Research
Instrument Development
Flowing Atmospheric-Pressure Afterglow Ionization Source
The flowing atmospheric-pressure afterglow (FAPA) is an ambient desorption/ionization source based on a direct-current atmospheric-pressure glow discharge (APGD). It directly desorbs and ionizes molecules from sample surfaces for detection by mass spectrometry. We not only use FAPA-MS for various applications, but also examine the fundamental behavior of the source and develop strategies to expand its utility.
Solution-Cathode Glow Discharge Ionization Source
Originally developed for atomic emission spectroscopy (AES), the solution‑cathode glow discharge (SCGD) can outperform conventional AES sources such as the inductively coupled plasma (ICP). Comprised of a low power APGD between a metal rod and flowing liquid solution, the SCGD is a simple design that overcomes drawbacks associated with high-power plasmas for elemental analysis.
Tandem Laser-Induced Breakdown Spectroscopy and Mass Spectral Imaging
Dual imaging is achieved through laser ablation and excitation of samples followed by simultaneous optical-emission and mass-spectrometric detection.
Portable/Fieldable Instrumentation
Many spectrometric techniques are viewed as a laboratory-bound. Recent advances in fabrication methods, electronics, and vacuum pump design have led to the development of fieldable/portable mass and optical spectroscopy devices.
Computational Data Analysis
Automated data processing is essential due to the complexity of spectra from mixtures and natural samples. In mass spectrometry, information is embedded in both the mass-to-charge and time domains. We developed a cross-correlation algorithm to extract this information to differentiate related signals. Spectral complexity can be decreased by 95%. Computational graphs can be used to visual the chemical relationship between series of molecules in a sample.
Fundamental Characterization
Flow Visualization and Fluid Dynamics
Schlieren imaging and computational fluid dynamics enables understanding of the transport of gaseous species from an ion source into a mass spectrometer.
Acoustic Levitation
Acoustic waves can form standing waves with stable and unstable regions capable of levitating small objects and liquids. While suspended in these fields, reactions can proceed inside droplets in container-free environments.
Unique Gas-Phase Synthesis
Plasmas produce a range of energetic species that can be tuned by adjusting parameters such as power and gas composition. These species can be used for unique gas-phase ion-ion and ion-molecule chemistry to rapidly modify inert substances. We create plasma reactors to synthesize alkenes, ketones, and carboxylic acids from simple aliphatic precursors.
Spin-Trapping EPR for Plasma Diagnostics
Plasma diagnostics can be performed using Electron Paramagnetic Resonance (EPR) to detect and quantify radical species from plasma-based ionization sources such as FAPA, DART, and SCGD.
Applications
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Astrobiology
Our work in the Rensselaer Astrobiology Research and Education Center (RARE) focuses on prebiotic chemistry and the origins of life. Projects include prebiotic syntheses and polymerization in microdroplets, constraining early Earth environments by mass spectral analysis of fluid inclusions in ancient minerals, characterizing organic compounds in meteorite samples, and developing analysis techniques for future planetary missions and returned samples.
Environmental Monitoring
Our research with The Jefferson Project at Lake George aims to understand the growth and proliferation of harmful algal blooms in Lake George and Lake Chautauqua in NY to assess changes in the environment and limnological conditions. The Shelley Lab analyzes phytotoxins using HPLC-MS and is developing machine learning models to predict toxin levels from weather and lake conditions.
Archaeometry and Heritage Artifact Analysis
Handheld spectroscopic instrumentation can be taken in the field to directly analyze archeological materials. Recent projects include on-site analyses of painted and unpainted sections of plaster walls at the Cataract House, Niagara Falls, NY.
Forensic Analysis and Nuclear Safeguards
Mass spectrometry and Raman spectroscopy can measure the organic species in gunshot residue, which provides more selective information than traditional inorganic analysis.
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Accurate, precise and rapid methods for on-site uranium enrichment assays can be achieved using a low-power, atmospheric-pressure SCGD and portable mass spectrometer.