Nanowires: from Microchip Integrated Synthesis to Application Examples

Both the high demand in the downscaling of electronic devices and the novel properties of nanowires (NWs) as a result of their high surface-to-volume (S/V) ratio and their quantum mechanical properties have driven NWs to be among the favorite research areas in recent years and are expected to remain one of the hot topics in the next decade. Thus the synthesis of NWs which is under intensive study is not only aimed at basic research but also for a wide spectrum of device fabrication and applications.The aim of this research is to explore simple synthesis techniques of metal oxide (semiconductor) and metal-metal oxide hybrid nanostructures with proper contact lines on different substrates and investigate NWs for various device applications. Three novel synthesis routes were developed and utilized in this thesis: Thin Film Fracture (TFF),Flame Transport Synthesis (FTS) and Thermal Annealing Method (TAM). As compared to many other synthesis techniques in the literature, the here used techniques are cost effective, can be easily scaled up, offer a less complex synthesis processes and offer easy integration of NWs into lithographically patterned chips. The three synthesis techniques employed in synthesizing both 1D semiconductor and semiconductor-metal hybrid structures spanning from device fabrication to results will be presented. Both FTS and TFF approaches are implemented for the fabrication of the semiconductor (mainly ZnO) nano-microstructures based UV photodetectors. Comparison of the UV photodetectors performances built from interpenetrating ZnO nano-microstructures fabricated by burner-FTS (B-FTS) and crucible-FTS (C-FTS) techniques will also be presented. Fastest response/recovery time constant (~32 ms) and an on/off ratio ~4.5103 at 2.4 V under 365 nm UV light irradiation for the B-FTS based photodetectors is reported. The growth mechanism, properties and measurements as sensor devices will be presented in detail. Besides that the TFF based ZnO NW specimens showed a promising result as oxygen gas sensors. 1D semiconductor-metal hybrid structures are fabricated using TFF and TAM techniques and offer additional functionalities. A controlled shrinking of Ti NWs (TFF) by electrochemical oxidation, TiO2-Ti hybrid NWs with a promising potential as NWFET have been demonstrated. In addition to the interesting FET characteristics, the hybrid NWFET showed a drastic and fast response in the drain current when it is exposed to different partial pressures of oxygen gas. One of the most important feature of these NWs is that they all exhibit granular structure. This characteristic makes them suitable especially for sensoric applications. The other novel approach for the chip integrated synthesis of iron oxide nanostructures with a variety of unique characteristics is TAM. A thermally initiated diffusion, oxidation and reshaping of Fe thin film in atmospheric air condition driven for the synthesis of single crystalline iron oxide NWs. Detailed investigations on the NWs proved that some specimens are able to form metal-metal oxide hybrid nanostructure with an iron-rich core region, the detailed characteristics are described as well

Burden of disease scenarios for 204 countries and territories, 2022–2050: a forecasting analysis for the Global Burden of Disease Study 2021

