Phase Transitions and Nonlinear Optical Property Modifications in BaGa4Se7.

Phase transitions can change the crystal structure and modify the physical properties of crystals. In this work, we investigate the phase transition behavior in BaGa4Se7, an important middle infrared (mid-IR) nonlinear optical (NLO) crystal, in the temperature range from room temperature to 1173 K. Interestingly, the BaGa4Se7 crystal undergoes a reversible ferroelastic phase transition at T = 528 K, resulting in the presence of a newly discovered phase (γ-phase) at the higher temperature. The experimental temperature dependence of optical birefringence, as well as the first-principles birefringence and NLO coefficients, reveals that the γ-phase exhibits larger birefringence and better NLO properties compared with those of the low-temperature phase (α-phase). This work demonstrates that phase-transition-induced structural modification can improve the mid-IR NLO properties, which would provide an effective avenue to obtain materials with good optoelectronic performance.

Synthesis, Structure, and Optical Properties of a 0D Hybrid Organic-Inorganic Metal Halide (C5N2H14Cl)GeCl3.

Due to the flexible structural tunability and excellent photoelectric performance, hybrid organic-inorganic metal halides (OIMHs) have attracted intensive attention and become a hot topic in the field of materials. It is important and necessary to explore new OIMHs and study their structure-property relationship. In this work, a new lead-free OIMH, (C5N2H14Cl)GeCl3, is synthesized by the combination of hydrothermal and solution methods. This compound features a zero-dimensional structure composed of inorganic [GeCl3]- trigonal pyramids surrounded by isolated Cl- anions and organic (C5N2H14)2+ cations. Preliminary characterization and first-principles calculations are performed to study its basic optical properties. Interestingly, (C5N2H14Cl)GeCl3 shows weak blue emission under ultraviolet excitation, and the intrinsic mechanism is discussed.

Evolution of Structures and Optical Properties in a Series of Infrared Nonlinear Optical Crystals LixAg1-xInSe2 (0 ≤ x ≤ 1).

In this work, a number of new infrared nonlinear optical (NLO) crystals of LixAg1-xInSe2, in which the ratio x of Li/Ag varies in a wide range from 0 to 1, are investigated. Structural analysis reveals that the space group of LixAg1-xInSe2 evolved from I4̅2d in AgInSe2 to Pna21 in LiInSe2 as x increases from low values (0, 0.2, 0.37) to large values (0.55, 0.78, 0.81, 1). Compared to other Li/Ag coexisting chalcogenides such as LixAg1-xGaS2 and LixAg1-xGaSe2, the structural distortions in LixAg1-xInSe2 are much more prominent. This may explain the limited crystallization region in the phase graph of the tetragonal structure LixAg1-xInSe2. The fundamental optical absorption edges in these LixAg1-xInSe2 compounds are determined from the direct electronic transitions and the band gaps Eg gradually increase as the lithium content increases, consistent with the first-principles calculations. The composition x = 0.78 is calculated to have a good set of optical properties with a large NLO coefficient (dpowder = 28.8 pm/V) and moderate birefringence (Δn ∼ 0.04). Accordingly, the Li0.78Ag0.22InSe2 crystal is grown by the modified Bridgman-Stockbarger method, and it exhibits a wide transparency range from 0.546 to 14.3 µm at the 2% transmittance level.

(C5N2H14)GeBr4: A 2D Organic Germanium Bromide Perovskite with Strong Orange Photoluminescence Properties.

Hybrid organic-inorganic metal halide (OIMH) perovskites are regarded as potential photoluminescent (PL) materials and have attracted intensive attention. Here, we select 1-methylpiperazine as an organic component and successfully obtain a two-dimensional (2D) Ge-based OIMH perovskite, (1-mpz)GeBr4. It features a 2D layered structure composed of distorted [GeBr6]4- octahedra with organic (C5H14N2)2+ located between the layers. (1-mpz)GeBr4 exhibits strong orange color under ultraviolet (UV) light and possesses good PL stability for over 2 months. The photoluminescence quantum efficiency is measured to be 7.15% at room temperature, which is the largest among all reported low-dimensional Ge-based perovskites. Experimental measurements, combined with first-principles calculations, reveal that its PL property is attributed to self-trapped excitons (STEs) from [GeBr6]4- groups. From the deduced structure-property relationship, Ge-based OIMH PL perovskites with good stability and high PL efficiency can be expected.

