Temperature-controlled Sample Holder Research Articles

Total Luminescence Spectroscopy for Quantification of Temperature Effects on Photophysical Properties of Photoluminescent Materials.

Quantification of the temperature effects on the optical properties of photoluminescent (PL) materials is important for a fundamental understanding of both materials optical processes and rational PL materials design and applications. However, existing techniques for studying the temperature effects are limited in their information content. Reported herein is a temperature-dependent total photoluminescence (TPL) spectroscopy technique for probing the temperature dependence of materials optical properties. When used in combination with UV-vis measurements, this TPL method enables experimental quantification of temperature effects on fluorophore fluorescence intensity and quantum yield at any combination of excitation and detection wavelengths, including the fluorophore Stokes-shifted and anti-Stokes-shifted fluorescence. All model polyaromatic hydrocarbon (PAH) and xanthene fluorophores exhibited a strong excitation- and emission-wavelength dependence in their temperature effects. However, the heavy-atom effects used for explaining the strong temperature dependence of brominated anthracenes are not operative with xanthene fluorophores that have heavy atom substitutions. The insights from TPL measurements are important not only for enhancing the fundamental understandings of the materials photophysical properties but also for rational measurement design for applications where the temperature sensitivity of the fluorophore fluorescence is critical. An example application is demonstrated for developing a sensitive and robust ratiometric fluorescence thermometric method for in situ real-time monitoring of sample temperatures inside a fluorescence cuvette placed in a temperature-controlled sample holder.

In Situ Raman Spectroscopy Monitoring of Material Changes During Proton Irradiation.

Organic molecules are prime targets in the search for life on other planetary bodies in the Solar System. Understanding their preservation potential and detectability after ionic irradiation, with fluences potentially representing those received for several millions to billions of years at Mars or in interplanetary space, is a crucial goal for astrobiology research. In order to be able to perform in situ characterization of such organic molecules under ionic irradiation in the near future, a feasibility experiment was performed with polymer test samples to validate the optical configuration and the irradiation chamber geometry. We present here a Raman in situ investigation of the evolution of a series of polymers during proton irradiation. To achieve this goal, a new type of Raman optical probe was designed, which documented that proton irradiation (with a final fluence of 3.1014 at·cm-2) leads to an increase in the background level of the signal, potentially explained by the scission of the polymeric chains and by atom displacements creating defects in the materials. To improve the setup further, a micro-Raman probe and a temperature-controlled sample holder are under development to provide higher spectral and spatial resolutions (by reducing the depth of field and laser spot size), to permit Raman mapping as well as to avoid any thermal effects.

Arduino based temperature controlled sample holder using a power transistor and its application to measure the band gap of a silicon p–n diode

This experiment is developed with the aim of designing a temperature-controlled sample holder by using a commonly available power transistor as the heating element. Most temperature-controlled sample holders use commonplace heaters, which are made of high resistance materials like nichrome 80/20 (80% nickel, 20% chromium) wire and similar materials. The fabrication of this temperature-controlled sample holder also leads to the usage of high power electronic components, like power transistors and power resistors which are, otherwise, neglected in most laboratory experiments. Moreover, to develop this system, Arduino Uno Rev3 and resistance temperature detector (RTD) were used for the purposes of data acquisition and temperature measurement, respectively. Arduino is a single board micro-controller and RTD functions as a temperature sensor. This experiment serves as a good example of application and unification of basic concepts of electronics, heat and thermodynamics and offers an insight into data acquisition. The experiment is non-proprietary, and the apparatus is entirely made from off-the-shelf items. Thus, reconstruction and use will be simple and inexpensive. The power transistor, along with the power resistors, generates enough heat to raise the temperature of the sample holder by about 100 K. Also, to exhibit the working of the sample-holder, the energy band gap of the material of a p–n junction diode (silicon) has been determined experimentally using the setup.

