Robert J. O'Reilly

Glassy carbon electrodes (GCEs) have gained increased attention for the sensitive electrochemical detection of heavy metals due to their excellent chemical stability, wide potential window, and good electrical conductivity. These characteristics make GCEs an effective platform for sensor development. In particular, nanomaterial-modified GCEs have emerged as a promising strategy, offering enhanced sensitivity, selectivity, and faster response compared to conventional analytical techniques. This review summarizes recent advances over the past five years in the use of GCEs modified with chemically synthesized nanoparticles for the simultaneous detection of multiple heavy metal ions, including cadmium, lead, mercury, and chromium. It also includes how quantum chemical methods have aided our understanding of these phenomena. Heavy metals pose significant environmental and public health risks, with well-documented neurological, cardiovascular, reproductive, and carcinogenic effects, highlighting the need for accurate and rapid monitoring methods. Regulatory limits established by organizations such as the World Health Organization and the Environmental Protection Agency further emphasize the demand for highly sensitive detection technologies. This review examines the fundamental properties of GCEs, common nanomaterial modification techniques, and their application in multi-ion detection systems. Key advantages such as cost-effectiveness, portability, and adaptability to diverse sample matrices are highlighted. Current challenges, including electrode fouling, selectivity, and matrix interference, are also addressed, along with future perspectives for improving GCE-based sensors for real-world environmental monitoring.

Carbazole-based molecules play a significant role in dye-sensitized solar cells (DSSCs) due to their advantageous properties. Carbazole derivatives are known for their thermal stability, high hole-transport capability, electron-rich (p-type) characteristics, elevated photoconductivity, excellent chemical stability, and commercial availability. This review focuses on DSSCs, including their structures, working principles, device characterization, and the photovoltaic performance of carbazole-based derivatives. Specifically, it covers compounds such as 2,7-carbazole and indolo[3,2-b]carbazole, which are combined with various acceptors like benzothiadiazole, thiazolothiazole, diketopyrrolopyrrole, and quinoxaline, as reported over the past decade. The review will also outline the relationship between molecular structure and power-conversion efficiencies. Its goal is to summarize recent research and advancements in carbazole-based dyes featuring a D-π-A architecture for DSSCs. Additionally, this review addresses the evolution of carbazole-based hole-transport materials (HTMs), which present a promising alternative to the costly spiro-OMeTAD. We explore the development of novel HTMs that leverage the unique properties of carbazole derivatives to enhance charge transport, stability, and overall device performance. By examining recent innovations and emerging trends in carbazole-based HTMs, we provide insights into their potential to reduce costs and improve the efficiency of DSSCs.

We herein report successful syntheses of both nickel cobalt sulfide (NCS) and its composite with zeolite (NCS@Z) using a solvothermal method. Techniques such as EDX analysis, SEM, and molar ratio determination were used for product characterization. The incorporation of NCS significantly changed the surface roughness and active sites of the zeolite, improving the efficiency of methylene blue degradation and its reusability, especially under UV irradiation. In comparing the pseudo-first order rates, the highest degradation efficiency of methylene blue was achieved with NCS-2@Z, having a degradation extent of 91.07% under UV irradiation. This environmentally friendly approach offers a promising solution for the remediation of methylene blue contamination in various industries.

This article investigates the environmentally friendly synthesis and characterization of carbon dots (CDs) derived from soybean biomass, in conjunction with their composites containing potassium chloride (KCl) or zeolite. By using an environmentally sustainable synthetic approach, this study sought to unlock the potential of these materials for various applications. The physicochemical properties of the CDs and composites were comprehensively analyzed using various techniques including scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. In addition, various optical properties such as UV–Vis absorption, band gap, and excitation–emission behavior were investigated. A key finding to arise from this study was that the inclusion of a doping agent such as KCl or zeolite significantly reduced the size of the resulting CDs. In this light, whereas the undoped species are associated with average sizes of 8.86 ± 0.10 nm, those doped with either zeolite or KCl were associated with average sizes of 3.09 ± 0.05 and 2.07 ± 0.05 nm, respectively. In addition, it was shown that doping with either zeolite or KCl resulted in an alteration of the elemental composition of the CDs and influenced their optical properties, especially their excitation-dependent emission. These promising results point to potential applications in environmental sensing and energy-related fields.

