Carbon
nanomaterials have been employed as crucial supports to increase surface
loading and electronic conductivity. In addition, there are widely
synergistic effects between the metallic species and the carbon supports
for accelerated and stable electrocatalysis. In this work, a rhodium
nanocrystal hybrid with single-walled carbon nanotubes (Rh/SWNTs)
is reported to be an advanced catalyst for electrocatalytic reactions.
SWNTs, as good electron acceptors, could modulate the electronic structure
of Rh NPs and produce optimized electron polarization, which can give
a high-performance interface catalyst. More eye catching are the excellent
hydrogen evolution reaction (HER) properties in acid and alkali achieved
by Rh/SWNTs with small overpotential (at 10 mA cm–2) and Tafel slope (25 mV and 20 mV dec–1 in 0.5
M H2SO4, 48 mV and 27 mV dec–1 in 1.0 M KOH, respectively). Meanwhile, such electron polarization
could also improve the oxygen evolution reaction (OER) and oxygen
reduction reaction (ORR) properties. The Rh/SWNTs show high efficiency
in overall water splitting and an integrated zinc–air battery
with a low cell voltage of 1.59 V at 10 mA cm–2 and
a high open-circuit voltage of 1.42 V. This work highlights an electron
polarization strategy on the interface between Rh and SWNTs to develop
a high-performance multifunctional hydrogen and oxygen catalyst.
This paper reports an investigation into the characteristics of femtosecond laser (800-nm central wavelength) in the ablation of human dental enamel, dentine, and cementum at various laser fluences from 0.2 to 3.68 J/cm(2) with single and multiple pulses. The femtosecond laser interaction with cementum is reported for the first time. Ablation thresholds were determined to be 0.58, 0.44, and 0.51 J/cm(2) for enamel, dentine, and cementum, respectively. Under the average laser fluences of 1.13 to 3.68 J/cm(2), clean ablated surfaces without debris and microcracks were obtained. Laser fluence was found to influence the ablated diameter and depth, whereas under a certain fluence, pulse number only affects the depth, without affecting the diameter. The ablation mechanism is found to be based on multi-photon absorption, not previously known for femtosecond laser ablation of dental materials. The low thermal loads of 0.708, 1.44, and 0.404 J/cm(3) required for ablating enamel, dentine, and cementum, determined for the first time, are beneficial for minimizing the heat-affected zones and micro-damage. The Raman spectroscopic analysis of phosphate shows that the chemical components of the tooth remain intact before and after the fs-laser ablation. It also shows that different dental tissues respond differently to the laser irradiation.
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