An alternative activation method was developed via binding electroless catalysts onto silicon substrates with 3-aminopropyltriethoxysilane (APTS) self-assembled monolayers (SAMs). Atomic force microscopy, Auger electron spectroscopy and X-ray photoelectron spectroscopy were used to characterize the laden of tin-free Pd(Ⅱ)-based nanoparticles on silicon surfaces. The results indicate that the formation of coordination bonds between Pd ions and nitrogen atoms of APTS SAMs serves the important binding mechanism. Electroless copper deposition was successfully initiated by the catalyzed substrates and high quality Cu deposition was obtained. Owing to the chemically bound catalyst, this approach has advantages over the conventional Sn-Pd combined activation process, including reduced steps and improved longevity of initiator and enhanced adhesion of the deposition to the substrates.

The specific absorption rate (SAR) values of aqueous suspensions of magnetite particles with different diameters varying from 7.5 to 416nm were investigated by measuring the time-dependent temperature curves in an external alternating magnetic field (80kHz, 32.5kA/m). Results indicate that the SAR values of magnetite particles are strongly size dependent. For magnetite particles larger than 46nm, the SAR values increase as the particle size decreases where hysteresis loss is the main contribution mechanism. For magnetite particles of 7.5 and 13nm which are superparamagnetic, hysteresis loss decreases to zero and, instead, relaxation losses (Neel loss and Brownian rotation loss) dominate, but Brown and Neel relaxation losses of the two samples are all relatively small in the applied frequency of 80kHz.

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.

The assembly of synthetic, controllable molecules is one of the goals in nanotechnology. The primary objective of this contribution is to selectively immobilize DNA on gold via electric potential control. The self-assembly monolayer (SAM) was prepared with 2-aminoethanethiol (AET) on the gold electrode. A new approach based on electric potential was firstly used to control DNA immobilization covalently onto the SAM with the activation of 1-ethyl-3(3-dimethyl-aminopropyl)-carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHS) in low ionic strength solution. The influence of electric potential on DNA immobilization was investigated by means of cyclic voltammogram, A.C. impedance, auger electron spectrometer as well as atomic force microscope (AFM) on template-stripped gold surface. The result proves that controlled potential can affect the course of DNA immobilization. More negative potential can restrain the DNA immobilization, while the more positive potential can accelerate the DNA immobilization. It is of great significance for the control of DNA self-assembly and will find wide application in the fields of DNA-based devices.

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.