Transient-Absorption Spectroscopy of Cis–Trans Isomerization of N,N-Dimethyl-4,4′-azodianiline with 3D-Printed Temperature-Controlled Sample Holder

The laboratory unit demonstrates a project-based approach to teaching physical chemistry laboratory where upper-division undergraduates carry out a transient-absorption experiment investigating the kinetics of cis–trans isomerization of N,N-dimethyl-4,4′-azodianiline. Students participate in modification of a standard flash-photolysis spectrometer by adding a temperature-controlled sample holder. The sample holder design is open-source and can be reproduced with the 3D-printing technology. Students build the experimental setup, perform the transient spectroscopy experiment, and analyze the obtained kinetics data to estimate the activation energy, enthalpy, entropy, and Gibbs free energy of cis–trans isomerization of N,N-dimethyl-4,4′-azodianiline.

Use of in situ Fourier transform infrared spectroscopy to study freezing and drying of cells.

An infrared spectrum gives information about characteristic molecular vibrations of specific groups in molecules. Fourier transform infrared spectroscopy can be applied to study lipids and proteins in cells or tissues. Spectra can be collected during cooling, heating, or dehydration of a sample using a temperature-controlled sample holder or a sample holder for controlled dehydration. In the current chapter, acquisition and analysis of infrared spectra during cooling, warming, or dehydration is described. Spectra analysis involving assessment of specific band positions, areas, or ratios is described. Special emphasis is given on studying membrane phase behavior and protein denaturation in cells or tissues. In addition, methods are presented to determine the water-to-ice phase change during freezing, dehydration kinetics, and the glass transition temperature of amorphous systems.

Laser scanning microscopy in cryobiology.

Laser scanning microscopy is emerging as a powerful imaging tool in cryobiology. The basic microscopy system can be combined with various imaging modalities including Raman spectroscopy, fluorescence correlation spectroscopy, fluorescence lifetime imaging, or multiphoton imaging. Multiphoton imaging can be used to study intracellular ice formation at the subcellular level. A Raman imaging modality can be used for chemical mapping of frozen samples. A Raman spectrum gives information about characteristic molecular vibrations of specific groups in molecules. Raman images can be used to determine the localization of intra- and extracellular constituents and the various forms of water in freeze-concentrated solutions. Spectra can be collected during freezing and thawing of a sample using a temperature-controlled sample holder. In this chapter, various advanced cryoimaging methods are described. Special emphasis is given on the different imaging modalities that can be used to study the various aspects of cryopreservation.

Investigations of thermotropic phase behavior of newly developed synthetic PEGylated lipids using Raman spectro‐microscopy

In this article, a temperature-controlled Raman spectro-microscopic technique has been utilized to detect and analyze the phase behaviors of two newly developed synthetic PEGylated lipids trademarked as QuSomes, which spontaneously form liposomes upon hydration in contrast to conventional lipids. The amphiphiles considered in this study differ in their hydrophobic hydrocarbon chain length and contain different units of polyethylene glycol (PEG) hydrophilic headgroups. Raman spectra of these new artificial lipids have been recorded in the spectral range of 500-3100 cm(-1) by using a Raman microscope system in conjunction with a temperature-controlled sample holder. The gel to liquid phase transitions of the sample lipids composed of pure 1,2-dimyristoyl-rac-glycerol-3-dodecaethylene glycol (GDM-12) and 1,2-distearoyl-rac-glycerol-3-triicosaethylene glycol (GDS-23) have been revealed by plotting peak intensity ratios in the C-H stretching region as a function of temperature. From this study, we have found that the main phase transitions occur at a temperature of approximately 5.2 and 21.2 degrees C for pure GDM-12 and GDS-23, respectively. Furthermore, the lipid GDS-23 also shows a postphase transition temperature at 33.6 degrees C. To verify our results, differential scanning calorimetry (DSC) experiments have been conducted and the results are found to be in an excellent agreement with Raman scattering data. This important information may find application in various studies including the development of lipid-based novel substances and drug delivery systems.

