Fabrication of peptide-encapsulated sodium alginate hydrogel for selective gallium adsorption.

Peptides are recognized as promising adsorbents in metal selective recovery. In this study, the designed gallium-binding peptide H6GaBP was immobilized by the polysaccharide polymer sodium alginate (SA) for gallium recovery. The synthesized H6GaBP@SA microspheres exhibited a maximum adsorption capacity of 127.4 mg/g and demonstrated high selectivity for gallium at lower pH values. The adsorption process aligned well with the pseudo-second-order equation and Langmuir model. To elucidate the adsorption mechanism, a comprehensive characterization including molecular docking, scanning electron microscope coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetry analysis (TGA), were conducted. These analyses revealed that gallium ions were initially adsorbed through electrostatic interaction by H6GaBP@SA, followed by a cation exchange reaction between Ga(OH)2+ and Ca2+, as well as coordination between gallium and histidine residues on the peptide. Moreover, the H6GaBP@SA exhibited improved thermal stability compared to sole sodium alginate microspheres, and the coordination of gallium with peptides can also defer the decomposition rate of the adsorbents. Compared to other adsorbents, the peptide-encapsulated hydrogel microspheres exhibited superior gallium selectivity and improved adsorption capacity, offering an environmentally friendly option for gallium recovery.

Tapered fiber radiation sensor based on Ce/Tb:YAG crystals for remote γ-ray dosimetry.

A novel tapered fiber-optic radiation sensor (TFRS) based on cerium (Ce) and terbium (Tb) co-doped YAG scintillation crystals is demonstrated for the first time. Using the CO2 laser-heated method, a Ce/Tb:YAG crystal is well embedded into silica glass cladding without any cracks. The scintillation light emitted from the YAG scintillation crystal can be directly coupled into the derived silica optical fiber by the tapered region. The loss of the derived optical fiber is 0.14 dB/cm, which is one order of magnitude lower than the 1.59 dB/cm of the YAG crystal in the TFRS. Subsequently, strong photo- and radio-luminescence of Tb3+ (5D4→7F5) ions in TFRS are achieved under ultraviolet light and high-energy ray excitation, respectively. In particular, a prominent remote radiation response of the TFRS is presented under excitation by γ-rays through fusion splicing with multimode optical fibers. The response is approximately four times larger than that of a plastic scintillation fiber (BCF-12) sensor. Furthermore, the results possess high stability as well as a good linearity between the radiation dose rate and the response intensity. The TFRS in combination with an all-silica fiber system is a promising candidate for remote radiation detection.