Article InfoThis work reports the synthesized plasmonic silver nanoparticles (Ag-NPs)by SILAR (successive ionic layer adsorption and reaction)technique on glass substrates with 5, 8, 11, 14 and 17 SILAR cycles and effect on the optical properties of the thin films (TFs). The absorbance data of the as-synthesized Ag-NPs thin films were obtained using UVVis (Ultraviolet visible) spectroscopy at room temperature in the wavelength range of 250nmto 900nm. The transmittance, absorption coefficient, optical bandgap, refractive index and extinction coefficient were experimentally measured. The absorption peaks of(450, 455, 470, 455, 500) nm, and optical energy band gaps of (2.20, 2.16, 2.12, 2.11, 1.84) eV with absorption coefficient approximately 10 -12 cm -1 were identified for the SILAR cycles, which agree to a particular characteristics of the silver nanoparticles surface plasmon resonance band. The results showed a red shift from 450nm to 500nm by increasing the SILAR cycles from 5 to 17 cycles, which is attributed to coalescence of Ag nanoparticles at higher SILAR deposition cycles. An increase in the refractive index of the films from 1.55 to 2.51 observed, with approximate average value of 1.92, may be due to the optical properties of silver nanoparticles. This study revealed that Ag-NPs synthesized by SILAR technique gives good optical properties with excellent absorption bands in the visible region, which has potential applications in technology.
Integrated water vapour (IWV) is the total amount of precipitable water in an atmospheric column between the Earth’s surface and space. The implication of its variability and trend on the Earth’s radiation budget and precipitation makes its monitoring on a regular basis important. ERA-Interim reanalysis (ERA) and radiosonde (RS) data from 1988 to 2018 were used to investigate variability and trend in IWV over Peninsular Malaysia. ERA performed excellently when gauged with RS. Trend analysis was performed using the non-parametric Mann–Kendall and Theil–Sen slope estimator tests. ERA and RS IWV revealed double fluctuations at the seasonal time scale, with maxima in May and November, which are the respective beginnings of the southwest monsoon (SWM) and northeast monsoon (NEM) seasons, as well as coincidental peaks of precipitation in the region. IWV decreased in a southeast–northwest orientation, with regional maximum domiciled over the southeastern tip of the region. Steep orography tended to shape intense horizontal gradients along the edges of the peninsular, with richer gradients manifesting along the western boundary during SWM, which harbours more water vapour in the peninsular. IWV trends, both at the annual and seasonal time series, were positive and statistically significant at the 95% level across the stations, except at Kota Bharu, where a nonsignificant downward trend manifested. Trends were mostly higher in the NEM, with the greatest rate being 0.20 ± 0.42 kgm−2 found at Penang. Overall, the IWV trend in Peninsular Malaysia was positive and consistent with the upward global changes in IWV reported elsewhere.
In this study seasonal and inter-annual patterns as well as trend in the total precipitable water vapour (TPW) over Malaysia, based on a 30-year data from MERRA-2, have been evaluated using least square regression method. Indicator TPW revealed a pair of minima in February/August and maxima in May/November with highest and lowest long-term means found in East Malaysia. Long-term seasonal variability of TPW exhibited latitudinal dependency in both the NEM and SWM seasons. Indicator TPW showed respective southeast-northwest and southwest-northeast spatial distribution in West and East Malaysia, with the highest statistically significant positive trend found in the former.
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