Tanya Hutter

High Resolution Image Download MS PowerPoint Slide Studtite is a common nuclear fuel cycle material that has been the focus of considerable research due to its role as a uranium ore concentrate. In a laboratory setting, studtite is commonly synthesized via the addition of liquid-phase hydrogen peroxide to an aqueous uranyl nitrate solution. The product produced from this process is a very fine, pale-yellow powder with crystals of ∼0.1 μm in their largest dimension. In this work, we implement a small modification to this process by introducing hydrogen peroxide in the vapor phase. This change eliminates mechanical agitation and increases crystallization time, resulting in crystals measuring 10–20 μm. Due to the thermal decomposition mechanism of studtite, this increased crystal size is preserved through heating, leading to large crystals of both metastudtite and α-UO 3 . Raman spectroscopy and powder X-ray diffraction are used to determine crystallographic information and structures, and scanning electron microscopy is used to visually compare samples produced via the traditional method and our vapor diffusion method. The samples obtained using this technique open the door to future investigations in which large single crystals are required for full structural characterization.

Simultaneous monitoring of multiple biomarkers in tissues is critical for biomedical applications. However, few existing platforms enable concurrent in vivo detection. This study presents a compact mid-infrared transflection optical fiber probe for label-free, simultaneous monitoring of three physiologically relevant biomarkers – ethanol, glucose, and lactate. The probe comprises two silver halide fibers - one with an angled tip and one gold-coated as mirror - housed in polyetheretherketone tubing and surrounded by a semi-permeable membrane. With an outer diameter of only 1.1 mm, this is the smallest mid-infrared transflection probe reported to date. Coupled with a quantum cascade laser, the probe achieves ~1 mM detection limits for the three compounds. Peak deconvolution was deployed to resolve overlapping spectral features, enabling quantification of individual compounds in mixtures. Validation was performed in ex vivo human skin against microdialysis. Additionally, monitoring of the concentration changes for all three compounds in the skin was demonstrated. This study reports a 1.1-mm diameter mid-infrared transflection fiber probe, the smallest reported to date, enabling label-free, simultaneous detection of ethanol, glucose, and lactate, with validation in ex vivo human skin and comparison to microdialysis.

This work investigated the feasibility of fiber optic sensors embedded in clothing for real-time monitoring of leg movements. Two lightweight plastic optical fibers were sewed into elastic bands and attached firmly around the knees to detect joint bending by measuring changes in light transmission. Experimental testing showed that the optical fibers can reliably distinguish different postures and movements, including squatting, sitting, and walking. The results demonstrate that garment-integrated optical sensing offers a comfortable, minimally-invasive approach that can be applied for applications such as patient monitoring and personalized rehabilitation feedback. © 2026 The Authors.

Abstract Competitive adsorption of CO2 and reservoir fluids near caprocks impacts CO2 trapping and leakage. Conventional adsorption quantification techniques fail to distinguish between physisorption and chemosorption interactions. Therefore, we aim to (i) develop a novel Fourier-transform infrared (FTIR) spectroscopy workflow to quantify the CO2:CH4 competitive adsorption within caprocks, (ii) evaluate the influence of rock chemical compositions on CO2:CH4 competitive adsorption, and (iii) investigate the geochemical changes in clay minerals when exposed to CO2 under varying concentrations. Attenuated total reflectance (ATR) FTIR was used to estimate CO2 and CH4 adsorption in caprock components such as Na-montmorillonite (Na-MMT), kaolinite, and activated carbon as a porous shale proxy. The solid samples were crushed and sieved to the same grain size, and positioned on the ATR surface. Pure CO2, CH4, and their mixtures were flowed over the samples while monitoring spectral infrared changes at different gas concentrations. Gas adsorption was quantified by calibrating the peaks of the FTIR spectra to the relative changes in gas concentration in the sample. The analysis of the FTIR spectra showed that the ATR technique could quantify the adsorption peaks of CO2 and CH4, and detect shifts in the material-specific peaks caused by gas adsorption. In the case of CO₂ adsorption on the tested rock components, a consistent increase was observed in the physisorption-related IR peaks, particularly within the C=O bending (at approximately 667 cm⁻¹ wavelength) and asymmetric stretching (at approximately 2349 cm⁻¹ wavelength) regions. These increases reflect enhanced CO₂ population near the solid surfaces with increasing partial pressure. Among the tested materials, Na-MMT exhibited the most prominent peak increase, followed by kaolinite, and then activated carbon, indicating a higher adsorption affinity driven by its greater surface area, interlayer spacing, and exchangeable cation sites. Additionally, CH₄ showed significantly weaker IR activity and a plateauing trend in peak heights, consistent with limited physisorption and the low IR-activity nature of the molecule. These observations confirm a stronger interaction between CO₂ and the tested solid surfaces compared to CH₄. These results not only highlight the physisorption behavior of gases in caprock components, but also provide critical insights into the geochemical interactions at the gas-solid interface. The introduced experimental method leverages IR spectroscopy to quantify the competitive adsorption and interfacial interactions of CO2 with reservoir fluids and rock components. Unlike conventional methods, this method accurately quantifies the multi-gas adsorption capacity of caprock systems without requiring sophisticated gas chromatography setups. These advancements offer a transformative approach to optimizing CO2 storage processes while enabling a precise assessment of CO2 leakage potential, thereby addressing key challenges in carbon sequestration projects.

