Stabilization and Large Nonlinearity of Gold Nanoparticles Functionalized with a π‐Conjugated Polymer

Gold nanoparticles protected by a novel π‐conjugated polymer [poly(p‐phenylene ethynylene) containing pendent disulfide and bipyridine groups] are synthesized and characterized. The polymer can stabilize the gold nanoparticles effectively. The nonlinear optical properties of the gold nanoparticle colloid solutions in toluene are investigated by using the Z‐scan technique at a wavelength of 532 nm and pulse width of 4 ns. The gold‐nanoparticle colloid solutions show an exceptional nonlinear absorption effect, which simultaneously contains the saturated absorption resulting from third‐order nonlinearity and a large reverse‐saturated absorption resulting from fifth‐order nonlinearity. In addition, asymmetric self‐focusing refractive effects are investigated in the colloid solutions.     

Influence of Capping Ligands on the Self—organization of Gold Nanoparticles into Superlattices from CTAB Reverse Micelles

Gold nanoparticles with size 3-10nm (diameter) were prepared by the reduction of HAuCl4 in a CTAB/octane 1-butanol/H2O reverse micelle system using NaBH4 as the reducing agent.The as-formed gold nanoparticle colloid was characterized by UV/vis absorption spectrum and transmission electron microscopy(TEM).Various capping ligands,such as alkylthiols with different chain length and shape,trioctylphosphine(TOP),and pyridine are used to passivate the gold nanoparticles for the purpose of self-organization into superstructures.It is shown that the ligands have a great influence on the selforganization of gold nanoparticles into superlattices,and dodecanethiol C12H25SH is confirmed to be the best ligand for the self-organization.Self-organization of C12H25SH-capped gold nanoparticles into 1D,2D and 3D supperlattices has been observed on the carbon-coated copper grid by TEM without using any selective precipitation process.     

Ag-PVA和Ag-PVA/TiO2复合超薄膜的制备及性能研究

用3种方法制备了银纳米粒子-聚乙烯醇复合体系,其中用加热还原法所得体系中Ag纳米粒子的尺寸较大(15nm),其表面等离子体共振吸收峰较宽,最大吸收波长位于420nm;用室温硼氢化钠还原法得到的复合体系的吸收峰蓝移至409nm,且峰形较窄,Ag纳米粒子的平均粒径为8.7nm;低温NaBH4还原法所得体系吸收峰进一步蓝移至397nm,此时Ag纳米粒子粒径最小(3.5nm).将室温还原法所得Ag-PVA复合体系旋涂成膜,所得薄膜光滑、透明、均匀性好,该法适用于制备多层薄膜,以调控薄膜的厚度和光谱性质.将Ag-PVA复合体系与钛酸四丁酯(Ti(O_nBu)₄)的乙醇溶液交替旋涂得到Ag-PVA/TiO₂有机/无机复合薄膜.紫外-可见吸收光谱研究表明,随着Ag-PVA层数的增加,薄膜的表面等离子体共振吸收强度呈线性增加,但是TiO₂层数的增加对吸收光谱没有明显影响.Ag-PVA/TiO₂有机/无机复合薄膜将金属纳米粒子、有机高分子与无机半导体材料结合在一起,这种多层纳米结构在光电、催化功能薄膜等方面具有潜在的应用前景.     

硫化铜纳米棒的低热固相合成及其光学性能

在表面活性剂PEG-400存在的条件下,以醋酸铜和硫代乙酰胺为原料,利用低热固相化学反应,一步制备出分散均匀的硫化铜纳米棒.X射线粉末衍射和能量散射X射线能谱分析证明,产物为纯六角相的硫化铜.透射电镜和扫描电镜形貌分析表明,产物为棒状,直径为80～100nm,长度为200～500nm.紫外-可见光谱和光致发光光谱表明,硫化铜纳米棒的紫外和荧光最大吸收和发射波长与常规硫化铜相比均发生了明显的蓝移,表明所制备的硫化铜纳米棒具有良好的光学性质.     

