Supersensitive metal free in-situ synthesized graphene oxide@cellulose nanocrystals acetone sensitive bioderived sensors.

A series of graphene oxide@cellulose nanocrystal (GO@CNC) nanoparticles (NPs) were synthesized in this study using a room temperature-based simple modified hummers process. The morphological structures, as well as chemical characteristics of these materials, were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and other techniques. The results show that the as-prepared nanoparticles are made up of crystallite grains with an average size of around 7.82, 14.69, 10.77, 7.82, and 12.51 nm for GO, CNC, GO1@CNC1, GO2@CNC3, and GO3@CNC3 respectively, and OH & COOH functionalities on the NPs' surfaces. GO@CNC NPs exhibit significantly better sensing characteristics towards acetone when compared to virgin GO nanoplatelets; specifically, the optimal sensor based on GO3@CNC3 NPs showed the highest response (60.88 at 5 ppm), which was higher than that of the virgin GO sensor at 200 °C operating temperature and including those reported. Furthermore, the sensors have a high sensitivity towards acetone in sub-ppm concentrations as well as a detection limit of 5 ppm, making it a viable candidate for diabetes breath testing.

Elucidating the Trajectory of the Charge Transfer Mechanism and Recombination Process of Hybrid Perovskite Solar Cells.

Perovskite-based solar cells (PSCs) have attracted attraction in the photovoltaic community since their inception in 2009. To optimize the performance of hybrid perovskite cells, a primary and crucial strategy is to unravel the dominant charge transport mechanisms and interfacial properties of the contact materials. This study focused on the charge transfer process and interfacial recombination within the n-i-p architecture of solar cell devices. The motivation for this paper was to investigate the impacts of recombination mechanisms that exist within the interface in order to quantify their effects on the cell performance and stability. To achieve our objectives, we firstly provided a rationale for the photoluminescence and UV-Vis measurements on perovskite thin film to allow for disentangling of different recombination pathways. Secondly, we used the ideality factor and impedance spectroscopy measurements to investigate the recombination mechanisms in the device. Our findings suggest that charge loss in PSCs is dependent mainly on the configuration of the cells and layer morphology, and hardly on the material preparation of the perovskite itself. This was deduced from individual analyses of the perovskite film and device, which suggest that major recombination most likely occur at the interface.

Blood Ketone Bodies and Breath Acetone Analysis and Their Correlations in Type 2 Diabetes Mellitus.

Analysis of volatile organic compounds in the breath for disease detection and monitoring has gained momentum and clinical significance due to its rapid test results and non-invasiveness, especially for diabetes mellitus (DM). Studies have suggested that breath gases, including acetone, may be related to simultaneous blood glucose (BG) and blood ketone levels in adults with types 2 and 1 diabetes. Detecting altered concentrations of ketones in the breath, blood and urine may be crucial for the diagnosis and monitoring of diabetes mellitus. This study assesses the efficacy of a simple breath test as a non-invasive means of diabetes monitoring in adults with type 2 diabetes mellitus. Human breath samples were collected in Tedlar™ bags and analyzed by headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME/GC-MS). The measurements were compared with capillary BG and blood ketone levels (ß-hydroxybutyrate and acetoacetate) taken at the same time on a single visit to a routine hospital clinic in 30 subjects with type 2 diabetes and 28 control volunteers. Ketone bodies of diabetic subjects showed a significant increase when compared to the control subjects; however, the ketone levels were was controlled in both diabetic and non-diabetic volunteers. Worthy of note, a statistically significant relationship was found between breath acetone and blood acetoacetate (R = 0.89) and between breath acetone and ß-hydroxybutyrate (R = 0.82).

Malaria in children under-five: A comparison of risk factors in lakeshore and highland areas, Zomba district, Malawi.

