Highly Stable CsPbBr3@MoS2 Nanostructures: Synthesis and Optoelectronic Properties Toward Implementation into Solar Cells.

Halide perovskites (HPs) have gained significant interest in the scientific and technological sectors due to their unique optical, catalytic, and electrical characteristics. However, the HPs are prone to decomposition when exposed to air, oxygen, or heat. The instability of HP materials limits their commercialization, prompting significant efforts to address and overcome these limitations. Transition metal dichalcogenides, such as MoS2, are chemically stable and are suitable for electronic, optical, and catalytic applications. Moreover, it can be used as a protective media or shell for other nanoparticles. In this study, a novel CsPbBr3@MoS2 core-shell nanostructure (CS-NS) is successfully synthesized by enveloping CsPbBr3 within a MoS2 shell for the first time. Significant stability of CS-NSs dispersed in polar solvents for extended periods is also demonstrated. Remarkably, the hybrid CS-NS exhibits an absorption of MoS2 and quenching of the HP's photoluminescence, implying potential charge or energy transfer from HPs to MoS2. Using finite difference time domain simulations, it is found that the CS-NSs can be utilized to produce efficient solar cells. The addition of a MoS2 shell enhances the performance of CS-NS-based solar cells by 220% compared to their CsPbBr3 counterparts. The innovative CS-NS represents important progress in harnessing HPs for photovoltaic and optoelectronic applications.

Plasmon-Enhanced Perovskite Solar Cells Based on Inkjet-Printed Au Nanoparticles Embedded into TiO2 Microdot Arrays.

The exceptional property of plasmonic materials to localize light into sub-wavelength regimes has significant importance in various applications, especially in photovoltaics. In this study, we report the localized surface plasmon-enhanced perovskite solar cell (PSC) performance of plasmonic gold nanoparticles (AuNPs) embedded into a titanium oxide (TiO2) microdot array (MDA), which was deposited using the inkjet printing technique. The X-ray (XRD) analysis of MAPI (methyl ammonium lead iodide) perovskite films deposited on glass substrates with and without MDA revealed no destructive effect of MDA on the perovskite structure. Moreover, a 12% increase in the crystallite size of perovskite with MDA was registered. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) techniques revealed the morphology of the TiO2_MDA and TiO2-AuNPs_MDA. The finite-difference time-domain (FDTD) simulation was employed to evaluate the absorption cross-sections and local field enhancement of AuNPs in the TiO2 and TiO2/MAPI surrounding media. Reflectance UV-Vis spectra of the samples comprising glass/TiO2 ETL/TiO2_MDA (ETL-an electron transport layer) with and without AuNPs in TiO2_MDA were studied, and the band gap (Eg) values of MAPI have been calculated using the Kubelka-Munk equation. The MDA introduction did not influence the band gap value, which remained at ~1.6 eV for all the samples. The photovoltaic performance of the fabricated PSC with and without MDA and the corresponding key parameters of the solar cells have also been studied and discussed in detail. The findings indicated a significant power conversion efficiency improvement of over 47% in the PSCs with the introduction of the TiO2-AuNPs_MDA on the ETL/MAPI interface compared to the reference device. Our study demonstrates the significant enhancement achieved in halide PSC by utilizing AuNPs within a TiO2_MDA. This approach holds great promise for advancing the efficiency and performance of photovoltaic devices.

A Comprehensive Approach to Improving Emergency Obstetric and Newborn Care in Kigoma, Tanzania.

