Solution processed graphene structures for perovskite solar cells

Organometallic trihalide perovskite light absorber based solar cells have drawn increasing attention because of their recent rapid increase in power conversion efficiency (PCE). These photovoltaic cells have relied significantly on transparent conducting oxide (TCO) electrodes which are costly and brittle. Herein, solution processed transparent conductive graphene films (TCGFs) are utilized, for the first time, as an alternative to traditional TCO electrodes at the electron collecting layer in perovskite solar cells (PSCs). By investigating and optimizing the trade-off between transparency and sheet resistance (Rs) of the graphene films, a PCE of 0.62% is achieved. This PCE is further improved to 0.81% by incorporating graphene structures into both compact and mesoporous TiO2 layers of the solar cell. We anticipate that the present study will lead to further work to develop graphene-based transparent conductive electrodes for future solar cell devices

Methanol Tolerant Oxygen Reduction Reaction electrocatalysis using Size-Specific Triphenylphosphine-Ligated Gold Nanoclusters

Version of record online: June 7, 2022The development of a stable and efficient Oxygen Reduction Reaction (ORR) electrocatalysts with high methanol tolerance is crucial for Direct Methanol Fuel Cells (DMFCs). Herein, triphenylphosphine (PPh3)-ligated gold nanoclusters and complexes (AuNCs), Au101(PPh3)21Cl5, Au9(PPh3)8(NO3)3, and Au1(PPh3)Cl supported on reduced graphene oxide (rGO) have been explored as methanol tolerant ORR electrocatalysts. Electrocatalytic performance of each AuNCs-rGO was determined through linear sweep voltammograms (LSV) and cyclic voltammetry (CV) and compared with Pt/C. Size-dependent ORR activity was observed which followed the size trend of Au101NC-rGO>Au9NC-rGO>Au1NC-rGO. Repeated LSV and chronoamperometry measurements revealed that the long-term stability over 24 hours followed the trend Au101NC-rGO>Au9NC-rGO∼Au1NC-rGO and all were more stable than Pt/C. The methanol tolerance of each AuNCs-rGO was also evaluated via LSV and CV. Size-independent methanol tolerance with no noticeable change in ORR performance of AuNCs-rGO was observed in the presence of methanol. AuNCs-rGO nanocomposites are promising cathode electrocatalysts for DMFCs.Hanieh Mousavi, Shailendra K. Sharma, Vladimir Golovko, Cameron J. Shearer, and Gregory F. Meth

Graphene Bridge for Photocatalytic Hydrogen Evolution with Gold Nanocluster Co-Catalysts

Published: 17 October 2022Herein, the UV light photocatalytic activity of an Au101NC-AlSrTiO3-rGO nanocomposite comprising 1 wt% rGO, 0.05 wt% Au101(PPh3)21Cl5 (Au101NC), and AlSrTiO3 evaluated for H2 production. The synthesis of Au101NC-AlSrTiO3-rGO nanocomposite followed two distinct routes: (1) Au101NC was first mixed with AlSrTiO3 followed by the addition of rGO (Au101NC-AlSrTiO3:rGO) and (2) Au101NC was first mixed with rGO followed by the addition of AlSrTiO3 (Au101NC-rGO:AlSrTiO3). Both prepared samples were annealed in air at 210 °C for 15 min. Inductively coupled plasma mass spectrometry and high-resolution scanning transmission electron microscopy showed that the Au101NC adhered almost exclusively to the rGO in the nanocomposite and maintained a size less than 2 nm. Under UV light irradiation, the Au101NC-AlSrTiO3:rGO nanocomposite produced H2 at a rate 12 times greater than Au101NC-AlSrTiO3 and 64 times greater than AlSrTiO3. The enhanced photocatalytic activity is attributed to the small particle size and high loading of Au101NC, which is achieved by non-covalent binding to rGO. These results show that significant improvements can be made to AlSrTiO3-based photocatalysts that use cluster co-catalysts by the addition of rGO as an electron mediator to achieve high cluster loading and limited agglomeration of the clusters.Hanieh Mousavi, Thomas D. Small, Shailendra K. Sharma, Vladimir B. Golovko, Cameron J. Shearer and Gregory F. Meth

