Antimicrobial starch-citrate hydrogels were prepared by physical crosslinking of starch citrate, Poly(vinyl alcohol (PVA) and Polyethylene glycol (PEG) via the freeze–thaw technique. This ...starch-citrate hydrogel exhibited excellent antimicrobial activity against various bacteria strains such as Escherichia coli (gram negative), Staphylococcus pyogenes (gram negative), Salmonella thypimurium (gram positive) and Streptococcus aureus (gram positive). Most notably it showed antimicrobial activity against the multiple antibiotic resistant (M.A.R) superbugs (Klebsiella pneumoniae). Penicillin G loaded starch-citrate hydrogel was observed to exhibit a sustain release profile over 7 days. Penicillin G loaded starch-citrate hydrogel also exhibited synergistic antimicrobial activities against Salmonella thypimurium, Escherichia coli (E-coli) (O15:H7) and E-coli control (ATC 2925). The potential application of starch-citrate hydrogel as both antimicrobial agent and drug delivery carriers is therefore envisaged.
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We have documented the fabrication of manganese dioxide (MnO2) thin-film electrochemical capacitor (EC) prototypes with dual-planar electrode configuration. These EC prototypes exhibited good ...capacitive behaviors in mild Na2SO4 aqueous electrolyte. Enhanced capacitive behaviors of EC prototypes were observed upon prolonged voltammetric cycling which could be associated with microstructural transformation of MnO2 thin-film electrodes from densely packed plate-like to irregular petal-like surface morphology. Effects of voltammetric scan rates, prolonged voltammetric cycling, electrolyte composition, and electrolyte concentration on the surface morphology of MnO2 thin-film electrodes, and associated capacitive behaviors of MnO2 thin-film EC prototypes were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge (GCD) techniques. Results of both CV and EIS indicated that thin-film MnO2 EC prototypes exhibited the highest specific capacitance of 327 F/g in 0.2 M Na2SO4 aqueous electrolyte. Being environmentally benign and cheap, MnO2 thin-film electrochemical capacitors have high potential utility as pulsed power sources, as well as load-leveling functions in various consumer electronic devices.
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•Synthesis of carbon dots emitting fluorescence via thermal carbonisation of a-cellulose.•Synthesis method was optimised and carbon dots obtained were characterised.•Carbon dots were ...surface modified with Tris(hydroxymethyl)aminomethane (TRIS).•Surface modified carbon dots showed specificity towards cobalt (II) ion.
In this paper, a facile and green thermal carbonisation approach was adopted for the synthesis of carbon dots (CDs) from α-cellulose. The conditions during the synthesis have been optimised to produce CDs with highest fluorescence intensity. Later, tris(hydroxymethy)aminomethane (TRIS) was introduced to the isolated CDs as capping agent on the interface of the CDs. TRIS was chosen due to the well reported capability to interact with various metal ions to form complexes. Particularly in this study, TRIS has enhanced the specificity and sensitivity features of CDs to detect cobalt (II) ions, (Co(II) ions). The UV–vis absorption spectroscopy study performed has found that the CDs can effectively interact with TRIS, while the assembled CDs/TRIS system later can form complex with Co(II) ions. In this case, TRIS has acted as the bridge to bring CDs and Co(II) ions to a close proximity in distance, which subsequently promoted the energy transfer due to the good overlapping in the emission of the CDs with the absorbance of the Co(II) ions. The process was observed clearly by the concentration dependent fluorescence quenching in the presence of increasing amount of Co(II) ions. This has been demonstrated for the first time and the system has been suggested to be used as a single shot detection probe for Co(II) ions in aqueous media. The probe was found to be effective for the detection of Co(II) ions with a linear response up to 1.87 mM and a limit of detection of 16.84 μM. This study has presented some new insights on the surface interface interaction between CDs and its capping agent and demonstrated its potential application for metal ions sensing.
Nickel nanowires of controllable morphology were synthesized by a facile wet chemical reduction method using hydrazine hydrate as the reducing agent. Synthesis parameters such as reaction ...temperature, concentration of nickel ions, and pH of reaction medium were observed to have significant effects on the morphology of nickel nanowires formed. Only randomly aggregated nanoparticles were obtained at the reaction temperature of 30°C. However, visibly defined nickel nanowires of longitudinally aligned nanoparticles, and fully transformed, well-defined long and slender nanowires were obtained at reaction temperatures of 60°C and 120°C, respectively. Higher reaction temperature led to the formation of nickel nanowires of decreasing mean diameters, whereas increasing initial concentration of nickel ions resulted in the formation of nickel nanowires of larger mean diameters. Besides, well-defined nickel nanowires were formed at the reaction medium pH of 4–5. Henceforth, the morphology of nickel nanowires could be modulated readily via precise control of the synthesis parameters such as reaction temperature and initial concentration of nickel ions. Nickel nanowires of tailored morphology could potentially be useful for the fabrication of nanowire-based electronic or electrochemical devices.
•Nickel nanowires are prepared by a facile wet chemical reduction method.•Synthesis parameters significantly influenced the morphology of nickel nanowires.•Nickel nanowires are potential electrode materials for electrochemical devices.
