Biomolecules crucial for life, such as proteins, peptides, DNA, and amino acids, exhibit chirality, impacting pharmaceuticals where opposite handed drug molecules interact differentially with the body. Detecting molecular chirality is vital in Chemistry, and is often done through Circular Dichroism (CD) spectroscopy, measuring differential extinction of circularly polarized light by analytes. CD spectroscopy also aids in discerning protein conformational changes. However, conventional CD spectroscopy faces limitations, including poor size match and specialized UV optics requirements. An emerging approach involves using plasmonic nanomaterials to enhance molecular sensitivity and shift CD responses into the visible spectrum. In this project, our aim was to leverage hotspot junctions to assess the feasibility of single molecule detection. Anisotropic nanoparticle assemblies with chiral molecules may incur directional misalignment, leading to residual structural chirality, often masking the molecular response. To mitigate this, we employed an achiral substrate composed of isotropic nanospheres with low inherent chirality. We chose Bovine Hemoglobin (BHb) as our molecule of interest because of its absorption spectral overlap with the gold nanospheres (AuNSs) in visible region. We exploited dipole-dipole interactions between BHb and AuNSs dimers, inducing chirality in the plasmonic dimer through BHb presence in the nanogap, known as plasmon-coupled CD (PCCD). Correlated single-particle dark-field circular differential scattering (CDS) measurements were conducted on BHb-assisted AuNSs dimers to detect PCCD, and negative CDS signals were obtained. As a control, we further employed NaCl-mediated AuNS dimers and got low CDS signals, clearly indicating the absence of BHb. Our results underscore the potential of plasmonic nanomaterials in enhancing the sensitivity and applicability of CDS for single analyte detection, advancing molecular analysis and pharmaceutical research. In addition, the ability to detect single biomolecule and its conformational changes could have far-reaching consequences for understanding neurodegenerative diseases, such as Alzheimer’s and Parkinson’s.

CH stretching moieties can be used in quantitative infrared spectra analysis to probe the concentration of species in confined environments. The Beer-Lambert law is often used to perform such analyses. A useful venue for this analysis is interpreting the presence of guest molecules in porous metal organic frameworks (MOFs), allowing time-resolved analysis of molecular transport. It is therefore critical to understand if molecules diffused into MOFs possess different infrared cross sections. Temperature programmed desorption mass spectrometry (TPD-MS) and temperature programmed Fourier transform infrared spectroscopy (TP-IR), combined with density functional theory (DFT), are used to compare the integrated ν(CH) intensities with the presence of analytes diffused into the MOF. Using temperature programmed techniques under ultra-high vacuum (UHV) conditions, we demonstrate nonlinear integrated infrared intensity in the ν(CH)/ν(CD) moieties of four separate analytes following diffusion into UiO-67 MOFs: acetone, acetonitrile-d₃, isopropanol and n-heptane. These results have implications on the use of integrated infrared intensity for discerning molecular transport kinetics into and out of environments capable of forming hydrogen bonds with guest molecules.

Cyclic, oxygenated hydrocarbons are common intermediates in the pyrolysis mechanisms for biomass used to produce biofuels and chemical feedstocks. Despite the role of these molecules in both biofuel production and combustion, there is limited understanding of their thermal decomposition pathways. In order to investigate how the chemical structure of a cyclic, oxygenated hydrocarbon affects its pyrolysis mechanism, these experiments have identified products in the gas-phase pyrolysis of 2-pyrone (2H-pyran-2-one). This molecule is commonly observed in the pyrolysate of pineapple waste, rice husks, aluminum alginate, wood chips, and cellulose, yet little research has been conducted on 2-pyrone’s high-temperature chemistry. Experiments with pulsed, gas-phase pyrolysis at temperatures up to 1400 K were conducted with matrix-isolation FTIR identification of products. The FTIR spectra indicate the formation of carbon monoxide, carbon dioxide, acetylene, vinylacetylene, propyne, ethylene, and ketene, which have been observed in the pyrolysis of other cyclic, oxygenated hydrocarbons. However, several vibrational bands could not be assigned to known products in the literature and are theorized to belong to substituted ketenes such as formylketene and acryloyl ketene. Optimization and frequency calculations performed with Gaussian 09 at the B3LYP/6-311++G(d,p) support the assignments and demonstrate mechanisms consistent with the products’ vibrational spectra.