Sulfur-doped graphene with iron pyrite (FeS 2 ) as an efficient and stable electrocatalyst for the iodine reduction reaction in dye-sensitized solar cells

As an alternative to platinum (Pt), hybrid electrocatalysts based on sulfur-doped graphene with FeS2 microspheres (SGN-FeS2) were used as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). Benefiting from the high conductivity of SGN and excellent electrocatalytic activity of the FeS2, the bifunctional hybrid electrocatalyst-based device displays a power conversion efficiency (PCE) of 8.1%, which is comparable to that (8.3%) of traditional Pt CE-based DSSC, while also exhibiting excellent stability in ambient conditions. These characteristics, in addition to its low-cost and facile preparation, make the SGN–FeS2 hybrid an ideal CE material for DSSCs

Characterisation of the material and mechanical properties of atomic force microscope cantilevers with a plan-view trapezoidal geometry

Cantilever devices have found applications in numerous scientific fields and instruments, including the atomic force microscope (AFM), and as sensors to detect a wide range of chemical and biological species. The mechanical properties, in particular, the spring constant of these devices is crucial when quantifying adhesive forces, material properties of surfaces, and in determining deposited mass for sensing applications. A key component in the spring constant of a cantilever is the plan-view shape. In recent years, the trapezoidal plan-view shape has become available since it offers certain advantages to fast-scanning AFM and can improve sensor performance in fluid environments. Euler beam equations relating cantilever stiffness to the cantilever dimensions and Young’s modulus have been proven useful and are used extensively to model cantilever mechanical behaviour and calibrate the spring constant. In this work, we derive a simple correction factor to the Euler beam equation for a beam-shaped cantilever that is applicable to any cantilever with a trapezoidal plan-view shape. This correction factor is based upon previous analytical work and simplifies the application of the previous researchers formula. A correction factor to the spring constant of an AFM cantilever is also required to calculate the torque produced by the tip when it contacts the sample surface, which is also dependent on the plan-view shape. In this work, we also derive a simple expression for the torque for triangular plan-view shaped cantilevers and show that for the current generation of trapezoidal plan-view shaped AFM cantilevers, this will be a good approximation. We shall apply both these correction factors to determine Young’s modulus for a range of trapezoidal-shaped AFM cantilevers, which are specially designed for fast-scanning. These types of AFM probes are much smaller in size when compared to standard AFM probes. In the process of analysing the mechanical properties of these cantilevers, important insights are also gained into their spring constant calibration and dimensional factors that contribute to the variability in their spring constant.Ashley D. Slattery, Adam J. Blanch, Cameron J. Shearer, Andrew J. Stapleton, Renee V. Goreham, Sarah L. Harmer, Jamie S. Quinton, and Christopher T. Gibso

Carbon nanotubes in TiO₂ nanofiber photoelectrodes for high-performance perovskite solar cells

1D semiconducting oxides are unique structures that have been widely used for photovoltaic (PV) devices due to their capability to provide a direct pathway for charge transport. In addition, carbon nanotubes (CNTs) have played multifunctional roles in a range of PV cells because of their fascinating properties. Herein, the influence of CNTs on the PV performance of 1D titanium dioxide nanofiber (TiO2 NF) photoelectrode perovskite solar cells (PSCs) is systematically explored. Among the different types of CNTs, single-walled CNTs (SWCNTs) incorporated in the TiO2 NF photoelectrode PSCs show a significant enhancement (≈40%) in the power conversion efficiency (PCE) as compared to control cells. SWCNTs incorporated in TiO2 NFs provide a fast electron transfer within the photoelectrode, resulting in an increase in the short-circuit current (J sc) value. On the basis of our theoretical calculations, the improved open-circuit voltage (V oc) of the cells can be attributed to a shift in energy level of the photoelectrodes after the introduction of SWCNTs. Furthermore, it is found that the incorporation of SWCNTs into TiO2 NFs reduces the hysteresis effect and improves the stability of the PSC devices. In this study, the best performing PSC device constructed with SWCNT structures achieves a PCE of 14.03%

