Photochemical synthesis of gold nanorods

Gold nanorods have been synthesized by photochemically reducing gold ions within a micellar solution. The aspect ratio of the rods can be controlled with the addition of silver ions. This process reported here is highly promising for producing uniform nanorods, and more importantly it will be useful in resolving the growth mechanism of anisotropic metal nanoparticles due to its simplicity and the relatively slow growth rate of the nanorods.     

Photochemical and analytical applications of gold nanoparticles and nanorods utilizing surface plasmon resonance

In recent years, plasmonics has emerged as a promising tool in the fields of analytical chemistry and biochemistry. In particular, surface plasmon resonance at the surfaces of gold nanostructures has led to the development of widespread interest in gold nanoparticles. In this review, we describe some of the recent progress in the manufacture and use of gold nanoparticles, with particular emphasis on gold nanorods. Furthermore, the spectroscopic and photochemical applications of gold nanospheres and nanorods are described.     

A simple method to synthesize single-crystalline lanthanide orthovanadate nanorods

Single-crystalline tetragonal LnVO₄ (Ln=La, Nd, Sm, Eu, Dy) nanorods were prepared via a simple hydrothermal method, in the absence of any surfactant or template using cheap and simple inorganic salts as raw materials. The products were characterized by XRD, TEM, HRTEM, and PL. It has been shown that after the hydrothermal process, LaVO₄ transformed its crystal structure from monoclinic to tetragonal phase, but LnVO₄ (Ln=Nd, Sm, Eu, Dy) have not exhibited the structural change. This could be associated with the change of lanthanide ion radius. TEM and HRTEM results show that the nanorods are pure, structurally uniform, single crystalline, and most of them are free from dislocations. Further study reveals the nanorods grow along the [001] direction. A possible growth mechanism of lanthanide orthovanadate nanorods was also proposed. The advantages of our method for the nanorods synthesis lie in the high yield and the low temperature and mild reaction conditions, which permit large scale production at low cost.     

Photochemical cyclization of anils of polyfluoroaromatic ketones

Conclusions The UV irradiation of the anils polyfluoroaromatic ketones in strongly acidic media leads to photochemical cyclization to phenanthridines. The insertion of substituents into the anil molecule lowers the phototransformation rate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1606–1611, July, 1980.     

Two efficient cascade reactions to synthesize substituted furocoumarins

We have developed two efficient one-pot reactions to generate furo[3,2-c]coumarins and chlorofuro[3,2-c]coumarins through addition/cyclization/oxidation and chlorination. One cascade addition/cyclization/oxidation sequence of 1 with H(2)O in the presence of 20% CuCl as Lewis acid under an air atmosphere generated the 2-substituted-4 H-furo[3,2-c]chromen-4-one 2. Another sequence in the presence of 10% CuBr and excess CuCl(2) as the oxidant afforded the 3-chloro-2-substituted-4 H-furo[3,2- c]chromen-4-one 3.     

Characterization of the surface structure of gold nanoparticles and nanorods using structure sensitive reactions

The surface structure of gold nanorods has been determined by studying the behavior of electrochemical reactions sensitive to the structure and compared to that obtained by other structure characterization techniques. Lead underpotential deposition (UPD) reveals that the surface of the nanorods is composed by (111) and (110) domains, while (100) domains are practically absent from the surface. In the case of the oxygen reduction reaction, the formation of hydrogen peroxide as a final product of the reaction in the whole potential range also indicates that (100) domains are absent on the surface of the nanoparticles, corroborating the previous result. These results are compared with other surface structure information provided by other techniques.     

pH-triggered assembly of gold nanorods

The self-assembly of surfactant-protected gold nanorods (aspect ratio 3.3 +/- 0.3, 20.6 +/- 5.5 nm width, and 67.5 +/- 9.0 nm length) into ordered structures using adipic acid is presented. As made, the gold nanorods are coated with cationic surfactant, which gives them a net positive charge in aqueous solution. The pH-dependent assembly is directed by electrostatic interactions between the positively charged nanorods and negatively charged, deprotonated adipic acid. Absorption spectra and light scattering measurements of these nanorods suggest that aggregation is initiated in solution in the presence of adipic acid at pH 7-8, but not at pH 3, to form small assemblies of nanorods. Zeta potential measurements show that the assembly is significantly less positively charged in the presence of deprotonated adipic acid than when adipic acid is fully protonated.     

