Constructing B─N─P Bonds in Ultrathin Holey g-C3N4 for Regulating the Local Chemical Environment in Photocatalytic CO2 Reduction to CO.

The lack of intrinsic active sites for photocatalytic CO2 reduction reaction (CO2RR) and fast recombination rate of charge carriers are the main obstacles to achieving high photocatalytic activity. In this work, a novel phosphorus and boron binary-doped graphitic carbon nitride, highly porous material that exhibits powerful photocatalytic CO2 reduction activity, specifically toward selective CO generation, is disclosed. The coexistence of Lewis-acidic and Lewis-basic sites plays a key role in tuning the electronic structure, promoting charge distribution, extending light-harvesting ability, and promoting dissociation of excitons into active carriers. Porosity and dual dopants create local chemical environments that activate the pyridinic nitrogen atom between the phosphorus and boron atoms on the exposed surface, enabling it to function as an active site for CO2RR. The P-N-B triad is found to lower the activation barrier for reduction of CO2 by stabilizing the COOH reaction intermediate and altering the rate-determining step. As a result, CO yield increased to 22.45 µmol g-1 h-1 under visible light irradiation, which is ≈12 times larger than that of pristine graphitic carbon nitride. This study provides insights into the mechanism of charge carrier dynamics and active site determination, contributing to the understanding of the photocatalytic CO2RR mechanism.

Synergistic Electronic Interaction of Nitrogen Coordinated Fe-Sn Double-Atom Sites: An Efficient Electrocatalyst for Oxygen Reduction Reaction.

Double-atom site catalysts (DASs) have emerged as a recent trend in the oxygen reduction reaction (ORR), thereby modifying the intermediate adsorption energies and increasing the activity. However, the lack of an efficient dual atom site to improve activity and durability has limited these catalysts from widespread application. Herein, the nitrogen-coordinated iron and tin-based DASs (Fe-Sn-N/C) catalyst are synthesized for ORR. This catalyst has a high activity with ORR half-wave potentials (E1/2 ) of 0.92 V in alkaline, which is higher than those of the state-of-the-art Pt/C (E1/2  = 0.83 V), Fe-N/C (E1/2  = 0.83 V), and Sn-N/C (E1/2  = 0.77 V). Scanning electron transmission microscopy analysis confirmed the atomically distributed Fe and Sn sites on the N-doped carbon network. X-ray absorption spectroscopy analysis revealed the charge transfer between Fe and Sn. Both experimental and theoretical results indicate that the Sn with Fe-NC (Fe-Sn-N/C) induces charge redistribution, weakening the binding strength of oxygenated intermediates and leading to improved ORR activity. This study provides the synergistic effects of DASs catalysts and addresses the impacts of P-block elements on d-block transition metals in ORR.

A Highly Selective Schiff Base Based Chemodosimeter for the Detection of Perfluorooctanoic Acid by Optical Biosensor.

A simple imine derivative based sensor (IDP) has been synthesized and characterized by 1 H NMR, 13 C NMR and mass spectral techniques. IDP is more capable of detecting perfluorooctanoic acid (PFOA) in a selective and sensitive manner. The PFOA as a biomarker interacts with IDP and shows "TURN-ON" response by colorimetric and fluorimetric method. Under optimized experimental observations, the selective determination of PFOA using IDP among other competitors as biomolecules has been noticed. The detection limit is 0.31 × 10- 8 mol/L. The practical applications of the IDP is effectively evaluated in human biofluids and water samples.

MoS2 Nanoflowers Grown on Plasma-Induced W-Anchored Graphene for Efficient and Stable H2 Production Through Seawater Electrolysis.

Herein, it is found that 3D transition metal dichalcogenide (TMD)-MoS2 nanoflowers-grown on 2D tungsten oxide-anchored graphene nanosheets (MoS2 @W-G) functions as a superior catalyst for the hydrogen evolution reaction (HER) under both acidic and alkaline conditions. The optimized weight ratio of MoS2 @W-G (MoS2 :W-G/1.5:1) in 0.5 M H2 SO4 achieves a low overpotential of 78 mV at 10 mA cm-2 , a small Tafel slope of 48 mV dec-1 , and a high exchange current density (0.321 mA cm⁻2 ). Furthermore, the same MoS2 @W-G composite exhibits stable HER performance when using real seawater, with Faradaic efficiencies of 96 and 94% in acidic and alkaline media, respectively. Density functional theory calculations based on the hybrid MoS2 @W-G structure model confirm that suitable hybridization of 3D MoS2 and 2D W-G nanosheets can lower the hydrogen adsorption: Gibbs free energy (∆GH* ) from 1.89 eV for MoS2 to -0.13 eV for the MoS2 @W-G composite. The excellent HER activity of the 3D/2D hybridized MoS2 @W-G composite arises from abundance of active heterostructure interfaces, optimizing the electrical configuration, thereby accelerating the adsorption and dissociation of H2 O. These findings suggest a new approach for the rational development of alternative 3D/2D TMD/graphene electrocatalysts for HER applications using seawater.

