Characterization on Lead-Free Hybrid Perovskite [NH3(CH2)5NH3]CuCl4: Thermodynamic Properties and Molecular Dynamics.

It is essential to develop novel zero- and two-dimensional hybrid perovskites to facilitate the development of eco-friendly solar cells. In this study, we investigated the structure and dynamics of [NH3(CH2)5NH3]CuCl4 via various characterization techniques. Nuclear magnetic resonance (NMR) results indicated that the crystallographic environments of 1H in NH3 and 13C on C3, located close to NH3 at both ends of the cation, were changed, indicating a large structural change of CuCl6 connected to N-H···Cl. The thermal properties and structural dynamics of the [NH3(CH2)nNH3] cation in [NH3(CH2)nNH3]CuCl4 (n = 2, 3, 4, and 5) crystals were compared using thermogravimetric analysis (TGA) and NMR results for the methylene chain. The 1H and 13C spin-lattice relaxation times (T1ρ) exhibited similar trends upon the variation of the methylene chain length, with n = 2 exhibiting shorter T1ρ values than n = 3, 4, and 5. The difference in T1ρ values was related to the length of the cation, and the shorter chain length (n = 2) exhibited a shorter T1ρ owing to the one closest to the paramagnetic Cu2+ ions.

A prospect of cost-effective handling and transportation of graphene oxides: folding and redispersion of graphene oxide microsheets.

Controlling the assembly of 2D materials such as graphene oxides (GO) has a significant impact on their properties and performance. One of the critical issues on the processing and handling of GO is that they need to be in dilution solution (0.5 to 2.5 wt%) to maintain their high degree of exfoliation and dispersion. As a result, the shipment of GO in large quantity involves a huge volume of solvent (water) and thus the transportation costs for large sales volume would become extremely high. Through cross-sectional scanning electron microscopy and polarized optical microscopy together with x-ray diffraction and small-angle x-ray scattering studies, we demonstrated that the assembly and structure of GO microsheets can be preserved without restacking, when assembled GO via water-based wet spinning are re-dispersed into solution. A couple of alkyl ammonium bromides, CTAB and TBAB, as well as NaOH, were examined as coagulants and the resulting fibers were redispersed in an aqueous solution. The redispersed solution of fibers that were wet-spun into the commonly used CTAB and TBAB coagulation baths, maintained their physico-chemical properties (similar to the original GO dispersion) however, did not reveal preservation of liquid crystallinity. Meanwhile, the redispersed fibers that were initially spun into NaOH coagulation bath were able to maintain their liquid crystallinity if the lateral size of the GO sheets was large. Based on these findings, a cost-effective solid handling approach is devised which involves (i) processing GO microsheets in solution into folded layers in solid-state, (ii) transporting assembled GO to the customers, and (iii) redispersion of folded GO into a solution for their use. The proposed solid handling of GO followed by redispersion into solution can greatly reduce the transportation costs of graphene oxide materials by reducing the transportation volume by more than 90%.

Thermodynamic, Physical, and Structural Characteristics in Layered Hybrid Type (C2H5NH3)2MCl4 (M = 59Co, 63Cu, 65Zn, and 113Cd) Crystals.

The thermal, physical, and molecular dynamics of layered hybrid type (C2H5NH3)2MCl4 (M = 59Co, 63Cu, 65Zn, and 113Cd) crystals were investigated by thermogravimetric analysis (TGA) and magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The temperatures of the onset of partial thermal decomposition were found to depend on the identity of M. In addition, the Bloembergen-Purcell-Pound curves for the 1H spin-lattice relaxation time T1ρ in the rotating frames of CH3CH2 and NH3, and for the 13C T1ρ of CH3 and CH2 were shown to exhibit minima as a function of the inverse temperature. These results confirmed the rotational motion of 1H and 13C in the C2H5NH3 cation. Finally, the T1ρ values and activation energies Ea obtained from the 1H measurements for the H‒Cl···M (M = Zn and Cd) bond in the absence of paramagnetic ions were larger than those obtained for the H‒Cl···M (M = Co and Cu) bond in the presence of paramagnetic ions. Moreover, the Ea value for 13C, which is distant from the M ions, was found to decrease upon increasing the mass of the M ion, unlike in the case of the Ea values for 1H.

