Depletion of macrophages with clodronate liposomes partially attenuates renal fibrosis on AKI-CKD transition.

Clodronate liposomes are bisphosphonates encapsulated by liposomes that are known to induce macrophage depletion in vivo. In a previous study, clodronate liposomes improved renal ischemia/reperfusion (I/R) injury in mice, which may be due to effects on macrophage phenotypes. However, how inflammatory cytokines secretion participates is unknown. In this study, we investigated the effect of macrophages in the I/R kidney by depleting macrophages with clodronate liposomes and changing inflammatory cytokines. C57BL/6 mice underwent I/R injury with or without clodronate liposomes administration on Days 5 and 15. Tubular injury, collagen deposition, and fibrosis were detected and analyzed by histological staining, immunocytochemistry (IHC), flow cytometry (FACS), and reverse transcription-polymerase chain reaction (RT-PCR). Inflammatory cytokines were detected and analyzed by Western blotting and RT-PCR. We found that clodronate liposomes alleviated renal fibrosis and tissue damage on both Days 5 and 15. KIM-1, IL-10, and TGF-ß were reduced significantly in the clodronate liposomes treatment group. However, TNF-α was not different between the clodronate liposomes treatment group and the phosphate-buffered saline treatment group on either Day 5 or Day 15. Thus, clodronate liposomes can alleviate renal fibrosis and tissue damage and reduce the inflammatory cytokines IL-10 and TGF-ß, suggesting that clodronate liposomes alleviate renal fibrosis may because of M1/M2 polarization.

[Quality evaluation of Compound Cheqian Tablets based on UPLC-Q-TOF-MS/MS, network pharmacology and "double external standards" QAMS].

The Compound Cheqian Tablets are derived from Cheqian Power in Comprehensive Recording of Divine Assistance, and they are made by modern technology with the combination of Plantago asiatica and Coptis chinensis. To investigate the material basis of Compound Cheqian Tablets in the treatment of diabetic nephropathy, in this study, the chemical components of Compound Cheqian Tablets were characterized and analyzed by UPLC-Q-TOF-MS/MS, and a total of 48 chemical components were identified. The identified chemical compounds were analyzed by network pharmacology. By validating with previous literature, six bioactive compounds including acteoside, isoacteoside, coptisine, magnoflorine, palmatine, and berberine were confirmed as the index components for qua-lity evaluation. Furthermore, the content of the six components in the Compound Cheqian Tablets was determined by the "double external standards" quantitative analysis of multi-components by single marker(QAMS), and the relative correction factor of isoacteoside was calculated as 1.118 by using acteoside as the control; the relative correction factors of magnoflorine, palmatine, and berberine were calculated as 0.729, 1.065, and 1.126, respectively, by using coptisine as the control, indicating that the established method had excellent stability under different conditions. The results obtained by the "double external standards" QAMS approximated those obtained by the external standard method. This study qualitatively characterized the chemical components in the Compound Cheqian Tablets by applying UPLC-Q-TOF-MS/MS and screened the pharmacodynamic substance basis for the treatment of diabetic nephropathy via network pharmacology, and primary pharmacodynamic substance groups were quantitatively analyzed by the "double external stan-dards" QAMS method, which provided a scientific basis for clarifying the pharmacodynamic substance basis and quality control of Compound Cheqian Tablets.

Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) overexpression alleviates endoplasmic reticulum stress after acute kidney injury.

