Some of us view the physical world in a simple manner, accepting what they don’t understand. Others have an innate curiosity. We hunger to grasp the nature of the surrounding environment. We want to know how things work.
Spectroscopy helps bridge that knowledge gap. It is a method of understanding molecules by measuring the interaction of light and matter. By analyzing the amount of light absorbed or emitted by a sample, we can determine the sample’s components, characteristics and volume.
We use spectrometers, which perform spectroscopy, in basic research. However, we also use these instruments in applied sciences, including industrial, chemical, petrochemical, environmental, food and agriculture, metals and mining. We use spectroscopy to help discover life on our own, and distant planets.
We cross paths with spectrometers in our everyday lives. Associates use simple spectrometers at home improvement stores to analyze and match the paint color for redoing your bedroom. Researchers use it to develop cancer treatments. Spectrometers can also help monitor an oil spill and atmospheric conditions.
The benefits of spectroscopy are broad. It affects a large range of unexpected things, from improving the quality of your food to the hunt for criminals. We can apply various spectroscopic techniques in virtually every area of scientific research - from environmental analysis and biomedical sciences to space exploration.
We will go deep into the technology, including discussing Raman spectroscopy, a vibrational study of matter, fluorescence, and the Excitation-Emission Matrix.
The science has come a long way. Engineers have made improvements to detectors, software, and overall design. It has affected speed, miniaturization, price, and reliability.
Fluorescence is a type of photoluminescence where light raises an electron to an excited state. The excited state undergoes rapid thermal energy loss to the environment through vibrations, and then a photon is emitted from the lowest-lying singlet exited state. This process of photon emission competes for other non-radiative processes including energy transfer and heat loss.
Fluorescence is a spectrochemical method of analysis where the molecules of the sample are excited by light at a certain wavelength and emit light of a different wavelength. In conventional fluorescence, photons are emitted at higher wavelengths than the photons that are absorbed. Fluorescence spectroscopy is a technique used to characterize matter based on its fluorescing properties.
From vitamins to the water you use to take them, below you will find many examples of Fluorescecne Spectrscopy in your everyday life.
Fluorescence spectrometry is a fast, simple and inexpensive method to determine the concentration of a sample in solution based on its fluorescent properties. Those properties can characterize the nature of the sample under study.
Water contains many colored dissolved organic matter compounds. It’s important to know over time how these compounds change and may affect water quality.
Water treatment plants must measure what comes into its facility and what goes out. Spectroscopy is a powerful tool that can facilitate the measurement of these changes. These facilities must track how these materials change over time when it either physically binds with particles or reacts with natural organic bodies in water. Compounds may materialize in the form of bacteria, like in the interaction of a decomposing leaf in runoff. Scientists are interested in looking at the fate and transport of these compounds, controlling its concentration, and seeing the byproducts of the compounds.
Large water treatment facilities have analytical labs and many of them are starting to use spectroscopy to detect these changes. Fluorescence spectroscopy helps identify the concentrations of substances in the water. Undesirable substances can be eliminated downline in the treatment process.
HORIBA’s groundbreaking Aqualog A-TEEM (Absorbance–Transmission and Excitation-Emission Matrices) florescence and absorbance spectrometer measures both absorbance spectra and fluorescence Excitation-Emission Matrices (EEM) to detect colored dissolved organic matter. It’s the only true simultaneous absorbance-fluorescence system available. It’s a faster and more economical method for monitoring organics, making its measurements in a matter of seconds.
Like water treatment plants, researchers use fluorescence spectroscopy to measure dissolved organics in glacial ice. This helps to determine if life exits or existed at one time below the polar ice caps.
Scientists used a HORIBA Scientific Aqualog spectrofluorometer in a number of such experiments in Antarctica. They used the Aqualog to search for the fingerprints of microorganisms.
Knowledge like this also adds to our understanding of the possibilities of life on other, frozen planets.
Carbon nanodots are tiny particles made of carbon on the nanometer scale. Scientists can make it from various sources, such as bulk carbon or carbohydrates. They can even make it from biomass, which is a total mass of organisms. The cost of preparation can be cheap since these particles are easy to synthesize.