INTRODUCTION: To address high levels of maternal mortality in Kigoma, Tanzania, stakeholders increased women's access to high-quality comprehensive emergency obstetric and newborn care (EmONC) by decentralizing services from hospitals to health centers where EmONC was delivered mostly by associate clinicians and nurses. To ensure that women used services, implementers worked to continuously improve and sustain quality of care while creating demand. METHODS: Program evaluation included periodic health facility assessments, pregnancy outcome monitoring, and enhanced maternal mortality detection region-wide in program- and nonprogram-supported health facilities. RESULTS: Between 2013 and 2018, the average number of lifesaving interventions performed per facility increased from 2.8 to 4.7. The increase was higher in program-supported than nonprogram-supported health centers and dispensaries. The institutional delivery rate increased from 49% to 85%; the greatest increase occurred through using health centers (15% to 25%) and dispensaries (21% to 46%). The number of cesarean deliveries almost doubled, and the population cesarean delivery rate increased from 2.6% to 4.5%. Met need for emergency obstetric care increased from 44% to 61% while the direct obstetric case fatality rate declined from 1.8% to 1.4%. The institutional maternal mortality ratio across all health facilities declined from 303 to 174 deaths per 100,000 live births. The total stillbirth rate declined from 26.7 to 12.8 per 1,000 births. The predischarge neonatal mortality rate declined from 10.7 to 7.6 per 1,000 live births. Changes in case fatality rate and maternal mortality were driven by project-supported facilities. Changes in neonatal mortality varied depending on facility type and program support status. CONCLUSION: Decentralizing high-quality comprehensive EmONC delivered mostly by associate clinicians and nurses led to significant improvements in the availability and utilization of lifesaving care at birth in Kigoma. Dedicated efforts to sustain high-quality EmONC along with supplemental programmatic components contributed to the reduction of maternal and perinatal mortality.

Improving Maternal and Reproductive Health in Kigoma, Tanzania: A 13-Year Initiative.

The Program to Reduce Maternal Deaths in Tanzania was a 13-year (2006-2019) effort in the Kigoma region that evolved over 3 phases to improve and sustain the availability of, access to, and demand for high-quality maternal and reproductive health care services. The Program intended to bring high-quality care closer to more communities. Cutting across the Program was the routine collection of monitoring and evaluation data. The Program achieved significant reductions in maternal and perinatal mortality, a significant increase in the modern contraceptive prevalence rate, and a significant decline in the unmet need for contraception. By 2017, it was apparent that the Program was on track to meet or surpass many of the targets established by the Government of Tanzania. Over the following 2-plus years, efforts to sustain Program interventions intensified. In April 2019, the Program fully transitioned to Government of Tanzania oversight. Four key lessons were learned during implementation that are relevant to governments, donors, and implementing organizations working to reduce maternal mortality: (1) multistakeholder partnerships are critical; (2) demand creation for services, while critical, must rest on a foundation of well-functioning and high-quality clinical services; (3) it is imperative to not only collect robust monitoring and evaluation data, but to be responsive in real time to what the data reveal; and, (4) it is necessary to develop a deliberate sustainability strategy from the start. The Program in Kigoma demonstrates that decentralizing high-quality maternal and reproductive health services in remote, low-resource settings is both feasible and effective and should be considered in places with similar contexts. By embedding the Program in the existing health system, and through efforts to build local capacity, the improvements seen in Kigoma are likely to be sustained. Follow-up evaluations are planned, providing an opportunity to more directly assess sustainability.

Phase-dependent structural, optical, phonon and UV sensing properties of ZnS nanoparticles.

In order to investigate the influence of crystal structure on the photoresponse properties of ZnS nanoparticles under UV light exposure, electrical measurements on polyvinylpyrrolidone capepd cubic and hexagonal ZnS nanoparticles with average particle size 30-40 nm have been successfully carried out. Low-temperature solvothermal synthesis yields pure and highly crystalline w-ZnS nanoparticles with good stability. Different structures of prepared ZnS nanoparticles have been identified and confirmed with powder x-ray diffraction, high-resolution field-emission transmission electron microscopy and non-resonant Raman spectroscopic techniques, respectively. The energy band gap and emission properties of cubic and hexagonal ZnS have been studied using UV-vis absorption and photoluminescence spectroscopy. The interaction of phonons with free carriers and transport properties has a vital influence on the electronic and optical properties of nanomaterials. Hence, the resonant and non-resonant Raman spectral studies have been carried out for the prepared samples. Studies on the I-V characteristics and the mechanism behind the enhancement of photocurrent for the cubic and hexagonal ZnS nanoparticle-based photodetectors have shown an enhanced photocurrent for hexagonal ZnS nanoparticles rather than the cubic.