BACKGROUND: In Malawi, children under the age of five living in different geographical areas may experience different malaria risk factors. We compare the risk factors of malaria experienced by children under the age of five from Zomba district, who reside in lakeshore and highland areas. METHODS: We conducted a case control study of 765 caregivers, cases being children under-five who were diagnosed with malaria, and obtained matched controls from local health facilities and communities. We used a multivariate logistic regression to identify individual and household risk factors. RESULTS: In lakeshore areas, risk factors were households located one kilometer or less away from stagnant water (AOR: 2.246 95% CI: 1.269 to 3.975 P-value: 0.005); or if the household had obtained a mosquito bed net more than one year ago (AOR: 1.946 95% CI: 1.073 to 3.529 P-value: 0.028). In highland areas, risk factors were households which used a borehole/unprotected well (AOR: 1.962 95% CI: 1.001 to 3.844 P-value 0.050), communal standpipe (AOR: 3.293 95% CI: 1.301 to 8.332 P-value 0.012), and un-protected dug well in their yards (AOR: 16.195 95% CI: 2.585 to 101.464 P-value 0.003) as their drinking water sources. In highland areas, caregivers not attending health talks on malaria prevention messages was a risk factor (AOR: 2.518 95% CI: 1.439 to 4.406 P-value: 0.001). CONCLUSION: Children under the age of five living in highland areas experience different malaria risk factors compared to children living in lakeshore areas. Settling away from stagnant/open water source in lakeshore and encouraging caregivers to attend health talks on malaria prevention in highlands can help reduce malaria transmission. Nevertheless, using a mosquito bed net that is more than one year old is a common risk factor in both locations. Using new mosquito bed nets can significantly reduce the risk of contracting malaria in children under the age of five.

Sensing Technologies for Detection of Acetone in Human Breath for Diabetes Diagnosis and Monitoring.

The review describes the technologies used in the field of breath analysis to diagnose and monitor diabetes mellitus. Currently the diagnosis and monitoring of blood glucose and ketone bodies that are used in clinical studies involve the use of blood tests. This method entails pricking fingers for a drop of blood and placing a drop on a sensitive area of a strip which is pre-inserted into an electronic reading instrument. Furthermore, it is painful, invasive and expensive, and can be unsafe if proper handling is not undertaken. Human breath analysis offers a non-invasive and rapid method for detecting various volatile organic compounds thatare indicators for different diseases. In patients with diabetes mellitus, the body produces excess amounts of ketones such as acetoacetate, beta-hydroxybutyrate and acetone. Acetone is exhaled during respiration. The production of acetone is a result of the body metabolising fats instead of glucose to produce energy. There are various techniques that are used to analyse exhaled breath including Gas Chromatography Mass Spectrometry (GC-MS), Proton Transfer Reaction Mass Spectrometry (PTR-MS), Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS), laser photoacoustic spectrometry and so on. All these techniques are not portable, therefore this review places emphasis on how nanotechnology, through semiconductor sensing nanomaterials, has the potential to help individuals living with diabetes mellitus monitor their disease with cheap and portable devices.

Seasonal variation of malaria cases in children aged less than 5 years old following weather change in Zomba district, Malawi.

BACKGROUND: Malaria is seasonal and this may influence the number of children being treated as outpatients in hospitals. The objective of this study was to investigate the degree of seasonality in malaria in lakeshore and highland areas of Zomba district Malawi, and influence of climatic factors on incidence of malaria. METHODS: Secondary data on malaria surveillance numbers and dates of treatment of children <5 years of age (n = 374,246) were extracted from the Zomba health information system for the period 2012-2016, while data on climatic variables from 2012 to 2015 were obtained from meteorological department. STATA version 13 was used to analyse data using non-linear time series correlation test to suggest a predictor model of malaria epidemic over explanatory variable (rainfall, temperature and humidity). RESULTS: Malaria cases of children <5 years of age in Zomba district accounts for 45% of general morbidity. There was no difference in seasonality of malaria in highland compared to lakeshore in Zomba district. This study also found that an increase in average temperature and relative humidity was associated of malaria incidence in children <5 year of age in Zomba district. On the other hand, the difference of maximum and minimum temperature (diurnal temperature range), had a strong negative association (correlation coefficients of R2 = 0.563 [All Zomba] ß = -1295.57 95% CI -1683.38 to -907.75 p value <0.001, R2 = 0.395 [Zomba Highlands] ß = -137.74 95% CI -195.00 to -80.47 p value <0.001 and R2 = 0.470 [Zomba Lakeshores] ß = -263.05 95% CI -357.47 to -168.63 p value <0.001) with malaria incidence of children <5 year in Zomba district, Malawi. CONCLUSION: The diminishing of malaria seasonality, regardless of strong rainfall seasonality, and marginal drop of malaria incidence in Zomba can be explained by weather variation. Implementation of seasonal chemoprevention of malaria in Zomba could be questionable due to reduced seasonality of malaria. The lower diurnal temperature range contributed to high malaria incidence and this must be further investigated.

