Recent publications in Physical Sciences

Lei, Peng, Zhou, Ying, Zhu, Ruiqi, Liu, Yang, Dong, Chuan, and Shuang, Shaomin (2020) Novel strategy of electrochemical analysis of DNA bases with enhanced performance based on copper−nickel nanosphere decorated N,B−doped reduced graphene oxide. Biosensors and Bioelectronics, 147. 111735.
Design of suitable nanocomposites with tailored structures was significant in the fabrication of effective and reliable electrochemical sensors. Herein, the copper−nickel@nitrogen, boron−doped reduced graphene oxide (Cu–Ni@N,B−rGO) was successfully synthesized, which exhibited superior electrocatalytic performance towards guanine (G) and adenine (A) oxidation. The Cu–Ni NPs were sequentially decorated on N,B−rGO substrate via an environmentally friendly reduction strategy, which utilized glucose as reducer and stabilizing agent. The nanocomposites with large specific surface area, remarkable conductivity and high catalytic activity showed prominent synergistic effect owning to the uniform dispersion of Cu–Ni NPs on the surface of N,B−rGO. When applied to analysis of G and A using DPV, the wide linear ranges of 1.0–160.0 μM and 1.0–120.0 μM with the determination limits of 0.118 μM and 0.134 μM were obtained, respectively. The sensor was successfully applied to the detection of G and A in calf−thymus DNA with G/A ratio of 0.80. The facile preparation process and attractive sensing properties of the Cu–Ni@N,B−rGO nanocomposites made it a promising candidate for the development of advanced electrochemical sensor.

Zhu, Chengxi, Liu, Dong, Li, Yuye, Shen, Xiuli, Ma, Shuai, Liu, Yang, and You, Tianyan (2020) Ratiometric electrochemical aptasensor for ultrasensitive detection of Ochratoxin A based on a dual signal amplification strategy: engineering the binding of methylene blue to DNA. Biosensors and Bioelectronics, 150. 11814.
A novel ratiometric electrochemical aptasensor was developed for Ochratoxin A (OTA) detection based on the binding of methylene blue (MB) to DNA with a dual signal amplification strategy. The formation of dsDNA structures between ferrocene-labeled complementary DNA (Fc-cDNA), the OTA aptamer, and complementary helper DNA (hDNA) caused Fc away from the electrode, and allowed dsDNA to bind with a certain amount of MB. Here, a small oxidation current of Fc (IFc) and a large oxidation current of MB (IMB) were obtained. In the presence of OTA, its specific recognition with the aptamer induced the release of aptamer and hDNA from the electrode and subsequently the formation of hairpin structure for cDNA, which caused Fc close to the electrode and a weaker binding ability with MB. Then, an increased IFc and a decreased IMB were obtained. Based on this principle, OTA could be accurately quantified by measuring the ratiometric signal of IFc/IMB. Herein, the dual signal amplification strategy of the introduction of hDNA and the binding with MB after the OTA recognition was exploited to amplify the response signal. The obtained aptasensor showed a linear detection range from 10 pg mL1 to 10 ng mL1 and a detection limit of 3.3 pg mL1. The aptasensor was successfully applied to determine OTA in wheat, and the results were validated through HPLC-MS. Furthermore, by changing the target aptamers, this strategy could be universally used for the determination of various mycotoxins, showing prom-ising potential applications for mycotoxins monitoring in agricultural products and foods.

Li, Lin, Shi, Lihong, Jia, Jing, Jiao, Yuan, Gao, Yifang, Liu, Yang, Dong, Chuan, and Shuang, Shaomin (2020) “On-off-on” detection of Fe³⁺ and F⁻, biological imaging, and its logic gate operation based on excitation-independent blue-fluorescent carbon dots. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 227. 117716.
A fluorescent nanoprobe based on carbon dots (CDs) has been facilely synthesized by a one-step hydrothermal pyrolysis of salicylic acid and utilized for the sequential detection of Fe3+ and F− in vitro. The fluorescence of CDs can be extinguished dramatically by Fe3+ based on static quenching and subsequently recovery upon addition of F− due to the formation of stabler FeF3. The probe exhibits high selectivity and sensitivity toward Fe3+ and F− with a good linearity in the range of 10–300 μM and 0.1–200 μM, respectively, and a low detection limit of 52 nM and 8.5 nM, respectively. More importantly, as-prepared CDs with exceedingly fluorescence stability, negligible toxicity and superior biocompatibility have been expanded for detection Fe3+ and F− in living cell and Escherichia coli. Furthermore, an “AND” logic gate based on as-obtained CDs has been constructed.