Background: Future trends in disease burden and drivers of health are of great interest to policy makers and the public at large. This information can be used for policy and long-term health investment, planning, and prioritisation. We have expanded and improved upon previous forecasts produced as part of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) and provide a reference forecast (the most likely future), and alternative scenarios assessing disease burden trajectories if selected sets of risk factors were eliminated from current levels by 2050. Methods: Using forecasts of major drivers of health such as the Socio-demographic Index (SDI; a composite measure of lag-distributed income per capita, mean years of education, and total fertility under 25 years of age) and the full set of risk factor exposures captured by GBD, we provide cause-specific forecasts of mortality, years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life-years (DALYs) by age and sex from 2022 to 2050 for 204 countries and territories, 21 GBD regions, seven super-regions, and the world. All analyses were done at the cause-specific level so that only risk factors deemed causal by the GBD comparative risk assessment influenced future trajectories of mortality for each disease. Cause-specific mortality was modelled using mixed-effects models with SDI and time as the main covariates, and the combined impact of causal risk factors as an offset in the model. At the all-cause mortality level, we captured unexplained variation by modelling residuals with an autoregressive integrated moving average model with drift attenuation. These all-cause forecasts constrained the cause-specific forecasts at successively deeper levels of the GBD cause hierarchy using cascading mortality models, thus ensuring a robust estimate of cause-specific mortality. For non-fatal measures (eg, low back pain), incidence and prevalence were forecasted from mixed-effects models with SDI as the main covariate, and YLDs were computed from the resulting prevalence forecasts and average disability weights from GBD. Alternative future scenarios were constructed by replacing appropriate reference trajectories for risk factors with hypothetical trajectories of gradual elimination of risk factor exposure from current levels to 2050. The scenarios were constructed from various sets of risk factors: environmental risks (Safer Environment scenario), risks associated with communicable, maternal, neonatal, and nutritional diseases (CMNNs; Improved Childhood Nutrition and Vaccination scenario), risks associated with major non-communicable diseases (NCDs; Improved Behavioural and Metabolic Risks scenario), and the combined effects of these three scenarios. Using the Shared Socioeconomic Pathways climate scenarios SSP2-4.5 as reference and SSP1-1.9 as an optimistic alternative in the Safer Environment scenario, we accounted for climate change impact on health by using the most recent Intergovernmental Panel on Climate Change temperature forecasts and published trajectories of ambient air pollution for the same two scenarios. Life expectancy and healthy life expectancy were computed using standard methods. The forecasting framework includes computing the age-sex-specific future population for each location and separately for each scenario. 95% uncertainty intervals (UIs) for each individual future estimate were derived from the 2·5th and 97·5th percentiles of distributions generated from propagating 500 draws through the multistage computational pipeline. Findings: In the reference scenario forecast, global and super-regional life expectancy increased from 2022 to 2050, but improvement was at a slower pace than in the three decades preceding the COVID-19 pandemic (beginning in 2020). Gains in future life expectancy were forecasted to be greatest in super-regions with comparatively low life expectancies (such as sub-Saharan Africa) compared with super-regions with higher life expectancies (such as the high-income super-region), leading to a trend towards convergence in life expectancy across locations between now and 2050. At the super-region level, forecasted healthy life expectancy patterns were similar to those of life expectancies. Forecasts for the reference scenario found that health will improve in the coming decades, with all-cause age-standardised DALY rates decreasing in every GBD super-region. The total DALY burden measured in counts, however, will increase in every super-region, largely a function of population ageing and growth. We also forecasted that both DALY counts and age-standardised DALY rates will continue to shift from CMNNs to NCDs, with the most pronounced shifts occurring in sub-Saharan Africa (60·1% [95% UI 56·8–63·1] of DALYs were from CMNNs in 2022 compared with 35·8% [31·0–45·0] in 2050) and south Asia (31·7% [29·2–34·1] to 15·5% [13·7–17·5]). This shift is reflected in the leading global causes of DALYs, with the top four causes in 2050 being ischaemic heart disease, stroke, diabetes, and chronic obstructive pulmonary disease, compared with 2022, with ischaemic heart disease, neonatal disorders, stroke, and lower respiratory infections at the top. The global proportion of DALYs due to YLDs likewise increased from 33·8% (27·4–40·3) to 41·1% (33·9–48·1) from 2022 to 2050, demonstrating an important shift in overall disease burden towards morbidity and away from premature death. The largest shift of this kind was forecasted for sub-Saharan Africa, from 20·1% (15·6–25·3) of DALYs due to YLDs in 2022 to 35·6% (26·5–43·0) in 2050. In the assessment of alternative future scenarios, the combined effects of the scenarios (Safer Environment, Improved Childhood Nutrition and Vaccination, and Improved Behavioural and Metabolic Risks scenarios) demonstrated an important decrease in the global burden of DALYs in 2050 of 15·4% (13·5–17·5) compared with the reference scenario, with decreases across super-regions ranging from 10·4% (9·7–11·3) in the high-income super-region to 23·9% (20·7–27·3) in north Africa and the Middle East. The Safer Environment scenario had its largest decrease in sub-Saharan Africa (5·2% [3·5–6·8]), the Improved Behavioural and Metabolic Risks scenario in north Africa and the Middle East (23·2% [20·2–26·5]), and the Improved Nutrition and Vaccination scenario in sub-Saharan Africa (2·0% [–0·6 to 3·6]). Interpretation: Globally, life expectancy and age-standardised disease burden were forecasted to improve between 2022 and 2050, with the majority of the burden continuing to shift from CMNNs to NCDs. That said, continued progress on reducing the CMNN disease burden will be dependent on maintaining investment in and policy emphasis on CMNN disease prevention and treatment. Mostly due to growth and ageing of populations, the number of deaths and DALYs due to all causes combined will generally increase. By constructing alternative future scenarios wherein certain risk exposures are eliminated by 2050, we have shown that opportunities exist to substantially improve health outcomes in the future through concerted efforts to prevent exposure to well established risk factors and to expand access to key health interventions

Correction: Ambient condition-processing strategy for improved air-stability and efficiency in mixed-cation perovskite solar cells (Mater. Adv. (2020) DOI: 10.1039/d0ma00528b)

The authors regret that there is an interest that should have been declared that was omitted. The authors wish to declare that a patent application related to some of the content of this article has been filed. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers

Ambient condition-processing strategy for improved air-stability and efficiency in mixed-cation perovskite solar cells

Fabrication of efficient halide perovskite solar cells under ambient conditions and their stability remain a challenge due to the sensitivity of halide perovskites to moisture, oxygen, light, and temperature. Thus, there is a strong demand and interest to develop a method for fabricating perovskite solar cells with long-term stability and even better, such a fabrication method under ambient conditions. To this end, we use a chemical synthesis method and a solvent engineering technique to optimize halide perovskite thin film deposition in an ambient environment. We obtained pinhole-free films composed of large crystal grains and high crystal quality that result in excellent optoelectronic properties of the halide perovskite. We also report a low trap-density in the order of 1015 cm-3 for the polycrystalline perovskite thin film. Moreover, with an n-i-p solar cell structure, a maximum power conversion efficiency of ∼20.3% with excellent stability in ambient air (25-55%RH) for more than ten months of storage (>7000 hours) is achieved. The optimized solar cell without encapsulation retained ∼80% of its initial performance after ten months of storage with a T80 of ∼5035 hours. Our findings suggest that the performance and stability of the perovskite solar cells are highly dependent on the device architecture, grain morphology, trap density, and carrier mobility in the device before and after storage