Study on Paramagnetic Interactions of (CH3NH3)2CoBr4 Hybrid Perovskites Based on Nuclear Magnetic Resonance (NMR) Relaxation Time.

The thermal properties of organic-inorganic (CH3NH3)2CoBr4 crystals were investigated using differential scanning calorimetry and thermogravimetric analysis. The phase transition and partial decomposition temperatures were observed at 460 K and 572 K. Nuclear magnetic resonance (NMR) chemical shifts depend on the local field at the site of the resonating nucleus. In addition, temperature-dependent spin-lattice relaxation times (T1ρ) were measured using 1H and 13C magic angle spinning NMR to elucidate the paramagnetic interactions of the (CH3NH3)+ cations. The shortening of 1H and 13C T1ρ of the (CH3NH3)2CoBr4 crystals are due to the paramagnetic Co2+ effect. Moreover, the physical properties of (CH3NH3)2CoBr4 with paramagnetic ions and those of (CH3NH3)2CdBr4 without paramagnetic ions are reported and compared.

Nuclear quadrupole coupling parameters and structural nature of the nonlinear optical material Li2B4O7 by NMR.

The structural nature underlying the nonlinear optical (NLO) properties of Li2B4O7 is characterized by nuclear magnetic resonance (NMR). The rotation patterns of (11)B NMR were measured. We observed sixteen different spectra which were divided into two groups, corresponding to two types of boron atoms, 4-coordinated B(1) and 3-coordinated B(2), which have different boron-oxygen rings and lie at chemically inequivalent sites. From these results, the quadrupole parameter and the principal axis of the electric field gradient (EFG) tensor were determined for the two borons.

Structural characteristics for phase transitions of [N(CH3)4]2CuCl4 by (13)C CP/MAS NMR and (14)N NMR.

Structure geometry changes in [N(CH3)4]2CuCl4 near the phase transition temperature were studied by (13)C CP/MAS NMR and (14)N NMR spectrum. We distinguished the two chemically inequivalent N(1)(CH3)4 and N(2)(CH3)4 groups by (13)C CP/MAS NMR and (14)N NMR spectrum. The abrupt changes in chemical shifts and the split of the NMR signals near the phase transition temperatures for (13)C and (14)N are explained by a structural phase transition, implying that the structural geometry depends on the temperature. The mechanism behind this phase transition is based on ferroelasticity, and is also mainly related to the (14)N ions in N(CH3)4 ions. Furthermore, both phases III and IV exhibit ferroelastic properties with identical orientational domains.

Exploring the potential applications of lead-free organic-inorganic perovskite type [NH3(CH2)nNH3]MCl4 (n = 2, 3, 4, 5, and 6; M = Mn, Co, Cu, Zn, and Cd) crystals.

The organic-inorganic hybrid perovskite compounds have been extensively studied since the dawn of a new era in the field of photovoltaic applications. Up to now, perovskites have proven to be the most promising in terms of power conversion efficiency; however, their main disadvantages for use in solar cells are toxicity and chemical instability. Therefore, it is essential to develop a hybrid perovskite that can be replaced with lead-free materials. This review focuses on the possibility of applying lead-free organic-inorganic perovskite types [NH3(CH2)nNH3]MCl4 (n = 2, 3, 4, 5, and 6; M = Mn, Co, Cu, Zn, and Cd) crystals. We are seeking organic-inorganic hybrid perovskite materials with very high temperature stability or without phase transition temperature, and thermal stability. Thus, by considering the characteristics according to the methylene lengths and the various transition metals, we aim to identify improved materials meeting the criteria mentioned above. Consequently, the physicochemical properties of organic-inorganic hybrid perovskite [NH3(CH2)nNH3]MCl4 regarding the effects of various transition metal ions of the anion and the methylene lengths of the cation are expected to promote the development and application of lead-free hybrid perovskite solar cells.

