owing to its much higher basicity, trimethylamine is much more reactive. The smaller indium phosphide clusters react by indium ion transfer to trimethylamine. As the clusters become larger, however, the reaction probability decreases to zero.     

Mild and efficient one-pot synthesis of chiral β-chalcogen amides via 2-oxazoline ring-opening reaction mediated by indium metal

A simple and efficient procedure for the synthesis of β-seleno and β-thio amides via the ring-opening reaction of chiral 2-oxazolines in the presence of indium metal has been developed. Features of this method include the following: (i) easily and accessible starting materials; (ii) indium metal is more stable and less expensive then its respective salts; (iii) useful to excellent yields of β-chalcogen amides derivatives.     

Formate ester synthesis via reaction of 2-bromoethylamines with dimethylformamide

2-Bromoethylamines are converted to the corresponding formate esters in the presence of DMF. Both primary and secondary bromides are smoothly transformed to the esters in satisfactory yields. The reaction mechanism involves the formation of an aziridinium ion, which upon reaction with DMF forms a Vilsmeier-type intermediate that is further hydrolyzed to the corresponding formates. Participation of the β-amino group appears to control not only the regioselectivity but also the stereoselectivity of the reaction. Application of the reaction conditions to chiral substrates indicated that non-rearranged products are formed with retention of configuration at the reacting center.     

Graphene-like nanostructures: synthesis and use for preparation of catalysts and hydrogen storage composites

The results of the works aimed at synthesis of graphene-like nanomaterials by reduction of graphite oxide are summarized. The problems encountered on preparing graphene-metal catalysts applied in hydrogenation processes and reactions of decomposition of hydrocarbons to produce carbon nanofibers are discussed. Development of magnesium-graphene hydrogen storage composites is considered. The optimal preparation conditions and the functional characteristics of the obtained materials are given.     

Aqueous synthesis of III-V semiconductor GaP and InP exhibiting pronounced quantum confinement

A mild aqueous synthesis route was successfully established to synthesize well crystallized and monodisperse GaP and InP nanocrystals, which were proved to exhibit pronounced quantum confinement by room-temperature UV/Vis adsorption and photoluminescence (PL) spectra.     

Efficient synthesis of sulfonylguanidines via reaction of tetra-substituted urine with ArSO2NCO

An efficient synthesis of sulfonylguanidines via reaction of tetra-substituted urines with ArSO₂NCO has been developed with good yields, which provides a convenient way for synthesis of sulfonyl group protected guanidine from urine in one step.     

Controlled synthesis of responsive hydrogel nanostructures via microcontact printing and ATRP

Surfaces that are spatially functionalized with intelligent hydrogels, especially at the micro‐ and nanoscale, are of high interest in the diagnostic and therapeutic fields. Conventional methods of the semiconductor industry have been successfully employed for the patterning of hydrogels for various applications, but methods for fabricating precise 3 D patterns of hydrogels at the micro‐ and nanoscale over material surfaces remain limited. Herein, microcontact printing (µCP) followed by atom transfer radical polymerization (ATRP) was applied as a platform to synthesize temperature responsive poly(N‐isopropylacrylamide) hydrogels with varied network structures (e.g. different molecular weight crosslinkers) over gold surfaces. The XY control of the hydrogels was achieved using µCP, and the Z (thickness) control was achieved using ATRP. The controlled growth and the responsive behavior of hydrogels to temperature stimuli were characterized using Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). The results demonstrate that this platform allows for the controlled growth of hydrogel nanostructures using the controlled ATRP mechanism. It is also shown that the molecular weight of the crosslinker affects the rate of hydrogel growth. These PNIPAAm‐based crosslinked hydrogel patterns were also demonstrated to have a temperature‐dependent swelling response. Using this technique, it is possible to synthesize responsive hydrogel patterns over various surfaces for potential applications in the biomedical field. Copyright © 2009 John Wiley & Sons, Ltd.     

Stereoselective synthesis of 2-hydroxymorpholines and aminodiols via a three-component boro-Mannich reaction

The three-component coupling of an 1,2-aminoalcohol, a 1,2-dicarbonyl compound and a boronic acid was investigated. The reaction is supposed to proceed through the formation of a heterocyclic iminium species followed by the addition of the organoboron derivative. The diastereoselectivity of this process is discussed. Best results were observed when the probable intermediate was generated from a preformed 3-phenylthiomorpholin-2-ol. Products of this three-component boro-Mannich could be readily converted to the corresponding aminodiols by reduction with lithium aluminium hydride.     