Halide Perovskite Nanocrystals for Next‐Generation Optoelectronics

Colloidal perovskite nanocrystals (PNCs) combine the outstanding optoelectronic properties of bulk perovskites with strong quantum confinement effects at the nanoscale. Their facile and low-cost synthesis, together with superior photoluminescence quantum yields and exceptional optical versatility, make PNCs promising candidates for next-generation optoelectronics. However, this field is still in its early infancy and not yet ready for commercialization due to several open challenges to be addressed, such as toxicity and stability. Here, the key synthesis strategies and the tunable optical properties of PNCs are discussed. The photophysical underpinnings of PNCs, in correlation with recent developments of PNC-based optoelectronic devices, are especially highlighted. The final goal is to outline a theoretical scaffold for the design of high-performance devices that can at the same time address the commercialization challenges of PNC-based technology.acceptedVersionPeer reviewe

Halide Perovskite Nanocrystals for Next‐Generation Optoelectronics

Colloidal perovskite nanocrystals (PNCs) combine the outstanding optoelectronic properties of bulk perovskites with strong quantum confinement effects at the nanoscale. Their facile and low-cost synthesis, together with superior photoluminescence quantum yields and exceptional optical versatility, make PNCs promising candidates for next-generation optoelectronics. However, this field is still in its early infancy and not yet ready for commercialization due to several open challenges to be addressed, such as toxicity and stability. Here, the key synthesis strategies and the tunable optical properties of PNCs are discussed. The photophysical underpinnings of PNCs, in correlation with recent developments of PNC-based optoelectronic devices, are especially highlighted. The final goal is to outline a theoretical scaffold for the design of high-performance devices that can at the same time address the commercialization challenges of PNC-based technology.acceptedVersionPeer reviewe

Solvent free fabrication of micro and nanostructured drug coatings by thermal evaporation for controlled release and increased effects.

Nanostructuring of drug delivery systems offers many promising applications like precise control of dissolution and release kinetics, enhanced activities, flexibility in terms of surface coatings, integration into implants, designing the appropriate scaffolds or even integrating into microelectronic chips etc. for different desired applications. In general such kind of structuring is difficult due to unintentional mixing of chemical solvents used during drug formulations. We demonstrate here the successful solvent-free fabrication of micro-nanostructured pharmaceutical molecules by simple thermal evaporation (TE). The evaporation of drug molecules and their emission to a specific surface under vacuum led to controlled assembling of the molecules from vapour phase to solid phase. The most important aspects of thermal evaporation technique are: solvent-free, precise control of size, possibility of fabricating multilayer/hybrid, and free choice of substrates. This could be shown for twenty eight pharmaceutical substances of different chemical structures which were evaporated on surfaces of titanium and glass discs. Structural investigations of different TE fabricated drugs were performed by atomic force microscopy, scanning electron microscopy and Raman spectroscopy which revealed that these drug substances preserve their structurality after evaporation. Titanium discs coated with antimicrobial substances by thermal evaporation were subjected to tests for antibacterial or antifungal activities, respectively. A significant increase in their antimicrobial activity was observed in zones of inhibition tests compared to controls of the diluted substances on the discs made of paper for filtration. With thermal evaporation, we have successfully synthesized solvent-free nanostructured drug delivery systems in form of multilayer structures and in hybrid drug complexes respectively. Analyses of these substances consolidated that thermal evaporation opens up the possibility to convert dissoluble drug substances into the active forms by their transfer onto a specific surface without the need of their prior dissolution

Highly compact TiO2 films by spray pyrolysis and application in perovskite solar cells

Transparent and pinhole free hole‐blocking layers such as TiO2 grown at low temperatures and by scalable processes are necessary to reduce production costs and thus enabling commercialization of perovskite solar cells. Here, the authors compare the transport properties of TiO2 compact layers grown by spray pyrolysis from commonly used titanium diisopropoxide bisacetylacetonate ([Ti(OPri)2(acac)2]) precursor to films grown by spray pyrolysis of TiCl4. Spray pyrolysis provides insights into the interdependence of precursor chemistry and electron transport properties of TiO2 films and their influence on the performance of the perovskite solar cells. X‐ray diffraction and X‐ray photoelectron spectroscopy data confirm the chemical and structural composition of the obtained films. Thin film deposition at lower temperature (150 °C) are conducted using TiCl4 to evaluate the influence of crystal growth and topography by scanning electron microscopy and atomic force microscopy as well as thickness (profilometry) and transmittance (UV/Vis spectroscopy) on the power conversion efficiency of perovskite solar cells. TiO2 compact layers grown from TiCl4 enhance the power conversion efficiency by acting as superior electron transfer medium and by reducing hysteresis behavior, when compared to films grown using titanium diisopropoxide bisacetylacetonate. UV/Vis spectroscopy and external quantum efficiency studies reveal the correlation of transmittance on the power conversion efficiency.acceptedVersionPeer reviewe