Scientists produce carbon nanodots as stacks of a few graphene layers in a continuous two-dimensional carbon honeycomb. Due to the confined size, carbon nanodots have finite band-gap that can absorb and emit light.
Carbon nanodots are important because of its photoluminescence properties. Scientists can tune the color of the fluorescence from carbon nanodots by modifying its size and surface chemistry. Researchers use spectrofluorometers to measure the photoluminescence of these materials.
Medical practitioners introduce these nanosized materials into biological cells to color the cells and track the biological components. Manufacturers also use carbon nanodots in display technology.
Fluorescence spectroscopy is the key to new research into photovoltaic materials with the objective of developing more efficient, flexible and less costly solar cells.
A team of researchers use photoluminescence to gauge the quality of solar cells, materials that convert light to electricity. The luminescence of a solar cell can indicate the quality of the solar cell crystal. Semiconductors, which are the basis of solar cells, luminesce at a very specific wavelength.
Generally, the better the luminescence of the materials, the better the efficiency of the solar cells, so researchers measure the luminescence of samples to gauge the potential semiconductor properties.
Photoluminescence (PL) phenomena result from materials absorbing excitation light photons and raised into an excited state. In the case of semiconductors, these levels are typically above the bandgap of the material. When the excited species relax, it releases this excess energy in the form of luminescence or emission of photons. The emitted light is often characteristic of either the material or its surrounding environment, and can even provide information about local dynamics around emitting species.
PL is a powerful tool for semiconductor characterization in the various stages in its life cycle. That includes development, testing, quality control, and failure analysis.
Most modern semiconductor devices are engineered materials made from multilayered structures fabricated on wafers. Technicians dice these up into individual devices. The process of engineering the base material, fabricating the wafers and characterizing the devices made from these wafers all depend on techniques like PL.
One research team is trying to develop new materials. Besides silicon, they do some work with mostly thin film photovoltaic materials like cadmium telluride, copper, indium, gallium and selenide.
The team is part of a center with the long-term goal to help establish photovoltaic electricity as a major source of energy in the world.
Fluorescence spectroscopy, carried out by a Rutgers University researcher, found that the contents on the labels of over-the-counter supplements do not always match the ingredients.
Using a HORIBA Aqualog spectrofluorometer, the researcher characterized the substance in fish oil capsules popular for its health benefits. His team found that manufacturers chemically altered about 80 percent of the products tested without notifying the consumer of a change in the common name of the supplement.
Since the Federal Drug Administration does not police dietary supplements, counterfeit vitamins and minerals are only subject to voluntary scrutiny. That leaves it to private industry of the research sector to police these substances.
The nature of grapes for wine making affects the flavor, feel and color of the wine. So knowing its state during the maturing of these grapes is of paramount importance.
Fluorescence spectroscopy is beginning to take on a greater role in this process.
Most wineries have multiple brands and growing fields. Winemakers need to monitor these fruits for the phenolic content in the grape that will give it the desired color, flavor and mouthfeel.
Traditional methods of testing the grapes are slow, expensive and cumbersome. Fluorescence spectroscopy can characterize the phenolic content in grapes and wine faster, cheaper, and with greater flexibility than traditional methods, including Gas Chromatography-Mass Spectrometry, Liquid Chromatography-Mass Spectrometry, and Fourier Transform Infrared Spectroscopy.
Organic milk isn’t always what it’s billed to be. Organic milk is the product of cows that are grass-fed. But the vast majority of American milk comes from cows restricted to large, concrete-floored dairy barns. Farmers feed these cows grass in the form of cut hay, grain fodder and crude protein. That’s where most of our milk comes from.
In general, grass-fed milk tends to be higher in beneficial fats like conjugated linoleic acids and omega-3 fatty acids. Conventional milk is higher in omega-6 fats, which are more abundant in feed grains.
Yet, some unscrupulous sellers market their dairy barn milk as organic.