Real-time in vivo ethanol monitoring is important for understanding its physiological mechanisms and developing treatments for alcohol-related disorders. Mid-infrared (mid-IR) fiber sensors enable highly specific and sensitive detection of chemical species due to unique molecular vibrational absorption bands. This study presents the first mid-IR transflection optical fiber probe that is small enough to be suitable for in vivo monitoring. Ethanol quantification using mid-IR spectroscopy was demonstrated in synthetic solutions and in a biofluid, rat brain dialysate, spiked with ethanol at physiological concentrations using standard Fourier-transform infrared spectrometer (FTIR). The results showed a linear relationship between absorbance and concentration, with a limit of detection (LoD) of ~4 mmol/L in each fluid. The optical probe was fabricated using a 500 μm silver halide polycrystalline fiber aligned with a gold-coated short fiber, acting as a mirror, in a connector to maintain a predetermined distance between two fibers. The sample cavity was formed between the optical fiber and the gold-coated fiber. For performance optimization, optical back reflections were analyzed experimentally and numerically in fibers with end-face surfaces polished at varying angular deviations from the fiber axis. Experimental data were used to estimate and subtract back reflections from the detected signals to improve the signal-to-noise ratio (SNR) resulting in an LoD of 4 mmol/L for ethanol in synthetic solutions. The effects of optical pathlength and fiber end-face angle on probe’s performance were investigated, showing that a fiber with an end-face whose surface normal deviated by 10° from the fiber axis (averaged optical pathlength of 68 μm) achieved a 32.7% higher SNR compared to fiber with a surface normal aligned with the fiber axis (optical pathlength of 64 μm). This study is important for optimizing the sensor design, paving the way for advanced biomedical applications such as monitoring alcohol levels in tissues or detecting ethanol in various clinical scenarios.

Nanoporous silica waveguides can be used to improve the low sensitivity of near-infrared spectroscopic gas sensors by allowing the light propagating through the waveguide core to interact directly with molecules entering the pores. Here we report on a self-aligned fiber-to-waveguide configuration that offers a robust and cost-effective solution for coupling fibers to the nanoporous waveguide without the need for active alignment or expensive instrumentation. Our approach uses dedicated fiber-alignment structures next to the waveguide, fabricated at the same time as the waveguide, and made from the same material, thus eliminating the need for separate substrates, additional fabrication steps, and minimizing thermally induced optical misalignment. We present the optimized microfabrication process steps that allow for direct insertion of optical multimode silica fibers next to the multimode porous silica waveguide and provide structural and optical characterization. Gas sensing performance is evaluated using isopropyl alcohol vapor showing excellent sensitivity and detection limit of 1.76 ppm for a 10 mm long waveguide.

Selective detection of toxic volatile organics in the gas-phase is required for many applications. Here we report a novel optical waveguide for near infrared (NIR) spectroscopy for quantitative detection of volatile organic compounds (VOCs), enabling sensitive and selective measurements of multiple VOCs simultaneously. The adsorption of the VOC molecules inside the nanopores allows detection at a much lower concentration compared to traditional gas-cell detection, where infrared light propagates through the gaseous molecules in the free space. Results show that a 10 mm long porous core waveguide offers a significant enhancement in signal of 1800x per millimeter pathlength compared to a 400 mm long conventional gas-cell. Moreover, lowering the temperature of the waveguide facilitates increased adsorption of molecules inside the pores and maximizes the signal as demonstrated for gaseous toluene at four different concentrations. An increase in signal by a factor of 10 is observed as the temperature decreases from 70 to 10°C. At 10°C waveguide temperature, the limit of detection for toluene is 2.5 ppm. Additionally, we measured a binary mixture of toluene and 1-octene at different temperatures, showing the selectivity of the method. The combined effect of nanopore adsorption and temperature-assisted condensation allows for selective and sensitive on-chip detection of volatile organics. The proposed waveguide sensor technology has promising potential for industrial gas leak detection, air quality monitoring, and medical applications.

monitoring for chemical and biomedical applications.