Zero-Dimensional Hybrid Cd-Based Perovskites with Broadband Bluish White-Light Emissions.

Recently, low-dimensional organic-inorganic hybrid metal halide perovskites acting as single-component white-light emitting materials have attracted extensive attention, but most studies concentrate on hybrid lead perovskites. Herein, we present two isomorphic zero-dimensional (0D) hybrid cadmium perovskites, (HMEDA)CdX4 (HMEDA=hexamethylenediamine, X=Cl (1), Br (2)), which contain isolated [CdX4 ]2- anions separated by [HMEDA]2+ cations. Under UV light excitation, both compounds display broadband bluish white-light emission (515 nm for 1 and 445 nm for 2) covering the entire visible light spectrum with sufficient photophysical stabilities. Remarkably, compound 2 shows a high color rendering index (CRI) of 83 enabling it as a promising candidate for single-component WLED applications. Based on the temperature-dependent, powder-dependent and time-resolved PL measurements as well as other detailed studies, the broadband light emissions are attributed to self-trapped excitons stemming from the strong electron-phonon coupling.

Three-Dimensional Cuprous Lead Bromide Framework with Highly Efficient and Stable Blue Photoluminescence Emission.

Considering the instability and low photoluminescence quantum yield (PLQY) of blue-emitting perovskites, it is still challenging and attractive to construct single crystalline hybrid lead halides with highly stable and efficient blue light emission. Herein, by rationally introducing d10 transition metal into single lead halide as new structural building unit and optical emitting center, we prepared a bimetallic halide of [(NH4 )2 ]CuPbBr5 with new type of three-dimensional (3D) anionic framework. [(NH4 )2 ]CuPbBr5 exhibits strong band-edge blue emission (441 nm) with a high PLQY of 32 % upon excitation with UV light. Detailed photophysical studies indicate [(NH4 )2 ]CuPbBr5 also displays broadband red light emissions derived from self-trapped states. Furthermore, the 3D framework features high structural and optical stabilities at extreme environments during at least three years. To our best knowledge, this work represents the first 3D non-perovskite bimetallic halide with highly efficient and stable blue light emission.

A remarkable thermosensitive hydrogel cross-linked by two inorganic nanoparticles with opposite charges.

Herein, we report the successful synthesis of a series of poly (N-isopropylacrylamide) (PNIPA)/layered double hydroxides (LDHs)/nano-hydroxyapatite (nano-HA) hydrogels via in-situ radical polymerization. The internal morphology, thermo sensitivity, rheological properties, swelling behavior and hemocompatibility of the PNIPA/LDHs/HA composite hydrogels were systematically investigated. Results show that the hydrogels had a reversible sol-gel transformation around 33 °C. Interactions between the positively charged LDHs and negatively charged nano-HA particles created a highly porous hydrogel network. The composite hydrogels exhibited excellent hemocompatibility, incredible mechanical toughness and reversible swelling/deswelling behavior. To our knowledge, this is the first reported study to use two types of inorganic nanoparticle with opposing charges as hydrogel crosslinking agents. Based on its properties, we expect this hydrogel has broad applications potential in tissue engineering, drug delivery and biosensor development.

Role of Specificity Protein 1, Hepatocyte Nuclear Factor 1α, and Pregnane X Receptor in the Basal and Rifampicin-Induced Transcriptional Regulation of Porcine Cytochrome P450 3A46.

Cytochrome P450 (CYP) 3A46, one of human CYP3A4 homologs, functions as a key enzyme in the metabolism of xenobiotics in pigs. However, the regulatory mechanism for the transcriptional activation of CYP3A46 in porcine liver remains unknown. In this study, we confirmed that CYP3A46 is constitutively expressed in porcine primary hepatocytes, and its expression was significantly induced by rifampicin (RIF) instead of dexamethasone. We further found that a proximal GC box and a distal hepatocyte nuclear factor 1 (HNF1) binding site within the 5'-flanking region of CYP3A46 are the important cis-regulatory elements involved in regulating the constitutive expression of CYP3A46, via recruiting specificity protein 1 (Sp1) and HNF1α, respectively. Furthermore, we revealed that HNF1α and pregnane X receptor (PXR) activate the RIF-mediated transcription of CYP3A46 by binding to the distal HNF1 binding site and the proximal direct repeats of AGGTCA separated by 4 bases motif, respectively. Meanwhile, HNF1α is also involved in regulating RIF-induced expression of CYP3A4 through a novel distal HNF1 binding site identified in the xenobiotic-responsive enhancer module. In summary, our data demonstrate that several transcription factors, including Sp1, HNF1α, and PXR, function in the basal and RIF-mediated transcriptional regulation of CYP3A46 by binding to their related cis-regulatory elements in the proximal promoter and distal enhancer.