Fluorescence spectroscopy can produce a molecular fingerprint of the contents of the milk by measuring molecules based on luminescent signals in response to a beam of light. Testers can get results through fluorescence spectroscopy instantly, unlike more expensive technologies, like gas chromatography.
Fluorescence spectroscopy could help convince customers of the validity of those “organic” claims in the future.
Spectroscopy is beginning to play an important role in making sure that food meets quality and safety standards. pH, polarity, temperature, pressure, and viscosity affect food quality and safety. And all these characteristics can be measured with spectroscopy.
Researchers have identified naturally occurring fluorescent molecules in food. They are distinguishing those molecules with fluorescent properties that can tell us about a physical or chemical state, which in turn can tell us about that property and safety.
pH is an important property for food. Manufacturers have to be careful how it changes in meat, for example, since the wrong pH can create undesirable products or properties.
Most quality-testing solutions for usually require the destruction of some of the product for lab tests. And that testing can be a lengthy process. If the testing is on-site, the results may take a few hours. Off-site testing could take several days.
Chromatography and atomic absorption spectroscopy have historically been the common analytical techniques in the agriculture industry for a wide variety of analyses. Unfortunately, each method takes significant sample preparation and long delays to get the results.
Fluorescence spectroscopy offers a faster and cheaper opportunity for this analysis.
Olive oil includes phenolic compounds, which scientists believe, can contribute to a lower rate of coronary heart disease, and prostate and colon cancers. Phenolic compounds also affect sensory attributes and the oxidative stability of olive oils.
Various bioactivities of phenolic compounds are responsible for their chemopreventive properties, like antioxidant, anticarcinogenic, or antimutagenic and anti-inflammatory effects.
Researchers can use fluorescence spectroscopy, near-infrared spectroscopy and mid-infrared spectroscopy to measure those phenolic compounds and determine the makeup of olive oil. But fluorescence spectroscopy, they found, can do it faster.
Refined oils lack the antioxidants and anti-inflammatories that gives unrefined extra-virgin olive oil its phenolic benefits. Researchers have found that olive oils have unique fluorescent fingerprints.
Photodynamic therapy, which targets a specific group of tissues, is a treatment that is used primarily to treat cancers that are near an accessible surface of the body.
You need three things for photodynamic therapy - light, a photodynamic molecule or metal compound as the mediator, and the oxygen in the microenvironment. The product of this reaction, a reactive singlet oxygen species, kills the cancer.
Spectroscopy plays an important role in identifying the most productive photodynamic molecules to activate the process.
In photodynamic therapy, a cancer patient has a fiber optic light either inserted into, or placed just outside their body. This light emits visible wavelengths. It reacts with photosensitizer (photodynamic) molecules and provides energy to oxygen in the microenvironment. That, in turn, generates non-toxic singlet oxygen species, which shrink or kill the tumor.
Raman spectroscopy is a non-destructive chemical analysis technique which provides detailed information about chemical structure, phase and polymorphy, crystallinity and molecular interactions. The basis of Raman spectroscopy is the interaction of light with the chemical bonds within a material.
Raman is a light scattering technique, whereby a molecule scatters incident light from a high intensity laser light source. Most of the scattered light is at the same wavelength as the laser source and does not provide useful information – called Rayleigh Scatter. However, a small amount of light is scattered at different wavelengths, which depend on the chemical structure of the sample – we call this Raman Scatter.
Researchers commonly use the technique to create a structural fingerprint of a sample, identifying it through its Raman characteristics.
Raman bands arise from a change in the polarizability of the molecule due to an interaction of light with the molecule. When scientists plot these transitions as a spectrum, they can be used to identify the molecule observed. Researchers use Raman spectroscopy in chemistry to identify molecules and study chemical bonding and intramolecular bonds.
Paleobiology is the study of ancient life. One way to do that is to look at slivers of rocks for evidence of the earliest life on earth. Most likely, those discoveries will come from the similarity of specimens we find here on earth and deep beneath extraterrestrial bodies.
