Chemistry - Journal Articles
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Item Isothioureas as coupling partners in P–S bond formation through cross-dehydrogenative coupling(American Chemical Society (ACS), 2025-12-19) Courtney, Eimear; Reber, Gian L.; Liasiuk, Nikita; Jones, David J.; Research IrelandIsothioureas have been demonstrated as practical sulfur donors for mild, one-pot P–S bond formation. Treatment with piperidine releases thiolate, which undergoes aerobic oxidation to the corresponding disulfide. Subsequent cross-dehydrogenative coupling with phosphine oxides affords phosphinothioates and related compounds in high yields. The method proceeds under air, tolerates diverse organophosphorus functional groups, and avoids malodorous reagents or external oxidants, providing an efficient and operationally simple route to P–S-containing organophosphorus compounds.Item Ion-selective transport in surface-modified cellulose membranes for aqueous ionic thermoelectrics(Royal Society of Chemistry (RSC), 2025-09-02) Ashokan, Anjali; Rahme, Kamil; Palanisamy, Rupa Ranjani; Padmanathan, N.; Razeeb, Kafil M.; Biswas, Subhajit; Holmes, Justin D.; Higher Education Authority; Horizon 2020Efficient recovery of low-grade heat (≤100 °C) remains a significant challenge in sustainable energy conversion. Here, we report a strategy to enhance ionic thermoelectric performance in biocompatible regenerated cellulose (RC) membranes by tailoring their surface charge. Surface functionalisation was achieved using two oppositely charged organic moieties: 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) to introduce carboxyl groups, and 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHMAC) to graft quaternary ammonium functionalities. This work presents the first direct, side-by-side comparison of oppositely charged surface functional groups, carboxyl (TEMPO) and quaternary ammonium (CHMAC), on ionic thermoelectric behaviour in cellulose membranes. These modifications significantly increased the fixed surface charge density, promoting ion selectivity and enabling efficient ion transport under a thermal gradient. CHMAC-functionalised RC membranes exhibited the highest performance, with a Seebeck coefficient of +6.1 mV K−1 in a stacked membrane configuration using 0.1 mM HCl electrolyte, representing a tenfold enhancement compared to unmodified RC membranes. Correspondingly, ionic conductivity increased by up to 950-fold, with an ionic thermoelectric power factor of 1.38 μW m−1 K−2. This study establishes a clear link between surface charge engineering and thermodiffusion-enhanced ionic transport in RC membranes, offering a scalable and sustainable route for harvesting low-grade thermal energy using green, aqueous systems.Item Microneedle-based electrochemical sensors for real-time pH and sodium monitoring in physiological environments(Elsevier B.V., 2025-03-14) Rahman, Fahima; Ryan, Adam; Bocchino, Andrea; Galvin, Paul; Rodrigues Teixeira, Sofia; Research IrelandThis study proposes developing microneedle (MN) sensors for pH and sodium detection. MNs are minimally invasive, miniaturized needles capable of piercing the stratum corneum to access dermal interstitial fluid (ISF). They can offer accessible, quick, and precise point-of-care diagnostics, potentially replacing centralized laboratory testing. The study uses electrochemical techniques for sensor modification, detection, and in-vitro characterizations. This work aimed to create and validate a polymer-based disposable microneedle patch for future transdermal electrochemical sensing. Successful potentiometric sensor development for pH detection using SiOx as passivation layers with IrOx functionalization was demonstrated. Additionally, voltametric sodium sensors were achieved with ARcare passivation and PEDOT functionalization. Both pH and Na+ sensors exhibited linear responses within normal physiological levels across various solutions. The pH sensors showed sensitivity of −60.5 mV/pH and an accuracy of 97.7 % alongside an error margin of 2.3 %, while sodium sensors achieved a sensitivity of 3.29 nA/mM/mm2. Both sensors exhibit dynamic, rapid responses, along with good repeatability, stability, and selectivity. Over a twenty-one-day span for pH sensors and a fourteen-day period for sodium sensors, this study offers validation that microneedles serve as a viable foundation for wearable systems, enabling real-time, multiparameter biosensing of interstitial fluids.Item Ammonia sensing via pseudo molecular doping in uv-activated ambipolar silicon nanowire transistors(ACS American Chemical Society, 2025) Vardhan, Vaishali; Biswas, Subhajit; Tsetseris, Leonidas; Ghosh, Sayantan; Echresh, Ahmad; Hellebust, Stig; Huebner, Rene; Georgiev, Yordan M.; Holmes, Justin D.; Horizon 2020The potential of adsorbed gaseous molecules to create shallow electronic states for thermally excited charge carrier transport and to engineer silicon transistor properties has been largely overlooked compared to traditional substitutional impurities. This paper successfully modifies the electrical properties of ambipolar silicon junctionless nanowire transistors (Si-JNTs) using the reducing properties of ammonia (NH3) for selective detection. Physisorption of NH3 induces a dual response in both p- and n-type conduction channels of ambipolar Si-JNTs, significantly altering current and key parameters, including the “on” current (Ion), threshold voltage (Vth), and mobility (μ). NH3 interaction increases conduction in the n-channel and decreases it in the p-channel, acting as an electron donor and hole trap, as supported by Density Functional Theory (DFT) calculations. This provides a pathway for charge transfer and ″pseudo″ molecular doping in ambipolar Si-JNTs. This NH3-mediated molecular doping and conduction modulation in Si transistor enabled, for the first time, the electrical detection of gaseous NH3 at room temperature across a wide concentration range (200 ppb to 50 ppm), achieving high sensitivity (200 ppb) and precise selectivity under ultraviolet (UV) light. UV illumination dynamically modulates current and reveals distinct sensing features in the p- and n-channels of the dual-responsive Si-JNTs. The ambipolar Si-JNT sensor exhibits a fast response time of 1.91 min for 0.8 ppm of NH3 in the hole conduction channel and a high sensitivity of 80% for 0.8 ppm of NH3 in the electron conduction channel. This dual-channel approach optimizes sensor performance by leveraging the most responsive parameters from each channel. Furthermore, the ambipolarity of Si-JNTs broadens the parameter space for developing a multivariate calibration model, enhancing the selectivity of Si-JNT sensors for NH3 detection.Item Heterogeneous Fenton-type oxidative degradation of low-density polyethylene to valuable acid products using a nanostructured Fe–CeO2 solid solution catalyst(Royal Society of Chemistry, 2025-01-02) Breen, Rachel; Holmes, Justin D.; Collins, Gillian; Science Foundation IrelandThe chemical conversion of waste plastic polymers to useful commodity chemicals has become crucial to helping tackle the issue of global plastic waste today. Polyolefins maintain the highest production rate and lowest recycling rate worldwide due to their inert chemical structures. This work shows the synthesis of solid-solution Fe–CeO2 catalyst as an excellent heterogeneous catalyst for Fenton-type oxidative degradation of low-density polyethylene to achieve high yields of organic acids. The catalyst was synthesized in 3 molar ratios of Fe : Ce and it was found that the molar ratio of iron and cerium was crucial for catalytic performance with the Fe–CeO2 1 : 1 catalyst giving the highest yields of acid products. The catalyst achieved 91% mass loss and 71% organic acid at pH 7, with 1 wt% catalyst loading. The use of a multi-metal Fenton system resulted in a synergistic effect, displaying superior activity to systems with only one Fenton active metal. The heterogeneous nature of the catalyst allowed for easy recovery and demonstrated excellent recyclability in multiple cycles. The high recyclability performance was attributed to the stability of the solid solution structure.