Shen, Xiuli, Liu, Dong, Zhu, Chengxi, Li, Yuye, Liu, Yang, and You, Tianyan (2020) Photoelectrochemical and electrochemical ratiometric aptasensing: a case study of streptomycin. Electrochemistry Communications, 110. 106637.
There has been much interest in constructing ratiometric sensors using different sensing techniques because of their synergistic effect, although the simultaneous collection of the signals is challenging. Herein, we propose a ratiometric aptasensing strategy based on the dual-detection model with a photoelectrochemical (PEC) “signalon” and an electrochemical (EC) “signal-off”. As a proof-of-concept study, CdTe quantum dots (CdTe QDs) and a methylene blue-labeled aptamer (MB-Apt) were used to generate PEC and EC signals in the sensing system. The target-induced conformational change of MB-Apt pushed MB away from the electrode, thereby decreasing the EC signal; at the same time, the reduced steric hindrance favored the restoration of the PEC signal from the CdTe QDs. Thus, this PEC-EC strategy can achieve the PEC “signal-on” and EC “signal-off” states simultaneously, as well as allowing quantitative analysis of the target based on the ratio of the current intensities. As a model application, an aptasensor fabricated for streptomycin detection showed a wide linear range from 0.03 to 100 μM with a detection limit of 10 nM (S/N = 3). The proposed sensing platform displayed superior analytical properties compared with methods based on PEC or EC alone. Our work provides an efficient dual-detection modelbased ratiometric strategy for advanced analysis, and paves the way to the simultaneous acquisition of signals.

Li, Yuye, Liu, Dong, Zhu, Chengxi, Shen, Xiuli, Liu, Yang, and You, Tianyan (2020) Sensitivity programmable ratiometric electrochemical aptasensor based on signal engineering for the detection of aflatoxin B1 in peanut. Journal of Hazardous Materials, 387. 122001.
Accurately monitoring of aflatoxin B1 (AFB1), the most hazardous mycotoxin in agricultural products, is essential for the public health, but various testing demands (e.g. detection range, sensitivity) for different samples can be challenging for sensors. Here, we developed a sensitivity-programmable ratiometric electrochemical aptasensor for AFB1 analysis in peanut. Thionine functionalized reduced graphene oxide (THI-rGO) served as reference signal generator, ferrocene-labelled aptamer (Fc-apt) output the response signal. During analysis, the formation of Fc-apt-AFB1 complex led to its stripping from the electrode and faded the current intensity of Fc (IFc), while the current intensity of THI (ITHI) was enhanced. And ratiometric detection of AFB1 was achieved by using the current intensity ratio (ITHI/IFc) as quantitative signal. Compared with ratiometric strategies that highly rely on the labelled aptamers, the proposed strategy could regulate the value of ITHI/IFc by changing the modification of Fc-apt. And the detection sensitivity was found to be closely related to ITHI/IFc. Under the optimal conditions, the fabricated aptasensor with a dynamic range from 0.05–20 ng mL−1 and a detection limit of 0.016 ng mL−1 for AFB1 analysis. Besides, it exhibited excellent selectivity, reliability and reproducibility. The proposed sensitivity-programmable biosensor can be applied to detect various aptamer-recognized mycotoxins in agricultural sensing.

Mumtaz, Saira, Robertson, Mark J., and Oelgemöller, Michael (2019) Continuous flow photochemical and thermal multi-step synthesis of bioactive 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones. Molecules, 24 (24). 4527.
An effective multi-step continuous flow approach towards N-diaminoalkylated 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones, including the local anesthetic compound AL-12, has been realized. Compared to the traditional decoupled batch processes, the combined photochemical–thermal–thermal flow setup rapidly provides the desired target compounds in superior yields and significantly shorter reaction times.