Epithelial ovarian cancer (EOC) is one of the deadly cancers among the women. The higher mortality can be attributed to the lack of early symptoms at early stage and lack of sensitivity and specificity of clinical methods. Developing new techniques to improve such problems is vital. In this regard, bioconjugation technique is widely researched along with various ovarian cancer biomarkers as it could potentially improve the sensitivity, specificity, and reproducibility. This work focuses on employing laser induced breakdown spectroscopy (LIBS) in an optical based immunoassay to detect the CA125 ovarian cancer biomarker. To achieve this goal, we developed a sandwich type immunoassay utilizing the affinity of CA125 towards a specific RNA-Aptamer. In this regard, Ni-NTA (Nickel- Nitrilotriacetic acid) magnetic beads (MBs) were used to immobilize the CA125-His tag, followed by a magnetic separation process. Similarly, streptavidin modified silica micro beads were modified with a biotinylated RNA-aptamer. Once the silica modified beads were collected through centrifuging, it was then incubated with CA125 modified MBs. The final conjugate was purified by a magnet and then investigated with LIBS. The emission spectrum of silicon at 288.2 nm confirmed the sandwich type immunoassay is achieved. Further, we studied the specificity of this assay replacing CA125 with p53 (another tumor suppressing protein) and bovine serum albumin (BSA).

This study presents a novel filter-based Surface Enhanced Raman Scattering (SERS)substrate for the sensitive detection of cortisol, a key biomarker for stress levels that is produced by the adrenal glands. The filter is pre-treated with methanol and NaCl aqueous solution, followed by the deposition of silver nanoparticle (AgNP) deposition using a low-pressure suction filtration technique. The pre-treatment involves the gradual addition of methanol to the filter using low-pressure suction filtration technique and a subsequent 10-minute soaking the filters in NaCl aqueous solution. The AgNP are deposited using the Silver Mirror Reaction (SMR) technique. The enhancement of the filter is demonstrated by comparing the Raman spectrum of reference materials such as Rhodamine with a standard commercial silver substrate. The limit of detection (LOD) for both Rhodamine and cortisol are estimated and compared with Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and a commercial silver substrate.

Sulfur dioxide, a human-made air pollutant, is toxic to public health and the environment. US EPA lists sulfur dioxide (SO₂) as one of the six air pollutants regulated by National Ambient Air Quality (NAAQS) under the Clean Air Act. As part of efforts to determine the utility of molecular rotational resonance (MRR) spectroscopy for monitoring SO₂ and its removal from a point source, a K-band MRR technique has been employed for measuring the products of thermally energized mixtures of sulfur dioxide and oxygen in the presence of ammonium vanadium oxide as a catalyst. The observed MRR spectrum reveals the presence of sulfur dioxide, water vapor and ammonia due to the sensitivity of MRR to only polar species.The SO₂ removal is confirmed by monitoring its disappearance as NH₃forms. The present measurements have been further used to validate K-Band MRR for SO₂ removal. We notice that the K-band MRR maintains its linearity and other polar species in a mixture have no impact on the MRR signature of SO₂. The MRR limit of detection (LOD) determined in this study is   1%. Additionally, the accuracy and precision, as judged from present analysis, are satisfactory.

Zantac is a pharmaceutical drug commonly used for treating gastroesophageal reflux disorder, and stomach ulcers. This drug has been recently removed from the US market due to the presence of impurities of nitrosamine that contributes to an increased risk of liver, gastric and pancreatic cancers. In this work, a K-Band molecular rotational resonance spectrometer, which operates in 18-26GHz, has been examined for the fast detection of polar impurities in Zantac by measuring the rotational signatures of heated samples of Zantac at 100^°C. The initial analysis of the observed MRR spectrum confirms the presence of ammonia and water due to the current sensitivity of a K-Band MRR to small polar species. The present measurements have been further used to determine the content of ammonia using Henry constant and measured partial pressure. The work to improve the sensitivity, reproduce the data and validate MRR for the measuring impurities in Zantac is underway and the progress will be reported in this talk.

New analytical tools for monitoring chemical toxins in mouth rinses are highly desired for the development of an improved antiseptic substances and for the reduction of dental problems and tooth diseases. The presence of polar toxins in mouth rinses, however, may lead to unwanted chemical reactions which can degrade quality of mouthwash and its antiseptic capabilities. As part of the efforts to determine the purity of antiseptic substances, a K-Band Molecular Rotational Resonance Spectrometer, which operates at 18-26GHz, has been used to measure small polar toxins in the mouthwash mixture. The analysis of observed MRR spectrum shows a well-resolved rotational structure dominated by ethanol, water and small amount of propane due to the current sensitivity of MRR to polar species in a mouthwash mixture. The present measurements have been further employed to validate K-Band MRR for monitoring ethanol in mouthwash mixture. We notice that MRR maintains its linearity confirming its ability to monitor ethanol in the presence of other polar impurities. The work to improve this analytical method and quantify the amount of each toxins is underway and will be reported in this talk.