Effects of Annealing on the Structural and Optical Properties of Silver Thin Films

Silver thin films were prepared on glass substrates using chemical bath method. The thin films were annealed at different temperatures of 100 and 200oC for 1hour. The samples, as-prepared and annealed were  characterized using X-ray diffractometer (XRD) and Uv-Vis  spectrophotometer. XRD results revealed that silver films present a cubic phase with (111) preferred orientation. The XRD result and analysis also revealed that the intensity of the peaks and the crystallite size increase with increase in annealing temperature. All the films showed very low transmittance within the visible region with the 200oC annealed film having the highest at 1.4%. Reflectance was found to reduce from 65% for the as-deposited film to as low as 17% for the 200oC annealed film within the visible region of the wavelength. The reflectance reduces with increase in annealing temperature. The films also showed low percentage absorbance within the UV region of the wavelength with the 200oC annealed film having the highest absorbance of 2.79%.Keywords: Annealing, Thin films, XRD, Optical properties, Spectrophotometer, Silve

Effects of Temperature on Morphological, Structural and Optical Characteristics of CdTe Films for PV Applications

Cadmium telluride (CdTe) is a direct band gap semiconductor for direct light-to-electricity conversion. The films are promising photovoltaic materials for CdS/CdTe solar cells because of its energy band gap of 1.5 eV and higher absorption co-efficient (>104cm-1). This work presents the characterization of 1 μm CdTe films for photovoltaic applications. The films were deposited on cleaned glass substrates using thermal evaporation. The effect of annealing temperatures (as deposited, 400°C and 500°C) on morphological, structural and optical characteristics of CdTe films was investigated for an hour and characterized with Scanning Electron Microscope (SEM), Powder X-ray diffraction (PXRD) and UV-Visible spectrophotometer. The results revealed that the reflectance characteristics of CdTe films depend on the wavelength of electromagnetic spectra. The maximum percentage optical transmittance of CdTe films for as-grown, 400°C and 500oC films were 59%, 60% and 58% respectively at 800 nm wavelength. The absorbance decreases with increasing in wavelength and was found to be 1.65, 1.25 and 0.85 % for the as-grown, 400°C and 500oC films respectively. The absorption coefficient exhibits higher values in the shorter wavelength and decreases as the wavelength and temperatures increases and the band gap becomes wider. The SEM analyses showed that the films were homogenous and free from crystal defects. The results revealed that 1 μm CdTe film may be used as absorber layer in CdS/CdTe thin film solar cells. Keywords: CdTe, Glass substrate, Thermal evaporation, Annealing temperature, Energy band ga

Spray Pyrolysed Nanostructured Gold-Doped Tin Oxide (Auto) Thin Films

Nanostructured SnO2 thin films were grown by the chemical spray pyrolysis (CSP) method. Homemade spray pyrolysis technique is employed to prepare thin films. SnO2 is wide band gap semiconductor material whose film is deposited on glass substrate. A gold nanoparticle-doped tin oxide thin film (AuTO) was also prepared. UV-VIS (ultraviolet visible) spectroscopy and four-point probe analysis are done for optical and electrical analysis. UV-Visible absorption spectra show that the band gap of SnO2 thin film is 3.78 eV and 3.82 eV for AuTO. Band gap of SnO2 thin film can be tuned that it can be used in optical devices. The films have transmittance increases (to about 60%) and the absorbance decreases in the visible region of the electromagnetic spectrum. The electrical conductivity of the Tin Oxide is enhanced by functionalizing with the Gold nanoparticles. It is higher than that of the Tin oxide only; 0.77 x 10-2 (Ohm cm)-1 and 3.55 x 10-2 (Ohm cm)-1 for SnO2 and AuTO respectively. These properties reveal that Tin Oxide doped with gold can actually be a good material for a transparent conducting oxide to be used in photovoltaic fabrication and in electronics

Optimization of Absorber Layer and Operating Temperature of Copper Indium Gallium Selenide Solar Cells Using Different Metal Contacts

Device simulation was employed to investigate the effect of metal back contact electrodes on the performance of n-type CdS/p-CIGS thin film solar cells using varying thicknesses of absorber layer at operating temperature of 300K. The effect of working temperatures was also studied from 300K to 400K in steps of 10K. The simulations were carried out using standard solar cell capacitance simulator (SCAPS) 3.3.03 version software. The results showed better efficiencies at the optimized thickness of 3µm for all the back contact electrodes under study. The maximum efficiencies of 17.5 %, 15.5 %, 11.5 %, 3.5 % and 3 % were estimated for CIGS thin film solar cell at 300 K for platinum, gold, cobalt, silver and copper back contact electrodes respectively. The efficiency decreases as the operating temperatures increases from 300 K to 400 K. It is recommended that the optimized thickness of 3 µm is appropriate as absorber layer for efficient and cost effective CIGS thin film solar cells for economic reasons

An enhanced platform for cell electroporation: controlled delivery and electrodes functionalization

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Functionalized microelectrodes arrays with integrated microfluidic channels for single-site multiple