Das, Sourav, and Tordesillas, Antoinette (2019) Near real-time characterization of spatio-temporal precursory evolution of a rockslide from radar data: integrating statistical and machine learning with dynamics of granular failure. Remote Sensing, 11 (23). 2777.
This study builds on fundamental knowledge of granular failure dynamics to develop a statistical and machine learning approach for characterization of a landslide. We demonstrate our approach for a rockslide using surface displacement data from a ground based radar monitoring system. The algorithm has three key components: (i) identification of a regime change point t0 marking the departure from statistical invariance of the global velocity field, (ii) characterization of the clustering pattern formed by the velocity time series at t0 , and (iii) classification of velocity patterns for t>t0 to deliver a measure of risk of failure from t0 and estimates of the time of emergent and imminent risk of failure. Unlike the prevailing approach of analysing time series data from one or a few chosen locations, we make full use of data from all monitored points on the slope (here 1803). We do not make a priori assumptions on the monitored domain and base our characterization of the complex spatial patterns and associated dynamics only from the data. Our approach is informed by recent developments in the physics and micromechanics of failure in granular media and is configured to accommodate additional data on landslide triggers and other determinants of landslide risk readily.

Brice, Sara M., Phillips, Elissa J., Millett, Emma L., Hunter, Adam, and Philippa, Bronson (2019) Comparing inertial measurement units and marker-based biomechanical models during dynamic rotation of the torso. European Journal of Sport Science. (In Press)
Inertial measurement units (IMUs) enable human movements to be captured in the field and are being used increasingly in high performance sport. One key metric that can be derived from IMUs are relative angles of body segments which are important for monitoring form in many sports. The purpose of this study was to a) examine the validity of relative angles derived from IMUs placed on the torso and pelvis; and b) determine optimal positioning for torso mounted sensors such that the IMU relative angles match closely with gold standard torso-pelvis and thorax-pelvis relative angle data derived from an optoelectronic camera system. Seventeen adult participants undertook a variety of motion tasks. Four IMUs were positioned on the torso and one was positioned on the pelvis between the posterior superior iliac spines. Reflective markers were positioned around each IMU and over torso and pelvis landmarks. Results showed that the IMUs are valid with the root mean square errors expressed as a percentage of the angle range (RMSE%) ranging between 1% and 7%. Comparison between the IMU relative angles and the torso-pelvis and thorax-pelvis relative angles showed there were moderate to large differences with RMSE% values ranging between 4% and 57%. IMUs are highly accurate at measuring orientation data; however, further work is needed to optimize positioning and modelling approaches so IMU relative angles align more closely with relative angles derived using traditional motion capture methods.

Guo, Zhifang, Luu, Jenny, Blair, Victoria, Deacon, Glen B., and Junk, Peter C. (2019) Replacing mercury: syntheses of lanthanoid pyrazolates from free lanthanoid metals, pentafluorophenylsilver, and pyrazoles, aided by a facile synthesis of polyfluoroarylsilver compounds. European Journal of Inorganic Chemistry, 2019 (7). pp. 1018-1029.
The polyfluorophenylsilver complexes [Ag-2(C6F4Br-4)(2)(py)(3)] (py = pyridine) (1) and [{Ag2R2(py)(2)}(n)] [R = C6F5 (2); C6F4Br-3 (3); C6F4H-4 (4)] were prepared in reasonable yields by reactions of silver(I) oxide with the appropriate polyfluorobenzenes in pyridine. This simple and convenient synthesis is selective and does not lead to debromination of C6HF4Br-(3 or 4). Complex 1 is dinuclear with AgR2 and Ag(py)(3) units linked by a bridging polyfluoroaryl group and Ag center dot center dot center dot Ag interactions, whereas 2-4 are polymeric with alternating AgR2 and Ag(py)(2) units similarly linked. The trivalent lanthanoid pyrazolates, [Ln(Ph(2)pz)(3)(py)(2)]center dot 2thf (Ph(2)pz = 3,5-diphenylpyrazolate; Ln = Yb, 5, Er, 6, Dy, 7, Lu, 8; thf = tetrahydrofuran), [Ho(Ph(2)pz)(3)(py)(thf)] (9), [Ln(Ph(2)pz)(3)(py)(dme)]center dot solv (Ln = Tb, solv = 1.75PhMe, 10, Gd, solv = 1.5dme, 11; dme = 1,2-dimethoxyethane; PhMe = toluene), [Ln(Ph(2)pz)(3)(thf)(3)] (Ln = La, 12, Ce, 13, Nd, 14), [Ln(tBu(2)pz)(3)(py)(2)] (tBu(2)pz = 3,5-di-tert-butylpyrazolate; Ln = Yb, 15, Tm, 16, Ho, 17, Dy, 18), [Yb(Phtpz)(3)(py)(2)]center dot PhMe (19) (Phtpz = 3-Phenyl-5-(2 '-thienyl)pyrazolate) and [Nd(ttfpz)(3)(dme)(2)] (20) (ttfpz = 3-(2 '-thienyl)-5-(trifluoromethyl)pyrazolate) have been prepared by redox transmetallation/protolysis (RTP) reactions employing lanthanoid metals, pentafluorophenylsilver and the corresponding pyrazoles (pzH) in donor solvents. This is a new synthetic route in which AgC6F5 replaces the more commonly used Hg(C6F5)(2) or HgPh2. Yields are good to excellent if long crystallization times are used but the heavier Ln metals require activation with iodine to induce reaction. The monomeric structures exhibit eta(2)-bound pyrazolate ligands with eight-coordinate metal atoms for complexes 5-9 and 15-19, nine-coordinate metal atoms for complexes 10-14, and ten-coordinate metal atoms for complex 20.