A signal "on" photoelectrochemical biosensor for assay of protein kinase activity and its inhibitor based on graphite-like carbon nitride, Phos-tag and alkaline phosphatase.

A highly sensitive and selective photoelectrochemical (PEC) biosensor is fabricated for the detection of protein kinase activity based on visible-light active graphite-like carbon nitride (g-C3N4) and the specific recognition utility of Phos-tag for protein kinase A (PKA)-induced phosphopeptides. For assembling the substrate peptides, g-C3N4 and gold nanoparticles (g-C3N4-AuNPs) complex is synthesized and characterized. When the immobilized peptides on g-C3N4-AuNPs modified ITO electrode are phosphorylated under PKA catalysis, they can be specifically identified and binded with biotin functionalized Phos-tag (Phos-tag-biotin) in the presence of Zn(2+). Then, through the specific interaction between biotin and avidin, avidin functionalized alkaline phosphatase (avidin-ALP) is further assembled to catalyze its substrate of l-ascorbic acid-2-phosphate trisodium salt (AAP) to produce electron donor of ascorbic acid (AA), resulting an increased photocurrent compared with the absence of phosphorylation event. Based on the specific identification effect of Phos-tag, the fabricated biosensor presents excellent selectivity for capturing the phosphorylated serine residues in the substrate peptides. With the good photoactivity of g-C3N4 and ALP-catalyzed signal amplification, the fabricated biosensor presents high sensitivity and low detection limit (0.015 unit/mL, S/N = 3) for PKA. The applicability of this PEC biosensor is further testified by the evaluation of PKA inhibition by HA-1077 with the IC50 value of 1.18µM. This new strategy is also successfully applied to detect the change of PKA activity in cancer cell lysate with and without drug stimulation. Therefore, the developed PEC method has great potential in screening of kinase inhibitors and highly sensitive detection of kinase activity.

Transcriptional regulation of chicken cytochrome P450 2D49 basal expression by CCAAT/enhancer-binding protein α and hepatocyte nuclear factor 4α.

Chicken cytochrome P450 (CYP)2D49 is structurally and functionally related to human CYP2D6, which is an important drug-metabolizing enzyme. To date, little is known about the transcriptional regulation of this cytochrome. Through deletion analysis of the CYP2D49 promoter, we identified two putative degenerate CCAAT/enhancer-binding protein (C/EBP)-binding sites and an imperfect DR1 element (the site contains direct repeats of the hexamer AGGTCA separated by a one-nucleotide spacer motif) within regions -296/-274, -274/-226, and -226/-183, respectively, which may play critical roles in the transcriptional activation of the CYP2D49 gene. Electrophoretic mobility shift assays and chromatin immunoprecipitation assays showed that the putative C/EBP boxes and DR1 element in the CYP2D49 promoter are functional motifs that bind to C/EBPα and hepatocyte nuclear factor 4α (HNF4α), respectively. Furthermore, we studied the functional importance and relationships of these transcription factor-binding sites by examining the effects of mutation and deletion of these regions on promoter activity. These studies revealed that the two C/EBP-binding sites show a compensatory relationship and work cooperatively with the DR1 element to modulate the transcription of CYP2D49. The results of overexpressing C/EBPα and HNF4α in culture cells further confirmed that both C/EBPα and HNF4α contribute significantly to sustaining a high level of CYP2D49 transcription. In conclusion, the data indicate that the constitutive hepatic expression of CYP2D49 is governed by both C/EBPα and HNF4α. Further studies will be required to fully characterize the molecular mechanisms that modulate CYP2D49 expression.