Hyper-Rayleigh scattering (HRS) or incoherent second harmonic generation (SHG) technique has been used to investigate the second-order optical nonlinearities of nanoparticles and seems sensitive to nanoparticle surfaces. Here, more direct evidence that shows the importance of surfaces for HRS response of nanoparticles was experimentally obtained. Two CdS nanoparticles of 3 nm average diameter with different surface-capping molecules, CdS/AOT-SO3- (AOT-SO3- is anion of bis (2-ethylhexyl) sulfosuccinate, disodium salt) and CdS/Py/AOT-SO3- (Py represents pyridine molecule), were studied by HRS technique. The "per particle" first-order hyperpolarizability β values were evaluated to be 3.98×10-27 esu for the CdS/AOT-SO3- and 2.63×10-27 esu for the CdS/Py/AOT-SO3- nanoparticles. A reduction in β value is found when AOT-SO3- on CdS nanoparticle surface is replaced by pyridine. Similarly, the reduction of HRS signal intensity of a solution containing the CdS/AOT-SO3- nanoparticles was observed when increasing pyridine concentration in the solution. Furthermore, the dynamic process of the surface-capping molecule exchange was studied by detecting both HRS signal intensity and electroconductivity variations with time. Possible effect mechanism is discussed in terms of a two-level model approximation derived from molecular chromophores, when considering the influence of different surface-capping molecules on the polarity of Cd-S bonds at nanoparticle surfaces.

A new activation method has been developed for initiating electroless metal deposition on silicon substrates without SnCl2 sensitization and roughening condition. Silicon wafers are first coated with thiol-terminated self-assembled monolayers (SAMs), and then catalyzed with a stable tin-free Pd(II)-based colloidal solution. Atomic force microscopy (AFM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were used to characterize the step-by-step surfaces and study the binding mechanism of Pd(Ⅱ) with SAMs onto surfaces. Results show that Pd(II) oligomer particles are chemisorbed on pendant thiol surfaces through S-Pd bonds. This process involves fewer steps than the conventional Sn/Pd combined activation one. Furthermore, the chemical bound initiator possesses longevity and can be stored for a long time before metallization.

The one-dimensional coagulation of gold colloidal particles dispersed in organic solvent was investigated with transmission electron microscopy. The results indicate that the length of the nanoparticle chains can be modulated by changing the concentration of the solutions. It was also demonstrated that thewetting of the substrate surface hardly influenced themorphology of the nanoparticle chains, which revealed that the particle chains had been formed in the solution before deposition on the substrates. A general theoretical interpretation is provided to explain the linear coagulation of gold colloidal particles, on the basis of the asymmetrical distribution of the charges absorbed on the surface of the gold colloidal particles, as well as the action of the solvent molecules.

A novel core-shell structured composite, titania (TiO2) coated Mn-Zn ferrite nanoparticle, was prepared byhydrolysis of titanium (Ⅳ) chloride (TiCl4) in the presence of Mn-Zn ferrite nanoparticles synthesized with stearic acid gel method. The obtained samples were characterized by energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results show that spinel structural Mn-Zn ferrite nanoparticles (6 nm average diameter) or their aggregates are coated by TiO2 nanoshell with anatase structure for annealed sample. The magnetic measurements were carried out on a vibrating sample magnetometer (VSM), and the measurement results indicate the reduction of the magnetization of the TiO2 coated Mn-Zn ferrite nanoparticles compared with the uncoated ferrite nanoparticles. High coercivity also shows that the prepared uncoated and coated ferrite nanoparticles are not superparamagnetic.

The primary object of this contribution is to self-assemble DNA on 2-dimensional array of 1-dodecanethiol-encapsulated colloidal gold (2-DACG). The 2-DACG film was deposited by Langmuir-Blodgell (LB) technique. Through phase transfer of aqueous colloidal gold particles into ethanol solutions containing 1-dodecanethiol, the hydrophobic gold colloidal nanoparticles were accomplished. In the presence of traces of 1-dodecanethiol, the gold nanoparticels were transferred via LB technique to a freshly cleaned gold electrode and 2-DACG of close-packed, ordered monolayer was obtained. The 2-DACG was then used as a substrate for the immobilization of DNA under a controled potential of 0.20V vs. saturated calomel electrode (SCE). The properties of 2-DACG before and after the DNA assembly were investigated by means of transmission electron microscopy (TEM), atomic force microscopy (AFM), cyclic voltaininetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicated that 2-DACG deposited by LB technique was suitable as a substrate for DNA self-assembly.