Metal Ion Detection Using Silica Sol-gels Containing Silver Nanoparticles and Calcein Blue (CB)

Surface-enhanced Raman spectroscopy (SERS) is a spectroscopic technique which relies on the inelastic scattering of photons from a target molecule. SERS is both sensitive and specific; the technique produces a unique spectrum for all molecules while offering up to single molecule detection with proper conditions. However, acquisition of SERS spectra requires the presence of a suitable substrate, such as noble metal nanoparticles or roughened metal electrodes. Silica sol-gels are porous, amorphous silica matrices formed by the hydrolysis of a silicon containing precursor molecule. As a result of their unique structure, these compounds have a variety of unique properties, such as high surface area and low thermal conductivity. They can be easily modified, and metal-colloid-modified silica sol-gels represent a relatively unknown class of compounds which can function as substrates for SERS measurements. In this study, the fluorescent dye calcein blue (CB) was chosen as a target molecule due to its ability to interact with various metal ions. As a result, it has found use as an indicator in EDTA titrations and has potential applications in metal ion sensing devices. Thus, detection of calcein blue within modified sol-gels could lead to the development of new techniques for the detection of metal ions. Such techniques could have applications in fields such as water quality analysis or other environmental assays

An investigation of particle mixing in a gas-fluidized bed

Mechanism for particle movement in gas-fluidized beds was studied both from the theoretical and experimental points of view. In a two-dimensional fluidized bed particle trajectories were photographed when a bubble passed through

A New Nearctic Triclistus (Hymenoptera: Ichneumonidae)

[excerpt] When Townes and Townes (1959) revised the genus Triclistus along with the rest of the Nearctic Metopiinae, they decided not to describe what was thought likely to be an additional new species, because only one male specimen was known. More recently, additional specimens, both males and females, were collected. From the females, which are even more distinctive than the males, it was easily seen that the species described below is indeed a new one

Numerical computation of real or complex elliptic integrals

Algorithms for numerical computation of symmetric elliptic integrals of all three kinds are improved in several ways and extended to complex values of the variables (with some restrictions in the case of the integral of the third kind). Numerical check values, consistency checks, and relations to Legendre's integrals and Bulirsch's integrals are included

SERS-Based Detection of Calcein Blue Using Nanoparticle-Modified Silica Sol-Gels

Surface-enhanced Raman spectroscopy (SERS) has gained interest recently due to its compatibility with aqueous solutions and unique spectra for all molecules. These qualities make SERS an ideal technique for sensing applications; however, an appropriate substrate is needed for effective measurements. Silica sol-gels containing silver nanoparticles may be able to act as SERS substrates, given their porosity and high surface area, and may be able to act as sensors if modified with additional small molecules. In this study, the SERS activity of silica sol-gels containing silver nanoparticles and calcein blue (CB) was investigated to determine their suitability as metal ion sensors. Sol-gels were prepared via the base-catalyzed hydrolysis of tetramethyl orthosilicate (TMOS) in the presence of aqueous CB and silver nanoparticles. SERS measurements of synthesized sol-gels were obtained using a home built Raman spectrometer; obtained spectra indicate that sol-gels containing silver nanoparticles are viable substrates for the SERS of CB and thus may be viable as metal ion sensors

Integration effects of pylon geometry on a high-wing transport airplane

An investigation was conducted in the Langley 16-Foot Transonic Tunnel to determine the installation effects of a series of pylons that had differing cross-sectional shapes on the pressure distributions and aerodynamic characteristics of a 1/24-scale high wing transport. The tests were conducted at Mach numbers at 0.70 and 0.80 at angles of attack from -3 degrees to 4 degrees with the pylons tested at various toe angles between 5 degrees inboard and 5 degrees outboard. Results of this study indicate that the installed drag was lowest for the pylons with a compression pylon type design which kept the flow under the wing in the pylon/wing junction comparable to the clean wing velocities

Dependence of two-nucleon momentum densities on total pair momentum

Two-nucleon momentum distributions are calculated for the ground states of 3He and 4He as a function of the nucleons' relative and total momenta. We use variational Monte Carlo wave functions derived from a realistic Hamiltonian with two- and three-nucleon potentials. The momentum distribution of pp pairs is found to be much smaller than that of pn pairs for values of the relative momentum in the range (300--500) MeV/c and vanishing total momentum. However, as the total momentum increases to 400 MeV/c, the ratio of pp to pn pairs in this relative momentum range grows and approaches the limit 1/2 for 3He and 1/4 for 4He, corresponding to the ratio of pp to pn pairs in these nuclei. This behavior should be easily observable in two-nucleon knock-out processes, such as A(e,e'pN).Comment: 3 pages, 3 figure