Modification of gold nanorods using phosphatidylcholine to reduce cytotoxicity

Hexadecyltrimethylammonium bromide (CTAB), which is necessary for the preparation of gold nanorods (NRs), was extracted from a NR solution into a chloroform phase containing phosphatidylcholine (PC). After three extractions, the zeta potential of the NRs remained positive, but its magnitude decreased from +67 +/- 1 to +15 +/- 1 mV. Transmission electron microscopy and energy-dispersive X-ray analysis indicated that the NRs were passivated with PC. The PC layer on the NR surface contributed to the prevention of NR aggregation. The PC-passivated NRs showed low cytotoxicity in comparison with twice-centrifuged NRs. It was shown that a negligible amount of CTAB was dispersed in the NR solution after the extraction. The extraction using a chloroform phase containing PC was found to be a convenient way of replacing the CTAB with alternative capping agents such as PC. This is a key technique for preparing functional NRs that can have practical applications.     

Organo-soluble chiral thiol-monolayer-protected gold nanorods

Here, we report the synthesis and characterization of organo-soluble chiral thiol-monolayer-protected gold nanorods. The resulting gold nanorods respectively covered with two opposite enantiomers via the strong covalent Au-S linkage were found to not only be stable in both organic media and solid state, but also show optical activity. Their circular dichroism (CD) spectra exhibited a mirror image relationship, indicating that enantiomeric thiol surfactant on gold surface can produce the corresponding enantiomeric gold nanorods. The densely packed azobenzene thiol monolayer on gold surface exhibited a photoresponsive behavior upon irradiation with 254 nm light instead of 365 nm light, which was found to have an effect on plasmonic absorption of gold nanorods.     

Photochemical reactions. 152nd Communication. Photochemistry of acylsilanes; photolysis and thermolysis of cyclopropyl silyl ketones

The photolysis and thermolysis of the Cyclopropyl silyl ketones 3, 4 , and 5 are described. On n,π* excitation, the silyl ketones 3 and 4 undergo a Norrish-type-II reaction involving γ-H abstraction, cyclopropyl ring cleavage followed by retro-enolization to the acylsilanes 6 and (E/Z)- 12 , respectively. As a common product of 3 and 4 , the dihydrofuran 7 is formed via the alternative C(α)-C(β) cleavage of the cyclopropyl moiety. Compounds 6 , 7 , and (E/Z)- 12 are new types of acylsilane photoproducts. The irradiation of acylsilane 5 gave the analogous dihydrofuran 15 as the only product. On photolysis of 3 and 4 , products 8A + B and 13A + B , derived from a siloxy carbene intermediate, were found as well. On thermolysis of 3 and 4 , the acylsilanes 6 (80%), and (E)- 12 (33%) and (Z)- 12 (34%), respectively, are formed as the only products. Their formation may occur via a [1, 5] sigmatropic H-shift. The thermolysis of 5 gave the diene 16 whose formation can be explained by insertion of a siloxycarbene into the neighboring cyclopropane leading to the cyclobutene 28 as thermally unstable intermediate.     

High-temperature seedless synthesis of gold nanorods

We demonstrate seedless synthesis of gold nanorods at high temperatures up to 97 degrees C. Using the correct silver nitrate concentration is crucial for formation of rod-shaped particles at all temperatures. We observed a decrease of nanorod length with increasing temperature, while the width stays constant throughout the temperature range. From kinetics studies, we show 3 orders of magnitude increase in nanorod growth rate when the temperature is raised from room temperature to 97 degrees C. From the temperature dependence of the growth rate, we obtain a average activation energy for growth on all facets of 90 +/- 10 kJ mol(-1). High-temperature synthesis of gold nanorods presents a more attractive method for scalable flow-based production of gold nanorods.     

