Germanium Disk Research Articles

Preliminary studies into fluorescent semiconductor nanorods for the detection of latent fingermarks: Size matters, shape matters

The effect of the shape of semiconductor nanocrystals on their performance for visualising latent fingermarks was investigated for the first time. Highly luminescent CdSe/CdS core/shell nanocrystals in rod and spherical shapes were synthesised in organic solvent and transferred to aqueous solution using ligand exchange. The 3-mercaptopropionic acid coated nanorods and nanospheres were characterised using electron microscopy and UV-visible absorbance and luminescence spectrophotometry. A simple and rapid development of fresh to less than a week-old natural fingermarks from 4 donors (male and female) on non-porous surfaces including glass slides, aluminium foil and germanium disks using both CdSe/CdS core/shell nanorods and spherical dots was achieved, wherein nanorods demonstrated an enhanced development of ridge details in comparison to the spherical dots.

Compositional Differences between Size Classes of Dissolved Organic Matter from Freshwater and Seawater Revealed by an HPLC-FTIR System

The molecular complexity of dissolved organic matter (DOM) hinders its characterization. New approaches are thus needed for a better understanding of DOM reactivity and fate in aquatic systems. In this study, high-performance liquid chromatography (HPLC), using size-exclusion separation, was coupled with Fourier transform infrared spectroscopy (FTIR). A solvent-elimination interface was used to deposit DOM fractions onto a germanium disk that were then analyzed by FTIR. Samples included ultrafiltered DOM (UDOM) and fulvic acids from the St. Lawrence Estuary and its tributaries. Results showed significant compositional changes with molecular size and origin, especially in UDOM. Larger fractions of UDOM contained more carbohydrates, amides, aromatics/alkenes and aliphatics, while smaller fractions contained more carboxylate and OH groups. Small marine molecules (500-900 Da) were also enriched in sulfate groups that appeared bound to UDOM. Large marine molecules were the most amide-rich fractions. Fulvic acids were enriched in carboxylate and OH groups, showed little changes in composition, and appeared similar to small terrigenous (riverine) UDOM even in marine water. This work shows that an HPLC-FTIR system is a powerful and complementary tool in the characterization of DOM. The compositional changes observed may explain the reported contrasting reactivity and fate of DOM having different size and origin.

A New Route for Evaluating Short Chain Branching Distribution of High Density Polyethylene by Measuring Crystallizability of Molar Mass Fractions

A bimodal high density polyethylene (HDPE) has been successfully fractionated by analytical size exclusion chromatography into molar mass fractions with M w 's ranging from 3.6 kg/mol to 8 000 kg/mol, and subsequently deposited on germanium disks using the Lab Connections Transform method. After removal of the fractions from the disks, having masses in between 10 µg - 150 µg, differential scanning calorimetry has been successful in measuring the (re)crystallization and melting behavior of these fractions. Comparing the crystallization and melting peak temperatures of the fractions with those of narrow molar mass linear polyethylenes points to the HDPE being linear below and short chain branched above 100 kg/mol respectively. This value coincides roughly with the 'split' between the molar mass distributions resulting from the first and the second polymerization reactor - confirming the addition of 1-butene in the second reactor. http://dx.doi.org/10.5755/j01.ms.17.3.590

Nanostructural Silver and Gold Substrates for Surface-Enhanced Raman Spectroscopy Measurements Prepared by Galvanic Displacement on Germanium Disks

A germanium disk on which silver nanoparticles have been deposited by galvanic displacement is shown to be an inexpensive substrate for surface-enhanced Raman spectroscopy (SERS). The preparation, which is based on spontaneous reduction of silver cations at the surface of a germanium disk, is quick and requires nothing more than a Petri dish. The SERS enhancement of silver and gold substrates prepared in this way was measured using benzenethiol and was compared to enhancement of Klarite, a commercially available gold-coated nanoengineered SERS substrate. The enhancement provided by electrolessly deposited metals was found to be superior over Klarite and the reproducibility was generally below 15%. Furthermore, unlike the case for nanoengineered substrates, germanium disks can be polished and reused.

Scintillating Bolometers for Double Beta Decay Search

In the field of Double Beta Decay searches the possibility to have high resolution detectors in which a very large part of the natural background can be discriminated with respect to the tiny expected signal, results very appealing. This very interesting possibility can be fulfilled in the case of a scintillating crystal bolometer containing a DBD emitter whose transition energy exceeds the one of the natural 2615 keV gamma line of 208Tl. We present the results achieved in the development of bolometric light detectors for double beta searches. The detectors are 1 mm thick germanium disk coated with a layer of SiO2 in order to increase the light collection. The adopted temperature sensors are NTD Ge thermistors optimized to work at temperatures between 9 and 13 mK. A light detector with a considerable large area (35 cm2) was constructed and run in a test measurement. A 140 g CdWO4 crystal (116Cd has a DBD transition energy of 2802 keV) was operated as bolometer and the scintillation light was read by the light detector. The excellent results combined with extreme easy light detector assembly represent the first tangible proof demonstrating the feasibility of this kind of technique.