Competition as a design concept: polymorphism in self-assembled monolayers of biphenyl-based thiols

Self-assembled monolayers (SAMs) of two omega-(4'-methylbiphenyl-4-yl)alkanethiols (CH(3)(C(6)H(4))(2)(CH(2))(n)SH, BPn, n = 4, 6) on Au(111) substrates, prepared from solution at room temperature and subsequently annealed at temperatures up to 493 K under a nitrogen atmosphere, were studied using scanning tunneling microscopy (STM), high-resolution X-ray photoelectron spectroscopy (HRXPS), and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). In striking contrast to BPn SAMs with n = odd, for which only one phase is observed, the even-numbered BPn SAMs exhibit polymorphism. Irreversible phase transitions occur which involve three phases differing substantially in density and stability. Upon annealing, BP4 and BP6 transform into a beta-phase, which is characterized by an exceptionally high structural quality with virtually defect-free domains exceeding 500 nm in diameter. Exchange experiments, monitored by contact angle measurement, reveal that the beta-phase exhibits a dramatically improved stability. The fundamental differences in the phase behavior of even- and odd-numbered BPn SAMs are discussed in terms of two design strategies based on cooperative and competitive effects.     

3D rod-like copper oxide with nanowire hierarchical structure: Ultrasound assisted synthesis from Cu2(OH)3NO3 precursor,optical properties and formation mechanism

3-dimensional (3D) rod-like CuO with nanowire hierarchical structure has been synthesized successfully by a facile ultrasound assisted method combined with thermal conversion, using rouaite Cu₂(OH)₃NO₃ as the precursor. The product was characterized by XRD, SEM, TEM, HRTEM and FT-IR spectrum. Its optical properties were studied by means of UV–Vis diffuse reflectance absorption spectroscopy and photoluminescence (PL) spectrum. Series of control experiments have been performed to explore influencing factors to the product morphologies and a possible formation mechanism has been proposed. The results show that each CuO rod assembled by tens of nanowires is 200–300 nm in diameter and about 1000 nm in length. Each nanowire contains many interconnected nanoparticles with sizes of about 15 nm. Particularly, ultrasound processing was found beneficial to the formation of the 3D rod-like CuO with nanowire hierarchical structure.     

TiO2/十六烷基三甲基溴化铵有序交替层状纳米复合薄膜的制备与结构表征

近年来有序交替的层状纳米结构薄膜的制备吸引了研究者们的极大关注. 目前, 这类薄膜的制备方法研究得最多的是LB技术[1～3]、基于化学吸附的自组装成膜技术[4,5]和交替沉积组装技术[6～8]. 但这几种方法都有明显的缺陷[9,10], 其中,通过LB技术制备有序交替层状纳米复合薄膜需要昂贵的仪器, 而且由于层间是分子相互作用, 膜的稳定性较差; 基于化学吸附的自组装成膜技术由于需要高反应活性的分子和特殊的基底表面, 并且由于化学反应的产率很难达到100%, 因此通过这种方法制备结构有序的多层膜并不容易; 利用交替沉积的方法制备出具有实用厚度的纳米多层膜需要耗费大量的时间. 最近, 出现了一种称为蒸发诱导的超分子自组装方法, 由这种方法制备的纳米多层膜具有成膜速度快和膜有序度高等优点, 此外还可以通过改变成膜物质浓度和拉膜速度来控制薄膜的厚度, 但与LB膜相比其厚度无法在分子水平上控制. 利用这种方法制备多层膜目前的文献报道仅限于线形SiO2与有机物的组装[10～13]. 本文利用这种方法制备了TiO2/十六烷基三甲基溴化铵纳米复合薄膜并对其结构进行了表征, 结果表明所制备的薄膜具有TiO2/十六烷基三甲基溴化铵有序交替的层状结构.     

Optical limiting of gold nanoparticle aggregates induced by electrolytes

The electronic absorption spectra and optical-limiting (OL) properties of gold nanoparticle (AuNP) aggregates induced by KCl and NaCl have been investigated using 4.1-ns laser pulses at 532 nm. Although the individual AuNP colloid shows no optical-limiting effect, the AuNP aggregates exhibit significant optical-limiting characteristics. With an increased concentration of KCl and NaCl, the surface plasmon resonance (SPR) band shifts to a longer wavelength, and the optical-limiting performance is enhanced. Both the electronic absorption and optical limiting are influenced by the particle size. The larger the individual nanoparticle, the further red-shifted the SPR band and the stronger the optical limiting. Optical limiting of aggregates induced by KCl is stronger than that of aggregates induced by NaCl. Mechanistic studies reveal that free-carrier absorption is the dominant contributor to the optical limiting, with negligible contribution from nonlinear scattering.     

