Pradeep M Jayaweera

• BSc, PhD
• Senior Professor at University of Sri Jayewardenepura

Wastewater management is a crucial issue in most emergent nations with ever-growing global industrialization. From textiles to food, mankind uses dyes and pigments which pose a threat to the environment due to organic non-biodegradable dyes contained in wastewater. Rhodamine B (RhB) is a conventional colorant in many industries producing a large am...

The layered, acidic compound; α-TiP is widely popularized as a sorbent material for heavy metal removal from wastewater, as catalysts for biomass conversion and as an intermediate to produce high purity titanium dioxide particles. One of the conventional route for its synthesis is to react ilmenite with orthophosphoric acid under reflux conditions....

The average global temperature has not changed by more than 1° C over 10,000 years. It is predicted that the global temperature will rise by 3° C by the year 2100, unless action is taken to limit temperature increment to 1.5° C. Since the beginning of the century, the field of lithium-ion battery development has skyrocketed. Li-ion batteries have b...

Urea is used as a fertilizer, food supplement, and also as raw ingredient for the production of polymers and pharmaceuticals. If urea is not adequately processed, it can accumulate in the environment and pollute groundwater and surface water. Although urea is biodegradable, it has negative impacts on aquatic creatures in the long run. It courses eu...

Solid-state reaction of α-Ti(HPO4)2·H2O (α-TiP) and acetates of Co, Ni, or Cu at 500 °C and 800 °C produce a number of different metal titanium phosphate (MTiP) inorganic pigments with different colors and shades. At a given metal to α-TiP ratio and calcination temperature, the reaction produces several types of pigments such as phosphates M0.5TiO(...

Ilmenite is a naturally available black or steel-gray color mineral, called titanium iron oxide, FeTiO3.This valuable mineral comprises a significant amount of titanium that can be utilized as a titanium source to synthesize various materials. This study focused on synthesizing copper titanium phosphate compounds via an eco-friendly solid-state rea...

This study proposes a methodology to design the li-ion rechargeable cell with the cell mechanism, which is the combined effect of the reversible lithium intercalation-deintercalation and lithium polysulfide oxidation-reduction processes under normal laboratory conditions. As the result, a rechargeable cell using synthesized ilmenite-type cobalt tit...

Evolvulus alsinoides (family Convolvulaceae) is commonly known as "Nil Vishnukranthi" or "Shankhpushpi" in Sri Lanka and is used in the treatment of gastric ulceration. In our previous studies, we have investigated the in-vitro antacid potential of aqueous extract (aqE), ethanolic extract (EE) and hexane extract (HE) of E. alsinoides by neutralizat...

Antacid activity of combination of aqueous and ethanolic extracts.

Background: Evolvulus alsinoides L. is a perennial herb which belongs to the family Convolvulaceae and commonly known as "Vishnukranthi" in Sinhala or "Shankpushpi" in Sanskrit. The whole plant and the different parts of the plant are used in traditional medicine for many illnesses including gastric ulceration. The in vitro gastro-protective activi...

Nitrocellulose with silver nanoparticle (AgNP/NC) composite was prepared in situ using Ag(CH3CO2) and nitrocellulose without any reducing agent. The composite materials synthesized were spray coated onto glass substrates to obtain thin films. The AgNPs/NC composites were characterized by ultraviolet-visible, Fourier transform infrared, X-ray photoe...

Dye-sensitized solar cells (DSCs) assembled by natural dyes as a sensitizer recently made considerable attention. Use of inexpensive materials as the sensitizer in DSCs makes it more attractive devices for conversion of solar energy to electricity. UV–vis, fluorescence and fluorescence-excitation spectroscopic studies were used in this work to unde...

A simple and novel technique for the preparation of anatase TiO2 nanopowders using natural ilmenite (FeTiO3) as the starting material is reported. Digesting ilmenite with concentrated H3PO4 under refluxing conditions yields a white α-titanium bismonohydrogen orthophosphate monohydrate (TOP), Ti(HPO4)2·H2O, which can be easily isolated via gravity s...

Aggregation behavior of carotenoids

Lubricants are the substances used to lubricate machinery parts to reduce friction and increase their lifetimes. Producing environment-friendly lubricants from renewable feed stocks as alternatives to depleting petroleum based resources has attracted considerable attention in recent years. The lubricants prepared from renewable feed stocks exhibite...

