Chemical imaging is the analytical measurement of spectra and spatial, time information to develop a visual image of components distribution. The chemical imaging is based on the combination of spectroscopy and microscopy. It is designed to analyze heterogeneous chemical complexes’ spatial distribution and composition within a sample.

The chemical imaging system, also known as hyper-spectral imaging, measures continuous bands of spectral. Several results can be produced when measuring a particular data spectrum at a specific chemical component in a spatial location in chemical identification and quantification.

There are three components of imaging instrumentation: a spectrally selective element, a radiation source to illuminate the sample, and a detector array to collect the images. A hypercube is the format of data. The data format can be visually and mathematically a spectrally resolved images series or a spatially resolved spectra series. 

Applications of chemical imaging

Chemical imaging is mainly applied to either gel or solid samples. It is applied in chemistry, biology, medicine, and pharmacy. However, other selective and ultra-sensitive imaging techniques are in use in the application, which involves; fluorescence micro-spectroscopy or UV-visible. You can use many imaging systems to analyze samples of all sizes in biology and medicine. However, it would be best to employ different instrumentation to make observations widely in other systems.

The Chemical imaging technique is essential in understanding modern manufactured products. It is also crucial in non-destructive techniques to preserve the sample for further testing. Several materials derive their functionality from the spatial sample components distribution. Any irregularities or contaminants in printed micro-circuits or silicon wafers can fail the components in the semiconductor industry. The biological system functionality is based upon chemical gradients because of the specific arrangement of elements. Even minor chemical composition and distribution changes can act as an early disease indicator.

Principles of chemical imaging

Hyper-spectral shares the vibrational spectroscopic techniques fundamentals. However, it provides additional information through the simultaneous acquisition of spatially resolved spectra. 

Vibrational spectroscopy is based on the measurement of the interaction of light with matter. Any photon that interacts with the sample is either absorbed or scattered. Specific energy photons are absorbed, and the absorption pattern provides a fingerprint, or information, on the molecules present in the sample. Chemical imaging can be absorbed, emitted, transmitted, or scattered in an observation setup. The emission and scattering are the most sensitive, powerful, and expensive modes. 

Types of vibrational chemical imaging instruments

The implementation of chemical imaging is done by mid-infrared, Raman spectroscopy, and near-infrared spectroscopy. Each imaging technique has its unique strengths and weaknesses suited for different needs.

Mid-infrared chemical imaging

Mid-infrared spectroscopy can differentiate small changes in chemistry and structure and is therefore helpful in identifying unknown materials. Data in mid-infrared spectroscopy can be collected in reflectance, transmission, or emission mode. 

Near-infrared chemical imaging

The near-infrared chemical imaging has a phenomenon that helps eliminate the need for extensive sample preparation. The intact samples can be imaged through diffuse reflectance or transmittance.

Raman chemical imagingThe scattering of incident photons with the change in polarization with vibration gives rise to the Raman spectrum, as opposed to infrared absorption, which depends on a change in dipole moment with vibration. Raman chemical imaging system needs little or no sample preparation.