Layered aluminum double hydroxide chloride sorbents, LiCl•Al 2 (OH) 6 .nH 2 O, Li-LDH, have shown promising application in selective Li extraction from geothermal brines. Maintaining LiCl uptake capacity and retaining a long cycle life are critical to widespread application of sorbent materials. To elucidate the energetics of Li capture, enthalpies of LDH with different Li content have been measured by acid solution calorimetry. The formation enthalpies generally become less exothermic as the Li content increases, which indicates that Li intercalation destabilizes the structure, and the enthalpies seem to approach a limit after the Li content x = 2Li/Al exceeds 1. To improve stability, metal doping of the aluminum LDH structure with iron was performed. Introduction of a metal with greater electron density but a similar ionic radius was postulated to improve the stability of the LDH crystal structure. The calorimetric results from Fe-doped LDH samples corroborate this as they are more exothermic than LDH-lacking Fe. This suggests that Fe doping is an effective way to stabilize the LDH phase. K E Y W O R D Sheat capacity, high-temperature calorimetry, lithium aluminum hydroxide chloride, lithium extraction, sorbents

Abstract Upconverting luminescent nanoparticles are photostable, nonblinking, and low chemically toxic fluorophores that are emerging as promising fluorescent probes at the single molecule level. High luminescence intensity upconversion nanoparticles (UCNPs) have previously been achieved by doping with high amounts of rare-earth ions using high excitation power (>2.5 MW/cm2). However, such particles are inadequate for in vitro live-cell imaging and single-particle tracking, as high excitation power can cause photodamage. Here, we compared UCNP luminescence intensities with different dopant concentrations and presented more efficient (about seven times) UCNPs at low excitation power by increasing the concentrations of Yb3+ and Tm3+ dopants (NaYF4: 60% Yb3+, 8% Tm3+) and adding a core-shell structure.

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