What is Cathodoluminescence Spectroscopy?
Cathodoluminescence (CL) is an essential non-destructive analytical technique. It is the photon or light produced when the surface of a solid specimen is excited by a focused beam of high energy electron in a SEM. CL is useful in a wide range of applications including semiconductors, optoelectronics, dielectrics and ceramics. It also a powerful tool for investigations in geology, mineralogy, forensics, and life sciences.
What is Circular Dichroism?
Circular dichroism (CD) is the difference in the absorption of left-handed circularly polarised light (L-CPL) and right-handed circularly polarised light (R-CPL) and occurs when a molecule contains one or more chiral chromophores (light-absorbing groups). Circular dichroism (CD) spectroscopy is a spectroscopic technique where the CD of molecules is measured over a range of wavelengths. CD spectroscopy is used extensively to study chiral molecules of all types and sizes, but it is in the study of large biological molecules where it finds its most important applications.
What is Cryostats?
A cryostat (from cryo meaning cold and stat meaning stable) is a device used to maintain low cryogenic temperatures of samples or devices mounted within the cryostat. Low temperatures may be maintained within a cryostat by using various refrigeration methods, most commonly using cryogenic fluid bath such as liquid helium. Hence it is usually assembled into a vessel, similar in construction to a vacuum flask or Dewar. Cryostats have numerous applications within science, engineering, and medicine.
What is Ellipsometry?
Spectroscopic ellipsometry is a surface sensitive, non-destructive, non-intrusive optical technique widely used to determine film thickness and optical constants (n, k). Spectroscopic ellipsometry is ideal for a wide range of applications from fields such as semiconductors, photovoltaics, optoelectronics, optical and functional coatings, surface chemistry, and biotechnology.
What is Fluorescence Spectroscopy?
Fluorescence spectroscopy (also known as fluorometry or spectrofluorometry) is a type of electromagnetic spectroscopy which analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electrons in molecules of certain compounds and causes them to emit light; typically, but not necessarily, visible light. A complementary technique is absorption spectroscopy.
What is Flash Photolysis (Transient Absorption)?
The Laser Flash Photolysis technique provides one of the most effective methods for studying by direct measurement the reactions of transient species such as radicals, excited states or ions, in chemical and biological systems.
In flash photolysis, a short pulse of light is used to interact with a sample that has been placed in the optical path of a spectrometer. The result of this interaction can be either a transient absorption or an emission process. The changes in detector signal taking place following laser excitation may be due to a variety of processes such as electronic excitation producing a triplet state, cleavage of a molecule producing radicals, electron transfer, molecular rearrangement etc.
What is Glow Discharge?
A glow discharge is a plasma formed by the passage of electric current through a low-pressure gas. It is created by applying a voltage between two metal electrodes in a glass tube containing gas. When the voltage exceeds a certain value called the striking voltage, the gas in the tube ionizes, becoming a plasma, and begins conducting electricity, causing it to glow with a colored light. The color depends on the gas used. Glow discharge is widely used as a source of light in devices such as neon lights, fluorescent lamps, and plasma-screen televisions. Analyzing the light produced by spectroscopy can reveal much about the atomic interactions in the gas, so glow discharge is used in plasma physics and analytical chemistry. It is also used in the surface treatment technique called sputtering.
What is Raman Spectroscopy?
Raman spectroscopy is a light scattering technique, and can be thought of in its simplest form as a process where a photon of light interacts with a sample to produce scattered radiation of different wavelengths. Raman spectroscopy is extremely information rich, (useful for chemical identification, characterization of molecular structures, effects of bonding, environment and stress on a sample).
When monochromatic radiation is incident upon a sample then this light will interact with the sample in some fashion. It may be reflected, absorbed or scattered in some manner. It is the scattering of the radiation that occurs which can tell the Raman spectroscopist something of the samples molecular structure.
What is Photoluminescence (PL)?
PL is a contactless, non-destructive technique. PL studies photons emitted from a material or device when excited by an external light source. PL emissions may result from radiative recombination mechanisms such as direct bandgap, intersubband energies, excitonic states, defect states, and impurity level mechanisms. PL is more powerful for studying the luminescence properties of materials near and below the fundamental edge.
What is Photoreflectance (PR)?
Like PL, PR is a contactless, non-destructive technique. To characterize interband transitions above the band edge, Photoreflectance modulation spectroscopy method is useful. In a PR experiment the electric field is modulated in a sample via creation of electron-hole pairs by a pump source (laser or other light source) chopped at a given frequency. Periodic photoperturbation of the sample causes a derivative-like spectral feature at the critical-point transition of the reflectance spectrum. The derivative-like nature suppresses background effects and emphasizes structures localized in the energy region near direct interband transitions of semiconductors
What is Surface Plasmon Resonance Imaging (SPRi)?
Surface Plasmon Resonance (SPR) is an optical detection process that occurs when a polarized light hits a prism covered by a thin (gold) metal layer. Under certain conditions (wavelength, polarization and incidence angle) free electrons at the surface of the biochip absorb incident light photons and convert them into surface plasmon waves. A dip in reflectivity of the light is seen under these SPR conditions.