Exploring the Crystal Structure, Thermodynamics, and Molecular Dynamics of NH(CH3)3CuCl3·2H2O Organic-Inorganic Hybrid Perovskite.

Understanding the physical properties of the organic-inorganic hybrid NH(CH3)3CuCl3·2H2O is necessary for its potential applications. Initially, the monoclinic structure of this crystal was discussed via single-crystal X-ray diffraction. Moreover, the previously unknown phase transition temperature was 350 K, as revealed by differential scanning calorimetry and powder X-ray diffraction. Attributed to ferroelasticity, domain walls were observed between the temperatures T c (Low) (223 K) and T c (High) (350 K). Furthermore, changes in chemical shifts for 1H and 13C indicated alterations in the molecular environment, whereas a notable decrease in line width was attributed to increased molecular motion freedom. Subsequently, spin-lattice relaxation times (T 1ρ values) for 1H and 13C (indicative of energy transfer) were influenced by tumbling motions. The high activation energy barrier for molecular reorientation was associated with the tumbling motion of methyl groups around the triple symmetry axis. These foundational properties guide the development of efficient organic-inorganic hybrids suitable for practical applications.

NMR analysis of structural geometry and molecular dynamics in perovskite-type N(CH3)4CdBr3 crystal near high-temperature phase transition.

The NMR chemical shifts, linewidths, spin-lattice relaxation times in the rotating system T1ρ, and spin-lattice relaxation times in the laboratory system T1 were evaluated for the perovskite-type N(CH3)4CdBr3 crystal, aiming to understand the changes in the structural geometry and molecular dynamics from phase I to phase II. From the temperature-dependence of the 1H, 13C, 14N, and 113Cd NMR chemical shifts, the structural geometry underwent a continuous change, without anomalous changes around (TC = 390 K). However, the linewidths in phase I were narrower than those in phase II, indicating that the motional averaging effects were caused by the rapid rotation of the N(CH3)4 group. Sudden changes in T1 and T1ρ were observed near TC, for which the activation energy Ea in phase I was approximately 12 times larger than that in phase II; the small Ea values in phase II indicate a large degree of freedom for the methyl group and CdBr6 octahedra, whereas the large Ea in phase I was primarily attributed to the overall N(CH3)4 and the 113Cd in the CdBr6 groups. Consequently, the phase transition mechanisms of N(CH3)4CdBr3 are related to reorientation of the N(CH3)4 group and the arrangement of the CdBr6 groups.

Crystal structures, phase transitions, thermodynamics, and molecular dynamics of organic-inorganic hybrid crystal [NH(CH3)3]2ZnCl4.

Understanding the physical properties of organic-inorganic hybrid [NH(CH3)3]2ZnCl4 is necessary for its potential application in batteries and fuel cells due to its environmentally-friendly, and highly stable character. Here, we determine its overall properties in detail, such as its orthorhombic crystal structure, and phase transition temperatures associated with five different phases. Structural geometry was studied by the chemical shifts caused by the local field around 1H. No changes were observed for the environment around 1H for CH3, whereas the 1H chemical shifts around NH in the cation were shown due to the change in the hydrogen bond N‒H···Cl. This is related to the change in Cl around Zn in the anion. In addition, the coordination geometry of 14N and 1H around 13C exhibited increased symmetry at high temperatures. Finally, we were able to understand its molecular dynamics by the significant change with temperature observed from the spin-lattice relaxation time T1ρ values, which represent the energy transfer for the 1H and 13C atoms of the cation. The activation energies obtained from the T1ρ results were 3-4 times large at phase I (> 348 K) than at phase V and IV (< 286 K). The relaxations show that the energy barriers in phases IV and V are related to the reorientation of methyl groups around the triple symmetry axis, while the reorientation of methyl groups of the cation in phase I is related to as a whole.

Nuclear magnetic resonance study of superprotonic conductor Rb4LiH3(SO4)4 single crystals.

