Papers by Keyword: Self-Assembled Monolayer (SAM)

Abstract: In this study, a finely patterned lead zirconate titanate (PZT) film is fabricated by a combination of inkjet printing (IJP), chemical solution deposition (CSD), and surface energy controlling technology. The PZT film, which can be used as an actuator, has enough thickness after iterating the set of surface treatment, inkjet deposition, and baking. We confirmed the electrical characteristic of this film and drop ejection from inkjet head using it.

Abstract: Self-assembled monolayers (SAMs) deposition is being recently explored to help sealing the pores of a k=2.0 material. In order to enable a covalent chemical low-k surface functionalization by SAMs, a hydroxyl groups density as high as 1 to 2.5 OH groups/nm² is required. This surface modification must be carefully controlled to confine the k below 10%. In this paper, the effects of plasma temperature, time and power on the SAMs deposition and plasma-induced damage are investigated. The main findings are that there is always a trade-off between surface hydroxyl groups density and bulk damage. A thick modified layer allows the SAM molecules to penetrate inside the pores which results in a decreased porosity and an increased k value with respect to correspondent plasma-treated pristine substrates.

Abstract: A microarray-based immunoassay requires only small volume of the sample in each array spot, which leads to faster completion of the immunoreactions than with an ELISA (enzyme-linked immunosorbent assay) [. However, this method still has some technical limitations such as poor signal sensitivity, poor detection limit, large sample consumption, high evaporation rate, coffee stain effect, low signal/noise ratio (SNR) and poor quality images. Recently, SAM (Self-Assembled Monolayer) method was extensively researched for control the surface wettability [. Especially, hydrophobic SAM functionalizations which has low surface energy are possible to prevent sample evaporation [ and to achieve anti-biofouling on them. Therefore, an introduction of hydrophobic SAM would enhance the detection sensitivity on bio array chip [4]. In this work, we fabricated a highly selective and sensitive pre-patterned microarray structure by using MEMS (Micro-Electro-Mechanical-System) process and hydrophilic/hydrophobic SAMs with various precursors.

Abstract: XPS characterization of self-assembled monolayers (SAMs) of tetraphenylporphyrin bearing a rigid tripodal linker by chemisorption of the thiol-derivatized terminal groups on gold substrate is described. The surface structure of the SAMs bearing tripodal linker were analyzed by X-ray photoelectron spectroscopy (XPS), and electrochemical cyclic voltammetry (CV) measurements. XPS confirms the formation of porphyrin SAMs on Au surface and identified bonding configurations of porphyrin molecules in the chemisorption of SAMs. The film thickness values (36 Å) obtained by XPS agree well with the estimated value by assuming the vertical orientation of the molecules on the gold surface. Using the Au4f7/2 as an internal standard, a lower binding energies shift (1.8 eV) of S2p in the SAMs reveals that the porphyrins were chemisorbed onto the surface via sulfurgold bonds. Electrochemical CV measurements suggest near monolayer coverage of the tripodal porphyrins with good stability of the redox SAMs, which have promising application in the development of molecular based electronic device and memory architectures.

Abstract: In this research, a polydimethylsiloxane nanostamp for nanocontact printing was fabricated by replicating Si nanomoulds. Si moulds of various shapes and sizes were fabricated by interference lithography and deep reactive ion etching. As an anti-adhesion layer, octadecyltrichlorosilane was treated on Si nanomoulds. Further, superhydrophobic surfaces were obtained by self-assembled monolayer treatment on Si nanostructures.

Abstract: Using iron nitrate, bismuth nitrate, citric acid and glacial acetic acid as the raw materials, the BiFeO₃ thin films in crystalline state were prepared on FTO substrate with the self-assembled monolayers by liquid phase deposition after graded induction and annealing at 550°C for 30min. The physical phase composition, the surface morphology and dielectric properties of the thin films were characterized respectively by XRD, SEM, and Precision LCR Meter. This paper studied that the deposition temperature and the number of film layers had the effects on the thin films. The results show that the as-prepared thin films show the random orientation and good crystalline. When the deposition temperature is 70°C, the surface of the as-prepared thin film is smooth and uniform. The size of grain is 100nm. The thin film has a dense structure without the apparent pore phase. When the test frequency is between 1kHz and 1MHz, the loss of the thin films is decreased as the increase of the number of the film layers. When the number of the layers is 15, the dielectric constant of the thin films is 44 and the loss is 0.02 when the test frequency is 10kHz.