BACKGROUND: Mitochondrial biogenesis dysregulation and enhanced endoplasmic reticulum (ER) stress have been implicated in the progression of acute kidney injury (AKI). However, the interaction between these two events remains poorly understood. This study was designed to investigate the role of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) expression, a key factor in mitochondrial biogenesis, in renal ER stress at 24 h after AKI and the underlying mechanisms. METHODS: Mice were administered recombinant adenovirus encoding murine PGC-1α (100 µl, 1.0 × 109PFU/ml) or vehicle five days before renal ischemia reperfusion (I/R) or sham operation. Twenty-four hours after the operation, kidney and serum samples were collected for evaluation. RESULTS: We first confirmed that PGC-1α transfection elevated the PGC-1α levels and mitochondrial transcripts in the kidney 24 h after AKI. Then, we found PGC-1α overexpression improved renal function. PGC-1α transfection inhibited AKI-induced ER stress through the unfolded protein response (UPR) pathway, resulting in the suppression of apoptosis via both mitochondrial and ER pathways. Further study showed that the expression of mitofusin 2 (Mfn2), an interaction protein between mitochondria and ER, was increased after PGC-1α overexpression. We also found the expression of a novel ER stress regulator, hairy and enhancer of split 1 (Hes1), was decreased after PGC-1α transfection. CONCLUSIONS: Our findings reveal that mitochondrial biogenesis plays an important role in the progression of AKI-induced ER stress and provide useful evidence for research on organelle crosstalk during AKI.

Severe glomerular C3 deposition indicates severe renal lesions and a poor prognosis in patients with immunoglobulin A nephropathy.

AIMS: Glomerular complement 3 (C3) deposition is often observed in renal biopsies of patients with IgA nephropathy (IgAN); however, the relationship between the intensity of C3 deposition and the long-term prognosis of IgAN has rarely been reported. In this retrospective study, we aimed to evaluate the prognostic value of glomerular C3 deposition for IgAN progression. METHODS AND RESULTS: From June 2009 to June 2010, a total of 136 adult patients with IgAN were enrolled in the study. According to the intensity of glomerular C3 deposition, patients were divided into a glomerular C3high group (34 patients) and a glomerular C3low group (102 patients). The levels of clinical parameters, glomerular immune complexes, histopathological features, and serum cytokines of the two groups were compared. On the basis of an average of 105 months of follow-up, the predictive value of glomerular C3 deposition for IgAN progression was also investigated. Patients in the C3high group had more severe glomerular IgA, IgG, IgM, and complement factor H deposition, a higher percentage of mesangial hypercellularity (M1), and higher levels of segmental glomerulosclerosis (S1), tubular atrophy/interstitial fibrosis (T2), and crescents (C2) than those in the C3low group. Renal biopsies in the C3high group showed higher densities of interstitial inflammatory cells and higher levels of serum interferon-γ than those in the C3low group. Multivariate Cox regression analysis revealed that a higher intensity of glomerular C3 deposition remained as an independent predictor of serum creatinine doubling and end-stage renal disease. CONCLUSIONS: A high intensity of glomerular C3 deposition is associated with the severity of renal lesions, and predicts long-term poor renal survival for IgAN patients.

Nonsiliceous Mesoporous Materials: Design and Applications in Energy Conversion and Storage.

In this work, the progress in the design of nonsiliceous mesoporous materials (nonSiMPMs) over the last five years from the perspectives of the chemical composition, morphology, loading, and surface modification is summarized. Carbon, metal, and metal oxide are in focus, which are the most promising compositions. Then, representative applications of nonSiMPMs are demonstrated in energy conversion and storage, including recent technical advances in dye-sensitized solar cells, perovskite solar cells, photocatalysts, electrocatalysts, fuel cells, storage batteries, supercapacitors, and hydrogen storage systems. Finally, the requirements and challenges of the design and application of nonSiMPMs are outlined.

High renal DC-SIGN+ cell density is associated with severe renal lesions and poor prognosis in patients with immunoglobulin A nephropathy.