In this study, the gas-phase homolytic P–F and P–Cl bond dissociation energies (BDEs) of a set of thirty fluorophosphine (R¹R²P–F) and thirty chlorophosphine-type (R¹R²P–Cl) molecules have been obtained using the high-level W2 thermochemical protocol. For the R¹R²P–F species, the P–F BDEs (at 298 K) differ by up to 117.0 kJ mol⁻¹, with (H₃Si)₂P–F having the lowest BDE (439.5 kJ mol⁻¹) and F₂P–F having the largest BDE (556.5 kJ mol⁻¹). In the case of the chlorophosphine-type molecules, the difference in BDEs is considerably smaller (i.e., 72.6 kJ mol⁻¹), with (NC)₂P–Cl having the lowest P–Cl BDE (299.8 kJ mol⁻¹) and (HO)₂P–Cl having the largest (372.4 kJ mol⁻¹). We have further analyzed the effect of substituents in governing the P–F and P–Cl BDEs by considering the effect of substituents in the parent halogenated precursors (using molecule stabilization enthalpies) and the effect of substituents in the product radicals (using radical stabilization enthalpies). Finally, we have also assessed the performance of a wide range of DFT methods for their ability to compute the gas-phase P–F and P–Cl BDEs contained in this dataset. We find that, overall, the double hybrid functional DSD-PBEB95 offers the best performance for both bond types, with mean absolute deviations of just 2.1 (P–F BDEs) and 2.2 (P–Cl BDEs) kJ mol⁻¹.

Fluoroborane-type molecules (R¹R²B–F) are of interest in synthetic chemistry, but to date, apart from a handful of small species (such as H₂BF, HBF₂, and BF₃), little is known concerning the effect of substituents in governing the strength of the B–F bonds of such species toward homolytic dissociation in the gas phase. In this study, we have calculated the bond dissociation enthalpies (BDEs) of thirty unique B–F bonds at the CCSD(T)/CBS level using the high-level W1w thermochemical protocol. The B–F bonds in all species considered are very strong, ranging from 545.9 kJ mol⁻¹ in (H₂B)₂B–F to 729.2 kJ mol⁻¹ HBF₂. Nevertheless, these BDEs still vary over a wide range of 183.3 kJ mol⁻¹. The structural properties that affect the BDEs are examined in detail, and the homolytic BDEs are rationalized based on molecule stabilization enthalpies and radical stabilization enthalpies. Since polar B–F bonds may represent a challenging test case for density functional theory (DFT) methods, we proceed to examine the performance of a wide range of DFT methods across the rungs of Jacob′s Ladder for their ability to compute B–F BDEs. We find that only a handful of DFT methods can reproduce the CCSD(T)/CBS BDEs with mean absolute deviations (MADs) below the threshold of chemical accuracy (i.e., with average deviations below 4.2 kJ mol⁻¹). The only functionals capable of achieving this feat were (MADs given in parentheses): ωB97M-V (4.0), BMK (3.5), DSD-BLYP (3.8), and DSD-PBEB95 (1.8 kJ mol⁻¹).

We report that bifunctional moleculescontaining hydroxyl and carbonylfunctional groups can undergo an effective transfer hydrogenationvia an intramolecular proton-coupled hydride transfer (PCHT) mechanism.In this reaction mechanism, a hydride transfer between two carbonatoms is coupled with a proton transfer between two oxygen atoms viaa cyclic bond rearrangement transition structure. The coupled transferof the two hydrogens as H & delta;+ and H & delta;- is supported by atomic polar tensor charges. The activation energyfor the PCHT reaction is strongly dependent on the length of the alkylchain between the hydroxyl and carbonyl functional groups but relativelyweakly dependent on the functional groups attached to the hydroxyland carbonyl carbons. We investigate the PCHT reaction mechanism usingthe Gaussian-4 thermochemical protocol and obtain high activationenergy barriers (& UDelta;H (& DDAG;) (298)) of 210.5-228.3 kJ mol(-1) for chainlengths of one carbon atom and 160.2-163.9 kJ mol(-1) for chain lengths of two carbon atoms. However, for longer chainlengths containing 3-4 carbon atoms, we obtain & UDelta;H (& DDAG;) (298) values as low as 101.9kJ mol(-1). Importantly, the hydride transfer betweentwo carbon atoms proceeds without the need for a catalyst or hydridetransfer activating agent. These results indicate that the intramolecularPCHT reaction provides an effective avenue for uncatalyzed, metal-freehydride transfers at ambient temperatures.

