High Stability LED-Pumped Nd:YVO₄ Laser with a Cr:YAG for Passive Q-Switching

With improvements in light-emitting diode (LED) performance and a sharp decline in price, a light source with the irradiance of a laser and the cost of an LED is worthy of further study. We demonstrated a LED-pumped Nd:YVO4 laser in quasi-continuous-wave (QCW) and passively Q-switched (PQS) regime. With an incident pump energy of 6.28 mJ (150 μs pulses at 1 Hz), the Nd:YVO4 laser has an energy of 206 μJ at 1064 nm in the QCW regime. The optical conversion efficiency of the system is 4.1%, and the slope efficiency is 9.0%. A pulsed energy of 2.5 μJ was obtained with a duration of 897 ns (FWHM) in the PQS regime, which means the peak power is 2.79 W. The output energy stability is 97.54%

Hydrogenation of CuBTC Framework with the Introduction of a PtC Hydrogen Spillover Catalyst

Hydrogen uptake of a microporous metal organic framework, CuBTC, is increased 3.5-fold at 298 K and 20 bar upon the addition of a hydrogen spillover catalyst, from 0.17 to 0.61 wt %. Structural integrity upon mixing with the catalyst is important to achieve this level of uptake. Increasing the adsorption temperature to 323 K significantly reduces the rate of uptake, but 0.55 wt % uptake is observed when the experimental equilibration time is extended. The slow, pressure-independent uptake at 323 K, along with the desorption behavior is suggestive of a hydrogenation process of the CuBTC substrate. PXRD analysis suggests the hydrogenated sample remains intact and FTIR demonstrates hydrogenation of the carboxylate group of the BTC ligand but finds no evidence for hydrogenation of the carbons of the BTC ligand. Although hydrogenation of the CuBTC does not lead to readily desorbable H2, the results shed light on a possible mechanism of the hydrogen spillover process