Nowadays, different chemical and physical transfection techniques are used to delivery biomolecules of interest (e.g. DNA, RNA, proteins) into cells. Among the physical methods, electroporation generates transient pores in the plasma membrane by applying electrical pulses to suspended cells. One of its main limitations is the lack of spatio-temporal control over the process: it does not allow to select single cells (desirable requirement especially in highly heterogeneous tissues), and to monitor the transfection results in real-time. To circumvent these disadvantages, alternative microscale approaches are increasingly required. This work presents an integrated platform consisting of a gold microelectrode array (MEA) for singlesite electroporation and fluidic channels for controlled delivery of bio-chemical entities . In order to improve the efficiency of electroporation, the gold electrodes were coated with a thin film of nanostructured of Titanium Dioxide

Global Retinoblastoma Presentation and Analysis by National Income Level

Importance: Early diagnosis of retinoblastoma, the most common intraocular cancer, can save both a child's life and vision. However, anecdotal evidence suggests that many children across the world are diagnosed late. To our knowledge, the clinical presentation of retinoblastoma has never been assessed on a global scale. Objectives: To report the retinoblastoma stage at diagnosis in patients across the world during a single year, to investigate associations between clinical variables and national income level, and to investigate risk factors for advanced disease at diagnosis. Design, Setting, and Participants: A total of 278 retinoblastoma treatment centers were recruited from June 2017 through December 2018 to participate in a cross-sectional analysis of treatment-naive patients with retinoblastoma who were diagnosed in 2017. Main Outcomes and Measures: Age at presentation, proportion of familial history of retinoblastoma, and tumor stage and metastasis. Results: The cohort included 4351 new patients from 153 countries; the median age at diagnosis was 30.5 (interquartile range, 18.3-45.9) months, and 1976 patients (45.4) were female. Most patients (n = 3685 84.7%) were from low-and middle-income countries (LMICs). Globally, the most common indication for referral was leukocoria (n = 2638 62.8%), followed by strabismus (n = 429 10.2%) and proptosis (n = 309 7.4%). Patients from high-income countries (HICs) were diagnosed at a median age of 14.1 months, with 656 of 666 (98.5%) patients having intraocular retinoblastoma and 2 (0.3%) having metastasis. Patients from low-income countries were diagnosed at a median age of 30.5 months, with 256 of 521 (49.1%) having extraocular retinoblastoma and 94 of 498 (18.9%) having metastasis. Lower national income level was associated with older presentation age, higher proportion of locally advanced disease and distant metastasis, and smaller proportion of familial history of retinoblastoma. Advanced disease at diagnosis was more common in LMICs even after adjusting for age (odds ratio for low-income countries vs upper-middle-income countries and HICs, 17.92 95% CI, 12.94-24.80, and for lower-middle-income countries vs upper-middle-income countries and HICs, 5.74 95% CI, 4.30-7.68). Conclusions and Relevance: This study is estimated to have included more than half of all new retinoblastoma cases worldwide in 2017. Children from LMICs, where the main global retinoblastoma burden lies, presented at an older age with more advanced disease and demonstrated a smaller proportion of familial history of retinoblastoma, likely because many do not reach a childbearing age. Given that retinoblastoma is curable, these data are concerning and mandate intervention at national and international levels. Further studies are needed to investigate factors, other than age at presentation, that may be associated with advanced disease in LMICs. © 2020 American Medical Association. All rights reserved

Structural and Optical Properties of Chemically Synthesized Cu2ZnSnS4 (CZTS) Nanoparticles

The structural and optical properties of Cu2ZnSnS4 nanoparticles prepared by an affordable chemical route were investigated with the aim of determining suitability of the nanoparticles for photovoltaic applications. XRD characterization indicates phases that exhibit kesterite structure of CZTS. The crystallite sizes calculated for both CZTS nanoparticles specimen were comparable to those reported in literature. The absorbance was found to be considerably high within the visible region of the electromagnetic radiation while the transmittance was very low. Theoretical band-gap was calculated to be between 1.55 eV and 1.92 eV which are the ideal band-gap for solar cell absorber for high conversion efficiency

Clinical Presentations and Characteristics of Confirmed Covid-19 Patients over a 1-Year Period in a Private Health Facility in Ilorin, North-Central Nigeria

The first case of COVID-19 in Nigeria was confirmed on February 27, 2020.  Since then, many studies from government designated isolation centers have described the characteristics of patients with Covid-19. Even though COVID-19 testing and management are exclusively carried out at the NCDC-approved centers, majority of patients are referred from primary care facilities, both public and private owned. To our knowledge, there has been no studies regarding Covid-19 disease among the patients served by these centers. Our aim is to describe the clinical characteristics and outcome of COVID-19 cases seen at Olanrewaju Hospital, Ilorin, North Central Nigeria. This is a descriptive retrospective study of patients with confirmed COVID-19 seen over a one-year period. Records of all patients that tested positive using the real-time reverse-transcriptase-polymerase-chain-reaction (RT-PCR) were retrieved to extract relevant information. Data was analyzed using Epi Info 7.48 patients were analyzed. The mean age (standard deviation) was 50.0 years (17.89). Male sex predominates (58.3% vs 41.7%). Majority of patients were symptomatic (93.7%). Fever was most common presentation (75.6%). Shortness of breath was experienced by 11 patients (24.4%). Co-morbidities were found among 75% of the patients with hypertension being the commonest (45.9%). There were 6 deaths (12.5%), 5 of which occurred in the older age patients. Case fatality rate was significantly higher during the first wave than during the second wave 40% vs 5.6%, p < 0.05. The male gender, co-morbidities and older age groups are particularly prone to severe covid-19 infection with poorer outcome