Hughes, Terry P., Kerry, James T., Connolly, Sean R., Baird, Andrew H., Eakin, C. Mark, Heron, Scott F., Hoey, Andrew S., Hoogenboom, Mia O., Jacobson, Mizue, Liu, Gang, Pratchett, Morgan S., Skirving, William, and Torda, Gergely (2019) Ecological memory modifies the cumulative impact of recurrent climate extremes. Nature Climate Change, 9 (1). pp. 40-44.
Climate change is radically altering the frequency, intensity and spatial scale of severe weather events, such as heat-waves, droughts, floods and fires(1). As the time interval shrinks between recurrent shocks(2-5), the responses of ecosystems to each new disturbance are increasingly likely to be contingent on the history of other recent extreme events. Ecological memory-defined as the ability of the past to influence the present trajectory of ecosystems(6,7)-is also critically important for understanding how species assemblages are responding to rapid changes in disturbance regimes due to anthropogenic climate change(2,3,6-8). Here, we show the emergence of ecological memory during unprecedented back-to-back mass bleaching of corals along the 2,300 km length of the Great Barrier Reef in 2016, and again in 2017, whereby the impacts of the second severe heatwave, and its geographic footprint, were contingent on the first. Our results underscore the need to understand the strengthening interactions among sequences of climate-driven events, and highlight the accelerating and cumulative impacts of novel disturbance regimes on vulnerable ecosystems.

Lawn, Julian A., and Kosov, Daniel S. (2019) Coupled elastic membranes model for quantum heat transport in semiconductor nanowires. European Physical Journal B: Condensed Matter and Complex Systems, 92 (2). 43.
Presented here is a nanowire model, consisting of coupled elastic membranes with the purpose of investigating thermal transport in quasi-one-dimensional quantum systems. The vibrations of each elastic membrane are quantized and the flow of the vibrational energy between adjacent membranes is allowed. The ends of the nanowire are attached to thermal baths held at different temperatures. We derived quantum master equation for energy flow across the nanowire and obtained thermal currents and other key observables. We study the effects of a disordered boundary on the thermal current by randomizing the membrane radii. We evaluate the model as a nanowire analogue as well as study the effects of a disordered boundary on thermal conductivity. The calculations show that the membrane lattice model demonstrates diameter phonon confinement and a severe reduction in thermal conductivity due to surface roughness which is characteristic of semiconductor nanowires. The surface roughness also produces a length dependence of the thermal conductivity of the form κ = αLβ, with β dependent on disorder characteristics, in the otherwise ballistic regime. Finally, the parameters of the model are fitted to available experimental data for silicon nanowires and the results of the calculations are assessed against the experimental data.