Resonance light scattering spectroscopy study of interaction between gold colloid and thiamazole and its analytical application

In this paper, we used resonance light scattering (RLS) spectroscopy to study the interaction between thiol-containing pharmaceutical-thiamazole and gold colloid. At pH 5.2, the resonance light scattering spectrum of gold nanoparticles has a maximum peak at 555 nm and the RLS intensity is enhanced by trace amount of thiamazole due to the interaction between thiamazole and gold colloid. The binding of colloidal gold to thiamazole results in ligand-induced aggregation of colloidal gold, which was characterized by RLS spectrum, ultraviolet-visible (UV-Vis) spectrum, and transmission electron microscopy (TEM). Based upon the study, we proposed a highly sensitive, gold colloid-based assay using RLS spectrum to detect pharmaceuticals for the first time. The mechanism of binding interaction between Au colloid and thiamazole was also discussed.     

Pulse radiolysis studies of short-lived species in solid amino acids as precursors of radicals and detected by ESR

The aim of the study was to bring closer solid state radiation chemistry and ESR spectroscopy by looking for precursors of free radicals which give ESR signals. It has been performed using time-resolved spectrophotometry (pulse radiolysis of the solid state) and diffuse reflection spectrophotometry. Alanine has been especially considered as the most investigated amino acid, important for radiation dosimetry. Absorption of the transient (Λ maximum at 460 nm) is identified as the species during deamination. The stable absorption spectrum with the Λ maximum at 345 nm is due to the same radical as the one detected by ESR. Other amino acids: valine, threonine, glutamine and arginine show similar behaviour: microsecond spectrum of the intermediate appears always at longer wavelenghts. The transient spectrum changes into stable absorption in UV of a lower wavelenght. Along with the optical spectrum, the ESR spectrum appears, of similar stability. Also, other features indicate that the same radical is responsible for both the electronic and ESR spectrum. Some amino acids, like methionine give intensive transient absorption in the microsecond range but no ESR signal, after completion of consecutive fast reactions. In that case any optical absorption is due to the stable product of radiolysis, i.e. compounds with paired electrons only.     

绿色和黄色银胶的光化学制备及其共振散射光谱研究

研究了不同光源、光照时间、反应物浓度等对绿色银胶形成的影响,分别制备了绿色银胶和黄色银胶.透射电镜显示,它们的平均粒径分别为100nm和40nm.绿色银胶在393.9nm和713.3nm处有两个吸收峰;黄色银胶在419.3nm处有一较宽的吸收峰.它们的最强共振散射峰位于470nm处;绿色银胶在340nm和80nm还有两个小共振峰.     

Reaction of metallotetraphenylporphyrins on hydroxyl-modified silver colloid and Ag2O colloid by surface-enhanced Raman scattering.

This paper reports a novel reaction of metallotetraphenylporphyrins on hydroxyl-modified silver colloid and Ag2O colloid. Surface-enhanced Raman spectra of Ag(II) and Cu(II) complexes of tetraphenylporphyrin (TPP) adsorbed on the hydroxyl-modified Ag colloid and Ag2O colloid have been studied. The time-dependent SERS spectra of MTPP (M = Ag, Cu) on hydroxyl-modified Ag colloid were recorded and dramatic change on SERS spectra was observed. The final spectra were found to be strikingly different from the corresponding normal Raman spectra (NRS), with the appearance of new Raman bands at 1614. 1417, 947, 674 and 292 cm(-1). The UV-visible absorption spectrum of MTPP on hydroxyl-modified Ag colloid exhibits a broad shoulder near 460 nm. Similar spectral phenomena were also observed for AgTPP and CuTPP adsorbed on Ag2O colloid. The observed spectral alterations were ascribed to new species formation due to the irreducible oxidation of MTPP on the colloids.     

