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Item Variations in crystals of flufenamic acid of its methyl and tert-butyl analogues as impurities as determined by partial dissolutions(Royal Society of Chemistry, 2024-11-22) Bourke, Timothy; Chiarella, Renato A.; Moynihan, Humphrey A.; Irish Research Council; Science Foundation IrelandAchieving specified levels of impurities is one the key goals of crystallisation processes in manufacturing. The mode of impurity incorporation and the variation of impurity levels throughout crystal batches are key factors affecting the performance of crystallisations in terms of achieving purity specifications. Evaluation of the distribution of impurities in crystals of flufenamic acid (FFA) using a controlled partial dissolution approach is described. 2-(3-Tolylamino)benzoic acid (MeFA) and 2-((3-(tert-butyl)phenyl)amino)benzoic acid (tBuFA), analogues of FFA in which the trifluoromethyl group has been replaced by a methyl group or by a tert-butyl group respectively, were selected as the impurities. Thermal analysis suggests formation of a solid solution between FFA and MeFA isostructural to FFA form III. The stepwise dissolution approach was initially demonstrated on samples of pure FFA crystals and was then extended to evaluate the distribution of levels of MeFA and tBuFA impurities. The impurity levels are shown as varying with dissolution midpoint. Stepwise dissolution was usefully applied to FFA crystal of various morphologies, while for crystals with extremely needle-like morphology, a segmentation analysis approach was more practical. The work presented outlines a method for evaluating the distribution of impurities in crystalline materials using commonly available analytical and particle sizing methods.Item Rapid and high-precision cavity-enhanced spectroscopic measurement of HONO and NO2: Application to emissions from heavy-duty diesel vehicles in chassis dynamometer tests and in mobile monitoring(Elsevier B.V., 2025-12-16) Wang, Meng; Liu, Wenyang; Ding, Xiang; Liu, Tao; Zhou, Wenxin; Lou, Shengrong; Venables, Dean S.; Varma, Ravi; Huang, Cheng; Chen, Jun; National Natural Science Foundation of China; National Key Research and Development Program of China; Science Foundation IrelandNitrous acid (HONO) is crucial in atmospheric chemistry as it is a major precursor for hydroxyl radicals (OH), the dominant atmospheric oxidant. Hydroxyl radicals are essential in the formation of secondary air pollutants like ozone and particulate matter. This study presents a newly developed Incoherent Broadband Cavity Enhanced Absorption Spectroscopy (IBBCEAS) system for precise and rapid measurements of HONO and nitrogen dioxide (NO2) emissions. The instrument's optical cavity (formed by two mirrors separated by 96 cm and with reflectivity of 0.99955 at 378 nm) resulted in an effective optical path length of 1.4 km. With an integration time of 5 s, the 1σ measurement precisions for HONO and NO2 were 0.19 ppb and 0.48 ppb with overall measurement uncertainties of 10 % and 7 %, respectively. Comparative analysis of the IBBCEAS and a commercial cavity-attenuated phase shift (CAPS) systems under non-emission conditions demonstrated excellent agreement (slope = 1.01 and R2 = 0.98). The instrument was applied to study HONO and NO2 emissions from heavy-duty vehicles in chassis dynamometer tests and mobile monitoring. Chassis dynamometer tests revealed that HONO and NO2 emissions depend strongly on vehicle speed and driving conditions. We find a HONO/NOX ratio of 1.01 × 10−2 across the entire China-World Transient Vehicle Cycle (C-WTVC) driving cycle. Mobile monitoring in urban areas shows emission characteristics similar to those observed in chassis dynamometer tests. Frequent acceleration-deceleration patterns of diesel vehicles under congested traffic conditions lead to higher HONO and NO2 emissions compared to driving under steady speed conditions. Improving traffic flow conditions will help reduce HONO and NO2 emissions.Item Exploring the crystal landscape of mandelamide and chiral resolution via cocrystallization(American Chemical Society, 2025) Huang, Shan; Fitzgerald, Deirbhile; Koledoye, Samuel A.; Collins, Stuart G.; Maguire, Anita R.; Lawrence, Simon E.; Science Foundation Ireland; Irish Research CouncilThe crystal structures of (±)-mandelamide, S-mandelamide, and enantioenriched mandelamide (94 S : 6 R) were determined. Diastereomeric cocrystal pairs of S-mandelamide with both enantiomers of mandelic acid and proline were synthesized. The diastereomeric cocrystal pairs of S-mandelamide with S/R-mandelic acid form 1:1 cocrystals in each case, while the diastereomeric cocrystal pairs of S-mandelamide with proline have different stoichiometries. Preliminary investigation of this diastereomeric cocrystal system for chiral resolution shows promise.Item Pseudo molecular doping and ambipolarity tuning in si junctionless nanowire transistors using gaseous nitrogen dioxide(Wiley, 2024) Vardhan, Vaishali; Biswas, Subhajit; Ghosh, Sayantan; Tsetseris, Leonidas; Ghoshal, Tandra; Hellebust, Stig; Georgiev, Yordan M.; Holmes, Justin D.; Horizon 2020Ambipolar transistors facilitate concurrent transport of both positive (holes) and negative (electrons) charge carriers in the semiconducting channel. Effective manipulation of conduction symmetry and electrical characteristics in ambipolar silicon junctionless nanowire transistors (Si-JNTs) is demonstrated using gaseous nitrogen dioxide (NO2). This involves a dual reaction in both p- and n-type conduction, resulting in a significant decrease in the current in n-conduction mode and an increase in the p-conduction mode upon NO2 exposure. Various Si-JNT parameters, including “on”-current (Ion), threshold voltage (Vth), and mobility (µ) exhibit dynamic changes in both the p- and n-conduction modes of the ambipolar transistor upon interaction with NO2 (concentration between 2.5 – 50 ppm). Additionally, NO2 exposure to Si-JNTs with different surface morphologies, that is, unpassivated Si-JNTs with a native oxide or with a thermally grown oxide (10 nm), show distinct influences on Ion, Vth, and µ, highlighting the effect of surface oxide on NO2-mediated charge transfer. Interaction with NO2 alters the carrier concentration in the JNT channel, with NO2 acting as an electron acceptor and inducing holes, as supported by Density Functional Theory (DFT) calculations, providing a pathway for charge transfer and “pseudo” molecular doping in ambipolar Si-JNTs.Item Nanowood: a unique natural nanomaterial that can be obtained using household chemicals(ACS Publications, 2024) Nedrygailov, Ievgen; O’Brien, Darragh.; Monaghan, Scott; Hurley, Paul K.; Biswas, Subhajit; Holmes, Justin D.; Department of Agriculture, Food and the Marine, Ireland; Horizon 2020At the nanometer scale, electrolyte solutions behave differently compared to their bulk counterparts. This phenomenon forms the basis for the field of nanofluidics, which is dedicated to studying the transport of fluids within and around objects with dimensions of less than 100 nm. Despite the increasing importance of nanofluidics for a wide range of chemical and biochemical applications, the ability to study this field in undergraduate laboratories remains limited due to challenges associated with producing suitable nanoscale objects. This article outlines a straightforward procedure, using easily accessible materials and chemical reagents, to create nanofluidic membranes, called nanowood, containing channels with diameters less than 100 nm. We describe the fabrication process of nanofluidic channels in wood and demonstrate the presence of these nanochannels based on conductance measurements using electrochemical impedance spectroscopy.