Epitaxial deposition of silver ultra-fine nano-clusters on defect-free surfaces of HOPG-derived few-layer graphene in a UHV multi-chamber by in situ STM, ex situ XPS, and ab initio calculations.

The growth of three-dimensional ultra-fine spherical nano-particles of silver on few layers of graphene derived from highly oriented pyrolytic graphite in ultra-high vacuum were characterized using in situ scanning tunneling microscopy (STM) in conjunction with X-ray photoelectron spectroscopy. The energetics of the Ag clusters was determined by DFT simulations. The Ag clusters appeared spherical with size distribution averaging approximately 2 nm in diameter. STM revealed the preferred site for the position of the Ag atom in the C-benzene ring of graphene. Of the three sites, the C-C bridge, the C-hexagon hollow, and the direct top of the C atom, Ag prefers to stay on top of the C atom, contrary to expectation of the hexagon-close packing. Ab initio calculations confirm the lowest potential energy between Ag and the graphene structure to be at the exact site determined from STM imaging.

Photoluminescence and hydrogen gas-sensing properties of titanium dioxide nanostructures synthesized by hydrothermal treatments.

Titanium dioxide (TiO(2)) nanostructures were synthesized by microwave-assisted and conventionally heated hydrothermal treatment of TiO(2) powder. The tubular structures were converted to a rodlike shape by sintering the samples at various temperatures in air for 3 h. This was accompanied by phase transformation largely influenced by the method of synthesis and the mode of heating. The X-ray diffraction results are in agreement with the structural transformation indicating the gradual changes in the phase and crystallinity of the as prepared samples. The tubular structure is found to collapse at high temperature. UV-vis-IR spectroscopic results suggest that nanorods tend to absorb photons of higher energy (λ = 280 nm) than nanotubes (λ = 300 nm) but emit photons with lower energy than nanotubes. It was found that the nanotubes have a sharper photoluminance emission line at 340 nm that is absent in the nanorods. We also found that nanotubes have higher efficiency, lower threshold sensing temperature, longer response time, and shorter recovery time for hydrogen gas sensing than nanorods.

Synthesis and characterization of potential iron-platinum drugs and supplements by laser liquid photolysis.

Highly crystalline nanospherical iron-platinum systems were produced by 248 nm laser irradiation of a liquid precursor at different laser fluences, ranging from 100-375 mJ/cm(2). The influence of laser intensity on particle size, iron composition, and structure was systematically investigated. Different nanostructures of iron-platinum alloy and chemically disordered iron-platinum L10 phase were obtained without annealing. The prepared precursor solution underwent deep photolysis to polycrystalline iron-platinum nanoalloys through Fe(III) acetylacetonate and Pt(II) acetylacetonate. Fe(II) and Pt(I) acetylacetone decomposed into Fe(0) and Pt(0) nanoparticles. We found that the (001) diffraction peak shifted linearly to a lower angle, with the last peak shifting in opposition to the others. This caused the face-centered cubic L10 structure to change its composition according to laser fluence. The nanostructures were shown to contain iron and platinum only by energy-dispersive spectroscopy at several spots. The response of these iron-platinum nanoparticles to infrared depends on their stoichiometric composition, which is controlled by laser fluence.

Formation of tungsten oxide nanostructures by laser pyrolysis: stars, fibres and spheres.

In this letter, the production of multi-phase WO3 and WO3-x (where x could vary between 0.1 and 0.3) nanostructures synthesized by CO2-laser pyrolysis technique at varying laser wavelengths (9.22-10.82 mm) and power densities (17-110 W/cm2) is reported. The average spherical particle sizes for the wavelength variation samples ranged between 113 and 560 nm, and the average spherical particle sizes for power density variation samples ranged between 108 and 205 nm. Synthesis of W18O49 (= WO2.72) stars by this method is reported for the first time at a power density and wavelength of 2.2 kW/cm2 and 10.6 µm, respectively. It was found that more concentrated starting precursors result in the growth of hierarchical structures such as stars, whereas dilute starting precursors result in the growth of simpler structures such as wires.