Synthesis of Poly[（3-octanoylpyrrole-2,5-diyl）-p-nitrobenzylidene] and Its Third-order Nonlinear Optical Property

Introduction Nonlinearoptical(NLO)organicpolymers havereceivedincreasingattentionbecauseoftheir excellentbehaviorandgoodprospectsforapplica- tiontohightechnologiessuchasopticalcommuni- cation,highdensityopticalstorageandall-optical informationprocess[1_4].Thepoly[heteroarylene- methines]andtheirderivativesareregardedaspo- tentiallyapplicativeNLOmaterials[5_8],buttheir solubilityandfilm-formingperformancearenot goodwhichisabottleneckproblemfortheapplica- tionofthesepolymers.Inthisstudy,anovel…     

Light Absorption by the Clusters of Colloidal Gold and Silver Particles Formed During Slow and Fast Aggregation

Spectra of absorption (400–800 nm) by the aggregates of colloidal gold (5, 15, and 30 nm in diameter) and silver (20 nm in diameter) particles were studied experimentally and theoretically. It was revealed that, during fast aggregation corresponding to the diffusion-limited cluster aggregation (DLCA), the pattern of spectra is dependent on the size of primary particles. Spectra with the additional absorption maximum in the red region are observed for 15 and 30 nm gold and 20 nm silver particles, while the absorption spectrum for 5 nm particles is characterized by only one maximum shifted to the red region. The slow aggregation resulted in a decrease in plasmon absorption peak with no marked shift to the red region and to the broadening of long-wave absorption wing. From data on electron microscopy, typical branched DLCA-clusters were formed during fast aggregation, whereas small compact aggregates and a noticeable number of single particles were observed in a system during slow aggregation. The computer model of the diffusion-limited cluster-cluster aggregation was used to explain these results. Optical properties of aggregates were calculated using coupled dipole method (CDM or DDA) and the exact method of a multipole expansion. Corrections for the size effect were introduced into the bulk optical constants of metals for nanosized particles. It was shown that a modified version of DDA (Markel et al.,Phys. Rev. B, 1996, vol. 53, no. 5, p. 2425) allows us to explain the pattern of experimental spectra of DLCA-aggregates and their dependence on a monomer size. The exact method was applied to calculate the extinction cross sections of metallic aggregates demonstrating strong electrodynamic interaction between particles. The number of higher multipoles that are required to adequately describe this interaction is much larger than the number of terms of an ordinary Mie series and is the main obstacle to the exact calculation of the spectra of metallic aggregates with a large number of particles.     

侧链含偶氮苯发色团的聚酰亚胺薄膜的制备及其三阶非线性光学和光存储性能的研究

将4,4'-二氨基三苯甲烷(DTM)单体与均苯四甲酸酐(PMDA)进行缩聚反应,再与对-硝基苯基重氮氟硼酸盐进行重氮偶合反应,然后经酰亚胺化合成了侧链含偶氮苯发色团的聚酰亚胺非线性光学材料(NLOPI).通过红外光谱对产物进行了结构表征.对产物的紫外-可见吸收光谱研究发现,在330和490nm处出现侧链偶氮苯发色团的特征吸收.通过简并四波混频方法(DFWM)测定侧链含偶氮苯发色团的聚酰亚胺薄膜的三阶非线性极化率χ⁽³⁾=4.58×10^-18m²/W.在DFWM中,前向泵浦光I_f和探测光I_p是主要的写入光,而后向泵浦光I_b是主要的读出光.证实了光致偶氮分子的顺反异构能够导致光信息存储的特性.     

Synthesis of temperature and pH-responsive crosslinked micelles from polypeptide-based graft copolymer

We report a method for synthesizing small-diameter ZnO nanorods at room temperature (20 °C), under normal atmospheric pressure (1 atm), and using a relatively short reaction time (1 h) by adding gallium salts to the reaction solution. The ZnO nanorods were, on average, 92 nm in length and 9 nm in diameter and were single crystalline in nature. Quantitative analyses revealed that gallium atoms were not incorporated into the synthesized nanocrystals. On the basis of the experimental results, we propose a mechanism for the formation of small-diameter ZnO nanorods in the presence of gallium ions. The optical properties were probed by UV-Vis diffuse reflectance spectroscopy. The absorption band of the small-diameter ZnO nanorods was blue-shifted relative to the absorption band of the ~230 nm diameter ZnO nanorods (control samples). Control experiments demonstrated that the absence of metal ion-containing precipitants (except ZnO) at room temperature is essential, and that the ZnO nanorod diameter distributions were narrow for the stirred reaction solution and broad when prepared without stirring.     