Garcinol, a well-known medicinal phytochemical, was extracted and isolated from the dried fruit rinds of Garcinia quaesita Pierre. In this study, garcinol has successfully used to reduce silver ions to silver in order to synthesize G-AgNPs. The formation and the structure of G-AgNPs were confirmed by UV-Visible spectroscopy, FTIR spectroscopy and T...

The water soluble fraction (WSF) of diesel particulate matter (DPM), an environmental pollutant was used to synthesize silver nanoparticles (AgNPs). FTIR, fluorescence and UV-Vis data suggest that water soluble oxygenated PAHs in the WSF of DPM are capped to the surface of AgNPs providing the stability. The particle size, the size distribution, and...

Ilmenite mineral sand was used to synthesize titanium bismonohydrogen orthophosphate monohydrate, Ti(HPO4)2·H2O, and titanium phosphate, TiP2O7, two white pigments suitable in cosmetic applications. Ti(HPO4)2·H2O was obtained after digesting ilmenite in 85% phosphoric acid at 150 °C for 5 hours. On standing, unreacted ilmenite and white Ti(HPO4)2·H...

Introduction: Biosynthesized silver nanoparticles (AgNPs) have good antimicrobial properties comparable to chemically synthesized silver nanoparticles. Further, they have good potential as antibiofilm agents.Methods: AgNPs were synthesized from Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923) an...

Titanium dioxide (TiO2) has wide applications in food industry, cosmetics, pharmaceuticals and manufacturing industries due to its' many properties such as photocatalytic activity and stability. In this study, biosynthesis of TiO2 nanoparticles was achieved by using Baker's yeast. TiO2 nanoparticles were characterized by X-ray Diffraction (XRD), UV...

Green silver nanoparticle (AgNP) biosynthesis is facilitated by the enzyme mediated reduction of Ag ions by plants, fungi and bacteria. The antimicrobial activity of green AgNPs is useful to overcome the challenge of antimicrobial resistance. Antimicrobial properties of biosynthesized AgNPs depend on multiple factors including culture conditions an...

BACKGROUND Silver nanoparticles (AgNPs) are increasingly being used in medical applications. Therefore, cost effective and green methods for generating AgNPs are required. OBJECTIVES This study aimed towards the biosynthesis, characterisation, and determination of antimicrobial activity of AgNPs produced using Pseudomonas aeruginosa ATCC 27853. M...

Annual scientific sessions of Faculty of Medical Sciences, University of Sri Jayewardenepura, Sri Lanka.

This investigation identified that ion-exchange chromatography can efficiently remove iron from the leaching of ilmenite by HCl. The strong basic anionic-exchange resin IRA 410 Cl is capable of retaining the negatively charged iron chloro complex from 20% HCl leachate of ilmenite. Oxidative conversion of Fe2+ to Fe3+ facilitates the iron exchange t...

Background The antibacterial activity of 21 nm TiO2 nanoparticles (NPs) and particles modified with Garcinia zeylanica (G. zeylanica) against Methicillin resistant Staphylococcus aureus was investigated in the presence and absence of light. Results Surface modification of TiO2 NPs with the adsorption of G. zeylanica extract, causes to shift the ab...

Acid leaching of ilmenite (FeTiO3) obtained from beach sand was found to be more effective when roasted with ZnO or ZnS at 900 °C. Remarkably higher iron and titanium leaching rates were observed when compared with normal ilmenite in 5.0 M HCl at 30 °C and 6.0 M H2SO4 at 110 °C, respectively. Roasting of ilmenite with ZnO or ZnS converts acid resis...

a b s t r a c t Radical cations, dications and oxidized intermediate species of three carotenoids, namely, β-carotene, lycopene and norbixin, were generated in CH 2 Cl 2 solutions via chemical oxidation using anhydrous FeCl 3 . UV–vis, fluorescence and fluorescence-excitation spectroscopic studies were performed to understand and compare the nature...

The surface photochemistry of nitric acid (HNO3) adsorbed on hematite (α-Fe2O3) particle surfaces under various environmental conditions has been investigated. Surface product formation and photochemistry of adsorbed nitrate studied using X-ray photoelectron spectroscopy (XPS). Adsorbed nitrate resulted from gas phase nitric acid adsorption showed...

