Synthesis and Features of Luminescent Bromo- and Iodohectorite Nanoclay Materials

Abstract

Abstract:The smectites represent a versatile class of clay minerals with broad usage in industrial applications, e.g., cosmetics, drug delivery, bioimaging, etc. Synthetic hectorite Na 0.7 (Mg 5.5 Li 0.3 ) [Si 8 O 20 ](OH) 4 is a distinct material from this class due to its low-cost production method that allows to design its structure to match better the applications. In the current work, we have synthesized for the first time ever nanoclay materials based on the hectorite structure but with the hydroxyl groups (OH − ) replaced by Br − or I − , yielding bromohectorite (Br-Hec) and iodohectorite (I-Hec). It was aimed that these materials would be used as phosphors. Thus, OH − replacement was done to avoid luminescence quenching by multiphonon de-excitation. The crystal structure is similar to nanocrystalline fluorohectorite, having the d 001 spacing of 14.30 Å and 3 nm crystallite size along the 00l direction. The synthetic materials studied here show strong potential to act as host lattices for optically active species, possessing mesoporous structure with high specific surface area (385 and 363 m 2 g −1 for Br-Hec and I-Hec, respectively) and good thermal stability up to 800 • C. Both materials also present strong blue-green emission under UV radiation and short persistent luminescence (ca. 5 s). The luminescence features are attributed to Ti 3+ /Ti IV impurities acting as the emitting center in these materials.

Hectorite-CTAB–alginate composite beads for water treatment: kinetic, isothermal and thermodynamic studies

“…20,22,39 The symmetric stretching of Mg-O was observed at 457 cm −1 , which corresponded to the octahedral units of hectorite-type clay minerals. 15 The incorporation of CTAB to Hec-40 and BHec-40 produced asymmetric and symmetric C-H strain vibrations of the CTAB at 2924 and 2850 cm −1 , respectively. 15,22,40,41 Furthermore, the pure alginate presented typical broad bands at 3437 cm −1 (OH stretching).…”

“…15 The incorporation of CTAB to Hec-40 and BHec-40 produced asymmetric and symmetric C-H strain vibrations of the CTAB at 2924 and 2850 cm −1 , respectively. 15,22,40,41 Furthermore, the pure alginate presented typical broad bands at 3437 cm −1 (OH stretching). In addition, the crosslinking in beads is liable for shiing the wavenumber of the carboxyl peak from 1615 cm −1 (C]O group) to 1627 cm −1 or 1620 (COO-asymmetric stretching), representing the appearance of intermolecular hydrogen bridges.…”

“…30,71 The K L and q max values from the Langmuir isotherm equation are used to obtain the correlation between the mass of the adsorbent and the volume of the adsorbate by modifying eqn (5). Modication of eqn (1) and (5) will show the relationship between the mass of the adsorbent and the volume of waste that can be overcome, as shown in eqn (15) and (16).…”

“…13,14 Hectorite is a 2 : 1 smectite clay with exceptional properties as an adsorbent for metal ions and cationic dyes. 15,16 Hectorite adsorption behavior comes from the oxygen deformity of Mg-O octahedra and Si-O tetrahedra. 17 Hectorite is occurred naturally, although the presence of impurities requires pretreatment before can be used as adsorbent.…”

Shortwave UV Blue Luminescence of Some Minerals and Gems Due to Titanate Groups

“…The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/min13010104/s1, Table S1: Mineral and synthetic compounds on which Ti-related blue luminescence (possibly BSL) has been described or inferred [1,27,29,39,79,83,[88][89][90][91][92][93][94][95][96][97][98][99][100][101]. Table S2: Data associated with Figure 5, mineral & formula, Ti-O distance, emission maxima (in nm and eV), bibliographic sources for luminescence and Ti-O distance [1,9,16,29,40,77,[89][90][91][92][102][103][104][105][106][107][108][109][110][111][112][113][114][115][116]…”