Kershaw, Vincent F., and Kosov, Daniel S. (2019) Non-equilibrium Green's function theory for non-adiabatic effects in quantum transport: inclusion of electron-electron interactions. Journal of Chemical Physics, 150. 074101.
Non-equilibrium Green's function theory for non-adiabatic effects in quantum transport [Kershaw and Kosov, J. Chem. Phys. 147, 224109 (2017) and J. Chem. Phys. 149, 044121 (2018)] is extended to the case of interacting electrons. We consider a general problem of quantum transport of interacting electrons through a central region with dynamically changing geometry. The approach is based on the separation of time scales in the non-equilibrium Green's functions and the use of the Wigner transformation to solve the Kadanoff-Baym equations. The Green's functions and correlation self-energy are non-adiabatically expanded up to the second order central time derivatives. We produce expressions for Green's functions with non-adiabatic corrections and a modified formula for electric current; both depend not only on instantaneous molecular junction geometry but also on nuclear velocities and accelerations. The theory is illustrated by the study of electron transport through a model single-resonant level molecular junction with local electron-electron repulsion and a dynamically changing geometry.

Bryan, Allana, Doran, Greg, Flakelar, Clare, Howitt, Julia, Oelgemoeller, Michael, and Shields, Linda (2019) Clinical waste - a major environmental burden. Australian Hospital and Healthcare Bulletin, Summer. pp. 14-16.
[Extract] When we examine the effects of waste on our lives and the environment, one type of waste is often overlooked: hospital waste confers a huge impact on the environment and a potential threat to human health. This study examined the volume of waste from an Australian hospital's operating theatres.

Harvell, C. D., Montecino-Latorre, D., Caldwell, J. M., Burt, J. M., Bosley, K., Keller, A., Heron, S. F., Salomon, A. K., Lee, L., Pontier, O., Pattengill-Semmens, C., and Gaydos, J. K. (2019) Disease epidemic and a marine heat wave are associated with the continental-scale collapse of a pivotal predator (Pycnopodia helianthoides). Science Advances, 5. eaau7042.
Multihost infectious disease outbreaks have endangered wildlife, causing extinction of frogs and endemic birds, and widespread declines of bats, corals, and abalone. Since 2013, a sea star wasting disease has affected > 20 sea star species from Mexico to Alaska. The common, predatory sunflower star (Pycnopodia helianthoides), shown to be highly susceptible to sea star wasting disease, has been extirpated across most of its range. Diver surveys conducted in shallow nearshore waters (n = 10,956; 2006-2017) from California to Alaska and deep offshore (55 to 1280 m) trawl surveys from California to Washington (n = 8968; 2004-2016) reveal 80 to 100% declines across a similar to 3000-km range. Furthermore, timing of peak declines in nearshore waters coincided with anomalously warm sea surface temperatures. The rapid, widespread decline of this pivotal subtidal predator threatens its persistence and may have large ecosystem-level consequences.

Malara, Danilo, Høj, Lone, Oelgemoeller, Michael, Malerba, Martino, Citarrella, Gabriella, and Heimann, Kirsten (2019) Sensitivity of live microalgal aquaculture feed to singlet oxygen-based photodynamic therapy. Journal of Applied Phycology, 31 (6). pp. 3593-3606.
Highly nutritional microalgal species are extensively used in aquaculture as live feedstock. Due to difficulties in maintaining microalgae in axenic conditions, they represent a potential pathogen carrier and disease vector in aquaculture ponds. Photodynamic therapy (PDT) via singlet oxygen (1O2) production is a promising sterilization technique in aquaculture. Here, we report on the sensitivity of aquaculture-relevant microalgae towards 1O2 generated by the cationic photosensitizer TMPyP. Possible PDT sterilization protocols of contaminated microalgae cultures were evaluated using the luminescent bacterium Vibrio campbellii ISO7 as a model aquaculture pathogen. Species specific sensitivity of microalgae to TMPyP-mediated PDT was demonstrated and found to be strongly influenced by the nature and architecture of their respective cell wall. While cytotoxicity was not evident against Nannochloropsis oculata, toxicity of 1O2 was dose-, time- and light activation-dependent against Tisochrysis lutea, Tetraselmis chui, Chaetoceros muelleri and Picochlorum atomus. The 1O2-resilient N. oculata was sterilized when incubated under light in the presence of V. campbellii ISO7 (up to 107 CFU mL−1) and 20 μM TMPyP; hence, TMPyP based PDT sterilization of N. oculata could be suitable for aquaculture hatcheries. This study also suggests that PDT using cationic porphyrins such as TMPyP holds potential as an algicidal treatment in aquaria and aquaculture systems (but more research using opportunistic and toxic species is needed for confirmation).