Summary Kerogen constitutes a significant volume of organic-rich mudrocks (ORMs) and affects fluid flow in these tight rocks. However, its interaction in contact with formation and injected water is poorly understood, which can pose challenges in the quantification of hydrocarbon production and reserves, water production, and fracturing fluid flowback in ORMs. In this paper, we elucidate the physicochemical mechanisms governing kerogen-water interactions by measuring water adsorption and desorption isotherms using infrared (IR) spectroscopy methods. The results demonstrated that kerogen exhibits sorption-induced swelling behavior. The water adsorption isotherms revealed significant hysteresis and a sharp increase in adsorption at relative humidity (RH) levels above 60%. Water adsorption on kerogen disrupts hydrogen bonds between kerogen molecules, exposing additional binding sites and loosening the structure. This process facilitates the entry of subsequent water molecules, ultimately leading to the formation of water clusters. Swelling of kerogen molecules can potentially have significant impacts on the production strategies deployed in ORMs. For instance, exposure of the rocks to excess water during hydraulic fracturing can cause additional swelling and blockage of flow pathways. It can also potentially explain excessive water production in some ORM formations and can enhance the prediction of water production by honoring the thermal maturity and chemical structure of kerogen.

Abstract Rationale: A smart breath monitoring mask is designed to measure respiration by integrating advanced sensors and AI-driven algorithms. This portable and non-invasive device monitors key respiratory metrics in real-time, such as inspiratory and expiratory flow rate, tidal volume, vital capacity, end-tidal oxygen (O2), and carbon dioxide (CO2) levels. In COPD patients, compromised gas exchange and ventilation-perfusion imbalance can lead to hypoxic pulmonary vasoconstriction and hypercapnia, causing acid-base disorders and shifting the primary respiratory drive from CO2 to O2. This shift makes it crucial to monitor both gases to understand a patient's respiratory status to identify risks of hypoxia or hypercapnia and provide early intervention. Method: The mask is in the early stages of development at the Mechanical Engineering Department of the University of Texas at Austin. The mask is equipped with off-the-shelf sensors such as flow rate, CO2, O2, temperature and humidity, etc. Mask sensor data collected from a healthy volunteer at rest. The volunteer was instructed to breathe normally for 1 minute, hold breath for 30 seconds, and then breathe normally again. The same volunteer was then instructed to do 4 second box breathing (Figure) while wearing the mask and following a visual breathing animation. Result: Continuous real-time monitoring of multiple breathing parameters the enables monitoring of end tidal O2 and end-tidal CO2, humidity, and temperature change according to user's breathing pattern. Additionally, calculation of vital capacity, inspiratory & expiratory residual volume, inspiratory capacity and other metrics is possible. Conclusion: A wearable mask can be a useful approach for breath-by-breath analysis in COPD patients to gain deeper understanding of their breathing physiology. This device can also be used as a tool to monitor the breathing exercise routine in COPD patients to keep track of their progress and adjust their exercise routine based on the physiological response collected from this device.Ongoing work is focused on improving sensor performance, miniaturization and clinical testing to further explore the potential of this device in understanding breathing physiology through breath-by-breath analysis for COPD patients.

. A detection limit of 8.91 mM for glucose was achieved. The results highlight the potential of the proposed optical fiber probe for molecular detection and analysis, offering a promising solution for chemical and biomedical applications.

