Detecting cancer cells before any symptoms appear is essential for successful treatment, especially for epithelial ovarian cancer (EOC) with few or no symptoms at the early stages. Although there are methods that have been developed to identify the cancer cells, scientists are looking for other novel promising methods to detect that early stage, also cheap and user-friendly. Here, we cross-link elemental particles to a specific functional group of the targeted biomolecules based on a covalent and non-covalent linking chemistry to improve the sensitivity and the selectivity of biomarker detection. In this presentation, we look into the sandwich type of micro-particle immunoassay with pair of Fe3O4 and silicon micro-particles used for highly-selective detection of specific cancer antigen human epididymis protein-4 (HE4) in which U.S. Food and Drug Administration (FDA) accepted recently as a biomarker for monitoring EOC patients. The cancer biomarkers are quantified via detecting the silicon using Laser-induced breakdown spectroscopy (LIBS).

Cancer mortalities are common due to the lack of diagnostic at the early stages in many countries. Recent studies discovered that the heavy metals in the human colon could cause the colon cancer. The conventional cancer detection techniques suffer from the insensitiveness, imprecision, slowness, cumbersomeness of sample preparation, and some time show conflicting results. Hence an accurate, reliable, and rapid detection technique is essential for the early diagnostic and prevention of heavy metals accumulation induced colon cancers. In this work, calibration-free laser-induced breakdown spectrometer (LIBS) was applied on several cancerous and normal colon tissues collected from the colon cancer infested patients aged 40 — 60 years. The results showed the presence of carcinogenic heavy metals including lead (Pb), chromium (Cr), and mercury (Hg) in the malignant colon tissues, while the healthy tissues were devoid of these elements. The accuracy of the LIBS results was validated by comparing the results obtained using a standard inductively coupled plasma atomic emission spectroscopy (ICP-OES). This study demonstrated that LIBS technique is very effective for rapid, precise early detection of the heavy metals accumulation in malignant colon tissues.

Gallbladder cancer is associated with high death rates due to its no effective treatment. Gallstones are the most common risk factor for gallbladder cancer. Continuous efforts have been made to understand the morphology, development, and compositions of gallstones, but to the best of our knowledge, the mechanism of their formation is not properly known. In the present work, the spectral lines of elements and molecular bands in cholesterol gallstone have been monitored using laser-induced breakdown spectroscopy (LIBS). The LIBS spectra of cholesterol gallstone exhibit spectral lines of inorganic (Ca, Mg, Na, Al, K) and organic (C, H, N, O) elements as well as electronic spectra of CN Violet band, NH band, and C₂ Swan band. We have also recorded the Fourier transform infrared (FTIR) spectra of cholesterol gallstone, which show vibrational bands of CN, NH, and C₂ molecules. These studies are likely to reveal the mechanism of gallstone formation.

Green tea is a type of tea made from the leaves and buds of Camellia sinensis. To ensure the interests of Green Tea producers and consumers the precise identification of tea varieties is of great significance. Thus, Laser-induced breakdown (LIB) Spectra of Green tea have been recorded for the its compositional analysis.LIB Spectra of the sample shows the presence of molecular bands of CN and C₂ molecule in addition to the spectral signature of the elements like Carbon(C), Manganese (Mn), Magnesium (Mg), Iron (Fe), Aluminium (Al) etc. The concentration of C and N is corelated to the atomic lines of C and N and molecular band of CN and C₂. Thus, the results of present work reveal that LIBS technique is a direct, straight forward and easy method for detection of elements and some specified molecule present in the sample.

In the present work, elemental and molecular compositions of Ayurvedic medicine have been performed using Photoacoustic Spectroscopy (PAS) and Laser-Induced Breakdown Spectroscopy (LIBS) techniques. The molecular bands of Protein, Carbohydrate, Flavonoid, and Chlorophyll, etc., have been observed using the PAS technique. PAS is based on the detection of photon-induced acoustic (PA) signals generated via non-radiative transition processes. The spectral lines of organic elements (C, H, N, and O) as well as the spectral lines of minerals (Al, Ca, Fe, Mg, Na, Si, and Sr) have been observed in the Laser-induced Breakdown (LIB) spectrum of the medicine. The presence of the spectral lines of organic elements is due to the photo fragments of the organic compounds present in the medicine. The molecular band of CN molecule in the LIB spectrum of the medicine further confirms the medicines' organic compound. Thus, along with LIBS, PAS is a suitable technique for the complete compositional analysis of Ayurvedic medication.

