School of Chemistry - Research Publications
Now showing items 1-12 of 467
Stretching vibration is a spectator in nucleophilic substitution
(AMER ASSOC ADVANCEMENT SCIENCE, 2018-07-01)
How chemical reactions are influenced by reactant vibrational excitation is a long-standing question at the core of chemical reaction dynamics. In reactions of polyatomic molecules, where the Polanyi rules are not directly applicable, certain vibrational modes can act as spectators. In nucleophilic substitution reactions, CH stretching vibrations have been considered to be such spectators. While this picture has been challenged by some theoretical studies, experimental insight has been lacking. We show that the nucleophilic substitution reaction of F- with CH3I is minimally influenced by an excitation of the symmetric CH stretching vibration. This contrasts with the strong vibrational enhancement of the proton transfer reaction measured in parallel. The spectator behavior of the stretching mode is supported by both quasi-classical trajectory simulations and the Sudden Vector Projection model.
Volatile chemical emissions from fragranced baby products
(SPRINGER INTERNATIONAL PUBLISHING AG, 2018-08-01)
Fragranced consumer products have been associated with adverse effects on human health. Babies are exposed to a variety of fragranced consumer products, which can emit numerous volatile organic compounds (VOCs), some considered potentially hazardous. However, fragranced baby products are exempt from disclosure of all ingredients. Consequently, parents and the public have little information on product emissions. This study investigates VOCs emitted from a range of fragranced baby products, including baby hair shampoos, body washes, lotions, creams, ointments, oils, hair sprays, and fragrance. The products were analysed using gas chromatography/mass spectrometry (GC/MS) headspace analysis. Of the 42 baby products tested, 21 products made claims of green, organic, or all-natural. Results of the analysis found 684 VOCs emitted collectively from the 42 products, representing 228 different VOCs. Of these 684 VOCs, 207 are classified as potentially hazardous under federal regulations, representing 43 different VOCs. The most common VOCs emitted were limonene, acetaldehyde, ethanol, alpha-pinene, linalool, beta-myrcene, acetone, and beta-pinene. A comparison between ingredients emitted and ingredients listed reveals that only 5% of the 684 VOCs, including 12% of 207 potentially hazardous VOCs, were listed on the product label, safety data sheet, or website. More than 95% of both green and regular products emitted one or more potentially hazardous VOCs. Further, emissions of the most prevalent VOCs from green, organic, or all-natural products were not significantly different from regular products. Results from this study can help improve public awareness about emissions from baby products, with the aim to reduce pollutant exposure and potential adverse effects on babies.
An Fe(iii)-doped coordination polymer of Mn-13-clusters with improved activity for the oxygen reduction reaction
(ROYAL SOC CHEMISTRY, 2019-04-21)
Fe(iii) dopants have been introduced into a porous coordination polymer of Mn13-clusters to form composite materials. The resulting Fe@Mn13-polymer showed enhanced oxygen reduction reaction (ORR) activity, making it a low-cost and noble-metal-free ORR electrocatalyst.
Ultrathin Ni(II)-based coordination polymer nanosheets as a co-catalyst for promoting photocatalytic H-2-production
(ROYAL SOC CHEMISTRY, 2019-06-11)
Ni(ii) coordination polymer nanosheets (Ni-CPNS) were prepared via a top-down liquid ultrasonication exfoliation method. For the first time, Ni-CPNS was used as a co-catalyst (Ni-CPNS@CdS) via a mechanical grinding strategy. The optimized Ni-CPNS@CdS catalyst reached a super high visible-light photocatalytic hydrogen production activity of 10 210 μmol h-1 g-1, exceeding that of bare CdS nanoparticles by 1480%. Our work can open new avenues towards the design of stable and cheap CPNS co-catalysts to replace expensive and rare noble metals for photocatalysis processes.
Ni (II)-Doped Anionic Metal-organic Framework Nanowire Arrays for Enhancing Oxygen Evolution Reaction
(Royal Society of Chemistry, 2019)
Herein, an anionic metal-organic framework nanowire array not only directly grew on Cu foam, but also captured Ni(ii) ions at an ultra-small particle level. The hybrid material exhibited high activity with low overpotential (310 mV at 20 mA cm-2 in 1.0 M KOH solution) toward the oxygen evolution reaction (OER) (1 M KOH), with performance comparable to that of the precious metal benchmark. These findings may expand the field of MOFs for scaled-up water electrolysis.
Ni(II)-based coordination polymers for efficient electrocatalytic oxygen evolution reaction
(ROYAL SOC CHEMISTRY, 2018-01-01)
The exploration of highly efficient, stable and cheap water oxidation electrocatalysts using earth-abundant elements is still a great challenge. Herein, alkaline-stable cationic Ni(ii) coordination polymers (Ni-CPs) were successfully obtained under hydrothermal conditions, which could stabilize the incorporation of Fe(iii) to form Fe-immobilized Fe@Ni-CPs. The newly developed Ni-based CPs were used for the first time as an effective electrocatalyst for the oxygen evolution reaction in strong alkaline media.
A Mn13-cluster based coordination polymer as a co- catalyst of CdS for enhanced visible- light driven H2 evolution
(ROYAL SOC CHEMISTRY, 2018-08-28)
A coordination cluster-based polymer was used for the first time as a noble-metal-free co-catalyst of CdS, giving rise to significantly enhanced photocatalytic H2 production. This work demonstrates the feasibility of cluster materials in assembling highly-active and low-priced photocatalysts.