Abstract α-UO 3 is a common intermediate compound found in the nuclear fuel cycle, yet the exact crystal structure of this material has long been debated. Inconsistent computational and experimental data in previous works has led to varying conclusions between authors. To ensure the validity of our results in this work, the structural and spectroscopic signatures of pure phase α -UO 3 are investigated using powder X-ray diffraction and optical vibrational spectroscopy (infrared and Raman). Rietveld refinement of powder X-ray diffraction data on pure phase α -UO 3 collected in this work allows us to propose an alteration to the currently accepted C2mm structure (a = 3.9705 Å, b = 6.8553 Å, c = 4.15955 Å, α = β = γ = 90°) for α -UO 3 with no uranyl [UO 2 2+ ] bonds. Raman spectra collected using two excitation wavelengths (two instruments using 532 nm and one 785 nm) are presented, and differences with recently published results are discussed. Infrared spectra from two instruments used here agree well with recently published results, but the spectral range encompassed in our data extends past what has been reported with modern techniques. Additionally, we provide tentative vibrational mode assignments based on density functional perturbation theory calculations and resulting phonon eigenvector visualizations. Unexpected features in the optical vibrational spectra of α -UO 3 are explained by unique features in the structure we present.

for evaporation rate control. Theoretical calculations and experimental data were used to quantify device's performance and capabilities. Experiments conducted with deionized water and with aqueous glucose solutions demonstrate the device's capability to achieve up to a 10-fold concentration increase. The study also addresses potential issues such as analyte loss and the influence of various parameters like sweeping gas flow rates and liquid feeding rates on the concentration process. This work demonstrates the potential of the micro-3D printed device as a reliable and efficient method for sample concentration, critical for enhancing detection sensitivities for various applications such as bioassays and biosensors.

The unclear mechanisms of ethanol metabolism in the brain highlight the need for a deeper understanding of its metabolic pathways. This study used in vivo microdialysis to simultaneously sample ethanol and its metabolites, acetaldehyde and acetate, in the rat striatum following self-administration of ethanol, emphasizing the natural oral exposure route. To enhance the self-administration, rats underwent two-bottle-choice and limited access training. Dialysate samples, collected every 10 min for 2.5 h, were analyzed using gas chromatography with flame ionization detection (GC-FID). The measured time courses of dialysate concentrations of ethanol, acetaldehyde, and acetate provided insights into dynamics of ethanol metabolism. Notably, in a subject with low ethanol consumption (0.29 g/kg), the concentration of acetaldehyde remained below the limit of detection throughout the experiment. However, the acetate concentration was clearly increased after ethanol consumption in this subject and was comparable to that of other rats with higher ethanol consumption. Compared with focusing only on peak values in the time-courses of concentrations of ethanol and its metabolites, calculating areas under curves provided better models of the relationships between ethanol intake and individual ethanol metabolites, as indicated by the R-square values for the linear regressions. This approach of using the area under the curve accounts for both the amplitude and duration of the concentration profiles, reducing the impact of variations in individual drinking patterns. In vivo microdialysis enables concurrent sampling of brain metabolites during oral ethanol administration, contributing insights into metabolite dynamics. To our knowledge, this paper is the first to report measurement of all three analytes in the brain following self-administration of ethanol. Future studies will explore regional variations and dynamics post-ethanol dependence, further advancing our understanding of ethanol metabolism in the brain.

Sterilization of devices is important in hospitals, operating theatres, and emergency rooms. Microdialysis allows in vivo sampling of small molecules and is used for clinical studies. Microdialysis probes are made of soft, flexible, porous polymeric membranes. They have been traditionally disinfected using either ethanol (which fails to eliminate all microbes and doesn't satisfy regulatory requirements) or ethylene oxide gas and gamma irradiation (that are expensive and resource-intensive). In this work, three methods for microdialysis probe-sterilization were studied - autoclave and two chemicals (commercially available sterilization solutions): Sporox II and MetriCide. Following sterilization, the regenerated cellulose membranes were characterized under scanning electron microscopy and by measuring the changes in pore characteristics using nitrogen sorption. To determine the effect of sterilization on analyte diffusion through the membrane, microdialysis probes were fabricated, sterilized and tested with two analytes; ethanol and dopamine. The autoclaved membranes suffered thermo-mechanical damage and were deemed unfit for further testing. Probes sterilized with the chemical solutions were subsequently characterized by in vitro microdialysis experiments performed under regulated mass flux conditions. It is concluded that autoclaving is not a suitable sterilization technique for the cellulose membranes, while both of the chemical sterilizers were found to be good candidates for sterilization.

experimental results with numerical simulations enabled us to calculate diffusion coefficients of molecules in the microdialysis membranes and study the extent of the depletion effect caused by continuous microdialysis sampling, thus providing additional insights for probe selection and data interpretation.