Synthesis of Upper-Rim Sulfanylpropyl- and p-Methoxyphenylazo-Substituted Calix[4]arenes as Chromogenic Sensors for Hg2+ and Ag+ Ions.

A series of calix[4]arenes with upper-rim sulfanylpropyl and p-methoxyphenylazo groups (compounds 8-10) were synthesized and found to be effective chromogenic sensors for selectively detecting Hg2+, Hg+, and Ag+ ions among 18 screened metal perchlorates. In comparison to previously reported diallyl- and dithioacetoxypropyl-substituted calix[4]arenes (5, 6, 14, 15, and 16) and the newly synthesized compound 7, the distal (5,17)-disulfanylpropyl-substituted di-p-methoxyphenylazocalix[4]arene 9 demonstrated superior performance with a limit of detection of 0.028 µM for Hg2+ ions in a chloroform/methanol (v/v = 399/1) cosolvent. Job's plot revealed 1:1 binding stoichiometry for all these upper-rim sulfanylpropyl- and p-methoxyphenylazo-substituted calix[4]arenes 8-10 with Hg2+ ions, and Benesi-Hildebrand plots from ultraviolet/visible (UV-vis) titration spectra were used for the determination of their association constants. Our findings indicated that the distal orientation of two p-methoxyphenylazo and two sulfanylpropyl groups in calix[4]arenes 8-10 is more favorable for binding Hg2+ ions than the proximal (5,11-) orientation; moreover, the adjacent sulfanylpropyl groups exhibited superior coordination as ligands compared to the allyl and thioacetoxypropyl groups. Notably, compounds 8-10 displayed a comparable trend in their association with Ag+ ions, albeit with 1 order of magnitude lower binding constants and a distinct binding mode compared to Hg2+ ions. UV-vis spectroscopy, Job's plots, high-resolution mass spectrometry, and 1H nuclear magnetic resonance titration studies are presented and discussed.

Mimicking Metalloenzyme Microenvironments in the Transition Metal-Single Atom Catalysts for Electrochemical Hydrogen Peroxide Synthesis in an Acidic Medium.

Electrochemical reduction of oxygen into hydrogen peroxide in an acidic medium offers an energy-efficient and green H2 O2 synthesis as an alternative to the energy-intensive anthraquinone process. Unfortunately, high overpotential, low production rates, and fierce competition from traditional four-electron reduction limit it. In this study, a metalloenzyme-like active structure is mimicked in carbon-based single-atom electrocatalysts for oxygen reduction to H2 O2 . Using a carbonization strategy, the primary electronic structure of the metal center with nitrogen and oxygen coordination is modulated, followed by epoxy oxygen functionalities close to the metal active sites. In an acidic medium, CoNOC active structures proceed with greater than 98% H2 O2 selectivity (2e- /2H+ ) rather than CoNC active sites that are selective to H2 O (4e- /4H+ ). Among all MNOC (M = Fe, Co, Mn, and Ni) single-atom electrocatalysts, the CoNOC is the most selective (> 98%) for H2 O2 production, with a mass activity of 10 A g-1 at 0.60 V vs. RHE. X-ray absorption spectroscopy is used to identify the formation of unsymmetrical MNOC active structures. Experimental results are also compared to density functional theory calculations, which revealed that the structure-activity relationship of the epoxy-surrounded CoNOC active structure reaches optimum (ΔG*OOH ) binding energies for high selectivity.

Investigation on broadband emission of two-dimensional melamine lead iodide perovskite (2D-C3H8N6PbI4): An experimental and theoretical approach.