To investigate the molecular dynamics of a Rb4LiH3(SO4)4 crystal below superionic phase transitions, we examined the temperature dependences of the NMR spectra and the spin-lattice relaxation time, T1, of the (1)H, (7)Li, and (87)Rb nuclei. The symmetry of (1)H signals resembles the Pake doublet containing a pair of dipolar-coupled protons. From the temperature dependence of T1, the activation energy of proton at high temperature is twice of those of (7)Li and (87)Rb. A striking feature was the formation of the weak hydrogen bond creating a significant influence of proton at high temperatures due to the mobility of the hydrogen-bond protons. And, we compared these data with (1)H and (7)Li results for (NH4)4LiH3(SO4)4 and K4LiH3(SO4)4 crystals, which have similar structures.

Crystal structures, phase transitions, and nuclear magnetic resonance of organic-inorganic hybrid [NH2(CH3)2]2ZnBr4 crystals.

Organic-inorganic hybrid [NH2(CH3)2]2ZnBr4 crystals were grown via slow evaporation, and their monoclinic structure was determined using single-crystal X-ray diffraction (XRD). The two phase transition temperatures at 401 K (T C1) and 436 K (T C2) were defined using differential scanning calorimetry and powder XRD. In the nuclear magnetic resonance spectra, a small change was observed in the 1H chemical shifts for NH2, 13C chemical shifts for CH3, and 14N resonance frequency for NH2 near T C1. 1H spin-lattice relaxation times T 1ρ and 13C T 1ρ for NH2 and CH3, respectively, rapidly decreased near T C1, suggesting that energy was easily transferred. NH2 in the [NH2(CH3)2]+ cation was significantly influenced by the surrounding environments of 1H and 14N, indicating a change in the N-H⋯Br hydrogen bond with the coordination geometry of the ZnBr4 anion. These fundamental properties open efficient avenues for the development of organic-inorganic hybrids, thus qualifying them for practical applications.

Investigation of the structure, phase transitions, molecular dynamics, and ferroelasticity of organic-inorganic hybrid NH(CH3)3CdCl3 crystals.

Understanding the physical and chemical properties of the organic-inorganic hybrid NH(CH3)3CdCl3 is essential for its application. Considering its importance, a single crystal of NH(CH3)3CdCl3 was grown with an orthorhombic structure at 300 K. The phase transition temperatures were determined to be 345 (TC3), 376 (TC2), and 452 K (TC1) (phases IV, III, II, and I, respectively, starting from a low temperature). The partial decomposition temperature was 522 K (Td). Furthermore, the NMR chemical shifts of the 1H, 13C, and 113Cd atoms of the cation and anion varied with increasing temperature. Consequently, a significant change in the coordination geometry of Cl around Cd in CdCl6 and a change in the coordination geometry of H in NH was associated with changes in the N-H⋯Cl hydrogen bond near the phase transition temperature. The 13C activation energy Ea obtained from the spin-lattice relaxation time was smaller than that of 1H Ea, suggesting that energy transfer around 13C is easier. Additionally, a comparison of the twin domain walls measured via optical polarizing microscopy and Sapriel's theory indicated that the crystal structure in phase III was more likely to be orthorhombic than hexagonal.

Investigating the physicochemical properties, structural attributes, and molecular dynamics of organic-inorganic hybrid [NH3(CH2)2NH3]2CdBr4·2Br crystals.

An in-depth understanding of the physicochemical properties of the organic-inorganic hybrid [NH3(CH2)2NH3]2CdBr6 whose structure corresponds to the formulation [NH3(CH2)2NH3]2CdBr4· 2Br is essential for its application in batteries, supercapacitors, and fuel cells. Therefore, this study aimed to determine the crystal structure, phase transition, structural geometry, and molecular dynamics of these complexes. Considering its importance, a single crystal of [NH3(CH2)2NH3]2CdBr6 was grown; the crystal structure was found to be monoclinic. The phase transition temperatures were determined to be 443, 487, 517, and 529 K, and the crystal was thermally stable up to 580 K. Furthermore, the 1H, 13C, 14N, and 113Cd NMR chemical shifts caused by the local field surrounding the resonating nucleus of the cation and anion varied with increasing temperature, along with the surrounding environments of their atoms. In addition, 1H spin-lattice relaxation time T1ρ and 13C T1ρ, which represent the energy transfer around the 1H and 13C atoms of the cation, respectively, varied significantly with temperature. Consequently, changes in the coordination geometry of Br around Cd in the CdBr6 anion and the coordination environment around N (in the cation) were associated with changes in the N-H···Br hydrogen bond. The structural geometry revealed critical information regarding their basic mechanism of organic-inorganic hybrid compounds.