Recent fatalities due to methanol and 1-propanol toxicity in alcohol-based hand sanitizers has led the U.S. Food and Drug Administration (FDA) to ban 594 different hand sanitizer brands. The FDA also introduced methanol testing in alcohol-based hand sanitizers before allowing the products to enter the United States This requirement creates a need for inexpensive, rapid, and portable testing methods to measure methanol and 1-propanol concentrations in alcohol-based hand sanitizers. Here we study the performance of infrared (IR) spectroscopy for measuring methanol and 1-propanol concentrations in an alcohol-based hand sanitizer, and compare the performance of two portable spectrometers, Texas Instruments near-infrared (NIR) spectrometer (TI NIR) and NeoSpectra mid-infrared (MIR) spectrometer. The IR absorbance spectra were measured in transmission mode at different path lengths for 52 different hand sanitizer samples spiked with 0%–1% v/v concentrations of methanol and 1-propanol. A partial least-squares regression analysis shows ability to detect contaminant concentrations with a correlation coefficient of determination ( r 2 ) up to 0.99 and root mean square error of prediction as low as 0.34% v/v.

With the increased demand for hand-held and ambient gas sensors, it is imperative to develop sensors that can offer both selective and sensitive detection. Gas preconcentration is a widely tried and tested method to increase the sensitivity of gas detectors. While it effectively lowers the limit of detection, it does not impact the selectivity of the detector. Therefore, preconcentrator materials have mostly been used in conjunction with selective detectors. In this work, we use the preconcentration method with a nonselective small and portable photoionization detector to introduce selectivity. For this purpose, we use a relatively slow heating rate, that allows for gradual desorption and analytes from the preconcentrator material–nanoporous silica. The characteristic desorption temperature of the volatile organic compounds (VOC) from the preconcentrator allows selective detection of the VOC. In this work, we study the effect of surface functionalization, to make it hydrophobic, and observe the adsorption–desorption behavior of polar (isopropyl alcohol) and non-polar (octane) gas molecules. The hydrophobic silica surface was found to improve the adsorption of non-polar octane, while it reduced the adsorption of polar isopropyl alcohol. The desorption temperature for isopropanol remained unchanged for both functionalized and non-functionalized preconcentrators; however, the desorption temperature for octane increased by 10 °C when the functionalized hydrophobic pSiO2 was used. We also observed the presence of humidity, a known interferent, did not heavily impact the sensing performance. These results are promising evidence that functionalized porous silica integrated with a photoionization detector can be used for selective gas detection in the ambient atmosphere.

microdialysis was performed on the mixture of the three compounds, and the collected sample was measured using IR to demonstrate the capability of quantifying the concentrations of the three analytes simultaneously. Lastly, to overcome the limitations of the microdialysis technique, direct measurement using evanescent-field IR spectroscopy can be a potential alternative. A hydrophobic polymer coating that adsorbs ethanol and excludes water, could improve sensitivity. Sorption kinetics in polymethyl methacrylate (PMMA) and polydimethylsiloxane (PDMS) coatings on an ATR crystal were measured. Both polymers demonstrate preferential adsorption of ethanol over water.

Introduction: Complex metabolic disruption is a major aspect of the pathophysiology of traumatic brain injury (TBI). Pyruvate is an intermediate in glucose metabolism and considered one of the most clinically informative metabolites during neurocritical care of TBI patients, especially in deducing the lactate/pyruvate ratio (LPR) - a widely-used metric for probing the brain's metabolic redox state. LPR is conventionally measured offline on a bedside analyzer, on hourly accumulations of brain microdialysate. However, there is increasing interest within the field to quantify microdialysate pyruvate and LPR continuously in near-real-time within its pathophysiological range. We have previously measured pure standard pyruvate in-vitro using mid-infrared transmission, employing a commercially available external cavity-quantum cascade laser (EC-QCL) and a microfluidic flow cell and reported a limit of detection (LOD) of 0.1 mM. Research question: The present study was to test whether the current commercially available state-of-the-art mid-infrared transmission system, can detect pyruvate levels lower than previously reported. Materials and methods: We measured pyruvate in perfusion fluid on the mid-infrared transmission system also equipped with an EC-QCL and microfluidic flow cells, tested at three pathlengths. Results: We characterised the system to extract its relevant figures-of-merit and report the LOD of 0.07 mM. Discussion and conclusion: The reported LOD of 0.07 mM represents a clinically recognised threshold and is the lowest value reported in the field for a sensor that can be coupled to microdialysis. While work is ongoing for a definitive evaluation of the system to measuring pyruvate, these preliminary results set a good benchmark and reference against which future developments can be examined.