Werner, Daniel, Deacon, Glen B., and Junk, Peter C. (2019) Trapping CS₂²⁻ and S₃²⁻ between two ytterbium formamidinates. Inorganic Chemistry, 58 (3). pp. 1912-1918.
Treatment of [YbII(DippForm)2(thf)n] (n = 2 (1aYb), n = 1 (1bYb); DippForm = N,N′-bis(2,6-diisopropylphenyl)formamidinate), with either excess CS2 or S8 gives [YbIII2(DippForm)4(CS2)] (3) and [YbIII2(DippForm)4(S2)0.5/(S3)0.5] (4) respectively. 3 is a new addition to an exclusive class of compounds containing the CS22− dianion, and 4 is the first crystallographically characterized example of a rare-earth trisulfide complex.

Olsen, Alex, Konovalov, Dmitry A., Philippa, Bronson, Ridd, Peter, Wood, Jake, Johns, Jamie, Banks, Wesley, Girgenti, Benjamin, Kenny, Owen, Whinney, James, Calvert, Brendan, Rahimi Azghadi, Mostafa, and White, Ronald D. (2019) DeepWeeds: a multiclass weed species image dataset for deep learning. Scientific Reports, 9. 2058.
Robotic weed control has seen increased research of late with its potential for boosting productivity in agriculture. Majority of works focus on developing robotics for croplands, ignoring the weed management problems facing rangeland stock farmers. perhaps the greatest obstacle to widespread uptake of robotic weed control is the robust classification of weed species in their natural environment. the unparalleled successes of deep learning make it an ideal candidate for recognising various weed species in the complex rangeland environment. This work contributes the first large, public, multiclass image dataset of weed species from the Australian rangelands; allowing for the development of robust classification methods to make robotic weed control viable. The DeepWeeds dataset consists of 17,509 labelled images of eight nationally significant weed species native to eight locations across northern Australia. This paper presents a baseline for classification performance on the dataset using the benchmark deep learning models, Inception-v3 and ResNet-50. These models achieved an average classification accuracy of 95.1% and 95.7%, respectively. We also demonstrate real time performance of the ResNet-50 architecture, with an average inference time of 53.4 ms per image. These strong results bode well for future field implementation of robotic weed control methods in the Australian rangelands.

de Bruin-Dickason, Caspar N., Deacon, Glen B., Jones, Cameron, Junk, Peter C., and Wiecko, Michal (2019) Functionalised alkaline earth iodides from Grignard synthons "PhAeI(thf)ₙ" (Ae = Mg‐Ba). European Journal of Inorganic Chemistry, 2019 (7). pp. 1030-1038.
Derivatisation of Grignard synthons "PhAeI(thf)(n)" (Ae = Mg-Ba) prepared in situ from reactions of metal filings and iodobenzene provides a one-pot synthesis of heteroleptic N donor alkaline earth iodide complexes. Protolysis of "PhAeI(thf)(n)" with 3,5-diphenylpyrazole (Ph(2)pzH) yields pyrazolate complexes [Mg-2(mu-Ph(2)pz)(2)(I)(2)(thf)(3)] (1), [Ae(Ph(2)pz)(I)(thf)(4)] (Ae = Ca (2), Sr (3)), and [Ba-2(Ph(2)pz)(2)(mu-I)(2)(thf)(8)] (4). Addition of the Ae-Ph moiety to carbodiimide MesN=C=NMes (Mes = 2,4,6-(CH3)(3)C6H2) gave a series of benzamidinate iodide complexes [Ca-2{(MesN)(2)CPh}(2)(mu-I)(2)(thf)(4)] (6), [Sr{(MesN)(2)CPh}(I)(thf)(4)] (7), and [{Ba{(MesN)(2)CPh}(mu-I)(thf)(3)}(infinity)] (8). By contrast a symmetrical magnesium complex [Mg{(MesN)(2)CPh}(2)(thf)] (5) was obtained by Schlenk redistribution. These syntheses proceed without pre-activation of the metal for strontium and barium, and after activation with 2 mol-% iodine for calcium. The heavy alkaline earth metal complexes are the first examples of heteroleptic halide pyrazolate or amidinate complexes for strontium and barium. Complexes 1, 3, 4 and 6-8 were characterised crystallographically, revealing diverse structural chemistry of heteroleptic amidinate and pyrazolate iodide complexes across the alkaline earth series. A highlight is [Ba{(MesN)(2)CPh}(mu-I)(thf)(3)](infinity) (8) - an iodide bridged infinite 1-D polymer.