The rate of leaching of iron from ilmenite (FeTiO 3) in hydrochloric acid (HCl) solutions is greatly enhanced by the presence of ultraviolet (UV) light. The magnitude of the air purged UV light illuminated leaching rate is approximately twofold higher than the N 2 purged leaching rate under dark conditions. The enhanced rate is attributed to the ph...

A low-cost photoconductive dual-band detector based on a ZnO film sensitized with lead sulfide quantum dots (PbS-QDs) is reported. The UV response arises from the interband absorption of UV radiation by ZnO, and the IR response is due to the absorption in the PbS-QDs. The detector exhibits UV response from 200 to 400 nm with a peak responsivity of...

Mineral dust aerosol is indisputably an important component of the Earth’s atmosphere and provides a reactive surface for heterogeneous chemistry to occur. These reactions can alter concentrations of key trace atmospheric gases as well as change the physicochemical properties of the dust particles. The focus of this Perspective article is on severa...

The β-sitosterol moiety was known to bind acyclic carotenoids phytoene and phytofluene. Recently it was reported that impurities of β-sitosterol from plant sources ruled out isolation from those sources. These studies showed that common β-sitosterol contained many impurities which can be separated by using a chromatotron. Studies also showed that β...

The adsorption of nitrogen dioxide on gamma aluminium oxide (gamma-Al(2)O(3)) and alpha iron oxide (alpha-Fe(2)O(3)) particle surfaces under various conditions of relative humidity, presence of molecular oxygen and UV light has been investigated. X-Ray photoelectron spectroscopy (XPS) is used to monitor the different surface species that form under...

Alizarin complexone (AC) adsorbed onto nano-porous TiO2 films show complexation with Fe2+ ions, and de-complexation in the presence of UV light in a reversible manner. FTIR and DRFT-IR studies indicate that surface anchoring of AC result from carboxylate groups and 2-OH group. Coordination of Fe2+ ions onto the surface results from the 1-hydroxy an...

The quality of the letters printed on the tobacco cigarettes, brand name "John Player™" is found to be viscosity dependent on the ink used for printing. The viscosity changes of the ink used, cause the printed letters to be smudged and of poor quality. At present selection of bad quality prints are done by visual identification, as no scientific te...

Oppositely charged SPADNS and rhodamine B (RhB) molecules show strong electrostatic ion pair interactions viaN+< group of RhB with three –SO3− groups of SPADNS. TiO2 surface-adsorbed SPADNS molecules generate remarkably enhanced photocurrents when electrostatically attached number of RhB units with SPADNS increase. Ionic association constants were...

The adsorption, thermal, and UV reactions of ethanol over a TiO2(110) single-crystal surface have been studied in the presence and the absence of molecular oxygen. Adsorption of ethanol is dissociative at room temperature and gives rise to two C1s peaks of equal intensities (at 285.2 and 286.5 eV) attributed to -CH3 and -CH2O- groups, respectively....

Diffuse reflectance FTIR studies indicate that alizarin red (1,2-dihydroxy-9-10-anthraquinone sulfonic acid) undergoes reversible acid/base induced linkage isomerization on nano-porous TiO2 surfaces. It is also possible to convert molecules from surface orientation, ARS-(TiO2-1,9) to the ARS-(TiO2-1,2) by thermal activation.

Bromopyrogallol red (BPR), an anionic dye material was used in nano-porous photoelectrochemical cells as the sensitizer in conjunction with a fluorescent cationic dye, rhodamineB (RhB) and acridine orange (AO). The overlap between absorption and emission spectra of BPR/RhB and the formation of a strong associated complex influences the photoelectro...

A novel dinuclear ruthenium(II) complex bridged by dianionic bridge 3-(2-phenol)-5-(pyridin-2-yl)-1,2,4-triazole in which the ruthenium metal atoms are bound through N,N coordination to the pyridine and triazole and O,N coordination to the triazole and phenolate is described. The electrochemical, spectroscopic and photophysical behaviour of the dim...

Nonionic nature of As(III) in aqueous solutions, pH less than nine makes it a difficult form of arsenic which cannot be efficiently removed from drinking water by conventional ion exchange and adsorption chromatographic techniques. In the presence of TiO2 photocatalyst and UV radiation, nonionic H 3AsO3 can be readily oxidized to the anionic form o...

Bromopyrogallol-red and pyrocatechol-violet, the two triphenylmethane-type ligands, can be readily complexed with [Co(1,10-Phen)2]2+ moiety. The resulting complexes are capable of enhancing photovoltaic properties when compared with the corresponding ligands. Absorption and photocurrent action spectra suggest that a low-lying weak electronic charge...

