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In the present study, MnO2 nanoparticles were synthesized by simple facile hydrothermal method. The structural, morphological, and electrochemical behaviour of the synthesized nanoparticles were analyzed by XRD, SEM/EDX and CV. XRD confessed that the tetragonal structure of bare MnO2. The crystallite size of MnO2 nanoparticles obtained at MnCl2: KMnO4 (0.5: 0.4 M) was found to be 9.2 nm. The nanorod structures of the synthesised MnO2 nanoparticles were revealed by morphological studies. The electrochemical behaviour of nanorod like MnO2 nanoparticles showed a specific capacitance of 91 Fg−1 at lower scan rate of 10 mV s−1.

The suggested work concentrates on preparing ZnO and the surfactant sodium hexametaphosphate (SHMP)-assisted pure and Sn4+-doped ZnO photocatalysts to degrade the organic dye methyl orange (MO). For that, a low-temperature hydrothermal technique was employed. For preparing the surfactant-assisted Sn-doped ZnO photocatalyst, varied levels (5, 10 and 15 mM) of Sn4+ ions have been employed. The prepared products were investigated for their structural, optical and morphological properties. The results of structural analysis reveal the hexagonal wurtzite phase of ZnO. The band gap of ZnO estimated using Kubelka–Munk function revealed a reduction from 3.34 to 3.28 eV on 5 mM of Sn4+ doping and then stepped up as the concentration of doping increases. The photocatalytic response of the catalysts was analysed to degrade the organic dye methyl orange (MO) under solar light irradiation. The surfactant-assisted ZnO doped with 5 mM of Sn4+ ions displayed better performance (90%) than the ZnO (76%) and the surfactant-assisted ZnO (80%) in MO degradation.

SnO2 nanoparticles (NPs) were synthesized by facile hydrothermal method in the presence of polyethylene glycol (PEG), cetyl trimethylammonium bromide (CTAB) and sodium hexametaphosphate (SHMP) as surfactant. The synthesized samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high resolution scanning electron microscopy (HRSEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), UV–visible diffuse reflectance spectroscopy (UV–visible DRS) and photoluminescence (PL). The XRD studies revealed that the position of diffraction peaks agreed well with the reflection of a tetragonal structure of SnO2 phase. The structure of the SnO2 did not change by introducing surfactants but the crystallite size was decreased. The optical studies revealed a clear blue shift in the band gap energy (Eg) with a decrease in particle size. The PL intensity of SHMP assisted NPs is lower than that of bare SnO2 and other surfactant assisted SnO2 NPs, which indicated the suppression of the recombination of the photogenerated carriers. These results reveal that SHMP assisted SnO2 NPs is suitable for further electrochemical and photocatalytic activity. The surfactant (SHMP) assisted SnO2 photocatalyst exhibited the increased photocatalytic activities compared with the bare SnO2 photocatalyst. Furthermore, the SHMP assisted SnO2 electrode exhibited the increased supercapacitor performances.

An effective disaster early warning system is instrumental in evacuation to reduce the disaster impact. In an end-to-end early warning cycle, an effective community early warning dissemination mechanism plays an important role. The identification of the population at-risk to which the early warning needs to be directed and the clarity of the risk communication with social and cultural awareness are two key attributes to enhance early warning dissemination strategy. The objectives of this study are two-fold: (1) to carry out a village level early warning dissemination system audit in 24 selected villages in three districts of Northern and Eastern Provinces of Sri Lanka, and (2) to assess the reliability of the existing public addressing systems such as loud speakers, bells and drums (same technical devices are used for early warning dissemination during disaster alerts) in 44 religious places in the 24 selected villages. The study provided set of recommendations to increase the effectiveness of the existing early warning dissemination method using the locally available resources and to develop the religious places as early warning dissemination nodes by improving the technical reliability of the existing public addressing systems.

