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

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

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

Infinitesimal Variations of Hodge Structure at Infinity

By analyzing the local and infinitesimal behavior of degenerating polarized variations of Hodge structure the notion of infinitesimal variation of Hodge structure at infinity is introduced. It is shown that all such structures can be integrated to polarized variations of Hodge structure and that, conversely, all are limits of infinitesimal variations of Hodge structure (IVHS) at finite points. As an illustration of the rich information encoded in this new structure, some instances of the maximal dimension problem for this type of infinitesimal variation are presented and contrasted with the "classical" case of IVHS at finite points

User's guide for atmospheric carbon monoxide transport model

In the winter months of Fairbanks, Alaska, a highly stable air temperature inversion creates high levels of carbon monoxide (CO) concentrations. As an aid to understanding this problem, a CO transport computer model has been created which provides a useful tool when used in conjunction with other measurement and analytic studies of traffic, meteorology, emissions control, zoning, and parking management. The model is completely documented and illustrated with several examples. Named ACOSP (Atmospheric CO Simulation Program), it predicts expected CO concentrations within a specific geographic area for a defined set of CO sources. At the present time, the model is programmed to consider automobile emissions as the major CO source and may include estimates of stationary sources. The model is coded for computer solution in the FORTRAN programming language and uses the finite-element method of numerical solution of the basic convective-diffusion equations. Although it has a potential for real-time analysis and control, at the present time the model will be most valuable for investigating and understanding the physical processes which are responsible for high CO levels and for testing remedial control measures at high speed and low cost

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

Principal sources and dispersal patterns of suspended particulate matter in nearshore surface waters of the northeast Pacific Ocean

The author has identified the following significant results. Release-recovery paths of drift cards released in conjunction with ERTS-1 overflight show that nearshore surface currents along the central and northern California coast flowed southward at an average rate in excess of 10 cm/sec (8.5 km/day) during August and September 1973 (California Current). By the middle of October 1973, the nearshore surface currents had reversed and the dominant flow velocity was northward at an average rate in excess of 20 cm/sec (17 km/ day) (Davidson Current). The August-September data suggested the presence of counterclockwise gyres in Monterey Bay and the Gulf of the Farallones, but by the middle of October, the gyres were no longer evident. Imagery of April 1973 showed well developed plumes of suspended sediment in Monterey Bay from the Salinas River and in the Gulf of the Farallones from San Francisco Bay. ERTS-1 imagery provides an effective means of monitoring timber harvest in the redwood forest along the northern California coast. ERTS-1 imagery also clearly portrays contrasting topographic belts characterized by fluvial erosion and by mass movement. The most visually apparent and most persistent river mouth suspended sediment plumes are associated with those rivers that drain belts of topography that appear to have been eroded primarily by mass movement