Histopathology of dairy cows' hooves with signs of naturally acquired laminitis

O objetivo deste trabalho foi investigar as alterações histológicas no casco de vacas leiteiras sem e com lesões de laminite, naturalmente, adquirida. Utilizaram-se animais de descarte sem lesões macroscópicas no casco (G1 n=9) e com lesões macroscópicas associadas à laminite sem (G2 n=23), ou com claudicação (G3 n=7). Após o abate, amostras da junção derme-epiderme das regiões solear, axial e dorsal do casco foram obtidas e processadas, histologicamente, nas colorações de HE e PAS. Avaliou-se, semiquantitativamente, às cegas e por um mesmo pesquisador, congestão, hemorragia e infiltrado inflamatório na derme das regiões solear, axial e dorsal. Avaliou-se infiltrado inflamatório na lâmina dermal das regiões axial e dorsal. A morfologia das células epidermais e a presença de irregularidades em três regiões do comprimento da membrana basal (MB) foram examinadas na coloração de PAS. Os escores das lesões nas diferentes regiões do casco no mesmo grupo e nos diferentes grupos para cada região do casco foram comparados através de análises não paramétricas (P<0,05). Infiltrado inflamatório na derme de todas as regiões do casco foi detectado em todos os grupos sem diferença estatística (P>0,05). Vacas sem lesões macroscópicas secundárias à laminite (G1) apresentaram escores de inflamação e alteração de células epidermais semelhantes aos dos grupos com lesões de laminite, sugerindo a existência de fase prodrômica para a doença em bovinos. A MB apresentou irregularidades com intensidade variável ao longo de seu comprimento (P<0,05), porém, sem diferença entre grupos (P>0,05). O padrão de irregularidades na MB encontrado não foi relatado até o momento e não se assemelha ao colapso de MB descrito em equinos e bovinos com laminite induzida. Concluiu-se que, mesmo na ausência de lesões macroscópicas no casco causadas por laminite, vacas leiteiras apresentam lesões histológicas compatíveis com inflamação da junção derme-epiderme como em animais afetados. A membrana basal de bovinos sem e com lesões de laminite apresenta irregularidades com distribuição irregular ao longo de seu comprimento que precisam ser melhor estudadas

Repositioning of the global epicentre of non-optimal cholesterol

High blood cholesterol is typically considered a feature of wealthy western countries1,2. However, dietary and behavioural determinants of blood cholesterol are changing rapidly throughout the world3 and countries are using lipid-lowering medications at varying rates. These changes can have distinct effects on the levels of high-density lipoprotein (HDL) cholesterol and non-HDL cholesterol, which have different effects on human health4,5. However, the trends of HDL and non-HDL cholesterol levels over time have not been previously reported in a global analysis. Here we pooled 1,127 population-based studies that measured blood lipids in 102.6 million individuals aged 18 years and older to estimate trends from 1980 to 2018 in mean total, non-HDL and HDL cholesterol levels for 200 countries. Globally, there was little change in total or non-HDL cholesterol from 1980 to 2018. This was a net effect of increases in low- and middle-income countries, especially in east and southeast Asia, and decreases in high-income western countries, especially those in northwestern Europe, and in central and eastern Europe. As a result, countries with the highest level of non-HDL cholesterol—which is a marker of cardiovascular risk—changed from those in western Europe such as Belgium, Finland, Greenland, Iceland, Norway, Sweden, Switzerland and Malta in 1980 to those in Asia and the Pacific, such as Tokelau, Malaysia, The Philippines and Thailand. In 2017, high non-HDL cholesterol was responsible for an estimated 3.9 million (95% credible interval 3.7 million–4.2 million) worldwide deaths, half of which occurred in east, southeast and south Asia. The global repositioning of lipid-related risk, with non-optimal cholesterol shifting from a distinct feature of high-income countries in northwestern Europe, north America and Australasia to one that affects countries in east and southeast Asia and Oceania should motivate the use of population-based policies and personal interventions to improve nutrition and enhance access to treatment throughout the world.</p