BACKGROUND AND AIMS: In this observational cohort study, we assessed the prognostic value of DC-SIGN+ cells in the pathogenesis and progression of IgA nephropathy (IgAN). METHODS AND RESULTS: A total of 139 adult IgAN patients were enrolled into this study from June 2009 to June 2010. We characterised DC-SIGN+ cells by immunohistochemistry or immunofluorescence in renal biopsy tissue. Correlations between the DC-SIGN, intercellular adhesion molecule 3 (ICAM-3), CD4 and CD8 were evaluated. Patients were classified into the DC-SIGNhigh and DC-SIGNlow groups. Depending on an average of 100-month follow-up, the predictive value of DC-SIGN+ cells in IgAN progression was analysed. DC-SIGN+ cells were found frequently in IgAN kidneys while rarely observed in normal kidneys, and almost all DC-SIGN+ cells expressed MHC-II. We also found that DC-SIGN+ cells were adjacent to ICAM-3-positive CD4+ and CD8+ lymphocytes. The density of DC-SIGN+ cells was positively and linearly correlated with the density of ICAM-3+ cells, CD4+ cells and CD8+ cells in renal biopsy tissues. In the DC-SIGNhigh group, the degree of renal lesion and inflammatory cell infiltration was more severe compared to the DC-SIGNlow group. Patients in the DC-SIGNhigh group also had increased incidences of deteriorating renal function during the follow up compared to patients in the DC-SIGNlow group. CONCLUSIONS: DC-SIGN+ cells probably served as a potential contributor to exacerbate local inflammatory response. The density of DC-SIGN+ cells was associated with the severity of renal lesions of the patients. High renal DC-SIGN+ cell density might be used as a predictor of poor prognosis in patients with IgAN.

Synthesis and Application of an Aldazine-Based Fluorescence Chemosensor for the Sequential Detection of Cu²âº and Biological Thiols in Aqueous Solution and Living Cells.

A fluorescence chemosensor, 2-hydroxy-1-naphthaldehyde azine (HNA) was designed and synthesized for sequential detection of Cu(2+) and biothiols. It was found that HNA can specifically bind to Cu(2+) with 1:1 stoichiometry, accompanied with a dramatic fluorescence quenching and a remarkable bathochromic-shift of the absorbance peak in HEPES buffer. The generated HNA-Cu(2+) ensemble displayed a "turn-on" fluorescent response specific for biothiols (Hcy, Cys and GSH) based on the displacement approach, giving a remarkable recovery of fluorescence and UV-Vis spectra. The detection limits of HNA-Cu(2+) to Hcy, Cys and GSH were estimated to be 1.5 µM, 1.0 µM and 0.8 µM, respectively, suggesting that HNA-Cu(2+) is sensitive enough for the determination of thiols in biological systems. The biocompatibility of HNA towards A549 human lung carcinoma cell, was evaluated by an MTT assay. The capability of HNA-Cu(2+) to detect biothiols in live A549 cells was then demonstrated by a microscopy fluorescence imaging assay.

Biliverdin Reductase A (BVRA) Mediates Macrophage Expression of Interleukin-10 in Injured Kidney.

Biliverdin reductase A is an enzyme, with serine/threonine/tyrosine kinase activation, converting biliverdin (BV) to bilirubin (BR) in heme degradation pathway. It has been reported to have anti-inflammatory and antioxidant effect in monocytes and human glioblastoma. However, the function of BVRA in polarized macrophage was unknown. This study aimed to investigate the effect of BVRA on macrophage activation and polarization in injured renal microenvironment. Classically activated macrophages (M1macrophages) and alternative activation of macrophages (M2 macrophages) polarization of murine bone marrow derived macrophage was induced by GM-CSF and M-CSF. M1 polarization was associated with a significant down-regulation of BVRA and Interleukin-10 (IL-10), and increased secretion of TNF-α. We also found IL-10 expression was increased in BVRA over-expressed macrophages, while it decreased in BVRA knockdown macrophages. In contrast, BVRA over-expressed or knockdown macrophages had no effect on TNF-α expression level, indicating BVRA mediated IL-10 expression in macrophages. Furthermore, we observed in macrophages infected with recombinant adenoviruses BVRA gene, which BVRA over-expressed enhanced both INOS and ARG-1 mRNA expression, resulting in a specific macrophage phenotype. Through in vivo study, we found BVRA positive macrophages largely existed in mice renal ischemia perfusion injury. With the treatment of the regular cytokines GM-CSF, M-CSF or LPS, excreted in the injured renal microenvironment, IL-10 secretion was significantly increased in BVRA over-expressed macrophages. In conclusion, the BVRA positive macrophage is a source of anti-inflammatory cytokine IL-10 in injured kidney, which may provide a potential target for treatment of kidney disease.

Crown Ether Copolymerized Polyimide Film: Enhanced Mechanical, Thermal Properties and Low Dielectric Constant under High Frequency.