In the recent past, Sri Lanka has been experiencing an increase of intensity and frequency of natural disasters. Therefore, the study was carried out to introduce an Open Source application to collect the field level information and to identify the flood inundation areas through a 3D model. The case study area included 48 Grama Niladhari Divisions in Manmunai North Divisional Secretariat (DS), Batticaloa District, Sri Lanka. The study helped to analyze the role of OpenStreetMap (OSM) to support the mapping of the flood risk level of the study area. This objective was achieved by collecting flood exposure data through community participatory method using OSM, which was integrated into a Digital Elevation Model (DEM). Elevation points were collected using Google Earth and TCX Converter. The flood hazard maps were created using inputs such as water depth and flood extent of the DEM and verified through a local community participatory mapping exercise. Next, vulnerability maps were generated based on factors such as building characteristics of houses, population of the areas and the availability of assistance during the flood scenarios in 2010 and 2011. Finally, the flood risk map of the study area was prepared in combination with hazard and vulnerability maps. The study produced a user-friendly application of open source and GIS to develop a 3D flood risk model for the identification of flood risk levels. Exposure data have been uploaded into the OSM, therefore, it can be accessed anytime, anywhere and by anyone. The extent of study area is 2593 ha; where about 25,000 families live and there are more than 32,000 buildings. The building footprint database was established using JavaOSM and Bing satellite imagery. It was updated with the building attributes produced by the data collection exercise. This study showed that when the water level increases in the lagoon, nearly 25 GN Divisions (GNDs) out of 48 GNDs are under high flood risk. The developed online geospatial database in OpenStreetMap is an important asset, since it supports the preparation of an emergency flood risk management plan, which helps to accelerate the emergency response and flood mitigation plan for the study area.

Nickel diselenide (NiSe2) had been conflated from the reaction of nickel acetate tetra hydrate (C4H14NiO8) with selenium (Se) powder by simple hydrothermal method at 200 °C for 5 hrs. The structural analysis revealed that the synthesized samples are consists of cubic structure. The electrochemical performance was obtained from the cyclic voltammetery (CV) and galvanostatic charge discharge (GCD) profiles. The prepared NiSe2 exhibited the specific capacitance value of 384 Fg−1 at scan rate of 2 mVs−1. The obtained results ensure that the NiSe2 nanoparticles could act as an enhanced working electrode for the upcoming generation of supercapacitors.

Bare and Zn doped SnO2 nanoparticles (NPs) were synthesized by hydrothermal method using Sodium hexametaphosphate (SHMP) as a capping agent. The structural, morphological and optical properties of the synthesized NPs were examined using XRD, FTIR, HRSEM, TEM, UV–visible DRS and PL. The XRD results indicated a good crystallinity of the sample and confirmed the tetragonal structure, and well agreed with the results of TEM. The chemical bondings of Sn–O–Sn functional group were confirmed by FTIR absorption peaks appearing at 650 cm−1. The spherical like morphology was observed in HRSEM analysis. EDS spectra confirmed the presence of elements Sn, Zn and O. Further, the optical band gaps of doped NPs were decreased due to the effect of band gap shrinkage. The photocatalytic performance of the doped NPs was tested by the degradation of Methyl violet (MV) under sunlight. Compared to the bare and SHMP assisted SnO2 photocatalysts, the doped NPs showed enhanced photocatalytic activities. In addition, the electrochemical performance of the doped NPs was investigated by CV, GCD and EIS studies. The results of capacitance behavior revealed the improved capacitance performance for SnO2 on Zn doping. The obtained results confirmed that this material is promising candidate for photocatalytic and supercapacitor application.

Bare and Zr doped SnO2 nanoparticles (NPs) were synthesized by hydrothermal technique using Sodium hexametaphosphate (SHMP) as a surfactant. The structural, functional, morphological, chemical composition and optical properties of the synthesized nanoparticles were characterized. The photocatalytic performance of the synthesized nanoparticles is carried out under sunlight irradiation using methyl violet (MV) dye. Additionally, the electrochemical behavior of the synthesized nanoparticles is investigated as supercapacitor electrode materials through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies. The experimental results revealed that incorporation of Zr into the SnO2 matrix had increased the photocatalytic activity and electrochemical performance compare with the bare and SHMP assisted SnO2 nanoparticles.

In this paper, we report the synthesis of tellurium (Te) doped ZnO nanocrystals for photocatalytic applications. X-ray diffraction, Fourier transforms infrared, photoluminescence and field emission scanning electron microscope are the techniques employed to characterize the properties of the prepared products. The photocatalytic activities of the undoped and doped ZnO are analyzed by the degradation of brilliant green (BG). The results of the degradation reveal that ZnO doped with Te has higher photocatalytic performance than undoped ZnO.