Temperature-controlled Sample Stage Research Articles

A facile microencapsulation of phase change materials within silicone-based shells by using glass capillary devices

A facile microfluidic approach to prepare encapsulated n-tetradecane and n-hexadecane as phase change materials (PCMs) within silicone-based shells, using a glass capillary device, is demonstrated. In this method, double emulsion droplets comprising PCMs as the innermost fluid and photopolymerizable silicone oil as the middle fluid were prepared using the device. As the PCMs and the silicone oil are not immiscible, the droplets were immediately subjected to UV irradiation to solidify the middle fluid to form microcapsule shells. The stable phase change of the encapsulated PCMs was directly observed using an optical microscope equipped with a temperature-controlled sample stage, which indicated that the microcapsules could be used for thermal energy storage. Thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. Importantly, the encapsulation ratio of PCMs can be tuned by changing the flow rates of the innermost and middle fluids that generate the emulsion droplets in the glass capillary device.

Versatile variable temperature and magnetic field scanning probe microscope for advanced material research.

We have built a variable temperature scanning probe microscope (SPM) that covers 4.6 K-180 K and up to 7 T whose SPM head fits in a 52 mm bore magnet. It features a temperature-controlled sample stage thermally well isolated from the SPM body in good thermal contact with the liquid helium bath. It has a 7-sample-holder storage carousel at liquid helium temperature for systematic studies using multiple samples and field emission targets intended for spin-polarized spectroscopic-imaging scanning tunneling microscopy (STM) study on samples with various compositions and doping conditions. The system is equipped with a UHV sample preparation chamber and mounted on a two-stage vibration isolation system made of a heavy concrete block and a granite table on pneumatic vibration isolators. A quartz resonator (qPlus)-based non-contact atomic force microscope (AFM) sensor is used for simultaneous STM/AFM operation for research on samples with highly insulating properties such as strongly underdoped cuprates and strongly correlated electron systems.

On the formation of Bi2S3-cellulose nanocomposite films from bismuth xanthates and trimethylsilyl-cellulose

The synthesis and characterization of bismuth sulfide-cellulose nanocomposite thin films was explored. The films were prepared using organosoluble precursors, namely bismuth xanthates for Bi2S3 and trimethylsilyl cellulose (TMSC) for cellulose. Solutions of these precursors were spin coated onto solid substrates yielding homogeneous precursor films. Afterwards, a heating step under inert atmosphere led to the formation of thin nanocomposite films of bismuth sulfide nanoparticles within the TMSC matrix. In a second step, the silyl groups were cleaved off by vapors of HCl yielding bismuth sulfide/cellulose nanocomposite films. The thin films were characterized by a wide range of surface sensitive techniques such as atomic force microscopy, attenuated total reflection infrared spectroscopy, transmission electron microscopy and wettability investigations. In addition, the formation of the nanoparticle directly in the TMSC matrix was investigated in situ by GI-SWAXS using a temperature controlled sample stage.

Variation of the sample temperature due to white bias light irradiation during the spectral responsivity measurement of solar cells and its effect on the measurement result

The temperature variation of solar cells due to white bias light irradiation during the spectral responsivity measurement and its effect on the spectral responsivity measurement result were investigated for various types of solar cells, such as crystalline silicon (c-Si), Cu(In,Ga)Se2 (CIGS), and dye-sensitized solar cells (DSSCs). For the investigation, a spectral responsivity measurement system, which can employ the well-known sample temperature control methods (such as the “temperature controlled sample stage” method and the “forced air cooling” method) has been used. Hence, the availability of these sample temperature control methods has also been tested. Through the investigation, it was found that the actual temperature of the solar cells located under the AM1.5G-approximated white bias light can be increased significantly during the spectral responsivity measurement, depending on the sample temperature control methods applied. In addition, it was also found that the increase of sample temperature can lead to a significant error in the measured spectral responsivity, depending on the types of solar cells being measured. In addition, a simple analytic model based on the classical heat transfer theory was developed to understand the temperature variation of the solar cells under the spectral responsivity measurement environment.

