Division of Chemistry

Epsilon near zero (ENZ) materials have potential in various applications such as all-optical switching and quantum information. Materials that support ENZ modes include metamaterials, semiconductors, and transparent conducting oxides (TCOs) like indium tin oxide (ITO). ITO supports an ENZ mode in the near-infrared (IR), giving rise to large nonlinearities and enabling strong optically induced changes in its refractive index. Recently, a perovskite TCO, La-doped BaSnO3 (LBSO) has demonstrated wide tunability of the ENZ wavelength ranging from the near IR to mid-IR regions. In this work, we use a reflective gold layer to access the Ferrell-Berreman (FB) mode of LBSO, a special class of leaky optical mode that occurs at the material’s ENZ wavelength. The FB mode has strong extinction, making it an ideal candidate for reflection modulation. Here, we interrogate the charge carrier dynamics of multiple Au-coated LBSO samples with varying ENZ wavelengths, paying special attention to the tuning behavior of the FB mode. We find that, upon UV excitation, injected charge carriers are long-lived compared to other transparent conducting oxides and that the photoexcited carriers induce strong modulation of the FB mode. This Au-coated LBSO shows promise for infrared optical switching applications, especially those requiring high thermal stability.

A redox-active tetrapyrazinoporphyrazine ligand was used as a platform for the design of multimetallic coordination complexes. The first paramagnetic homo- and heterotrimetallic complexes have been obtained as crystals through the reaction of iron(II) octaethyltetrapyrazinoporphyrazine, FeII(Et8TPyzPz), with 3d- (FeII, CoII) and 4f-metal (DyIII) iodides. In these conditions, tetrapyrazinoporphyrazine can coordinate to metals to form exo- and endocyclic complexes when coordination is observed both in the center and on the periphery of a macrocycle. Crystal structures of the complexes have been determined from single-crystal X-ray diffraction analysis, and their compositions are {TBA+}2[FeIII2(Et8TPyzPz)·(FeIII2)2]2– (1), {TBA+}2[FeIII2(Et8TPyzPz)·(CoIII2)2]2– (2), and {TBA+}2[FeIII2(Et8TPyzPz)·(DyIIII3)2]2– ·4C6H4Cl2 (3). The central iron(II) atom forms four shorter N–Fe bonds (1.917(3)–1.927(3) Å) and two longer I–Fe bonds (2.68 Å).Two exocyclic metal iodides are coordinated to the periphery of the Et8TPyzPz macrocycle. The iron(II) and cobalt(II) atoms are tetracoordinated when inserted into the N2-pockets to form both M–Nmeso and M–Npyrazine bonds of 2.14 and 2.24 Å for Fe(II) and 2.10 and 2.16 Å for Co(II), respectively. The exocyclic Dy ions, when introduced into the N3-pockets to form the Dy–N bonds of 2.43 and 2.66–2.75 Å, respectively, have distorted octahedral geometry. Optical and magnetic properties of the solids were investigated. The [FeIII2(Et8TPyzPz)2–·(MIx)2]2– units contain a low-spin diamagnetic central Fe(II) ion and high-spin exocyclic FeII, CoII, and DyIII nuclei. Exocoordinated metal ions are antiferromagnetically coupled through the diamagnetic {FeIII2(Et8TPyzPz)}2– unit. The Soret and the Q-bands are observed in the spectra of starting {FeII(Et8TPyzPz)} and complexes 1–3 at 336–348and 645–655nm, supporting preservation of the Et8TPyzPz2– macrocycle at complex formation. At the same time, broad and intense bands appear at 495–526 nm in the visible range, and lower-energy bands are observed near the Q-band at 700 nm. The latter bands can be attributed to metal-to-macrocycle charge transfer (CT) in 1–3. CT is supported by DFT calculations.

Simulating chemical reactions on quantum computers has the potential to offer insight that cannot be gained practically from conventional quantum-chemical approaches on classical computers. This is because quantum computing provides a platform for efficient, high-level electronic structure calculations that approach the full configuration interaction (FCI) limit. Herein we apply the cascaded variational eigensolver (CVQE) algorithm to simulate the unimolecular dissociation of fluoromethane (CH3F) by two pathways: (1) CH3F → CH2 + HF and (2) CH3F → CHF + H2. We compare the results of CVQE calculations on the ibm_torino quantum computer to Hartree-Fock and FCI calculations on a classical computer. Our results suggest that quantum computing with CVQE can provide high-level electronic structure information for chemical reactions and other cases that require the simulation of multiple geometries.

Antimony oxide is a common synergist for brominated aromatic flame retardants. These are combined in plastic housings for electronics from televisions to computers, as well as plastics used in transportation vehicles such as automobiles, ships and aircraft. Antimony is deemed a critical metal that is insufficiently mined to meet demands; hence, routes for its recovery are essential. Conventional pyrolysis results in substantial antimony loss and toxic emissions, whereas solvent-based recycling relies on time-consuming and hazardous sequential steps of debromination followed by antimony recovery. Here, we introduce isothermal-clamped flash Joule heating (IC-FJH), which generates a spatially isothermal reaction zone and enables simultaneous debromination and Sb recovery within seconds. Ultrafast isothermal heating stabilizes Sb predominantly as the metal, achieving a recovery yield of ~90% and a purity of >97%, reducing losses from vapor-phase transport and from residual solids. At the same time, IC-FJH achieves deep debromination, reducing toxic brominated organic species by 34 to 51%, compared to slow heating conditions. The toxic brominated organics were converted into inorganic streams, predominantly forming HBr with 83% recovery. By life-cycle assessment, IC-FJH reduces resource consumption by 72%, climate change burdens by 65%, water use by 80%, and polycyclic aromatic hydrocarbon formation by 100% compared to conventional pathways. Overall, IC-FJH offers a viable route for the sustainable recovery of antimony and the end-of-life management of e-waste, while advancing cleaner production and a circular economy.