Abstract: In this paper, titanium ammonium fluoride ((NH₄)TiF₆), strontium nitrate (Sr(NO₃)₂) and boric acid (H₃BO₃) were used as raw materials, the precursor solution was prepared with molar ratio of AHFT/SN/BA=1/1/3. SrTiO₃ dielectric thin films were deposited with the self-assembled monolayers (SAMs) by the liquid-phase deposition on FTO substrate. X-ray diffraction (XRD), scanning election microscopy (SEM) and Agilent E4980A precision LCR Meter were used to characterize the SrTiO₃ films. The precursor solution concentration and the pH values of precursor solution had the effects on the dielectric properties of the as-prepared thin films. When the precursor concentration was 0.0125mol/L, the crystallization of as-prepared SrTiO₃ thin films was high and the grain sizes on the film surface were even and dense. When the frequency was 15~100KHz, the optimal dielectric constant was up to 1060, the minimal dielectric loss was 4.053. As pH=3.30, the frequency of the as-prepared SrTiO₃ thin films was 15~100KHz. The optimal dielectric constant was up to 1060, too. The minimal dielectric loss was 1.914. The optimal dielectric constants were 346.3 and 424.1 when the pH was 3.1 and below 3.5 respectively. The minimal dielectric losses were respectively 18.10 and 54.82.

Abstract: The surface topography and growth behavior of self-assembled monolayers (SAMs) formed from vinyltriethoxysilane (VTES) at a constant temperature (20°C) on silicon dioxide substrates were investigated using atomic force microscopy (AFM). Two methods for silanization were introduced: vapor phase deposition and deposition from a solution. The influence of deposition conditions on the topography of silane films was also studied. The property of modified SiO₂ substrates surface was characterized by static water contact angle measurements. The experimental results revealed that the silane films deposited from the solution method grew via islands, whereas this is not the case for vapor phase deposition. The roughness of the layers deposited via solution method first decreased and then increased with the VTES concentration increasing, while the roughness of the layers deposited via vapor phase increased straight. Furthermore, the adsorption types for silane being adsorbed on SiO₂ substrates were also investigated. The results indicated that there were two adsorption types in both deposition processes: physisorption and chemisorption.

Abstract: This paper investigated a method that proteins were immobilized on platinum surface based on silicon substrate according to the concept self-assembled monolayers. At first, we produced actived carboxyl groups through surface modification of platinum surface on silicon substrate in reaction solution, and then utilized condensation reaction between proteins and carboxyl groups to immobilize proteins (cattle IgG). Secondly, we showed SEM photographs of surface morphologies of immobilization cattle IgG on silicon wafer. EDS energy spectrum microanalysis of cattle IgG immobilization on silicon wafer was also obtained by means of SEM. By contrast,it was evident that proteins (cattle IgG) can be immobilized effectively on the platinum surface on silicon using the experimental methods. Finally, there were tests of I-V characteristic and I-T characteristic of immobilized cattle IgG which demonstrated its temperature coefficient is .

Abstract: In this current study it was investigated the influence of positively and negatively charged surfaces on apatite nucleation process from a supersaturate solution containing calcium and phosphorus (SBF solution). Glass slides were coated with polyelectrolytes thin films using a standard method to produce self-assembled monolayers (SAMs). Slides without treatment were used as control. Positive and negative glass slides were soaking in simulated body fluid (1.5 SBF) for 2, 8, 24 and 96 hours. The surfaces were characterized by scanning electron microscopy (SEM). Accordingly, the apatite mineralization was observed on all surfaces, no matter the surface charge. No remarkable morphological changes were verified between the precipitate in both positive and negative surfaces. It suggests that the crystal growth is not influenced by the initial attraction between either a negative surface and Ca²⁺ ions or a positive one and PO₄^3- ions.