A temperature-controlled sample stage for in situ micro-X-ray diffraction: Application to Mars analog mirabilite-bearing perennial cold spring precipitate mineralogy

A temperature-controlled sample stage with an operational range of ~60 °C above or below ambient laboratory temperature (~ −35 to 85 °C) was constructed for in situ X-ray diffraction of minerals and materials using a Bruker D8 Discover diffractometer with θ-θ geometry. The stage was primarily designed for characterizing mirabilite-bearing samples from a Mars analog High Arctic perennial cold spring at an in situ temperature. Operation of the stage was demonstrated through the analysis of a synthetic sample of the hydrated sodium sulfate, mirabilite (Na 2 SO 4 ·10H 2 O). Mirabilite was held at −25 °C for approximately two hours without significant dehydration and then incrementally warmed to ambient laboratory temperature at 5 °C intervals, during the acquisition of in situ diffraction data. At ambient laboratory temperature, the mirabilite dehydrated and only polycrystalline thenardite (Na 2 SO 4 ) remained. Preliminary analysis of the cold spring precipitates demonstrates that when mirabilite is present in the sample the dehydration reaction is occurring between collection and analysis at ambient laboratory temperature. This temperature-controlled stage was designed for versatility and ease of X-ray access, with applications that can extend to many geological and planetary settings, including Mars analog environments.

Ambient Surface Mass Spectrometry Using Plasma-Assisted Desorption Ionization: Effects and Optimization of Analytical Parameters for Signal Intensities of Molecules and Polymers

Results are presented on the optimization and characterization of a plasma-assisted desorption ionization (PADI) source for ambient mass spectrometry. It is found that by optimizing the geometry we can increase ion intensities for valine and by tuning the plasma power we can also select a more fragmented or less fragmented spectrum. The temperature of the surface rises linearly with plasma power: at 19 W it is 71 °C and at 28 W it is 126 °C. To understand if the changes in signal intensity are related to thermal desorption, experiments using a temperature-controlled sample stage and low plasma power settings were conducted. These show markedly different signal intensities to experiments of equivalent surface temperature but higher plasma power, proving that the mechanisms of ionization and desorption are more complicated than just thermal processes. Four different polymers, poly(methyl methacrylate) (PMMA), poly(ethylene terephthalate) (PET), poly(lactic acid) (PLA), and poly(tetrafluoroethylene) (PTFE), are analyzed using PADI. Mass spectra are obtained from all the polymers in the negative ion mode and from PMMA and PLA in the positive ion mode. For each polymer, characteristic ions are identified showing the ability to identify materials. The ions are formed from bond cleavage with O and CH(2) as common adducts. Ions were detected up to m/z 1200 for PTFE.

Infrared Matrix-Assisted Laser Desorption/Ionization Orthogonal-Time-of-Flight Mass Spectrometry Employing a Cooling Stage and Water Ice As a Matrix

Although water ice has been utilized in the past as a matrix for infrared matrix-assisted laser desorption/ionization mass spectrometry (IR-MALDI-MS), it has not found a wider use due to limitations in the analytical performance and technical demands on the employment of the necessary cooling stage. Here, we developed a temperature-controlled sample stage for use with an orthogonal time-of-flight mass spectrometer (MALDI-o-TOF-MS). The stage utilizes a combination of liquid nitrogen cooling and counterheating with a Peltier element. It allows adjustment of the sample temperature between ~-120 °C and room temperature. To identify optimal irradiation conditions for IR-MALDI with the water ice matrix, we first investigated the influence of excitation wavelength, varied between 2.7 and 3.1 μm, and laser fluence on the signal intensities of molecular substance P ions. These data suggest the involvement of transient melting of the ice during the laser pulse and primary energy deposition into liquid water. As a consequence, the best analytical performance is obtained at a wavelength corresponding to the absorption maximum of liquid water of about 2.94 μm. The current data significantly surpass the previously reported analytical features. The particular softness of the method is, for example, exemplified by the analysis of noncovalently bound holo-myoglobin and of ribonuclease B. This is also the first report demonstrating the analysis of an IgG monoclonal antibody (MW ~ 150 kDa) from a water ice matrix. Untypical for MALDI-MS, high charge states of multiply protonated species were moreover observed for some of the investigated peptides and even for lacto-N-fucopentaose II oligosaccharides. Using water ice as matrix is of particular interest for MALDI MS profiling and imaging applications since matrix-free spectra are produced. The MS and tandem MS analysis of metabolites directly from frozen food samples is demonstrated with the example of a strawberry fruit.

