New Room-Temperature Molecular Ferroelectric (C₆H₁₆N₂O)CdBr₄·H₂O with Preferable Luminescent Properties

Abstract

Organic–inorganic hybrid materials are easy to modify, which makes it possible to construct multifunctional ferroelectrics directionally and apply the built-in electric field and switching properties of ferroelectrics to multidisciplinary fields. Particularly, the coupling of photoluminescence and ferroelectricity in a single hybrid material facilitates its novel applications in lighting sensors, memory devices, and other multifunctional applications. Based on the photoluminescent molecule 4-(2-aminoethyl) morpholine (AEM), here, a room-temperature ferroelectric (C6H16N2O)CdBr4·H2O (AEM-CdBr 4 ) is designed and obtained, which crystallizes in a polar orthorhombic space group of Pca21. A reversible ferroelectric–paraelectric phase transition was confirmed at 353 K through experimental results, such as differential scanning calorimetry (DSC) curves, variable-temperature Raman spectroscopy, and photoluminescence (PL) spectroscopy. The crystal exhibits ferroelectricity at room temperature with a saturation polarization of approximately 8 μC/cm2. The photoluminescence of compound AEM-CdBr 4 is mainly derived from the monomeric fluorescence emission of the AEM molecule and is not directly related to the energy band structure of the crystal. This room-temperature molecular-type ferroelectric AEM-CdBr 4 with photoluminescence will provide new ideas for the design of new multifunctional ferroelectrics.

New Room-Temperature Ferroelectrics with Photoluminescent Properties

“…Furthermore, the point charge method was employed to determine the spontaneous polarization directions of both crystalline materials based on their room-temperature crystal structure . Using the atomic configuration of OAO-MnCl 4 as an example, we considered a specific configuration comprised of the manganese ion, the two nearest nitrogen atoms, and the four chloride ions as a single unit.…”

“…To obtain a more Furthermore, the point charge method was employed to determine the spontaneous polarization directions of both crystalline materials based on their room-temperature crystal structure. 31 Using the atomic configuration of OAO-MnCl 4 as an example, we considered a specific configuration comprised of the manganese ion, the two nearest nitrogen atoms, and the four chloride ions as a single unit. In this way, there are two such configurations in one unit cell, considering manganese ions and nitrogen ions carry positive charges and chloride ions carry negative charges, as shown in Figure 1.…”

“…44 At 373 K, the intensity of this vibrational-mode Raman peak decreases slightly due to thermal vibrations, etc., but the peak position does not change significantly, indicating the continued existence of the [MnCl 4 ] 2− anion at 373 K. Also, we attribute the apparent appearance of Raman bands around 2950 cm −1 to the symmetrical stretching pattern of methylene. 31 According to the relevant studies of the Raman spectrum of water molecules, there are generally three Raman vibrational modes containing two symmetric and one asymmetric vibrational mode at 1610, 3250, and 3400 cm −1 , respectively. 45,46 Therefore, we assigned the weak Raman band at 3373 cm −1 to the asymmetric vibrational modes of water.…”

Tin-based organic–inorganic metal halides with a reversible phase transition and thermochromic response

“…40 In addition, our group synthesized the compound (CASD) 2 MnBr 4 (CASD = 8-chloro-5-azonia-spiro [4.5] decane), which exhibits a large SHG response. 33 Currently, most of the organic-inorganic phase transition perovskites reported are based on lead (Pb), [41][42][43] antimony (Sb), 37 bismuth (Bi), 44,45 cadmium (Cd), [46][47][48] and manganese (Mn). [49][50][51] In spite of this, there are still some problems associated with potential toxicity and environmental pollution, which limit the further applications of these materials.…”

“…Currently, most of the organic–inorganic phase transition perovskites reported are based on lead (Pb), 41–43 antimony (Sb), 37 bismuth (Bi), 44,45 cadmium (Cd), 46–48 and manganese (Mn). 49–51 In spite of this, there are still some problems associated with potential toxicity and environmental pollution, which limit the further applications of these materials.…”