Researchers are looking for fossils of microorganisms in rock, or at least their chemical signatures. Nature has long ago consumed the interior of those cells, yet carbon signatures are sometimes left behind by the bacteria’s cell wall. The carbon molecules are one indicator of life.
Scientists use Raman spectroscopy to identify the fossil. They do it using thin strips of rocks they shaves off from larger pieces, so thin it becomes transparent.
Raman spectroscopy gives researchers a spectrum of whatever material it is. If there’s carbon present, it’s one piece of evidence that life once existed there.
Researchers use Raman spectroscopy to characterize microscopic pieces of plastic that invade our environment. These materials, those both engineered and those that are the product of decomposition, might pose health hazards. Scientists use Raman spectroscopy to trace the trail of microplastics that are becoming a greater threat to our surroundings.
There’s a breakthrough underway in law enforcement that can have a deep impact on crime-solving efforts. Body fluid traces are important because they are the main source of DNA evidence. Currently, police use various biochemical tests to detect and identify body fluids.
But those tests are destructive – they alter the sample. The tests are also presumptive, and generate many false positives.
Raman spectroscopy and ATR FTIR (Attenuated Total Reflectance Fourier-transform infrared spectroscopy) are vibrational technologies that are more sensitive and can more accurately identify body fluids.
Researchers are using Raman technology as the first method to develop a universal, confirmatory test of body fluids. Raman is also a non-destructive technique and does not affect the sample as it’s tested.
Gunshot reside can also be examined using Raman spectroscopy to identify the caliber of the weapon used in a discharge. Investigators can use Raman to match the residue found on a victim or perpetrator with a sample of the gunshot residue in a test.
Shady suppliers will counterfeit expensive drugs because of its economic value. That includes lifestyle drugs like Viagra, Cialis, Lipitor, or vital drugs like Hyzaar, a blood pressure medication, Tamiflu, a vaccine for influenza, and Plavix, a blood thinner. Selling imitations of these drugs can earn someone a substantial profit.
The Food and Drug Administration’s Trace Examination Section of its Forensic Chemistry Center is responsible for examining the legitimacy of these and other items.
Investigators often use a combination of infrared spectroscopy and Raman spectroscopy to identify different components used to make a prescription tablet.
Raman has its advantages. It’s a non-destructive technique and preserves the evidence. It also allows investigators to analyze very small particles. Raman lets investigators analyze some particles that infrared spectroscopy can’t because of its size.
Kidnapping. Homicide. Improvised explosive devices. Each have an element in common – duct tape. Law enforcement’s ability to discriminate among the hundreds of variations of these materials can go a long way in helping to solve crimes.
Through extensive research, the Federal Bureau of Investigation cataloged a large database of duct tape profiles for criminal investigations. Law enforcement characterizes these common tapes by looking at three properties - a polymeric (polymer) backing, an adhesive and a fabric reinforcement between the backing and adhesive.
In 2016, unknowing officials threw the residents of Flint, Michigan into turmoil. Scientists discovered their drinking water supplies contained unhealthy levels of lead.
The city, two years earlier, changed the drinking water source for the city from Lake Huron and the Detroit River to the cheaper Flint River. Lead leached from the lead water pipes into the drinking water, due to insufficient water treatment, exposing over 100,000 residents.
Lead carries serious health hazards for children, adults and pregnant women.
Scientists use inductively coupled plasma optical emission spectrometry, or ICP-OES to detect chemical elements, and is one of the most powerful and popular analytical tools for determining trace elements in numerous sample types.
Elemental analysis of water is one of the major applications for Inductively Coupled Plasma – Atomic Emission Spectrometry. It is capable of measuring up to 70 elements of the periodic table, and that with its tolerance to difficult matrices makes it the ideal tool for the analysis of many different types of water.
Near-Infrared (NIR) spectroscopy is widely applied in food science and technology research. It has become one of the most common analytical techniques in the sector due to its low costs, fast processing and non-destructive nature. Nowadays, NIR spectroscopy is a well-recognized technique in the wheat and cereal-processing industry for routine quality assessment.
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