The free energy of hydrogen adsorption (ΔGH) is a key descriptor for hydrogen evolution reaction (HER) kinetics in acids, although it is often limited in explaining facet- and strain-dependent catalytic activity. Here, we investigate the role of tensile strain on Pt(111) surfaces, focusing on the competitive adsorption between hydrogen and water. Combining computational and experimental studies, we demonstrate that tensile strain enhances hydrogen and water adsorption, resulting in the 1.3-fold enhancement in exchange current density compared to unstrained Pt(111). Our findings suggest that the ΔGH-based HER trends may not fully capture the influence of interfacial factors under structural deformation.

MXene quantum dots (QDs) have emerged as a promising class of zero-dimensional nanomaterials, attracting growing attention due to their remarkable physicochemical properties. Niobium carbide QDs (Nb2C QDs), derived from two-dimensional (2D) Nb2CTx, is a rising material with great potential in optical applications. Herein, nitrogen-doped Nb2C QDs (N–Nb2C QDs) were synthesized via sonication-assisted hydrothermal treatment. The obtained N–Nb2C QDs exhibit blue fluorescence with excitation-dependent emission. We developed a fluorescent sensor enabling N–Nb2C QDs for visual and quantitative detection of tetracycline (TC) antibiotics. The blue fluorescence of N–Nb2C QDs can be quenched by TC through static quenching and inner filter effect (IFE). The synergistic effect of both static quenching and IFE caused by TC makes the developed fluorescence sensor have a linear range for TC from 0.25 to 6.50 μM with a detection limit of 30.2 nM and a significant fluorescence color change from blue to cyan-green. Due to the simplicity and recognizable color change, a machine learning based approach was employed to determine the TC concentration from a visual fluorescence image. A convolutional neural network (CNN) architecture was used for the regression analysis. The model shows a strong predictive performance, achieving a coefficient of determination (R2) of 0.966, which reflects a high level of accuracy in estimating the TC concentrations.

Life on Earth is predominately based upon a single chirality set, but so-called “mirror life” - speculated life of the opposite chirality, either of artificial or natural origin - presents a low-likelihood, but high severity global biosecurity threat. Such an existential risk necessitates that technologies for surveillance and containment of mirror life are developed as a contingency. In this perspective, we propose a method for screening against mirror life hazards via an optical chirality assay, based upon circularly polarized luminescence (CPL) generated either via achiral fluorophores (via supramolecular chirality effects) or intrinsically chiral molecular probes. When bound to biological molecules, CPL-generating probes enable Enantioselective Differential Chiral Contrast (EDCC) imaging to verify chirality of a biological specimen. We set out why a multi-reporter panel approach – incorporating many CPL generating fluorescent/luminescent complexes – in conjunction with testing on conventional life’s chirality set, would be necessary to avoid false positives, and thereby screen against mirror life with a high degree of confidence. The all-optical approach could be deployed via recently innovated optical technologies, i.e. rapid CPL spectroscopy, CPL EDCC microscopes, and CPL EDCC cameras. We envisage that this CPL-based approach to screening against mirror life could be a useful tool for safeguarding against mirror life biohazards in a complimentary manner to any future legislative controls.

Secondary organic aerosol (SOA) formation from α-pinene ozonolysis has been widely studied owing to its important contribution to atmospheric organic aerosol. Many new mechanistic insights have been reported recently, diversifying potential α-pinene ozonolysis SOA formation pathways. However, our ability to integrate these mechanisms and kinetically simulate α-pinene ozonolysis SOA formation has not been fully evaluated. In this work, we updated the detailed α-pinene ozonolysis mechanism in the Master Chemical Mechanism (MCM) with processes including peroxy radical (RO2) unimolecular autoxidation and bimolecular reactions with HO2 and RO2, the fates of alkoxy radicals (RO), gas-particle partitioning, and condensed-phase dimer ester formation. A kinetic model was built to evaluate the new mechanism along with existing mechanisms in simulations of SOA mass concentrations and chemical composition. Uncertainties of key parameters such as reaction rate constants, product yields and volatilities, and gas-particle partitioning coefficients are tested to demonstrate the gaps in current understandings of the α-pinene ozonolysis mechanism. Our results suggest that uncertainties in MCM reactions, RO2 autoxidation, RO2 + RO2 dimerization kinetics, as well as the gas-particle partitioning parameters, all significantly impact α-pinene ozonolysis SOA simulations. Although the SOA mass concentrations can be well predicted by tuning the parameters within reasonable ranges, all models overestimate the SOA oxygen-to-carbon ratios and peroxide fractions, indicating unrecognized pathways. By comprehensively analyzing these uncertainties and gaps, this work provides new insights for future α-pinene ozonolysis mechanistic studies.