Polymer materials with a low dielectric constant and low dielectric loss have the potential to be applied to high-frequency signal transmissions, such as mobile phone antennas and millimeter wave radars. Two types of diamines, 4,4'-diamino-p-tetraphenyl (DPT) and crown ether diamine (CED), were prepared for ternary copolymerization with BPDA in this study. Cross-links with molecular chains were formed, increasing molecular chain distance by utilizing rings of CED. The MPI films exhibit a good thermal performance with the increase in CED addition, with Tg > 380 °C and CTE from -4 × 10-6 K-1 to 5 × 10-6 K-1. The Young's modulus can reach 8.6 GPa, and the tensile strength is above 200 MPa when 5% and 7% CED are introduced. These MPI films exhibit good mechanical performances. The dielectric constant of PI-10% film can go as low as 3.17. Meanwhile, the relationship between dielectric properties and molecular structure has been demonstrated by Molecular Simulation (MS). PI molecules are separated by low dielectric groups, resulting in a decrease in the dielectric constant.

Adhesion and Transparency Enhancement between Flexible Polyimide-PDMS Copolymerized Film and Copper Foil for LED Transparent Screen.

With the increasing demand for innovative electronic products, LED transparent screens are gradually entering the public eye. Polyimide (PI) materials combine high temperature resistance and high transparency, which can be used to prepare flexible copper-clad laminate substrates. The physical and chemical properties of PI materials differ from copper, such as their thermal expansion coefficients (CTEs), surface energy, etc. These differences affect the formation and stability of the interface between copper and PI films, resulting in a short life for LED transparent screens. To enhance PI-copper interfacial adhesion, aminopropyl-terminated polydimethylsiloxane (PDMS) can be used to increase the adhesive ability. Two diamine monomers with a trifluoromethyl structure and a sulfone group structure were selected in this research. Bisphenol type A diether dianhydride is a dianhydride monomer. All three of the above monomers have non-coplanar structures and flexible structural units. The adhesion and optical properties can be improved between the interface of the synthesized PI films and copper foil. PI films containing PDMS 0, 1, 3, and 5 wt% were analyzed using UV spectroscopy. The transmittance of the PI-1/3%, PI-1/5%, PI-2/3%, and PI-2/5% films were all more than 80% at 450 nm. Meanwhile, the Td 5% and Td 10% heat loss and Tg temperatures decreased gradually with the increase in PDMS. The peel adhesion of PI-copper foil was measured using a 180° peel assay. The effect of PDMS addition on peel adhesion was analyzed. PIs-3% films had the greatest peeling intensities of 0.98 N/mm and 0.85 N/mm.

Role of the Support Effects in Single-Atom Catalysts.

In recent years, single-atom catalysts (SACs) have received a significant amount of attention due to their high atomic utilization, low cost, high reaction activity, and selectivity for multiple catalytic reactions. Unfortunately, the high surface free energy of single atoms leads them easily migrated and aggregated. Therefore, support materials play an important role in the preparation and catalytic performance of SACs. Aiming at understanding the relationship between support materials and the catalytic performance of SACs, the support effects in SACs are introduced and reviewed herein. Moreover, special emphasis is placed on exploring the influence of the type and structure of supports on SAC catalytic performance through advanced characterization and theoretical research. Future research directions for support materials are also proposed, providing some insight into the design of SACs with high efficiency and high loading.

Palladium nanoparticles confined in uncoordinated amine groups of metal-organic frameworks as efficient hydrogen evolution electrocatalysts.

Hydrogen obtained through the electrolysis of water is a potential solution to the growing demand of human society for energy. In addition, water electrolysis generates less environmental pollution than fossil energy sources. However, the preparation of highly active and low-cost electrocatalysts remains a key challenge. Here, we report a facile and inexpensive method to prepare palladium nanoparticles (Pd NPs) supported on aminated (-NH2) metal-organic frameworks (MOF). The obtained electrocatalyst (Pd@Uio-66-NH2) exhibits excellent electrocatalytic performance for the hydrogen evolution reaction (HER), featuring an ultralow overpotential (34 mV at 10 mA cm-2), small Tafel slope (41 mV dec-1), and superior stability in acid electrolyte. Systematic characterization demonstrated that -NH2 can effectively stabilize palladium acetate as the Lewis base. Meanwhile, the strong interaction between the lone pair electrons and the d-orbital ensures that the Pd atoms are uniformly distributed in the MOF material, inhibiting the agglomeration of metal NPs in the reaction. This strategy provides an avenue to prepare inexpensive and highly active catalysts for HER in acidic media.