Use of organolithium compounds to synthesize organometallic derivatives of trivalent gold

Conclusions Employing organolithium compounds, the following organometallic derivatives of trivalent gold were obtained: di(n-butyl)auric chloride, di(n-butyl)auric bromide, phenylauric dibromide and diferrocenylauric chloride, which were isolated as their complexes with triphenylphosphine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2077–2078, September, 1971.     

Photochemical reactions of 7-aminocoumarins

The photochemical reactions of 4-methyl-7-diethylaminocoumarin with the dimethyl ester of acetylenedicarboxylic acid, diethyl ester of maleic acid, and N-phenylmaleimide in the presence of oxygen and acetophenone give products of the heterocyclization at C(₆) and C(₈) of coumarin fragment with participation of the diethylamino group. The stereochemical structure of the compounds synthesized was demonstrated using PMR spectroscopy. A mechanism was proposed for this reaction involving the formation of an -amino radical and its addition to the acetylene or olefin, accompanied by attack on the aromatic ring with subsequent aromatization.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 30–36, January, 1989.     

金纳米棒自组装的研究进展

金纳米棒具有独特的光电性能,其自组装形成的功能组装体能够展现出更加优异的整体协同性能,在纳米材料科学和生物医学领域中有广泛而重要的应用前景.本文从诱导自组装各种驱动作用力的角度,综述了金纳米棒自组装的最新研究进展,具体内容包括:表面张力引发的自组装、化学作用驱动如静电作用或氢键作用等引发的自组装以及生物分子识别作用引发的自组装.     

Photochemical reactions of allylphenoxide anions

Photochemical behaviour of sodium allylphenoxides 1a–3a was compared with that of corresponding neutral allylphenols 1b–3b, and a striking difference was found in reactivity as well as in course of the reaction. Remarkably higher photoreactivity of allylphenoxide anions, especially that of o-allylphenoxide 1a, is ascribed to the efficiency of electron transfer. The characteristic reaction products derived only from the anions were as follows: (a) intramolecular cyclization products, indanols 9, from 2a, (b) rearranged reduction products 10 from both 2a and 3a, and (c) degradative methanol-adduct 11 from 3a. Methanol-adducts 7 and photo-reduction products 6 were formed in either case. In addition cyclization products with the participation of O atom, 4 and 5, were obtained from 1a and 1b. Occurrence of the di-π-methane rearrangement was restricted to the reaction of neutral species 1b–3b. A mechanism based on electron transfer in the excited state is suggested for the course of the photoreaction.     

Photochemical reactions of 2,3-diphenylindoles

The UV irradiation of 2,3-diphenylindoles produces two photochemical reactions: a dehydrocyclization with formation of dibenzocarbazoles and a photo-oxygenation which yields benzophenones.Substituents on the 2,3-diphenylindole have a great influence on the reaction course and in most of the examples here studied only one product was formed.Some considerations about the excited states involved in these reactions are presented.     

A seedless approach to continuous flow synthesis of gold nanorods

A direct seedless method for the continuous synthesis of gold nanorods has been developed using a sequential rotating tube-narrow channel processing microfluidic configuration, with the stock feed solutions (HAuCl(4)/CTAB/acetylacetone and AgNO(3)/CTAB/carbonate buffer) being stable for weeks.     

Photochemical oxidation of 1,2,2,6,6-pentamethyl-4-piperidol by ketones

Chemistry of Heterocyclic Compounds -     

Label-free biosensing with lipid-functionalized gold nanorods

The fabrication of a label-free mass spectrometry and optical detection-based biosensor platform for the detection of low-abundance lipophilic analytes in complex mixtures is described. The biosensor consists of a lipid layer partially tethered to the surface of a gold nanorod. The effectiveness of the biosensor is demonstrated for the label-free detection of a lipophilic drug in aqueous solution and a lipopeptide in serum.