含有不同脂肪环胺侧基的聚丙烯酰胺保护的贵金属胶体制备的研究

<正> 近年来高分子保护金属胶体的研究在金属催化剂领域中受到人们的突出关注。自Hirai等人对聚乙烯吡咯烷酮保护的铂族金属胶体的系统研究工作发表之后,一项重要的研究进展是双金属胶体的制备成功。当前制备窄分布乃至单分散胶体的努力成为众多研究的集中目标,具有重要的理论意义和实际应用价值。Bradley等报道用金属蒸汽冷凝至含有高分子稳定剂的有机溶剂中制备得到2.0—5.0nm直径的金属胶体,Schmid等报道用水溶性三苯膦磺酸钠小分子配位体作为稳定剂制备得到直径为18.6±0.1nm的金胶体。Esumi等用在有机溶剂中热解乙酸钯的方法制备得到不同粒径的均一球形的钯金属胶体。     

Modification of the nanoscale structure of the J-aggregate of a sulfonate-substituted amphiphilic carbocyanine dye through incorporation of surface-active additives

The amphiphilic dye 3,3'-bis(2-sulfopropyl)-5,5',6,6'-tetrachloro-1,1'-dioctylbenzimidacarbocyanine (C8S3) self-aggregates in aqueous solution to form tubular J-aggregates with a diameter of 17.0 +/- 0.5 nm, a wall thickness of approximately 4 nm, and a length exceeding several hundred nanometers. The absorption spectrum shows the typical features expected for tubular J-aggregates with several sharp and red-shifted absorption bands. Morphological investigations using cryo-transmission electron microscopy (cryo-TEM) and spectroscopic investigations reveal a high stability of the tubular morphology but a tendency of the aggregates to assemble into ropelike bundles after several weeks of storage. It is found that aggregation in solutions containing additives such as alcohols or surfactants results in the formation of new types of aggregates. A second type of tubular aggregate with a diameter of 13.0 +/- 0.5 nm is observed when the solutions contain more than 10 wt % MeOH. On the time scale of days these tubular aggregates transform into ribbonlike structures characterized by a new absorption spectrum, and they convert after several weeks into giant tubes with diameters of up to 500 nm.     

Colloidal Synthesis of Gold Semishells

This work describes a novel and scalable colloid chemistry strategy to fabricate gold semishells based on the selective growth of gold on Janus silica particles (500 nm in diameter) partly functionalized with amino groups. The modulation of the geometry of the Janus silica particles allows us to tune the final morphology of the gold semishells. This method also provides a route to fabricating hollow gold semishells through etching of the silica cores with hydrofluoric acid. The optical properties were characterized by visible near-infrared (vis-NIR) spectroscopy and compared with simulations performed using the boundary element method (BEM). These revealed that the main optical features are located beyond the NIR region because of the large core size.     

The nanoscale description of acid penetration to the gold colloids encapsulated in silica sol–gel matrix

Various sizes of gold nano colloidal particles ranging from 5 nm to 100 nm of size were encapsulated in a silica based sol–gel, and these surfaces were exposed to a pH 1 acid solution. This enabled us to observe the process of solvent intrusion and interaction with gold colloids by the absorption spectrum as a function of time. The rate was analyzed by a single exponential analytical function, and the maximum rate was found for gold colloid of 15 nm size. The least acid interaction and colour change was observed for the size of 60 nm. It was speculated that the surface of these gold colloids were homogeneously covered by the sodium tetra-borate buffer which insulated silica gel layer, thus avoiding direct contact of the acid with the surface of the gold colloid. This study confirmed that the nano scale dopant size affects the rate of solvent penetration into a sol–gel cavity.