Perturbations at the gold surface of the biochip, such as an interaction between probe molecules immobilized on the chip and captured target molecules, induce a modification of resonance conditions which are in turn seen as a change in reflectivity and which can be measured. This is the basis for Surface Plasmon Resonance measurements.
What is Lasers?
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow.
A laser differs from other sources of light in that it emits light coherently. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers. Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i.e., they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond.
Among their many applications, lasers are used in optical disk drives, laser printers, and barcode scanners; fiber-optic and free-space optical communication; laser surgery and skin treatments; cutting and welding materials; military and law enforcement devices for marking targets and measuring range and speed; and laser lighting displays in entertainment.
What is Particle Sizes?
Particle size is a notion introduced for comparing dimensions of solid particles (flecks), liquid particles (droplets), or gaseous particles (bubbles).
The notion of particle size applies to:
The particle size of a spherical object can be unambiguously and quantitatively defined by its diameter. However, a typical material object is likely to be irregular in shape and non-spherical. The above quantitative definition of particle size cannot be applied to non-spherical particles. There are several ways of extending the above quantitative definition to apply to non-spherical particles. Existing definitions are based on replacing a given particle with an imaginary sphere that has one of the properties identical with the particle.
What is Gamma Spectroscopy?
Gamma spectroscopy is the science (or art) of identification and/or quantification of radionuclides by analysis of the gamma-ray energy spectrum produced in a gamma-ray spectrometer.
A Complete Gamma Spectroscopy System Consists of: Detector, Cooling System, Electronics, Analysis Software.
What is Alpha Spectroscopy?
Alpha spectroscopy is a quantification and identification of alpha-emitting nuclides plays a key role in site environmental characterization and radiation protection. Alpha spectroscopy is especially crucial for waste management and site decommissioning and decontamination applications.
What is Alpha/Beta Spectroscopy?
Alpha/Beta spectroscopy is a gas-flow proportional detector or dual-phosphor scintillation detector technologies.
What is Contact Angle?
Contact angle, θ, is a quantitative measure of wetting of a solid by a liquid. It is defined geometrically as the angle formed by a liquid at the three-phase boundary where a liquid, gas and solid intersect. The well-known Young equation describes the balance at the three-phase contact of solid-liquid and gas.
γsv = γsl + γlv cos θY
The interfacial tensions, γsv, γsl and γlv, form the equilibrium contact angle of wetting, many times referred as Young contact angle, θY.
Contact angles can be divided into static and dynamic angles. Static contact angles are measured when droplet is standing on the surface and the three-phase boundary is not moving. Static contact angles are utilized in quality control and in research and product development. Contact angle measurements are used in fields ranging from printing to oil recovery and coatings to implants.
When the three-phase boundary is moving, dynamic contact angles can be measured, and are referred as advancing and receding angles.
What is Surface Tension?
Surface tension is a measurement of the cohesive energy present at an interface. The molecules of a liquid attract each other. The interactions of a molecule in the bulk of a liquid are balanced by an equal attractive force in all directions. Whereas molecules on the surface of a liquid experience an imbalance.
The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension (ST). The molecules at the surface do not have the similar neighboring atoms on all sides and thus they cohere more strongly to those directly associated with them on the surface. This forms a surface ‘film’ that makes it more difficult to move an object through the surface than move it when it is completely immersed (Figure 1). The same situation also applies at the interface of the two liquids that do not mix together. In this case the term interfacial tension (IFT) is used. There are several different units for surface and interfacial tension; typically mN/m (which is equivalent to dynes/cm) is used.
What is Surface Free Energy?
Surface free energy or critical surface tension for a solid can be calculated by testing against a series of liquids and measuring the contact angles. This parameter quantifies the characteristics of the solid and indicates the intermolecular interactions between a liquid and a solid. The critical surface tension or the surface free energy obtained in this way can be regarded as the ‘surface tension’ of the solid substrate, which is a characteristic property of the solid in the same way as the surface tension is for a liquid.
What is Quartz Crystal Microbalance with Dissipation monitoring (QCM-D)?
The QCM-D technology is a real-time surface sensitive technique to monitor and characterize thin films on a surface in terms of adsorption, desorption, molecular interactions and structural properties. With the QCM-D technology, two parameters—frequency (related to mass/thickness) and dissipation (related to rigidity)—are monitored simultaneously, in real-time, as molecular layers form on the sensor surface.
A QCM sensor consists of a thin quartz disc sandwiched between a pair of electrodes. The sensor can be excited to oscillate at its resonance frequency by the application of an alternating voltage. The resonance frequency depends on the total oscillating mass of the sensor and sensor surface adhering layers, including coupled water. The frequency decreases when a thin film is attached to the sensor. If the film is thin and rigid the decrease in frequency is proportional to the mass of the film. In this way, the QCM operates as a very sensitive balance. Unlike all other QCMs, QCM-D monitors the frequency and energy dissipation response of the freely oscillating sensor, thus generating results more accurately and faster.
Common applications of QCM-D include measurements of proteins, polymers, surfactants and cells interacting with surfaces in liquid.