Processing on crystal growth, structure, thermal property, and nuclear magnetic resonance of organic-inorganic hybrid perovskite type [NH3(CH2)6NH3]ZnCl4 crystal.

Organic-inorganic hybrid compounds have recently gained significant attention in recent years due to their diverse applications. Herein, [NH3(CH2)6NH3]ZnCl4 crystals were grown, and their triclinic structure, phase transition temperature (TC = 408 K), and high thermal stability (Td = 584 K) was determined using X-ray diffraction (XRD), differential scanning calorimetry, and thermogravimetry measurements. By analyzing the chemical in response to temperature changes, we observed that the coordination geometry around 1H and 13C were highly symmetric below TC, whereas their symmetry was lowered above TC. The change of N-H⋯Cl hydrogen bond from XRD results and the change of 14N NMR chemical shifts was due to the changes to the coordination geometry of Cl- around Zn2+ in the ZnCl4 anion. The activation energy of 1H was three times greater than that of 13C, and this result indicates that the energy transfer of 13C was easier than those of 1H. We compared the results for [NH3(CH2)nNH3]ZnCl4 (n = 6) studied here with those for n = 2, 3, 4, and 5 obtained from previous studies. The characteristics of the length of CH2 in the methylene chain are expected to be used for potential applications in the near future.

Investigation on the organic-inorganic hybrid crystal [NH2(CH3)2]2CuBr4: structure, phase transition, thermal property, structural geometry, and dynamics.

Understanding the physical properties of the organic-inorganic hybrid [NH2(CH3)2]2CuBr4 is essential to expand its applications. The single [NH2(CH3)2]2CuBr4 crystals were grown and their comprehensive properties were investigated. The crystals had a monoclinic structure with the space group P21/n and lattice constants of a = 8.8651 (5) Å, b = 11.9938 (6) Å, c = 13.3559 (7) Å, and ß = 91.322°. The transition temperature from phase I to phase II was determined to be 388 K. Variations in the 1H nuclear magnetic resonance chemical shifts of NH2 and 14N NMR chemical shifts according to the temperature changes in the cation were attributed to vibrations of NH2 groups at their localization sites. The 1H and 13C spin-lattice relaxation times (T1ρ) in phase II changed significantly with temperature, indicating that these values are governed by molecular motion. The T1ρ values were much longer in phase I than in phase II, which means energy transfer was difficult. Finally, the activation energies for phases I and II were considered. According to the basic mechanism of [NH2(CH3)2]2CuBr4 crystals, organic-inorganic materials may have potential applications in various fields.

Crystal growth, phase transition, and nuclear magnetic resonance of organic-inorganic hybrid perovskite NH2(CH3)2CdCl3.

Understanding the physicochemical properties of organic-inorganic hybrid materials is essential to promote their applications. In this study, a single crystal of NH2(CH3)2CdCl3 was grown, and it exhibited a monoclinic structure. Its phase transition temperatures were 460 and 470 K, and it showed sufficient thermal stability. The changes in the NMR chemical shifts of each atom in the crystal with increasing temperature were determined; the chemical shift of 1H of NH2 in the NH2(CH3)2 cation changed with temperature, which was correlated to the changes in the chemical shift of 14N in NH2. The change in 113Cd chemical shifts indicate the change of six Cl atoms around Cd in CdCl6. Therefore, the change in the coordination geometry of CdCl6 is attributed to the change in the N-H⋯Cl hydrogen bond between the NH2(CH3)2 cation and CdCl6 anion. In addition, the 13C activation energies Ea obtained from the spin-lattice relaxation time T1ρ values are smaller than those of the 1H Ea values, suggesting that is free compared to 1H in the cation. We believe that this study furthers our fundamental understanding of organic-inorganic hybrid materials to promote their practical solar cell applications.