Cacao, a mesoamerican beverage similar to modern hot chocolate, is believed by archaeologists to have been drunk by the ancient Maya elite. Past analysis has often focused on highly decorative vessel forms that were only found in large sites with a social elite. We analyzed common drinking vessels for cacao to question if it was only the socially elite who had access to cacao. Focusing on the region of El Pillar, Belize in the Late Classical Period, we analyzed 35 archaeological sherds from 6 different regions, including sites with and without an elite population. The identification of cacao in ancient pottery sherds is dependent on the presence of the biomarkers theobromine, theophylline, and caffeine. Biomarkers are molecules that exist in high concentrations in the compound of interest, will survive burial, and are unique to that one compound. Samples of pottery are tested for presence of theobromine, theophylline and caffeine and if found to have measurable amounts of theobromine are considered indicative of cacao. Analysis is done by grinding off all outside surfaces to reduce contamination, pulverizing the inner clay matrix, extracting the biomarkers, and concentrating the extractions. These concentrated extractions are then most often analyzed via UPLC-MS. In order to obtain especially high selectivity and low limits of detection, our study utilized the novel technique of resonance enhanced multi-photon Ionization (REMPI) coupled with laser-desorption jet-cooling mass spectrometry. This technique isolates molecules in the cold gas phase where they can be selectively ionized through a two photon resonant process. We found evidence of cacao in samples from sites both with and without an elite.

A cavity ringdown spectrometer with a supersonic wind tunnel for measurements of excited species and radicals at low pressures and temperatures has been developed. The spectrometer has been used for measurements of metastable nitrogen molecules in the lowest excited electronic state, N₂(A³Σ_u⁺), in the supersonic test section of the wind tunnel. The tunnel has been operated in nitrogen at plenum pressure of P₀ = 200-250 Torr, with the flow expanding through a two-dimensional contoured nozzle to the Mach number of M = 3.6-4.6. The steady-state run time of the tunnel is approximately 10 s. The flow in the tunnel is excited by a repetitive ns pulse discharge operated in the plenum or in the nozzle throat. In the supersonic test section, absolute N₂(A³Σ_u⁺,v=0-2) populations at P = 0.8 Torr and T = 70 K are measured by Cavity Ring Down Spectroscopy (CRDS), using a tunable pulsed laser system operated at 10 Hz. During each run, 50 single-shot ring down traces are acquired, demonstrating good shot-to-shot reproducibility. The results demonstrate that the cavity ring down time is not affected by the supersonic flow. Further measurements of more complex radicals, such as HO₂, using a narrow linewidth tunable optical parametric oscillator (OPO) coupled to the supersonic wind tunnel, are currently under development.

We report a spectrometer employing optically-switched dual-wavelength cavity ring-down spectroscopy (OSDW-CRDS) for high-precision measurements of methane isotopic ratios. A wave-guide optical switch rapidly alternated between two wavelengths to detect absorption by two isotopologues using near-infrared CRDS. This approach alleviated common-mode noise that originated primarily from temperature and frequency fluctuations. We demonstrated the measurement of δD in natural abundance methane to a precision of 0.23 %, despite the lack of active temperature or frequency stabilization of the cavity. The ability of alternating OSDW-CRDS in improving isotope precision were measured by Allan deviation as varying switching time intervals (0.1 Hz ∼ 10 Hz) and the use of frequency-stabilizing cavity length. This system can be extended to a wide variety of applications such as isotope analysis of other species, kinetic isotope effects, ortho-para ratio measurements, and isomer abundance measurements. Furthermore, our technique can be extended to multiple isotopic analysis through the use of multi-port optical switches.

A high-resolution cavity enhanced absorption spectroscopy (CEAS) technique is presented for infrared absorption studies at temperatures between 77K and 300 K. An optical cavity with a pathlength of several kilometers is attached to a low temperature cryostat. The spectra are obtained with a tunable diode laser with resolution 0.0003 cm⁻¹. The output of the laser is modulated with an electro-optic modulator and coupled to an optical cavity. To illustrate the use of the technique, the first overtone of carbon monoxide at 298 K and 80 K and the first overtone transition of the acetylenic C-H stretch of propyne will be presented. The experiments are performed at pressures from 70 mTorr to 1 Torr. The combination of low pressures and temperatures makes this technique ideal for studies related to astrochemistry. The experimental set up will be used to simulate in the laboratory the kinetics and spectroscopy of molecules in the atmosphere of planets and satellites of the outer solar system.

Highly sensitive detection of methane is important for biomedical applications, environmental monitoring, and the detection of leaks in the gas and oil industry. An ultra-high sensitivity sensor employing a mid-IR (MIR) interband cascade laser (center wavelength of 3.37 micron) and a multi-pass cell (MPC) was developed for methane detection. The ultra-high sensitivity is achieved due to the high absorbance in the MIR, a long interaction path length, and the implementation of a wavelet denoising processing algorithm. The long interaction path of 580 m was achieved with a confocal MCP and the distance between the mirrors of 1 m. The performance of the sensor was tested in two measuring modes: direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS). For the sensor working in the DAS measurement mode the optimal set of sub-wavelet functions was determined and utilized for denoising and the minimum of the Allan deviation of the sensor of 3 ppb was achieved with an averaging time of 200 s. For the WMS measuring mode the sensor detection limit for methane of 560 ppt with 290 s averaging time was determined from the Allan deviation analysis. The developed sensor is suitable for a compact and portable design and has broad applicability in the high-sensitivity measurements of methane and other trace gases. This work was supported by the Robert A Welch Foundation, grant No A1546 and the T3 grant from Texas A and M University and Open Fund of State Key Laboratory of Applied Optics (SKLA02020001A12). [1] Jinbao Xia et al. A sensitive methane sensor of a ppt detection level using a mid-infrared interband cascade laser and a long-path multipass cell, Sensors and Actuators B: Chemical, 334, 129641 (2021). [2] Jinbao Xia: State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences Changchun, 130033, China