Coordination Engineering Induced d-Band Center Shift on Single-Atom Fe Electrocatalysts for Enhanced Oxygen Reduction.

Part of the performance of single-atom catalysts (SACs) is greatly influenced by the microenvironment around a single metal site, of which the oxygen reduction reaction (ORR) is counted as one of them. However, an in-depth understanding of the catalytic activity regulation by the coordination environment is still lacking. In this study, a single Fe active center with axial fifth hydroxyl (OH) and asymmetric N,S coordination embedded in a hierarchically porous carbon material (Fe-SNC) are prepared. Compared to Pt/C and most of the reported SACs, as-prepared Fe-SNC has certain advantages in terms of ORR activity and maintains sufficient stability. Furthermore, the assembled rechargeable Zn-air battery exhibits impressive performance. The combination of multiple findings revealed that the introduction of S atoms not only facilitates the formation of porous structures but also facilitates the desorption and adsorption of oxygen intermediates. On the other hand, with the introduction of axial OH groups, the bonding strength of the ORR intermediate is reduced, and even the central position of the Fe d-band is optimized. The developed catalyst is expected to lead to further research on the multiscale design of the electrocatalyst microenvironment.

The history, stereochemistry, ethnopharmacology and quality assessment of borneol.

ETHNOPHARMACOLOGICAL RELEVANCE: Borneol (BO) represents a global trade-driven spreading of ethnic medicine traceable to the classical age, and won its name specific to its original habitat "Borneo". BO shows broad spectral pharmacological effects, such as anti-inflammatory, analgesic, antipyretic, inducing resuscitation, and widely applied in the protection and treatment of cardiovascular and cerebrovascular diseases, used singly or mostly in compound formulae. AIM OF THE STUDY: Three stereoscopic configuration forms of BO, l-borneol (LB), d-borneol (DB), and dl-borneol (synthetic, SB), are formulated in broad spectral application, yet their diverse pharmacodynamic and pharmacokinetic properties caused by configurations, and accurate assay and quality assessment are often overlooked. A systematic review and analysis of lumped studies and applications is necessary to clarify the relationship between configuration and its original plant, analysis method, activity and side effect BO in order to guarantee the efficacy and safety during their application. MATERIALS AND METHODS: The public databases including PubMed, Web of Science, Google Scholar, China National Knowledge Infrastructure were referenced to summarize a comprehensive research and application data of BO published up to date. RESULTS: This review includes following sections: History and current status, Stereochemistry, Ethnopharmacology, and Quality assessment. In the section of history, the changes of the plant origins of the two isomeric forms of natural BO were described respectively, and the methods for synthetic racemate SB were also included. The section of stereochemistry deals with the stereoscopic structures, physical/chemical property, optical rotation of the three forms of BO, as well as the main related substances like isoborneol, obtained in SB via chemical transformation of camphor and turpentine oil. In the section of Ethnopharmacology, pharmacological activities and pharmacokinetics of different forms of BO were discussed. BO is usually used as an "adjuvant", by enhancing the permeability of the blood-brain barrier and intervene the ADME/T pathways of the other ingredients in the same formulation. In the section of quality assessment, the analytical methods, including chromatography, especially GC, and spectroscopy were addressed on the chiral separation of the coexisting enantiomers. CONCLUSIONS: This overview systematically summarized three forms of BO in terms of history, stereochemistry, ethnopharmacology, and quality assessment, which, hopefully, can provide valuable information and strategy for more reasonable application and development of the globally reputed ethnic medicine borneol with characteristics in stereochemistry.

Stabilizing iron single atoms with electrospun hollow carbon nanofibers as self-standing air-electrodes for long-time Zn - air batteries.