Connecting Titanium-Oxo Clusters by Nitrogen Heterocyclic Ligands to Produce Multiple Cluster Series with Photocatalytic H-2 Evolution Activities
(AMER CHEMICAL SOC, 2017-07-01)
We herein demonstrate the ability of nitrogen heterocyclic ligands in connecting polyoxotitanium complexes into crystalline multiple cluster series. Moreover, their bandgap and photocatalytic water-splitting behavior were studied. The highest H2 evolution activity reaches up to 42.80 μmol g-1 h-1 for PTC-46.
Improving the photocatalytic H-2 evolution activities of TiO2 by modulating the stabilizing ligands of the nanoscale Ti8O8-cluster precursors
(PERGAMON-ELSEVIER SCIENCE LTD, 2017-09-28)
Titanium-oxo clusters (TOCs) are important model complexes and potential precise single-source precursors of TiO2 materials. We report here a series of TiO2 samples derived from TOCs with the same wheel-like Ti8O8 clustercore but different stabilizing ligands. Our results demonstrate that the ligands on TOCs not only influence the phase-transition during themolysis, but more importantly tune the photocatalytic H2 evolution activities of the obtained TiO2 materials. Through 500 °C calcination, the nanosized Ti8O8 cluster stabilized by organic benzoate ligands gives rise to a TiO2 sample with H2 production rate of 611 μmol/h/g. When the stabilizing ligands are changed to inorganic SO42−, a significant improvement of H2 evolution activity has been achieved, resulting in a 7-times higher value of 4527 μmol/h/g. This work provides a new strategy to produce TiO2 with enhanced and tunable photocatalytic activities from titanium-oxo cluster precursors.
Influence of structure-activity relationships on through-space intervalence charge transfer in metal-organic frameworks with cofacial redox-active units
(ROYAL SOC CHEMISTRY, 2019-02-07)
Understanding charge transfer in redox-active metal-organic frameworks (MOFs) is of fundamental importance given the potential of these materials to be used in myriad applications including porous conductors, electrocatalysts and battery materials, amongst others. An important challenge is quantifying the spectroscopic features of these materials in order to elucidate their charge transfer properties. Herein, two topologically related Zn(ii) and Cd(ii) frameworks, [Zn2(DPPTzTz)2(SDC)2] (1-Zn) and [Cd2(DPPTzTz)2(SDC)2] (2-Cd) (where DPPTzTz = 2,5-bis(4-(4-pyridinyl)phenyl)thiazolo[5,4-d]thiazole and SDC = selenophene-2,5-dicarboxylate), incorporating cofacially stacked pairs of redox-active DPPTzTz ligands are presented. The differences in the through-space intervalence charge transfer properties of the mixed-valence forms of the two frameworks generated upon solid state spectroelectrochemical reduction are quantified using Marcus-Hush theory. Further, charge transfer theory is applied to calculate electron mobilities in both extended framework systems. A larger electronic coupling constant, Hab, of 118 cm-1 corresponding to an electron mobility, k, of 6.02 × 108 s-1 was observed for the Zn(ii) analogue compared to the Cd(ii) analogue (Hab = 61.2 cm-1 and k = 2.22 × 108 s-1) and was correlated primarily with the larger cofacial stacking distance and increasingly offset stacking geometry between DPPTzTz ligands in the latter. Establishing structure-activity relationships in electroactive MOFs, in addition to methods for quantifying their charge transfer properties, represents an important advance in fine tuning solid state materials for device applications.
An investigation into per- and polyfluoroalkyl substances (PFAS) in nineteen Australian wastewater treatment plants (WWTPs)
(ELSEVIER SCI LTD, 2019-08-01)
Quantifying the emissions of per- and polyfluoroalkyl substances (PFAS) from Australian wastewater treatment plants (WWTP) is of high importance due to potential impacts on receiving aquatic ecosystems. The new Australian PFAS National Environmental Management Plan recommends 0.23 ng L-1 of PFOS as the guideline value for 99% species protection for aquatic systems. In this study, 21 PFAS from four classes were measured in WWTP solid and aqueous samples from 19 Australian WWTPs. The mean ∑21PFAS was 110 ng L-1 (median: 80 ng L-1; range: 9.3-520 ng L-1) in aqueous samples and 34 ng g-1 dw (median: 12 ng g-1 dw; range: 2.0-130 ng g-1 dw) in WWTP solids. Similar to WWTPs worldwide, perfluorocarboxylic acids were generally higher in effluent, compared to influent. Partitioning to solids within WWTPs increased with increasing fluoroalkyl chain length from 0.05 to 1.22 log units. Many PFAS were highly correlated, and PCA analysis showed strong associations between two groups: odd chained PFCAs, PFHxA and PFSAs; and 6:2 FTS with daily inflow volume and the proportion of trade waste accepted by WWTPs (as % of typical dry inflow). The compounds PFPeA, PFHxA, PFHpA, PFOA, PFNA, and PFDA increased significantly between influent and final effluent. The compounds 6:2 FTS and 8:2 FTS were quantified and F-53B detected and reported in Australian WWTP matrices. The compound 6:2 FTS was an important contributor to PFAS emissions in the studied Australian WWTPs, supporting the need for future research on its sources (including precursor degradation), environmental fate and impact in Australian aquatic environments receiving WWTP effluent.