Reduced graphene oxide-multiwalled carbon nanotubes hybrid film with low Pt loading as counter electrode for improved photovoltaic performance of dye-sensitised solar cells

In this work, the role of reduced graphene oxide (rGO) with hyperbranched surfactant and its hybridisation with multiwalled carbon nanotubes (MWCNTs) and platinum (Pt) nanoparticles (NPs) as counter electrode (CE) were investigated to determine the photovoltaic performance of dye-sensitised solar cells (DSSCs). Sodium 1,4-is(neopentyloxy)-3-(neopentyloxycarbonyl)- 1,4-dioxobutane-2-sulphonate (TC14) surfactant was utilised as dispersing and stabilising agent in electrochemical exfoliation to synthesise graphene oxide (GO) as initial solution for rGO production prior to its further hybridisation and fabrication as thin film. A chemical reduction process utilising hydrazine hydrate was conducted to produce rGO due to the low temperature process and water-based GO solution. Subsequently, hybrid solution was prepared by mixing 1 wt% MWCNTs into the produced rGO solution. TC14-rGO and TC14-rGO_MWCNTs hybrid solution were transferred into fluorine-doped tin oxide substrate to fabricate thin film by spraying deposition method. Finally, the CE films were prepared by coating with thin Pt NPs. Photoanode film was prepared by a two-step process: hydrothermal growth method to synthesise titanium dioxide nanowires (TiO2 NWs) and subsequent squeegee method to apply TiO2 NPs. According to solar simulator measurement, the highest energy conversion efficiency (η) was achieved by using CE-based TC14-rGO_MWCNTs/Pt (1.553%), with the highest short current density of 4.424 mA/cm2. The highest η was due to the high conductivity of CE hybrid film and the morphology of fabricated TiO2 NWs/TiO2 NPs. Consequently, the dye adsorption was high, and the photovoltaic performance of DSSCs was increased. This result also showed that rGO and rGO_MWCNTs hybrid can be used as considerable potential candidate materials to replace Pt gradually

Countries experiences: review of district health management in developing and low developing countries

A strong healthcare system is characterized by efficient health service delivery, adequate manpower and resource generation, a sustainable financing system and good governance. District healthcare system is the one closest to the people and its performance in relation to resource allocation impacts directly on the community health status. Over the years, many of the developed nations have learned to prioritize it mainly because it remains the most ideal way of improving population health through activities of general health promotion, disease prevention and provision of basic medical care. In the developing countries, achievement of district health system is not uniform and even among countries with comparable income per capita, wide variations exist. While some have attained a commendable population health status by strengthening their district healthcare systems by redoubling government’s commitment, enhancing resource production, encouraging fairness in healthcare financing and adopting development-oriented health policies, many others are facing healthcare challenges from lack of political will, limited resource allocation and shortage of both manpower and service infrastructure. For these countries, there is an urgent need to transform the district health system so that new and existing health problems can be dealt with decisively and more efficiently. This will require a renewed commitment from the state governments, reprioritizing and readjustment of present health programs, an inter-sectorial collaboration that involves all relevant stakeholders including the communities, and a renewed investment in sustainable health policies that deliver maximum impact at minimal cost

Fabrication Rutile-Phased TiO2 Film with Different Concentration of Hydrochloric Acid Towards the Performance of Dye-Sensitized Solar Cell

In this study, one-step hydrothermal method is demonstrated to synthesis TiO2 double-layer structure by modifying the concentration of hydrochloric acid (HCl). The X-ray diffraction (XRD) pattern analysis suggested that the dominant peak is rutile phase. Interesting morphologies such as cauliflower, chrysanthemum flower or dandelion structures over the nanorods layer were revealed by FE-SEM images and showed substantial effects to the thin film performance. UV-vis absorption spectra of prepared TiO2 film is in UV limitation with band gap energy (Eg) range from 2.57eV to 3.0eV. The optimum photoelectric conversion efficiency of DSSC is 42.5% that exhibited the efficiency of 6.41% for the sample synthesized using equal proportion of de-ionized water and HCl amount or in another word in accordance of ratio 1:1. These results serve as a guidance principle for preparing high quality DSSC thin film

Performance of Dye-Sensitized Solar Cell Using Size-Controlled Synthesis of TiO2 Nanostructure