Developing iron-based single-atom catalysts (Fe SACs) with low cost, high activity and stability is vital for commercialising sustainable energy technologies. However, accurately controlling and identifying structure-activity relationships of Fe SACs remains a significant challenge. Herein, we report Fe/N co-doped carbon nanofiber membranes with highly exposed Fe-N4 sites (Fe/NCNFs), synthesized by electrospinning and pyrolysis. The three-dimensional (3D) hierarchical structure and atomically dispersed pyrrole-type Fe (III)-N4 active sites provide the as-prepared catalyst with a positive half-wave potential of 0.87 V and an ultralow Tafel slope of 53 mV dec-1. As an air cathode catalyst for liquid Zn - air batteries, it delivers a high open-circuit voltage (1.474 V), a large peak power density (190 mW cm-2) and a high durability of 2000 cycles at 5 mA cm-2. As a self-standing air cathode, the as-assembled solid-state Zn - air batteries also show stable cycling with a small discharge/charge voltage gap of 0.65 V, indicating great prospects for developing portable zinc - air batteries.

Polyimide/crown ether composite film with low dielectric constant and low dielectric loss for high signal transmission.

Dielectric properties of polyimide (PI) are constrained by its inherent molecular structure and inter-chain packing capacities. The compromised dielectric properties of PI, however, could be rescued by introducing trifluoromethyl and forming a host-guest inclusion complex with the introduction of crown ethers (CEs). Herein, we report PI/crown ether composite films as a communication substrate that could be applied under high frequency circumstances. In this work, three kinds of bisphenol A-containing diamine (2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(2-methyl-4-aminophenoxy)phenyl]propane, and 2,2-bis[4-(2-trifluoro methyl-4-aminophenoxy)phenyl]propane) are synthesized and polymerized with 4,4'-(hexafluoroisopropylidene)diphthalic anhydride to prepare low-dielectric PI films by means of thermal imidization. Crown ethers are introduced into the PI with different mass fractions to obtain three series of PI films. Following the combination of trifluoromethyl into the molecular chain of PI, high frequency dielectric loss of modified PI films can be effectively reduced. The properties of these materials (especially the dielectric properties) are thoroughly explored by crown ether addition. The results show that the crown ether addition process can offer crown ethers with increased free volume of PI matrix, thus allowing them to generate a special necklace-like supramolecular structure, which makes the crown ether disperse more uniformly in the PI matrix, resulting in improved dielectric properties. Importantly, the dielectric constant and dielectric loss of the composite films at high frequencies are remarkably reduced to 2.33 and 0.00337, respectively. Therefore, these composite films are expected to find extensive use as a 5G communication substrate at high frequencies in the future.

AIE fluorescent probe based on tetraphenylethylene and morpholine-thiourea structures for detection of HClO.

As an important signal molecule in the living body, hypochlorous acid (HClO) participates in various physiological processes. However, excessive hypochlorous acid will cause some oxidative damage. The organic aggregation-induced emission luminogens (AIEgens) based on tetraphenylethylene (TPE) structures have recently become research hotspots as fluorescent probe materials. In this paper, a kind of water-soluble fluorescent probe TPE-M based on TPE and morpholine-thiourea structures were designed and synthesized for the detection of HClO. Due to the introduction of morpholine structures, the TPE-M showed excellent water solubility. The fluorescence properties of the TPE-M were strongly affected by the polarity of the solvent. Besides, the cation-anion and reactive oxygen species recognition experiments indicated that the fluorescent probe TPE-M displayed a single recognition characteristic for HClO because of the existence of thiourea structures. The limit of detection for HClO was calculated to be 0.25 µM. The particle size distribution measurement under the water phase revealed that the particle size of the TPE-M was mainly centered at 150 nm. The recognition mechanism of HClO by the probe TPE-M was proposed and explained by mass spectra and Gaussian calculation. Furthermore, a cell imaging experiment proved that the TPE-M probe successfully detected HClO in Hela cells.

Iron-based single-atom electrocatalysts: synthetic strategies and applications.

