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The adsorption method is a promising route to recover Li + from waste lithium batteries and lithium-containing brines. To achieve this goal, it is vital to synthesize a stable and high adsorption capacity adsorbent. In this work, Li 4 Ti 5 O 12 nanorods are prepared by two hydrothermal processes followed by a calcination process. Then the prepared Li 4 Ti 5 O 12 nanorods are treated with different HCl concentrations to obtain a H 4 Ti 5 O 12 adsorbent with 5 μm length along the [100] direction. The maximum amount of extracted lithium can reach 90% and the extracted titanium only 2.5%. The batch adsorption experiments indicate that the H 4 Ti 5 O 12 nanorod maximum adsorption capacity can reach 23.20 mg g -1 in 24 mM LiCl solution. The adsorption isotherms and kinetics fit a Langmuir model and pseudo-second-order model, respectively. Meanwhile, the real adsorption selectivity experiments show that the maximum Li + adsorption capacity reaches 1.99 mmol g -1 , which is far higher than Mg 2+ (0.03 mmol g -1 ) and Ca 2+ (0.02 mmol g -1 ), implying these nanorods have higher adsorption selectivity for Li + from Lagoco Salt Lake brine. The adsorption capacity for Li + remains 91% after five cycles. With the help of XPS analyses, the adsorption mechanism of Li + on the H 4 Ti 5 O 12 nanorods is an ion exchange reaction. Therefore, this nanorod adsorbent has a potential application for Li + recovery from aqueous lithium resources., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

In the present study, a novel hybrid nanomaterial composed of core-shell structured Ag@carbon dot (CD) modified TiO 2 nanofibers (NFs) was successfully fabricated via a simple two-step strategy for the first time. Herein, the Ag@CDs-TiO 2 NFs are demonstrated to be an efficient SERS substrate. The strong LSPR-induced electromagnetic enhancement (EM) by Ag@CDs NPs and efficient charge transfer (CT) effect between Ag@CDs and TiO 2 NFs synergistically contribute to the excellent SERS enhancement. In addition, the Ag@CDs-TiO 2 NFs exhibit enhanced photocatalytic activity regarding the organic pollutant degradation under visible light irradiation because of the enhanced light absorption and improved separation of photo-generated electron-hole pairs. Thus, this new nanocomposite can be used as a sensitive SERS substrate for determining the catalytic activity and reaction kinetics during the photodegradation of methylene blue (MB). Compared with UV-vis spectroscopy, the SERS technique enables more accurate monitoring of the changes of adsorption molecules and actual catalytic process on the surface of the catalyst. These results are significant for the development of metal or semiconductor-based catalysts for ensuring optoelectronic, energy and environmental applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A water-soluble and colorimetric fluorescent probe with a large Stokes shift (139 nm) for rapidly detecting Hg 2+ , namely Hcy-mP, was synthesized by using an indole derivative and 2,4-dihydroxybenzaldehyde as starting materials. This probe demonstrates good selectivity for Hg 2+ over other metal ions including Ag + , Pb 2+ , Cd 2+ , Cr 3+ , Zn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , K + , Na + , Mg 2+ , and Ca 2+ in aqueous solution. With the increase in concentration of Hg 2+ , the color of the solution changed from pale yellow to pink and the fluorescence intensity decreased slightly. When 5-equivalents of EDTA were added to the solution with Hg 2+ , the fluorescence intensity of this probe was restored. The probe has been applied to the detection of Hg 2+ in real water samples. Moreover, this probe was confirmed to have low cytotoxicity and excellent cell membrane permeability. The effect of Hcy-mP-Hg 2+ towards living cells by confocal fluorescence was also investigated., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Semiconductor materials have been successfully used as surface-enhanced Raman scattering (SERS)-active substrates, providing SERS technology with a high flexibility for application in a diverse range of fields. Here, we employ a dye-sensitized semiconductor system combined with semiconductor-enhanced Raman spectroscopy to detect metal ions, using an approach based on the "turn-off" SERS strategy that takes advantage of the intrinsic capacity of the semiconductor to catalyze the degradation of a Raman probe. Alizarin red S (ARS)-sensitized colloidal TiO 2 nanoparticles (NPs) were selected as an example to show how semiconductor-enhanced Raman spectroscopy enables the determination of Cr(vi) in water. Firstly, we explored the SERS mechanism of ARS-TiO 2 complexes and found that the strong electronic coupling between ARS and colloidal TiO 2 NPs gives rise to the formation of a ligand-to-metal charge-transfer (LMCT) transition, providing a new electronic transition pathway for the Raman process. Secondly, colloidal TiO 2 nanoparticles were used as active sites to induce the self-degradation of the Raman probe adsorbed on their surfaces in the presence of Cr(vi). Our data demonstrate the potential of ARS-TiO 2 complexes as a SERS-active sensing platform for Cr(vi) in an aqueous solution. Remarkably, the method proposed in this contribution is relatively simple, without requiring complex pretreatment and complicated instruments, but provides high sensitivity and excellent selectivity in a high-throughput fashion. Finally, the ARS-TiO 2 complexes are successfully applied to the detection of Cr(vi) in environmental samples. Thus, the present work provides a facile method for the detection of Cr(vi) in aqueous solutions and a viable application for semiconductor-enhanced Raman spectroscopy based on the chemical enhancement they contribute.