A Raman spectral probe on polar w-ZnS nanostructures and surface optical phonon modes in nanowires.

In the present study, different morphologies of ZnS nanostructures have been synthesized through a hydrothermal method and their Raman spectral modes are investigated. Raman scattering from surface optical (SO) modes has been seen and identified as a strange shoulder band of LO at 340 cm-1 in nanowires (NWs) with a hexagonal wurtzite structure of ZnS in air medium. X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques have been used to confirm the hexagonal phase and the modulation in the surface during the growth process, which causes the translational symmetry breaking to activate the SO mode. The appearance of a strong SO mode in NWs has been obviously confirmed by the frequency downshift of the SO mode in different dielectric media with dielectric constants ranging from 1 to 2.56. The SO phonon mode shift due to the roughness in the NW faces has been estimated from the wave-vector that activates the SO mode and an approximate dielectric continuum (DC) model has been used to understand the SO modes in NWs. The surface perturbation responsible for the activation of the SO mode has been estimated and is compared with the surface modulation along the growth axis of the NW from the TEM images.

Optical, phonon and efficient visible and infrared photocatalytic activity of Cu doped ZnS micro crystals.

We report, the enhanced photocatalytic behaviour of Cu doped ZnS micro crystals. ZnS and different concentrations of Cu doped ZnS microcrystals were prepared. X-ray diffraction confirms the crystalline and phase of the particles. Morphology and sizes were studied using Scanning Electron Microscopy (SEM). Recorded optical absorption spectra show a band for around 365nm for pure ZnS, but there is a broad band in the near infrared regime for the Cu-doped ZnS microcrystals which are attributed to the d-d transitions of Cu2+ ions. Phonon properties of as-prepared samples were investigated using Raman spectroscopy. Present work we investigate the potential of ZnS and Cu doped ZnS as a photocatalyst. For this from the degradation of methylene blue dye in aqueous media the photocatalytic activity of pure and highest doped ZnS samples with the irradiation of white light and infrared, enhanced photocatalytic activity were observed. Mechanism of white light an IR light based photocatalytic activity is explained based on the electron-hole pair production.

Impaired response to amphetamine and neuronal degeneration in the nucleus accumbens of autoimmune MRL-lpr mice.

Spontaneous development of lupus-like disease in MRL-lpr mice is accompanied by a constellation of behavioral deficits, including blunted responsiveness to sucrose. Although autoimmunity-induced damage of limbic areas is proposed to underlie this deficit, the systemic nature of the disease precludes inference of a causal relationship between CNS damage and functional loss. Based on the stimulatory effects of d-amphetamine sulfate (AMPH) on sucrose intake, the present study pharmacologically probes the functional status of central dopaminergic circuits involved in control of behavioral reward. The response rates were compared between diseased MRL-lpr mice and congenic MRL +/+ controls tested in the sucrose preference paradigm. Neuronal loss was assessed by Fluoro Jade B (FJB) staining of nucleus accumbens and the CA2/CA3 region. While control mice significantly increased intake of sucrose solutions 60 min after administration of AMPH (i.p., 0.5 mg/kg), the intake in drugged MRL-lpr mice was comparable to those given saline injection. Increased FJB staining was detected in the nucleus accumbens and hippocampus of diseased mice, and AMPH treatment neither altered this nor other measures of organ pathology. The results obtained are consistent with previously observed changes in the mesolimbic dopamine system of MRL-lpr mice and suggest that the lesion in the nucleus accumbens and deficits in dopamine release underlie impaired responsiveness to palatable stimulation during the progress of systemic autoimmune disease. As such, they point to a neurotransmitter-specific regional brain damage which may account for depressive behaviors in neuropsychiatric lupus erythematosus.