Structure and phospholipase function of peroxiredoxin 6: identification of the catalytic triad and its role in phospholipid substrate binding

Peroxiredoxin 6 (Prdx6) is a bifunctional protein with glutathione peroxidase and phospholipase A(2) (PLA(2)) activities, and it alone among mammalian peroxiredoxins can hydrolyze phospholipids. After identifying a potential catalytic triad (S32, H26, D140) from the crystal structure, site-specific mutations were used to evaluate the role of these residues in protein structure and function. The S32A mutation increased Prdx6 alpha-helical content, whereas secondary structure was unchanged by mutation to H26A and D140A. Lipid binding by wild-type Prdx6 to negatively charged unilamellar liposomes showed an apparent rate constant of 11.2 x 10(6) M(-1) s(-1) and a dissociation constant of 0.36 microM. Both binding and PLA(2) activity were abolished in S32A and H26A; in D140A, activity was abolished but binding was unaffected. Overoxidation of the peroxidatic C47 had no effect on lipid binding or PLA(2) activity. Fluorescence resonance energy transfer from endogenous tryptophanyls to lipid probes showed binding of the phospholipid polar head in close proximity to S32. Thus, H26 is a site for interfacial binding to the liposomal surface, S32 has a key role in maintaining Prdx6 structure and for phospholipid substrate binding, and D140 is involved in catalysis. This putative catalytic triad plays an essential role for interactions of Prdx6 with phospholipid substrate to optimize the protein-substrate complex for hydrolysis.

Portable dynamic light scattering instrument and method for the measurement of blood platelet suspensions

No routine test exists to determine the quality of blood platelet transfusions although every year millions of patients require platelet transfusions to survive cancer chemotherapy, surgery or trauma. A new, portable dynamic light scattering instrument is described that is suitable for the measurement of turbid solutions of large particles under temperature-controlled conditions. The challenges of small sample size, short light path through the sample and accurate temperature control have been solved with a specially designed temperature-controlled sample holder for small diameter, disposable capillaries. Efficient heating and cooling is achieved with Peltier elements in direct contact with the sample capillary. Focusing optical fibres are used for light delivery and collection of scattered light. The practical use of this new technique was shown by the reproducible measurement of latex microspheres and the temperature-induced morphological changes of human blood platelets. The measured parameters for platelet transfusions are platelet size, number of platelet-derived microparticles and the response of platelets to temperature changes. This three-dimensional analysis provides a high degree of confidence for the determination of platelet quality. The experimental data are compared to a matrix and facilitate automated, unbiased quality testing.

Real-time monitoring of phase transitions of vacuum deposited organic films by molecular beam deposition LEED

We describe a special low energy electron diffraction (LEED) system that allows us to record diffraction patterns during the adsorption process of vacuum-deposited organic thin films. With this instrument that combines Knudsen cells within a reverse view LEED instrument we can evaporate three different organic materials independently and simultaneously from each other. In contrast to conventional LEED, this molecular beam deposition LEED (MBD–LEED) allows us to study the kinetics of structural phase transitions from the sub-monolayer regime up to several layers without changing the position of the sample which is located on a temperature-controlled sample holder. The performance of the device is demonstrated by a growth study of perylene-3,4,9,10-tetracarboxylic-dianhydride on Ag(110). A phase transition was in situ observed after the preparation of a single domain oriented homogeneous monolayer (“brick stone”) structure to a condensed (“herring bone”) structure which is commensurate in one direction.

Loading Effect and Temperature Dependence of Etch Rate in CF4 Plasma

Plasma etching of silicon, silicon dioxide, and silicon nitride in CF4 and CF4+O2 (up to 20%) was evaluated concerning exposed area dependence and temperature dependence of the etch rate with a modified barrel type plasma reactor having a temperature-controlled sample holder which enabled samples to be etched one by one. Experimental results related to the exposed area dependence of the etch rate showed that the etching mode was divided into two regions; the loading effect region, and the intrinsic region. The behavior of the etch rate, the activation energy for the etch rate, and the etch rate ratio for silicon and silicon nitride over silicon dioxide were obtained. The pattern undercut with excess etch time was also examined, and it became evident that suppression of the loading effect and improvement of the pattern undercut could be achieved by lowering the sample temperature.