► Facile synthesis of starch-maleate monoesters from native sago starch. ► Hydrophilicity of starch-maleate monoesters varied with degree of substitution. ► Composition of starch-maleate monoesters ...affected by the precipitating media used. ► Gel-to-particle transformation of starch-maleate monoesters by UV irradiation.
This paper documented a facile and green approach for synthesizing water soluble cross-linked starch-maleate monoester gel particles from native sago starch (Metroxylon sagu). Starch-maleate (SM) monoester gel was initially synthesized by reacting sago starch with maleic anhydride in an aqueous medium, and followed by precipitating in absolute ethanol. The transformation of starch-maleate gel into cross-linked gel particles of mean diameter 445±115nm occurred upon UV irradiation in the presence of cerium(IV) ammonium nitrate. The substitution of maleic anhydride onto starch chains was confirmed by FTIR spectroscopy, and the degree of substitution (DS) as determined by the back-titration method was within the range of 0.03–0.21. The water absorbency and hydrophilicity of SM samples of DS<0.03 was substantially lower than SM samples of DS>0.08. Being non-toxic, biocompatible and cheap, the potential utility of starch-maleate gel particles as drug delivery carriers in biomedical applications is therefore envisaged.
We report that fluorescent carbon nanodots (C-dots) can act as an optical probe for quantifying Sn(II) ions in aqueous solution. C-dots are synthesized by carbonization and surface oxidation of ...preformed sago starch nanoparticles. Their fluorescence is significantly quenched by Sn(II) ions, and the effect can be used to determine Sn(II) ions. The highest fluorescence intensity is obtained at a concentration of 1.75 mM of C-dots in aqueous solution. The probe is highly selective and hardly interfered by other ions. The quenching mechanism appears to be predominantly of the static (rather than dynamic) type. Under optimum conditions, there is a linear relationship between fluorescence intensity and Sn(II) ions concentration up to 4 mM, and with a detection limit of 0.36 μM.
Figure
Highly fluorescent carbon nanodots (CDs) were synthesized from preformed starch nanoparticles via a green synthetic method. The potential application of these CDs as a sensing probe for Sn(II) ions were evaluated. Our studies showed that CDs are highly sensitive and selective towards Sn(II) detection in aqueous system.
This work reports the study on the luminescence properties portrayed by carbon dots synthesized under different acid hydrolysis conditions. Sulphuric acid was employed to dehydrate and carbonize ...α-cellulose as starting precursor. We revealed that the emissions of carbon dots were strongly dependent on the reaction condition during the synthesis, which include hydrolysis time and temperature. Initial mild acid hydrolysis at 4 °C and followed by incubation at room temperature was found favourable to the production of carbon dots emitting green fluorescence, whereas higher temperatures of 50 and 70 °C would produce carbon dots emitting blue fluorescence. At fixed temperature of 50 °C, prolonged synthesis time could shift the emission of carbon dots from green to blue. The green emission was recorded to have a peak at 500 nm when excited at 450 nm; whereas the highest intensity for the blue emission was recorded at 456 nm when excited at 357 nm. Both as-synthesized carbon dots showed excitation-independent emission. The quantum yields for the green and blue carbon dots were evaluated to be 6.4% and 4.0% respectively. The carbon dots emitting blue emission was of better photostability as compared to the carbon dots emitting green fluorescence. Both types of carbon dots synthesized in this study showed significant pH-dependent trend with higher intensity at lower pH condition.
•Synthesized carbon dots from α-cellulose using sulphuric acid.•Different synthesis conditions produced carbon dots with different emissions.•Harsh carbonisation flavour the production of carbon dots with blue emission.•Mild carbonisation flavour the production of carbon dots with green emission.
Curcumin is a naturally occurring phytochemical with interesting therapeutical properties. However, it shows some limitations of low intrinsic solubility, fast degradation and poor bioavailability. ...In this study, curcumin was loaded onto amino-functionalised starch (amino-starch) nanoparticles via the nanoprecipitation method in an attempt to increase its water solubility. In this nanoprecipitation process, the amino-starch aqueous solution was added into excess ethanolic solution under stirring. Amino-starch nanoparticles were formed as organic solvent got separated from the amino-starch. Amino-starch nanoparticles with mean particle size of 163 nm were obtained by drop-wise addition of dissolved amino-starch solution into excess absolute ethanol solution containing curcumin. Amino-starch nanoparticles showed enhanced curcumin loading capacity of 0.76 mg mg-1 as compared to 0.33 mg mg-1 for native starch nanoparticles. Curcumin was observed to release out slowly from amino-starch nanoparticles over a period of 12 h. Therefore, the potential of amino-starch nanoparticles as the controlled release nanocarriers for curcumin was demonstrated.
Raw sago hampas (RSH) was grafted with oxygen-containing functional group through a functionalization process to form esterified sago hampas (ESH) for U(VI) adsorption and evaluated using adsorption ...kinetics, isotherm, and thermodynamics studies. Adsorption kinetics studies show that both adsorbents follow pseudo-second-order model while isotherm studies conclude that both adsorption processes fitted Sips isotherm model. Thermodynamic studies indicate both adsorption processes exhibited by the RSH and ESH were endothermic but spontaneous and non-spontaneous respectively. Strongs acids are tested to be the best desorption agents to release U(VI) from surfaces’ of RSH and ESH.
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