ABSTRACT
Plasmonic gold nanoparticles significantly improved the efficiency of a TiO2 and Eosin Y based dye-sensitized solar cell from 2.4 to 6.43%. The gold nanoparticles' sizes that were tested were 14 nm, 30 nm and 40 nm synthesized via the systematic reduction of citrate concentration using the Turkevich method. Prestine TiO2 without plasmonic gold nanoparticles yielded an efficiency of 2.4%. However, the loading of 40 nm gold nanoparticles into the TiO2 matrix yielded the highest DSSC efficiency of 6.43% compared to 30 nm (5.91%) and 14 nm (2.6%). The relatively high efficiency demonstrated by plasmonic gold nanoparticles is ascribed to light absorption/scattering, hot electron injection and plasmon-induced resonance energy transfer (PIRET), influenced by the size of the gold nanoparticles.
ABSTRACT
Laser assisted synthesis of silicon nanowires (SiNWs) was successfully achieved through the use of gold and nickel as catalysts. The diameter of the resulting SiNWs was found to be dependent on that of the catalyst in the case of gold catalyst. The gold catalysed silicon nanowires were unevenly curved and branched owing to the high kinetic energy possessed by gold nanoparticles (AuNPs) at relatively high processing temperature. The use of nickel as catalyst resulted in the formation of several SiNWs on a single nickel catalyst crystallite due to interconnection of the nickel metal crystallites at processing temperature. The morphology of SiNWs catalysed by both nickel and gold was controlled by optimising the laser energy during ablation.
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OBJECTIVES: This study aimed to evaluate nanosized eggshell-titanium dioxide (EB@TiO2) abrasiveness in comparison with calcium carbonate and hydrated silica-containing toothpaste. MATERIAL AND METHODS: Thirty-five bovine tooth enamels were prepared, and specimens randomly assigned to a sample group of five (n = 7), namely, Colgate regular, Colgate pro-relief, Sensodyne rapid relief, Sensodyne repair, and EB@TiO2. Half of the enamel surface was brushed with each respective sample group, while the other half was covered with a tap. STATISTICAL ANALYSIS: The mean roughness value (Ra) of the brushed and covered halves were measured using an atomic force microscope (AFM). To assess the surface morphology and changes, a scanning electron microscope (SEM) was performed. Using pair sample test and ANOVA, the Ra for the entire specimens were analyzed. A Bonferroni correction was used to identify the mean differences among the five groups (α=.05). RESULTS: The findings from this analysis show that all the tested toothpaste abraded the enamel significantly (p < 0.05). The abrasive value contained in toothpaste comprising calcium carbonate was lower than the silica toothpaste hydrated. CONCLUSION: Overall, Colgate regular had the lowest toothpaste abrasivity, followed by EB@TiO2, while Sensodyne rapid relief had the most enamel wear. The prominent feature of this study suggests that EB@TiO2 is suitable for oral use, as its abrasivity is comparable with calcium carbonate-containing toothpaste.
ABSTRACT
[This corrects the article DOI: 10.1155/2018/4216415.].
ABSTRACT
OBJECTIVES: Enamel erosion caused by high consumption of acidic drinks poses a significant public health concern. This study was aimed to determine the protective effect of eggshell-titanium dioxide composite (EB@TiO2) against erosive acids on tooth enamel. METHODS: Twenty prepared bovine tooth enamel specimens were randomly assigned to 5 sample groups (n=4): (1) unexposed tooth enamel; (2) exposed tooth enamel + HCI; (3) exposed tooth enamel + HCI + Colgate toothpaste; (4) exposed tooth enamel + HCI + Sensodyne toothpaste; and (5) exposed tooth enamel + HCI + EB@TiO2. The mean roughness value (R rms) of the exposed and unexposed tooth was measured with atomic force microscope (AFM). Scanning electron microscope (SEM) and Raman spectroscopy techniques were used to evaluate the surface morphology and changes. ANOVA was used to analyze the mean square roughness (R rms) values for all specimens. Bonferonni correction was used to identify the mean differences among the 5 groups (α=0.05). The R rms values measured for the unexposed and exposed specimens in HCI alone were statistically significant (P < 0.05). RESULTS: No significant differences were found for the unexposed and exposed specimens in HCI + toothpaste and EB@TiO2. The tooth enamel specimens exposed to HCI + Sensodyne had the highest R rms values, while specimens exposed to HCI + EB@TiO2 had the lowest R rms values. CONCLUSIONS: This study confirms that the investigated toothpaste provides protection against acidic substances. The study results further suggests that EB@TiO2 could be used to provide enhanced protection for tooth enamel.
