Relationship between interlayer anions and photoluminescence of layered rare earth hydroxides

Abstract

The effect of interlayer anions on the photoluminescence of layered rare earth hydroxides was investigated with the rare earth (RE)-doped layered gadolinium hydroxynitrate as a representative base matrix for efficient and stable anion-exchange reactions. Eu 3+ , Tb 3+ , and Ce 3+ were employed as RE activator ions for red, green, and blue emissions, respectively. The excitation and emission behaviors of Gd 1.80 RE 0.20 (OH) 5 XÁnH 2 O (LGdH:RE) were systematically compared for various interlayer inorganic and organic anions, where X = F À , Cl À , I À , OH À , ClO 3 À , S 2À , CO 3 2À , SO 4 2À , terephthalate, 2-naphthoate, and dodecylsulfate members were obtained by the exchange reaction of corresponding X = NO 3 À members.Interestingly, a close relationship was found between the UV-Vis absorption spectra of aqueous solutions containing X anions and the excitation behavior of LGdH:RE. Thus, NO 3 À , I À , and S 2À anions showing high absorbance in aqueous solution consistently shielded the excitation light for the 8 S 7/2 -6 I J transition of Gd 3+ and the 4f -5d interconfigurational transitions of Tb 3+ and Ce 3+ to turn off the corresponding emissions from LGdH:Eu, LGdH:Tb, and LGdH:Ce. In contrast, the effect of terephthalate and 2-naphthoate, despite high absorbance in aqueous solutions, was significantly different depending on the RE activator ion. It is proposed that an identical interlayer anion in the gallery of LRHs can filter or sensitize the UV energy for excitation of RE 3+ -doped LRHs and its role (whether as a filter, a sensitizer, or just a spacer) is determined by the nature of activator ions. 201-2457 † Electronic supplementary information (ESI) available: Additional XRD patterns and FT-IR spectra of Gd 1.80 RE 0.20 (OH) 5 XÁnH 2 O (LGdH:RE) where RE = Eu, Tb, and Ce and X = NO 3 À , F À , Cl À , I À , OH À , ClO 3 À , S 2À , CO 3 2À , SO 4 2À , terephthalate, 2-naphthoate, and dodecylsulfate. XRD patterns measured as a function of reaction time during the exchange reaction of Gd 1.80 Ce 0.20 (OH) 5 NO 3 ÁnH 2 O with Cl À and vice versa. See

M(II)Al4 Type Layered Double Hydroxides—Preparation Using Mechanochemical Route, Structural Characterization and Catalytic Application

“…The spectra of the solids contain a large number of bands. In all cases (Figures S8-S12), around 230, 240 and 255 nm, the peaks were related to the oxygen-to-metal charge transfer transitions, and the band of the interlamellar nitrate anions was clearly observable at 300-310 nm [35]. As expected, for the MgAl 4 -, ZnAl 4 -LDHs and MgZnAl 8 -LTH, there were no other adsorptions in the investigated wavenumber range (Figure S11).…”

Structure and Microwave Dielectric Behavior of A‐Site‐Doped Sr(1−1.5x)CexTiO3 Ceramics System

“…This phenomenon significantly increases oxygen loss and thus degrades the MW dielectric properties of SCT ceramics. 17 The addition of a small amount of ceria (x ≤ 0.2) reduces the peak area ratio of Ti 3+ /Ti 4+ ; by contrast, the addition of a large amount of ceria (x ≥ 0.3) inhibits this process because of the presence of excess amounts of Ce 4+ ions [Figs. 3(a)-(c) and Table II].…”

Antenna Effect on the Organic Spacer-Modified Eu-Doped Layered Gadolinium Hydroxide for the Detection of Vanadate Ions over a Wide pH Range

“…The 276 nm band is ascribed to 8 S 7/2 → 6 I J excitation of Gd 3+ , 31 which is shielded by NO 3 − strongly absorbing UV light shorter than 300 nm before the exchange reaction. 32 The absence of a broad band in the 200−350 nm range confirmed no efficient nonradiative energy transfer from organic spacer to Eu 3+ activator; that is, Eu 3+ was excited directly via the intra-4f 6 level rather than through a sensitized process involving spacer molecules. To improve the emission efficiency of REs, anions with a high effective absorption cross-section for UV are frequently introduced to sensitize the emission through internal conversion to the excited states of RE 3+ .…”