Entropy driven spontaneous formation of highly porous films from polymer-nanoparticle composites

doi: 10.1088/0957-4484/20/42/425602Nanoporous materials have become indispensable in many fields ranging from photonics, catalysis and semiconductor processing to biosensor infrastructure. Rapid and energy efficient process fabrication of these materials is, however, nontrivial. In this communication, we describe a simple method for the rapid fabrication of these materials from colloidal dispersions of Polymethyl Silsesquioxane nanoparticles. Nanoparticle-polymer composites above the decomposition temperature of the polymer are examined and the entropic gain experienced by the nanoparticles in this rubric is harnessed to fabricate novel highly porous films composed of nanoparticles. Optically smooth, hydrophobic films with low refractive indices (as low as 1.048) and high surface areas (as high as 1325 m2 g−1) have been achieved with this approach. In this communication we address the behavior of such systems that are both temperature and substrate surface energy dependent. The method is applicable, in principle, to a variety of nanoparticle-polymer systems to fabricate custom nanoporous materials.We gratefully acknowledge the financial support from National Institute of Health (Award number 2-U42RR014821) and the US army

Organosilicate nanoparticles and its applications in chem-biosensors, electronics, multifunctional coatings and textiles

This invention reports a novel technique for the rapid and cost-efficient synthesis of organosilicate nanoparticles (OSNPs) that have been successfully applied as individual building blocks for various applications. Doping these nanoparticles with fluorescent dyes results in highly fluorescent, biocompatible, water soluble nanoparticles with demonstrated long term photostability and with surface groups that can be readily used to attach various biological moieties. Fluorescent intensity of dye doped OSNPs (22.4 ± 5.3 nm) is shown to be 200 times brighter with 94% of the initial fluorescence intensity retained than the constituent dyes under continuous excitation for 10 minutes. In contrast, under identical test conditions, individual dye molecules retained only 58% of the initial fluorescence demonstrating that these nanoparticles have excellent utility in lifesciences research, forensics, chemical - biological sensors and biological imaging applications. Through our patented technology of novel bottom up fabrication technique, these nanoparticles have been used to fabricate highly porous transparent films. Optically smooth hydrophobic films with low refractive indices (as low as 1.048) and high surface areas (as high as 1325 m2/g) can be achieved on large area substrates. These unique materials can be readily interfaced with existing immunoassays in the form of inexpensive dip-stick assays for the sensitive detection of chemical and biological warfare agents or novel diagnostic strips for point of care applications. Our preliminary evaluation of these coatings in combination with dye doped OSNPs for construction of diagnostic immunoassays gave ~180 fold enhancement in fluorescence signal enhancement compared to traditional (microscope glass slide and fluorescent dye molecules) based assays. OSNPs used as filler elements within sol-gel based coatings have been shown to greatly enhance their structural stability, flexibility and wear resistance. Crack-free coatings (with thicknesses exceeding 30 microns)/novel multifunctional electrospun fibers have been successfully achieved by employing OSNP fillers (up to 75% by weight) within sol-gel compositions. POTENTIAL AREAS OF APPLICATIONS: *Chemical Biological sensors *Medical Diagnostics *Multifunctional coatings *Next generation Chemical-Biological protection textiles (Soldier technologies) PATENT STATUS: Non provisional patent application on file INVENTOR(S): Sangho Bok; Venumadhav Korampally; Luis Polo-Parada; Vamsi Mamidi; Keshab Gangopadhyay; William R. Folk; Purnendu K. Dasgupta and Shubhra Gangopadhyay CONTACT INFO: Wayne McDaniel, Ph.D.; [email protected] ; 573-884-330

Development and characterization of fluorescent dye-doped nanoparticles with enhanced fluorescence intensity and photostability [abstract]

Nanoscience Poster SessionWe report the development of fluorescent dye doped organosilicate nanoparticles (DOSNPs) synthesized from poly-methylsilsesquioxane(PMSSQ), resulting in high fluorescence intensity and excellent photostability. The surface modified DOSNPs have hydrophilic surfaces and hydrophobic cores that enhance water-solubility and protect the dyes from oxidation and phtobleaching. These DOSNPs show superior properties over conventional dyes such as high fluorescence intensity due to approximately hundred dye molecules per particle and photostability demonstrating 7% and 76% fluorescence decay under continuous excitation for rhodamine 6G (R6G) DOSNP and R6G molecules, respectively, and have potential to be used in many areas, for example, imaging, sensing and solar cells. DOSNPs, when conjugated to anti-fibronectin antibodies, increased sensitivity of detection by approximately 600 fold relative to individual dye molecules conjugated to antibody. The DOSNPs are being applied to the development of diagnostic devices to be used in the detection of drugs, metabolites and pathogens

Temporal Patterns in Perchlorate, Thiocyanate, and Iodide Excretion in Human Milk

BACKGROUND: Perchlorate and thiocyanate interfere with iodide uptake at the sodium–iodide symporter and are potential disruptors of thyroid hormone synthesis. Perchlorate is a common contaminant of water, food, and human milk. Although it is known that iodide undergoes significant diurnal variations in serum and urinary excretion, less is known about diurnal variations of milk iodide levels. OBJECTIVES: Variability in perchlorate and thiocyanate excretion in human milk has not been examined. Our objective was to determine variability of perchlorate, thiocyanate, and iodide in serially collected samples of human milk. METHODS: Ten lactating women were asked to collect six milk samples on each of 3 days. As an alternative, subjects were asked to collect as many milk samples as comfortably possible over 3 days. Samples were analyzed for perchlorate, iodide, and thiocyanate by ion chromatography coupled with mass spectrometry. RESULTS: Individual perchlorate, iodide, and thiocyanate levels varied significantly over time; there was also considerable variation among individuals. The iodide range, mean ± SD, and median for all samples (n = 108) were 3.1–334 μg/L, 87.9 ± 80.9 μg/L, and 55.2 μg/L, respectively. The range, mean ± SD, and median of perchlorate in all samples (n = 147) were 0.5–39.5 μg/L, 5.8 ± 6.2 μg/L, and 4.0 μg/L. The range, mean ± SD, and median of thiocyanate in all samples (n = 117) were 0.4 –228.3 μg/L, 35.6 ± 57.9 μg/L, and 5.6 μg/L. The data are not symmetrically distributed; the mean is higher than the median in all cases. CONCLUSIONS: Iodine intake may be inadequate in a significant fraction of this study population. Perchlorate and thiocyanate appear to be common in human milk. The role of these chemicals in reducing breast milk iodide is in need of further investigation