Analysis of the Structure, Thermal, and Molecular Dynamics of Organic-Inorganic Hybrid Crystal at Phases IV, III, II, and I: [NH2(CH3)2]2CdBr4.

A comprehensive understanding of the physicochemical properties of organic-inorganic hybrids is essential for their solid-state lighting applications. Therefore, a single crystal of [NH2(CH3)2]2CdBr4 was grown; the crystal structure was monoclinic, and the phase transition temperatures for the four phases IV, III, II, and I were 383 K (TC1), 417 K (TC2), and 427 K (TC3). Furthermore, the chemical shifts caused by the local field around 1H, 13C, 14N, and 113Cd changed continuously with temperature, especially near TC1, indicating that the local environment changes with temperature. Owing to the large change in 113Cd chemical shifts, the coordination geometry of Br around Cd in the CdBr4 tetrahedra changes near TC1. Therefore, it is proposed that Br plays a significant role in the N-H···Br hydrogen bond. Finally, the spin-lattice relaxation time T1ρ, representing the energy transfer around the 1H and 13C atoms of the cation, changed significantly with temperature. The activation energies obtained from the T1ρ results were two times larger at high temperatures than at low temperatures. This study provides an understanding of the fundamental properties of organic-inorganic hybrid compounds to broaden their applications.

Organic-inorganic hybrid [NH3(CH2)6NH3]ZnBr4 crystal: structural characterization, phase transitions, thermal properties, and structural dynamics.

Organic-inorganic hybrid [NH3(CH2)6NH3]ZnBr4 crystals were prepared by slow evaporation; the crystals had a monoclinic structure with space group P21/c and lattice constants a = 7.7833 Å, b = 14.5312 Å, c = 13.2396 Å, ß = 90.8650°, and Z = 4. They underwent two phase transitions, at 370 K (T C1) and 430 K (T C2), as confirmed by powder X-ray diffraction patterns at various temperatures; the crystals were stable up to 600 K. The nuclear magnetic resonance spectra, obtained using the magic-angle spinning method, demonstrated changes in the 1H and 13C chemical shifts were observed near T C1, indicating changing structural environments around 1H and 13C. The spin-lattice relaxation time, T 1ρ, increased rapidly near T C1 suggesting very large energy transfer, as indicated by a large thermal displacement around the 13C atoms of the cation. However, the environments of 1H, 14N, and C1 located close to NH3 in the [NH3(CH2)6NH3] cation did not influence it significantly, indicating a minor change in the N-H⋯Br hydrogen bond with the coordination geometry of the ZnBr4 anion. We believe that the information on the physiochemical properties and thermal stability of [NH3(CH2)6NH3]ZnBr4, as discussed in this study, would be key to exploring its application in stable, environment friendly solar cells.

Growth, structure, phase transition, thermal properties, and structural dynamics of organic-inorganic hybrid [NH3(CH2)5NH3]ZnCl4 crystal.

In this study, the physicochemical properties of [NH3(CH2)5NH3]ZnCl4 crystals were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis, and nuclear magnetic resonance (NMR). The crystals at 300 K had a monoclinic structure with C2/c space group and lattice constants are a = 21.4175 Å, b = 7.3574 Å, c = 19.1079 Å, ß = 120.5190°, and Z = 8. Three endothermic peaks at 256, 390, and 481 K were observed in the DSC curve. From the single-crystal XRD patterns, powder XRD patterns, and optical microscopy results based on the temperature change, the phase transition and melting temperatures were determined to be 390 and 481 K, respectively. NMR studies indicated no change in 1H chemical shifts, but a change in the chemical shifts for C2, located between C1 and C3 of the cation at 340 K. Increase in molecular motion caused an increase in the spin-lattice relaxation time, T1ρ, at low spinning rates, under magic-angle spinning rate conditions. This crystal showed a minor change in the N-H···Cl hydrogen bond, related to the coordination geometry of the ZnCl4 anion.