2-Bromophospholide ions: synthesis and theoretical study

DFT calculations at the B3 LYP/6-311++G(3df,2p) level indicate that the 2-bromophospholide ion could be stable toward self-arylation as a result of the lowered nucleophilicity of the in-plane phosphorus lone pair (the corresponding sigma(P) orbital is lowered by 0.7 eV compared with the corresponding orbital of the parent phospholide ion, and the negative charge at P is reduced from -0.435 to -0.369 e). Accordingly, the synthesis of 2-bromo-3,4-dimethylphospholide was successfully carried out by quantitative base-induced dealkylation of 2-bromo-1-(2-ethoxycarbonylethyl)-3,4-dimethylphosphole. This ion reacts with FeCl2 to give the corresponding 2,2'-dibromo-3,3',4,4'-tetramethyl-1,1'-diphosphaferrocene as a poorly stable mixture of meso- and rac-diastereomers in 18% yield.     

Efficient synthesis of 2-imino-1,2-dihydroquinolines and 2-imino-thiochromenes via copper-catalyzed domino reaction

A domino approach to 2-imino-1,2-dihydroquinolines and 2-imino-thiochromenes from sulfonyl azides, alkynes, and 2-acyl anilines or the potassium salt of 2-mercapto-benzaldehyde has been developed. This one-pot method is efficient and versatile.     

Microwave-promoted synthesis of amino-substituted 2-pyridone derivatives via palladium-catalyzed amination reaction

A rapid and efficient synthesis of amino-substituted 2-pyridones was demonstrated by palladium-catalyzed amination reaction under microwave irradiation. This high-speed synthesis provided a number of amino-substituted 2-pyridones from the corresponding bromo-2-benzyloxypyridines via palladium-catalyzed amination followed by hydrogenolysis of benzyl ether.     

Solvothermal synthesis of InP quantum dots and their enhanced luminescent efficiency by post-synthetic treatments

InP quantum dots (QDs) were solvothermally synthesized by using a greener phosphorus source of P(N(CH(3))(2))(3) instead of highly toxic P(TMS)(3) widely used, and subsequently subjected to a size-sorting processing. While as-grown QDs showed an undetectably low emission intensity, post-synthetic treatments such as photo-etching, photo-radiation, and photo-assisted ZnS shell coating gave rise to a substantial increase in emission efficiency due to the effective removal and passivation of surface states. The emission efficiency of the photo-etched QDs was further enhanced by a consecutive UV photo-radiation, attributable to the photo-oxidation at QD surface. Furthermore, a relatively thick ZnS shell on the surface of InP QDs that were surface-modified with hydrophilic ligands beforehand was photochemically generated in an aqueous solution at room temperature. The resulting InP/ZnS core/shell QDs, emitting from blue to red wavelengths, were more efficient than the above photo-treated InP QDs, and their luminescent properties (emission bandwidth and quantum yield) were comparable to those of InP QDs synthesized with P(TMS)(3). Structural, size, and compositional analyses on InP/ZnS QDs were also conducted to elucidate their core/shell structure.     

Basic alumina catalysed synthesis of substituted 2-amino-2-chromenes via three-component reaction

Substituted 2-amino-2-chromenes were obtained in excellent yield and selectivity simply by mixing malononitrile, α-naphthol and aromatic aldehydes in water in the presence of basic alumina as heterogeneous and reusable catalyst.     

A 2:1 coupling reaction of arynes with aldehydes via o-quinone methides: straightforward synthesis of 9-arylxanthenes

[reaction: see text] A novel coupling reaction, where an aldehyde and two molar amounts of an aryne are assembled selectively, has been demonstrated to afford diverse 9-arylxanthene derivatives in one step. o-Quinone methide arising from the [2 + 2] cycloaddition of an aldehyde with an aryne was postulated as a transient intermediate.     

Facial synthesis of trifluoromethylated xanthenes via tandem reaction of arynes and 2-trifluoroacetylphenols

A tandem insertion-nucleophilic cyclization reaction between arynes and 2-trifluoroacetylphenols has been described, providing trifluoromethylated xanthenes in good to excellent yield.     

A novel pyrrole synthesis via reaction of ketones with N-aminoimides

A new, mild synthesis of pyrroles using N-aminoimides and a ketone is described. The reaction has been utilized in the synthesis of dimeric morphinans containing a connecting pyrrole ring. The reaction appears to proceed through a diacylhydrazone intermediate, and it is suggested that the driving force behind the reaction is the facility with which a protonated imide moiety operates as a leaving group.