Six-circle diffractometer with atmosphere- and temperature-controlled sample stage and area and line detectors for use in the G2 experimental station at CHESS

A new diffractometer system was designed and built for the G2 experimental station at the Cornell High Energy Synchrotron Source (CHESS). A six-circle κ goniometer, which provides better access to reciprocal space compared to Eulerian cradles, was chosen primarily to perform large angle Bragg diffraction on samples with preferred crystallographic orientations, and can access both horizontal and vertical diffraction planes. A new atmosphere- and temperature-controlled sample stage was designed for thin film thermomechanical experiments. The stage can be operated in ultrahigh vacuum and uses a Be dome x-ray window to provide access to all scattering vectors above a sample’s horizon. A novel design minimizes sample displacements during thermal cycling to less than 160μm over 900°C and the stage is motorized for easy height adjustments, which can be used to compensate for displacements from thermal expansion. A new area detector was built and a new line detector was purchased. Both detectors cover a large region in reciprocal space, providing the ability to measure time-resolved phenomena. A detailed description of the design and technical characteristics is given. Some capabilities of the diffractometer system are illustrated by a strain analysis on a thin metal film and characterization of organic thin films with grazing incidence diffraction. The G2 experimental station, as part of CHESS, is a national user facility and is available to external users by application.

Temperature-dependent local electromagnetic characterization of electronic materials by scanning microwave near-field technique

We report a scanning microwave near-field microscope that allows temperature-dependent local electromagnetic characterization of electronic materials. We have established a temperature-controlled sample stage cooled by liquid nitrogen, so that the local electromagnetic properties of the sample could be studied through near-field microwave interaction at temperature varying from 80 to 300 K. Using this instrument, we have studied the magnetic phase transition of an Nd 0.7Sr 0.3MnO 3− δ thin film and an ion-pair complex magnetic material, as well as the homogeneity of the microwave surface resistance of a YBa 2Cu 3O 7− δ superconducting thin film. Experiment results have demonstrated the ability of temperature-dependent local microwave characterization of this microwave microscope for different kind of electronic materials.

Spatially resolved characterization of the microwave properties of superconducting thin films by low temperature microwave scanning near-field microscopy

In this paper, we established a microwave scanning near-field microscope to characterize the local microwave properties of high temperature superconducting thin film and devices. Using a coaxial cavity together with a niobium tip as the probe, the microwave surface resistance can be imaged nondestructively at 3 GHz for thin film samples with a spatial resolution of several micrometers. Temperature dependence of the local microwave property can also be obtained through a temperature controlled sample stage cooled by liquid nitrogen. With this technique, we have studied the local microwave characteristics, especially the microwave surface resistance of the high temperature superconducting thin film and device. We believe this technique would be quite helpful in evaluating and improving the performance of the superconducting microwave devices.

Atomic force microscope chamber for in situ studies of ice

To investigate the surface morphologies of biological systems in a controlled gaseous environment (e.g., the temperature, humidity and composition), most commercial atomic force microscopes require modification. We have designed a double-jacketed environmental chamber specifically for a Nanoscope IIIa (Digital Instruments, Santa Barbara, CA) force microscope. We use cold nitrogen and thermoelectric devices to control the temperature in the chamber; the nitrogen simultaneously serves to create an inert environment. We have also designed a temperature controlled sample stage utilizing thermoelectric devices for fine temperature regulation. A variation of this sample stage allows us to image samples in fluids at cold temperatures with an O-ringless configuration. The relative humidity within the chamber is also measured with commercially available relative humidity sensors. We investigate the surface morphology of ice Ih in its pure phase and shall extend the study to ice in the presence of biological molecules, such as antifreeze proteins. We present a detailed description of our design and our first images of polycrystalline ice and single crystals of ice grown in situ from the vapor.

Electron-diffraction study of rubidium-intercalated graphite.

Using an analytical scanning transmission electron microscope we monitored the in-plane structure of rubidium-intercalated graphite as it underwent the deintercalation process. Starting with a saturated, stage-1 sample and using a temperature-controlled sample stage to control the desorption process, we allowed the graphite to deintercalate over a period of many days. This created a series of unannealed structures of progressively higher stage number. The experiment encompassed a regime in which the dominant factor in determining the intercalant in-plane distribution changed from host-intercalant to intercalant-intercalant interactions. High-resolution electron diffraction techniques were used to follow the in-plane superlattice structure of the intercalant. Ordered commensurate superlattices were observed which were stable over the entire temperature range observed (79--300 K) . In addition, an amorphous phase was observed which underwent a phase transition to an incommensurate square array. Both commensurate and incommensurate transition structures were observed during the transition period. The incommensurate structure was not affected by temperature and does not match the general lattice parameters for incommen- surate lattices which have been previously reported in the alkali-metal-intercalated graphite compounds.