The mid-infrared (MIR) contains the strong absorption signatures of many molecules, such as Methane and Carbon Dioxide, that are of extreme interest in real-world sensing applications. The miniaturization of spectroscopic sensing equipment made possible by engineered silicon photonics has the potential to revolutionize the way we conduct emissions sensing in the MIR. Nanophotonic devices have greatly benefited from telecommunication technology in the near infrared (NIR) region. The industry has reached a level of maturity where high volume production of integrated circuitry can be done at low cost. Advances in materials engineering have shown that silicon based photonic devices can support optical propagation in the MIR past 8 microns with losses approaching those of the telecommunications band R. Shankar, I. Bulu, M. Loncar, Applied Physics Letters, 102, 051108, 2013.aking the region attractive for nanoscale sensor development. Absorption sensing with photonic devices has been demonstrated in silicon on sapphire C. Smith, R. Shankar, M. Laderer, M. Frish, M. Loncar, M. Allen, Optics Express, 23 5491, 2015. silicon nitride C. Ranacher, C. Consani, N. Vollert, A. Tortschanoff, M. Bergmeister, T. Grille, B. Jakoby, IEEE Photonics Journal, 10 2018. and metal assisted silicon on insulator C. Ranacher, C. Consani,, A. Tortschanoff, R. Jannesari, M. Bergmeister, T. Grille, B. Jakoby, Sensors and Actuators A: Physical, 277, 117, 2018.latforms, among others. These methodologies have demonstrated the ability to sense analyte concentrations as low as 5000 ppmv (parts per million by volume), which is the workplace limit in many North American constituencies. We present our current state of research on the development of a high-quality factor MIR silicon-on-sapphire (SOS) photonic gas sensor for use in lab-on-a-chip sensing applications. An optical parametric oscillator (OPO) will be used as a MIR source to pump a grating coupled SOS ring cavity immersed in a controlled CO₂ environment. The cavity will be geometrically engineered to allow for high sensitivity spectroscopy of the CO₂ fundamental at 2350 cm⁻¹via absorption of the cavity evanescent field. Design and optimization is conducted through the use of COMSOL Multiphysics and Lumerical software suites.

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Footnotes:

R. Shankar, I. Bulu, M. Loncar, Applied Physics Letters, 102, 051108, 2013.m C. Smith, R. Shankar, M. Laderer, M. Frish, M. Loncar, M. Allen, Optics Express, 23 5491, 2015., C. Ranacher, C. Consani, N. Vollert, A. Tortschanoff, M. Bergmeister, T. Grille, B. Jakoby, IEEE Photonics Journal, 10 2018., C. Ranacher, C. Consani,, A. Tortschanoff, R. Jannesari, M. Bergmeister, T. Grille, B. Jakoby, Sensors and Actuators A: Physical, 277, 117, 2018.p

Nonlinear spectroscopy provides important information about chemical systems that is not available from linear spectra alone. However, nonlinear spectroscopies have rarely been used for quantitative measurements due to the difficulty in obtaining accurate cross-sections. To overcome this limitation, we have been developing new methods to obtain accurate two-photon absorption (2PA) and stimulated Raman scattering (SRS) cross-sections of liquids and liquid solutions using ultrafast pump-probe spectroscopy. Here, we describe recent advances in measuring absolute SRS cross-sections of common liquid solvents based on a simple setup using single-wavelength pump and broadband probe pulses derived from a tunable repetition rate Yb:KGW laser. We obtain a two-dimensional transient absorption spectrum that is integrated over the time delay between the pump and the probe to obtain the Raman response as a frequency-dependent SRS spectrum. We model the overlap between the pump and probe beams in terms of the beam diameter, crossing angle, and refractive index of the solvent in order to determine accurate values for the SRS cross-sections based on the pump-probe signal strength. Specifically, we report absolute cross-sections for the C-H stretching modes of cyclohexane, dimethyl sulfoxide, acetonitrile, methanol, benzene, and toluene using Raman excitation wavelengths of 1030 nm (anti-Stokes), 515 nm (Stokes and anti-Stokes), and 343 nm (Stokes). The measured cross-sections follow the expected  ∼ ν⁴ frequency dependence. Our measurements also allow for direct comparison of the absolute SRS cross-sections for Stokes and anti-Stokes scattering from a single (515 nm) Raman excitation laser, which may be important for quantitative measurements using coherent nonlinear spectroscopies. For example, the SRS cross-sections that we measure for these solvents provide valuable internal reference standards for the determination of accurate 2PA cross-sections of solutes.

PROMO