Complexation of bromopyrogallol ligand with di(aqua)bis(oxalato)iron(II) moiety, [Fe(II)(H2O)2(C2O4)1]2−, shows enhanced photovoltaic properties when compared with the photovoltaic cells coated by bromopyrogallol ligand only. Electrochemical and absorption spectroscopic data suggest the nature of the lowest electronic transition of iron(II) complex...

Photovoltaic cells capable of generating high photo-current densities and voltages were fabricated using metallochromic triphenylmethane type dye materials by depositing nano-porous TiO2 films onto a thin film of SnO2 coated conducting glass. Two dye materials belonging to the triphenylmethane class namely, bromopyrogallol red and pyrocatechol viol...

The extent of metal−ligand orbital mixing and the degree of electronic coupling between [M(bpy)2]2+ fragments linked through a redox active 1,4-dihydroxy-2,5-bis(pyrazol-1‘-yl)benzene (p-L) bridge is described, where M is Os or Ru and bpy is 2,2‘-bipyridyl. This is the first reported example of osmium and ruthenium/osmium metals linked across a 1,4...

The process flow diagram for the multi-stage flash (MSF) desalination process is quiet complex, where it includes several stages for brine flashing, preheaters for feed seawater, two sections for heat recovery and rejection, cooling water stream, and brine recycle stream. The process fundamentals are analyzed in order to have a better understanding...

The heat transfer characteristics on the HTSC-surface in a pool of liquid nitrogen under conditions of slow increasing or decreasing transport current have been experimentally studied. It was observed that there are instabilities of heat transfer regimes regarding the small thermal disturbances (fluctuations). These unstable heat transfer regimes a...

The excited-state properties of mononuclear and dinuclear Ru(bpy)(2) complexes with bpzt(-) bridging ligand (bpy = 2,2'-bipyridine, and bpzt(-) = 3,5-bis(pyrazin-2-yl)-1,2,4-triazole) have been probed by resonance Raman (RR), excited-state absorption (ESA), and spectroelectrochemical techniques. Excited-state RR spectroscopy provides evidence of a...

Resonance Raman (RR) spectroscopic studies, supplemented by excited state absorption techniques, were used to probe the effect of modifications to the electronic environment on the excited states of mono- and di-nuclear Ru(II) polypyridyl complexes containing triazole-based bridging ligands. Ground state RR spectroscopy showed that coordination of...

Resonance Raman (RR) spectroscopic studies, supplemented by excited state absorption techniques, were used to probe the effect of modifications to the electronic environment on the excited states of mono- and di-nuclear Ru(II) polypyridyl complexes containing triazole-based bridging ligands. Ground state RR spectroscopy showed that coordination of...

Copper(I) and rhenium(I) complexes with the ligand dipyrido[3,2,-a:2′,3′-c]phenazine (dppz) and a number of substituted analogues have been synthesized. Their spectroscopic and electrochemical properties have been studied. It is found that the lowest-energy transition for the complexes is metal-to-ligand charge transfer (MLCT) in nature. This has a...

Some novel bis(2,2′-bipyridyl)ruthenium(II) complexes based on the ligands 1,4-dihydroxy-2,5-bis(pyrazol-1-yl)benzene (H 2 L p ) and 1,4-dihydroxy-2,3-bis(pyrazol-1-yl)benzene (H 2 L o ) have been prepared and characterized. The spectroscopic properties of the analogous H 2 L p complex containing deuteriated 2,2′-bipyridyl were also studied....

Raman spectroelectrochemical and X-ray crystallographic studies have been made for the binuclear copper(I) complex, [(Ph3P)2Cu(dpq)Cu(PPh3)2][BF4]2, where dpq is the bridging ligand 2,3-di(2-pyridyl)quinoxaline. The X-ray data show that the pyridine rings are twisted out of plane with respect to the quinoxaline ring which is itself non-planar. The...

Time-resolved resonance Raman spectroscopy of the lowest energy excited state of the 4,4'-bipyridyl ligand-bridged complex, [(CO)(5)W(L)W(CO5] (1), and Raman spectroscopy of electrochemically reduced 1, both give bands characteristic of the the L(.-) species. This confirms that the ligand L is negatively charged in the lowest energy exicited state...

Thesis (Ph. D.)--Queen's University of Belfast, 1996.