We obtain gas-phase homolytic Al–H bond dissociation enthalpies (BDEs) at the CCSD(T)/CBS level for a set of neutral aluminium hydrides (which we refer to as the AlHBDE dataset). The Al–H BDEs in this dataset differ by as much as 79.2 kJ mol-1, with (H2B)2Al–H having the lowest BDE (288.1 kJ mol-1) and (H2N)2Al–H having the largest (367.3 kJ mol-1). These results show that substitution with at least one –AlH2 or –BH2 substituent exerts by far the greatest effect in modifying the Al–H BDEs compared with the BDE of monomeric H2Al–H (354.3 kJ mol-1). To facilitate quantum chemical investigations of large aluminium hydrides, for which the use of rigorous methods such as W2w may not be computationally feasible, we assess the performance of 53 density functional theory (DFT) functionals. We find that the performance of the DFT methods does not strictly improve along the rungs of Jacob’s Ladder. The best-performing methods from each rung of Jacob’s Ladder are (mean absolute deviations are given in parentheses): the GGA B97-D (6.9), the meta-GGA M06-L (2.3), the global hybrid-GGA SOGGA11-X (3.3), the range-separated hybrid-GGA CAM-B3LYP (2.1), the hybrid-meta-GGA ?B97M-V (2.5) and the double-hybrid methods mPW2-PLYP and B2GP-PLYP (4.1 kJ mol-1).

The relative free energies of the isomers formed upon N-chlorination of each nitrogen atom within the DNA nucleobases (adenine, guanine, and thymine) have been obtained using the high-level G4(MP2) composite ab initio method (the free energies of the N-chlorinated isomers of cytosine have been reported at the same level of theory previously). Having identified the lowest energy N-chlorinated derivatives for each nucleobase, we have computed the free energies associated with chlorine transfer from N-chlorinated nucleobases to other unsubstituted bases. Our results provide quantitative support pertaining to the results of previous experimental studies, which demonstrated that rapid chlorine transfer occurs from N-chlorothymidine to cytidine or adenosine. The results of our calculations in the gas-phase reveal that chlorine transfer from N-chlorothymine to either cytosine, adenine, or guanine proceed via exergonic processes with ΔG ^o values of −50.3 (cytosine), −28.0 (guanine), and −6.7 (adenine) kJ mol^–1. Additionally, we consider the effect of aqueous solvation by augmenting our gas-phase G4(MP2) energies with solvation corrections obtained using the conductor-like polarizable continuum model. In aqueous solution, we obtain the following G4(MP2) free energies associated with chlorine transfer from N-chlorothymine to the three other nucleobases: −58.4 (cytosine), −26.4 (adenine), and −18.7 (guanine) kJ mol^–1. Therefore, our calculations, whether in the gas phase or in aqueous solution, clearly indicate that chlorine transfer from any of the N-chlorinated nucleobases to cytosine provides a thermodynamic sink for the active chlorine. This thermodynamic preference for chlorine transfer to cytidine may be particularly deleterious since previous experimental studies have shown that nitrogen-centered radical formation (via N–Cl bond homolysis) is more easily achieved in N-chlorinated cytidine than in other N-chlorinated nucleosides.

This study reports accurate gas-phase homolytic B–Cl bond dissociation energies, obtained using the benchmark-quality W1w thermochemical protocol, for a set of 25 chloroborane-type molecules (known herein as the BCl25BDE dataset). The BDEs of these species differ by as much as 136.5 kJ mol^-1 at 298 K, with (BH₂)₂BCl having the lowest BDE (388.5 kJ mol^-1 at 298 K) and (CH₃)HBCl having the highest (525.1 kJ mol^-1 ). Using the W1w BDEs as reference values, the accuracy of a diverse set of more economical DFT procedures (which may be applied to the study of molecules sufficiently large that the use of benchmark-quality methods such as W1w is rendered computationally prohibitive) have been investigated. As a result of this analysis, the most accurate methods for the computation of B–Cl BDEs are ωB97/A'VQZ (MAD = 3.0 kJ mol^-1 ) and M06/A'VTZ (MAD = 3.2 kJ mol^-1 ). The double-hybrid functional DSD-PBEP86 in conjunction with the A'VQZ basis set (MAD = 4.0 kJ mol^-1 ) was found to give the lowest largest deviation (LD = 6.4 kJ mol-1 ) of any of methods considered in this assessment study.