Tech Briefs Magazine - September 2021 - PIT-6

SPECTROSCOPY
by measuring the absolute reflectivity of vitrinite
on a polished sample. Depending
upon the reflectivity, the thermal maturity
of the sample may be determined.
Nanotechnology. The microscope spectrophotometer
is also advancing nanotechnology
and materials science based
on their ability to measure transmission,
reflectance, and emission spectra microscopic
sample areas. One rapidly growing
area of applications is in the development
and use of surface plasmon resonance
(SPR)[6, 7, 8].
Surface plasmons are excited by illuminating
a planar metallic surface or
nanoscale metallic particles with light
(Figure 4). Changes in the optical characteristics
of these materials occur when
these nanoparticles or surfaces interact
with other materials. As such, much work
is being done to develop new materials
that exhibit some form of plasmon resonance, but also to build
devices that feature these phenomena. The latter includes
biosensors and microfluidic device sensors of various types. The
microscope spectrophotometer measures how the spectra of the
SPR materials change under different conditions giving the
researcher the ability to characterize a new material, then to
" tune " that material for specific optical effects.
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
200 220 240
260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560 580 600 620 640 660 680 700 720 740 760 780 800
Wavelength (nm)
Figure 4. The UV-visible-NIR absorbance spectra of films of gold nanoparticles being developed as moisture
sensors. The red trace is from the dry surface of the film while the blue trace is from the wetted
surface of the film.
(Courtesy CRAIC Technologies, Inc.)
Conclusion
The microscope spectrophotometer is a hyphenated technique
that combines the optical microscope with a spectrophotometer
so that one can acquire spectra of microscopic sample areas. Such
instruments are capable of absorbance and reflectance spectra
from the deep UV through the visible and into the near infrared
regions. The microscope spectrophotometer can also measure
fluorescence and other types of emission spectra. These devices
have found uses in many fields including forensic science, semiconductor
and optical film thickness measurement, biotechnology,
and the latest in materials science.
References
1. S. Walbridge-Jones, Microspec tro pho tometry for textile fiber color
measurement, Identification of Textile Fibers, Woodhead Publishing,
2009, Pages 165-180,
2. Standard Guide for Microspectrophotometry in Forensic Paint
Analysis, American Society of Testing and Materials, https://
www.astm.org/Standards/E2808.htm
3. Buchnev, O., Podoliak, N., & Fedotov, V. A. (2018). Liquid crystalfilled
meta-pixel with switchable asymmetric reflectance and
transmittance. J. Molecular Liquids, 267, 411-414.
4. Rezaei, S. D., Hong Ng, R. J., Dong, Z., Ho, J., Koay, E. H.,
Ramakrishna, S., & Yang, J. K. (2019). Wide-gamut plasmonic color
palettes with constant subwavelength resolution. ACS nano, 13(3),
3580-3588.
5. " Methods for the petrographic analysis of coals - Part 5: Method of
determining microscopically the reflectance of vitrinite " , ISO 7404-5,
International Organization for Standardization, 2009,
http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.
htm?csnumber=42832
6. Ng, R.J.H., Krishnan, R.V., Dong, Z., Ho, J., Liu, H., Ruan, Q., Pey,
K.L. and Yang, J.K (2019). Micro-tags for art: covert visible and
infrared images using gap plasmons in native aluminum oxide.
Optical Materials Express, 9(2), 788-801.
7. Alali, M., Yu, Y., Xu, K., Ng, R.J., Dong, Z., Wang, L., Dinachali, S.S.,
Hong, M. and Yang, J.K. (2016). Stacking of colors in exfoliable
plasmonic superlattices. Nanoscale, 8(42), 18228-18234.
8. Jiang, M., Siew, S.Y., Chan, J.Y., Deng, J., Wu, Q.Y.S., Jin, L., Yang, J.K.,
Teng, J., Danner, A. and Qiu, C.W., (2020). Patterned resist on flat
silver achieving saturated plasmonic colors with sub-20-nm spectral
linewidth. Materials Today, 35, 99-105.
This article was written by Dr. Paul Martin, President, CRAIC
Technologies (San Dimas, CA). For more information, contact Dr. Martin at
paul.martin@microspectra.com, or visit http://info.hotims.com/79417-220.
6
Free Info at http://info.hotims.com/79417-726
Cov
ToC
Photonics & Imaging Technology, September 2021
Absorbance

https://www.astm.org/Standards/E2808.htm http://info.hotims.com/79417-726 http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=42832 http://info.hotims.com/79417-220 http://www.abpi.net/ntbpdfclicks/l.php?202109TBNAV

Tech Briefs Magazine - September 2021

Table of Contents for the Digital Edition of Tech Briefs Magazine - September 2021