Monitoring the grafting of epoxidized natural rubber by size‐exclusion chromatography coupled to FTIR spectroscopy

AbstractThe evaluation of heterogeneous polymeric species by a selective, dual detector size‐exclusion chromatography setup can provide accurate results on the incorporation of specific functional groups in copolymers as a function of the molar mass distribution. However, when non‐UV‐absorbing species are used in copolymerization reactions, the dual detector method becomes less reliable. By interfacing a Fourier transform infrared (FTIR) spectrometer with size‐exclusion chromatography (SEC), the problem can be overcome, making it possible to map non‐UV‐absorbing species as a function of the molar mass distribution. Coupling takes place via a solvent‐evaporation stage, which delivers the mobile phase as a dry, solvent‐free polymeric film onto a germanium disk. In this article, styrene and methyl methacrylate were grafted onto epoxidized natural rubber (ENR50) and analyzed by SEC. The accuracy of FTIR as a suitable detector was evaluated by comparing results from a dual detector SEC setup and FTIR coupled to SEC. FTIR proved to be a successful detector for the analysis of non‐UV‐absorbing species. This was consequently followed by the characterization of methyl methacrylate‐grafted ENR50. From the relevant data, Gram–Schmidt and contour plots could be made to indicate the incorporation of methyl methacrylate into the grafted epoxidized natural rubber as a function of the molar mass distribution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2539–2549, 2003

Separation and Identification of Sulfonamide Drugs via SFC/FT-IR Mobile-Phase Elimination Interface

Packed-column supercritical fluid chromatography with a mobile-phase gradient of carbon dioxide and methanol has been performed on a mixture of eight sulfonamides. The analytes were detected and identified with Fourier transform infrared spectrometry. A commercial mobile-phase elimination interface (LC-Transform®) was employed. A fixed-integral restrictor afforded the decompression zone between the column and germanium disk where the analytes were deposited. Excellent-quality infrared spectra were obtained for all eight separated analytes.

Gel Permeation Chromatography/Fourier Transform Infrared Interface for Polymer Analysis

A new solvent elimination interface capable of operating at elevated temperatures, here 145°C, has been used to collect polymer molecular weight fractions eluting from a gel permeation chromatogram and to prepare them for IR analysis. The sample is deposited continuously onto a rotating germanium disk which can subsequently be scanned with the use of GC/FT-IR software, allowing direct access to the polymer or copolymer composition as a function of molecular weight. Data are presented here for an ethylene-propylene copolymer which has a distinct bimodal molecular weight distribution. Both the concentration profile and the “composition distribution” are examined. For the polymer concentration profile, comparison is made between the chromatogram obtained with a differential refractive index (DRI) detector and the IR detector (plotting the absorbance as a function of time using Gram-Schmidt vector orthogonalization). The copolymer composition is determined from the relative absorbance of methyl and methylene groups in the CH stretching region. The results show a small change in propylene content as a function of molecular weight, and there is good agreement between composition calculated with the use of the Gram-Schmidt and point-to-point methods.

The continuous infrared spectroscopic analysis of reversed phase liquid chromatography separations

A method for HPLC/FTIR is discussed in which the effluent from a microbore HPLC is continuously deposited onto and eliminated from the surface of a circular rotating germanium crystal that has been aluminum coated on its opposite side. After deposition, the germanium disk is again rotated, this time in the sample compartment of an FTIR spectrometer while reflectance-absorbance infrared spectra are continuously collected. The novel germanium-aluminum deposition surface allows collection of reflectance-absorbance spectra that are free of the degrading effects of superposition phenomena characteristic of reflectance-absorbance spectra obtained on metal surfaces. Furthermore, germanium is impervious to aqueous solvent mixtures and, therefore, allows for the direct deposition of reversed phase separations, including those requiring acid modified mobile phases.

Chemical trapping and crystalline amorphous transition accompanying energetic proton and deuteron bombardment of silicon and germanium

Undoped single and polycrystalline silicon and germanium disks and internal reflection plates were bombarded with 15–38 keV H+1, D+1, H+2, and D+2 to fluences up to 2×1019 ions/cm2. The infrared and Raman local-mode frequencies of Si–H, Si–D, Ge–H, and Ge–D were observed in the ion implanted targets. The chemical trapping efficiencies of Si and Ge for the incident ions have been determined from infrared integrated absorption intensities of the hydride and deuteride bands. The chemical trapping efficiencies for D+1 and D+2 were found to be higher than those observed for H+1 and H+2 under equal ion energy and fluence conditions. The H or D/Si and H or D/Ge atom ratios approach 2 for high fluence bombardments. A trapping mechanism to account for these observations is presented. Laser Raman scattering data showed that the surface amorphization of Si and Ge occurred to a greater extent for D+1 compared to H+1 bombardments at equal fluence and incident ion energy. Annealing of H+1, D+1, H+2, and D+2 ion implanted surface regions was monitored by the laser Raman scattering technique. The amorphous-to-crystalline transition was shown to occur at 630 and 480 °C for Si and Ge, respectively.

Growth of Silicon and Germanium Disks

Growth of Silicon and Germanium Disks