Sanderson, Stephen, Philippa, Bronson, Vamvounis, George, Burn, Paul L., and White, Ronald D. (2019) Understanding charge transport in Ir(ppy)₃:CBP OLED films. Journal of Chemical Physics, 150 (9). 094110.
Ir(ppy)₃:CBP blends have been widely studied as the emissive layer in organic light emitting diodes (OLEDs), yet crucial questions about charge transport within the layer remain unaddressed. Recent molecular dynamics simulations show that the Ir(ppy)₃ molecules are not isolated from each other, but at concentrations of as low as 5 wt. % can be part of connected pathways. Such connectivity raises the question of how the iridium(iii) complexes contribute to long-range charge transport in the blend. We implement a kinetic Monte Carlo transport model to probe the guest concentration dependence of charge mobility and show that distinct minima appear at approximately 10 wt. % Ir(ppy)₃ due to an increased number of trap states that can include interconnected complexes within the blend film. The depth of the minima is shown to be dependent on the electric field and to vary between electrons and holes due to their different trapping depths arising from the different ionization potentials and electron affinities of the guest and host molecules. Typical guest-host OLEDs use a guest concentration below 10 wt. % to avoid triplet-triplet annihilation, so these results suggest that optimal device performance is achieved when there is significant charge trapping on the iridium(iii) complex guest molecules and minimum interactions of the emissive chromophores that can lead to triplet-triplet annihilation.

Bloomfield, Keith J., Prentice, I. Colin, Cernusak, Lucas A., Eamus, Derek, Medlyn, Belinda E., Rumman, Rizwana, Wright, Ian J., Boer, Matthias M., Cale, Peter, Cleverly, James, Egerton, John J.G., Ellsworth, David S., Evans, Bradley J., Hayes, Lucy S., Hutchinson, Michael F., Liddell, Michael J., Macfarlane, Craig, Meyer, Wayne S., Togashi, Henrique F., Wardlaw, Tim, Zhu, Lingling, and Atkin, Owen K. (2019) The validity of optimal leaf traits modelled on environmental conditions. New Phytologist, 221 (3). pp. 1409-1423.
The ratio of leaf intercellular to ambient CO2 (χ) is modulated by stomatal conductance (gs). These quantities link carbon (C) assimilation with transpiration, and along with photosynthetic capacities (Vcmax and Jmax) are required to model terrestrial C uptake. We use optimization criteria based on the growth environment to generate predicted values of photosynthetic and water‐use efficiency traits and test these against a unique dataset. Leaf gas‐exchange parameters and carbon isotope discrimination were analysed in relation to local climate across a continental network of study sites. Sun‐exposed leaves of 50 species at seven sites were measured in contrasting seasons. Values of χ predicted from growth temperature and vapour pressure deficit were closely correlated to ratios derived from C isotope (δ13C) measurements. Correlations were stronger in the growing season. Predicted values of photosynthetic traits, including carboxylation capacity (Vcmax), derived from δ13C, growth temperature and solar radiation, showed meaningful agreement with inferred values derived from gas‐exchange measurements. Between‐site differences in water‐use efficiency were, however, only weakly linked to the plant's growth environment and did not show seasonal variation. These results support the general hypothesis that many key parameters required by Earth system models are adaptive and predictable from plants' growth environments.

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