The performance and cost of electrocatalysts play an important role in the development and application prospects of energy conversion technology. Single-atom catalysts (SACs) have constituted a new frontier in the field of catalytic science in recent years. As a non-precious metal, iron (Fe)-SACs show great potential in the field of electrocatalysis, which is comparable to or even better than the performance of precious metal catalysts. However, a robust, generic synthetic strategy toward atomically dispersed Fe catalysts is still lacking, which is still a formidable challenge to maintain the dispersion of Fe atoms at high temperatures and to obtain high catalytic activity. In this review, the latest progress in the synthesis of Fe-SACs is introduced and summarized, and the electrochemical applications of Fe-SACs are further summarized and discussed. Herein, the relationship between the structural characteristics and performance of Fe-SACs is further introduced and discussed. Finally, the existing problems and development prospects of Fe-SACs are discussed.

Photoluminescence, thermal and surface properties of triarylimidazole-containing polyimide nanocomposite films.

In this work, a triarylimidazole-containing diamine 2-(4-methylphenyl)-4,5-bis(4-(4-amino-2-trifluoromethylphenoxy)phenyl)imidazole (MPBAI) was firstly synthesized and polymerized with 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) to prepare transparent polyimide (PI) films by means of thermal imidization. Then, inorganic nanoparticles including silica (SiO2), alumina (Al2O3) and silicon nitride (Si3N4) were separately introduced into the PI(MPBAI-CBDA) with different mass fractions of 0.02%, 0.10%, 0.50% and 2.50% to obtain three series of PI nanocomposite films. All these films were close to colorless and transparent, although the light transmittance showed a downward trend due to the introduction of nanoparticles. Moreover, as the content of inorganic nanoparticles increased, the fluorescence intensities of these films were increased. Comparatively, the improvement effect of nano-SiO2 was the most obvious. When the content of SiO2 was 2.50%, the maximum intensity of the fluorescence absorption peak was increased by 9.6 times, and the absolute fluorescence quantum yield reached 17.2%, about 5.2 times that of the original PI film. Moreover, the maximum absorption peak produced a red shift of 85 nm due to the addition of 2.50% Si3N4, which was probably caused by the weakening of fluorescence quenching effect and high permittivity. The nanocomposites exhibited high glass transition temperatures of around 300 °C and excellent thermal stabilities. The surface hydrophobicity was changed by adjusting the mass and type of nanoparticles. Thus, this work provided a simple way to improve the photoluminescence effect by introducing the nanoparticles. The functional films will be expected to be applied in some optical applications.

Solubility, thermal and photoluminescence properties of triphenyl imidazole-containing polyimides.

In this paper, three kinds of triphenyl imidazole-containing diamines including 2-phenyl-4,5-bis(4-(4-amino-2-trifluoromethylphenoxy)phenyl)imidazole (PBAI), 2-(4-methylphenyl)-4,5-bis(4-(4-amino-2-trifluoromethyl phenoxy)phenyl)imidazole (MPBAI) and 2-(4-trifluoromethylphenyl)-4,5-bis(4-(4-amino-2-trifluoromethylphenoxy)phenyl)imidazole (TFPBAI) were synthesized. Then, a series of polyimide (PI) films were prepared by the solution polymerization of the three diamines and various dianhydrides, such as 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 1,2,4,5-pyromellitic dianhydride (PMDA) and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), followed by thermal imidization. The effects of chemical structures on the solubilities and thermal, optical and electrochemical properties of polyimides were explored. All the polyimides exhibited higher glass transition temperatures around 300 °C and excellent solubilities in common polar solvents. The polyimide films derived from CBDA or 6FDA showed better optical properties with light color and transparent characteristics. The fluorescence test showed that the photoluminescence color of CBDA-based polyimide films is in the blue range in the CIE 1931 spectrum, while the polyimide film based on PMDA and 6FDA presented black or weak yellow light. However, all these polyimides in solution exhibited similar blue luminescence. Electrochemical tests indicated that the HOMO and LUMO values of these films were around -6.5 and -3.6 eV, and the energy gap difference was about 3.0 eV. Therefore, the triphenyl imidazole-containing polyimides exhibit comprehensive performance, which will be expected as a new kind of functional material for certain application in the optical and optoelectronics fields.