silicon and sodium-nitrate

This article describes the aqueous atom transfer radical polymerization synthesis of poly(3-sulfopropylmethacrylate) brushes onto gold and Si/SiO2 surfaces in a controlled manner. The effect of Cu(I)/Cu(II) ratio was examined, and a quartz crystal microbalance was used to study the kinetics of the brush synthesis. The synthesized brushes displayed a thickness from a few nanometers to several hundred nanometers and were characterized using atomic force microscopy, ellipsometry, Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The as-synthesized sulfonate brushes had very good ion-exchange properties for the ions tested in this study, i.e., Na+, K+, Cu2+, and Ag+. FTIR and XPS show that the metal ions are coordinating to sulfonate moieties inside the brushes. The brushes were easily loaded with silver ions, and the effect of silver ion concentration on silver loading of the brush was examined. The silver-loaded brushes were shown to be antibacterial toward both gram negative and gram positive bacteria. The silver leaching was studied through leaching experiments into water, NaNO3, and NaCl (physiological medium). The results from these leaching experiments are compared and discussed in the article.

Topics: Anti-Infective Agents; Drug Design; Ions; Methacrylates; Microscopy, Atomic Force; Nitrates; Polymers; Pseudomonas aeruginosa; Silicon; Silicon Dioxide; Silver; Sodium Chloride; Spectrometry, X-Ray Emission; Spectroscopy, Fourier Transform Infrared; Staphylococcus aureus; Sulfonic Acids

Cadmium (Cd) has received considerable attention because of its association with various human health problems. The behavior of adsorption-desorption of Cd at contaminated levels in two variable charge soils were investigated. The red soil (RAR) developed on the Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) adsorbed more Cd2+ than the red soil (REQ) derived from the Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult). The characteristics of Cd adsorption could be described by the Freundlich equation (r2 = 0.997 and 0.989, respectively, for the RAR and REQ) and the simple Langmuir adsorption equation (r2 = 0.985 and 0.977, respectively, for the RAR and REQ). The maximum adsorption values (Xm) that were obtained from the simple Langmuir model were 36.23 mmol Cd2+ kg(-1) soil and 31.15 mmol Cd2+ kg(-1) soil, respectively for the RAR and REQ. Adsorption of Cd2+ decreased soil pH by 1.28 unit for the RAR soil and 1.23 unit for the REQ soil at the highest loading. The distribution coefficient (kd) of Cd in the soil decreased exponentially with increasing Cd2+ loading. The adsorption of cadmium in the two variable charge soils was characterized by a rapid process that lasted approximately 15 min, followed by a slower but longer period. 85.5% and 79.4% of the added Cd were adsorbed within two hours by the RAR and REQ soil, respectively. More Cd2+ was adsorbed at 10 degrees C than at 25 degrees C or 40 degrees C. After five successive desorptions with 0.01 mol L(-1) NaNO3 solution, 53.3% of the total adsorbed Cd2+ in the RAR soil was desorbed and the corresponding value of the REQ soil was 46.5%, indicating that the RAR soil had a lower affinity for Cd2+ than the REQ soil at the same Cd2+ loading.

Topics: Adsorption; Cadmium; China; Hydrogen-Ion Concentration; Kaolin; Models, Theoretical; Nitrates; Silicon; Soil Pollutants; Temperature; Time Factors

This paper describes the fabrication of a micromachined miniaturized array of chambers in a 2-mm-thick single crystal (100) silicon substrate for the combinatorial screening of the conditions required for protein crystallization screening (including both temperature and the concentration of crystallization agent). The device was fabricated using standard photolithography techniques, reactive ion etching (RIE) and anisotropic silicon wet etching to produce an array of 10 x 10 microchambers, with each element having a volume of 5 microL. A custom-built temperature controller was used to drive two peltier elements in order to maintain a temperature gradient (between 12 and 40 degrees C) across the device. The performance of the microsystem was illustrated by studying the crystallization of a model protein, hen egg white lysozyme. The crystals obtained were studied using X-ray diffraction at room temperature and exhibited 1.78 A resolution. The problems of delivering a robust crystallization protocol, including issues of device fabrication, delivery of a reproducible temperature gradient, and overcoming evaporation are described.

Topics: Crystallization; Nitrates; Proteins; Silicon; Temperature