Titanium dioxide (TiO2) or titania shows a great interest in solar cell application due to its morphology and crystalline structure. Moreover, it is an affordable compound that could make solar cells more cost economical than traditional silicon solar cells. In this study, one-step hydrothermal method is demonstrated to synthesis rutile TiO2 nanorods and nanoflowers morphology in nanoscale dimension on different hydrothermal reaction times for Dye-sensitized solar cells application. Increasing the reaction time could influence in formation of higher crystalline rutile phase titania nanostructure before abruptly decreases as the prolong hydrothermal process carry out. The length of the nanorods produced shows increasing behaviour and the growth of nanoflowers are become denser obviously. Band gap estimation is 2.75 eV slightly lower than bulk rutile TiO2. It shows that the growth mechanism under different reaction times has great influences on the morphologies and alignment of the nanostructure. Further, the DSSCs fabricated using 15 hours reaction time exhibited the best photovoltaic performance with highest efficiency of 3.42% and highest short-circuit photocurrent of 0.7097V

Influence of annealing temperature on the sensitivity of nickel oxide nanosheet films in humidity sensing applications

Nickel oxide (NiO) nanosheet films were successfully grown onto NiO seed-coated glass substrates at different annealing temperatures for humidity sensing applications. NiO seed layers and NiO nanosheet films were prepared using a sol-gel spin coating and sonicated sol-gel immersion techniques, respectively. The properties of NiO nanosheet films at as-deposited, 300 ℃, and 500 ℃-annealed were examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet-visible (UV-vis) spectroscopy, and humidity sensor measurement system. The XRD patterns demonstrate that the grown NiO films have crystalline cubic structures at temperature of 300 ℃ and 500 ℃. The FESEM images show that the large porous nanosheet network spread over the layers as the annealing temperature increased. The UV-vis spectra revealed that all the nanosheet films have the average transmittance below than 50% in the visible region, with absorption edges ~ 350 nm. The optical band gap energy was evaluated in ranges of 3.39 to 3.61 eV. From the obtained humidity sensing results, it shows that 500 ℃-annealed film exhibited the best sensitivity of 257, as well as the slowest response time, and the fastest recovery time compared with others

Enhanced optical performance of tellurite glass doped with samarium nanoparticles for fiber optics application

We report on the optical efficiency of samarium nanoparticles (NPs) doped tellurite glasses experimentally, for the first time to the best of our knowledge. A high optical efficiency of samarium NPs doped tellurite glasses stable against crystallization was fabricated via melt- quenched technique. In particular, this work underlines the enhancement of optical properties with increasing samarium NPs concentration and the change of polarizability of tellurite glass network with the presence of samarium NPs. Using X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) analysis and transmission electron spectra (TEM), the amorphous arrangement, structural assignments and particle size had been revealed. The optical performance of samarium NPs doped tellurite glass was characterized by EL X-02C high accuracy ellipsometer and UV-Vis spectrophotometer. Based on ellipsometer and UV-Vis spectrophotometer, the refractive index was found slightly increases meanwhile the optical band gap is reduced with the presence of samarium NPs. The obtained value of electronic polarizability revealed that samarium NPs affect greatly on polarizability of tellurite glass network. The slightly increases and nonlinear variations of polarizability were found with increasing amount of samarium NPs. The metallization criterion was found to decreased which suggest that the samarium NPs doped tellurite glass tends to be more semiconductor. This is a first step towards high optical performance of tellurite glass with future applications in fiber optics and laser glass

Graphene oxide deposition on neodymium doped zinc borotellurite glass surface: optical and polarizability study for future fiber optics

Neodymium oxide doped tellurite-based glass has been widely documented for potential uses in optoelectronics, but graphene oxide (GO)-coated tellurite-based glass has rarely been reported. In this work, we compare two sets of glass series which were GO-coated and uncoated tellurite-based glass series denoted as ZBTNd-GO and ZBTNd, respectively. The two sets of glasses were fabricated via melt-quenched process. A set of glass was coated with GO using low-cost spray coating method. The structural and morphological properties of the glass samples were investigated to confirm the type of structure in glass and formation of graphene oxide on glass surface. The X-ray diffraction (XRD) pattern confirmed the amorphous structural arrangement in both sets of glass series. The morphological study proved the existence of GO layers on top of the ZBTNd-GO surface. The optical bandgap energy of ZBTNd-GO glass was found in the range of 3.253 eV–3.381 eV which was higher than ZBTNd glass. Meanwhile, the refractive index of ZBTNd-GO glass varies from 2.301 to 2.332 which was higher than ZBTNd glass due to the presence of functionalized oxygenated groups in GO structure. The oxide ion polarizability of ZBTNd-GO glass was found decreased due to the shift of optical band gap when coated with GO. This work offers a new form of glass that could be used as a new strategy to upgrade the current photonic materials