Novel two-dimensional melamine lead iodide perovskite (2D-C3H8N6PbI4) is synthesized to investigate its crystallinity, optical band gap and broadband emission properties and to make comparisons with 2D-C3H8N6PbCl4/2D-C3H8N6PbBr4 perovskites. Both experimental and density functional theory (DFT) interrogations on 2D-C3H8N6PbX4 (X = Cl, Br and I) are conducted. The crystal structure, morphology and percentile of Pb and halide elements are confirmed using scanning electron microscope (SEM), and energy dispersive spectrum (EDS), powder/single crystal X-ray diffraction (PXRD/SXRD), DFT and X-ray crystallography simulations. The optical band gaps of 2D-C3H8N6PbX4 perovskites are determined from the Tauc plot fitting of absorbance and DFT studies. Distinct broadband emission of 2D-C3H8N6PbX4 perovskites between 300 and 800 nm is observed, which can be fitted with multiple Gaussian distributions. The fittings of broad PL spectra from 2D-C3H8N6PbCl4/2D-C3H8N6PbBr4 perovskites confirm the involvement of both Dexter energy transfer from melamine cation and self-trapped excitons (STEs). However, the broadband emission of 2D-C3H8N6PbI4 is attributed only to the Dexter energy transfer from melamine cation and the absence of STEs is attributed to the larger lattice deformation of 2D-C3H8N6PbI4. Moreover, the involvement of spin-orbit coupling (SOC) in the energy transfer is clarified to attest that the broadband emission of 2D-C3H8N6PbI4 is distinct among its halide family.

Axial Chlorine Induced Electron Delocalization in Atomically Dispersed FeN4 Electrocatalyst for Oxygen Reduction Reaction with Improved Hydrogen Peroxide Tolerance.

Atomically dispersed iron sites on nitrogen-doped carbon (Fe-NC) are the most active Pt-group-metal-free catalysts for oxygen reduction reaction (ORR). However, due to oxidative corrosion and the Fenton reaction, Fe-NC catalysts are insufficiently active and stable. Herein, w e demonstrated that the axial Cl-modified Fe-NC (Cl-Fe-NC) electrocatalyst is active and stable for the ORR in acidic conditions with high H2 O2 tolerance. The Cl-Fe-NC exhibits excellent ORR activity, with a high half-wave potential (E1/2 ) of 0.82 V versus a reversible hydrogen electrode (RHE), comparable to Pt/C (E1/2 = 0.85 V versus RHE) and better than Fe-NC (E1/2 = 0.79 V versus RHE). X-ray absorption spectroscopy analysis confirms that chlorine is axially integrated into the FeN4. More interestingly, compared to Fe-NC, the Fenton reaction is markedly suppressed in Cl-Fe-NC. In situ electrochemical impedance spectroscopy reveals that Cl-Fe-NC provides efficient electron transfer and faster reaction kinetics than Fe-NC. Density functional theory calculations reveal that incorporating Cl into FeN4 can drive the electron density delocalization of the FeN4 site, leading to a moderate adsorption free energy of OH* (∆GOH* ), d-band center, and a high onset potential, and promotes the direct four-electron-transfer ORR with weak H2 O2 binding ability compared to Cl-free FeN4, indicating superior intrinsic ORR activity.

Construction of Mechanically Interlocked Fluorescence Photoswitchable [2]Rotaxane with Aggregation-Induced Emission and Molecular Shuttling Behaviors.

Here, we report the design, synthesis, and optical behaviors of a multistimuli responsive [2]rotaxane system constructed from noncovalent interactions between diarylethene (DAE)-based axle and a tetraphenylethene (TPE)-based macrocycle using a snapping supramolecular assembly approach. The shuttling behavior of the macrocycle (Ring-TPE) between dialkylammonium and urea stations could be realized by the influence of acid-base stimuli using 1H NMR spectroscopy. Switching between the open-form (OF) [2]rotaxanes (DAE-R1-OF and DAE-R2-OF) is highly reversible using external chemical stimuli. These rotaxane systems exhibit enhanced blue fluorescence in their aggregation states despite being weak or nonemissive in solution. A significant increase in fluorescence emission intensity of typical TPE in DAE-R1-OF and DAE-R2-OF at ca. 467 nm was observed as the water content was increased to ≥70% in CH3CN/H2O solvent mixtures. However, the fluorescence emission of TPE at its maximum aggregation state (95% fw) could be rapidly quenched upon UV light irradiation due to a very efficient energy transfer from the excited TPE (donor) to the closed form of DAE (acceptor). In contrast, OF DAE does not affect the fluorescence of the TPE unit, which remains at high level. Furthermore, the [2]rotaxanes showed excellent photochromic and fluorescent properties in solution, making them suitable for information storage and reversible photo-patterning applications.

Green synthesis of naphthyl derivative as an optical sensor for the detection of l-carnitine in food samples.

An economical and green approach to the synthesis of naphthyl derivative for detection of l-carnitine (3-hydroxy-4-N-trimethyl-aminobutyrate) is practically important. We developed a naphthyl derivative as a probe showing 'turn-on' response towards l-carnitine selectively at pH 7.2 through ICT mechanism with a good limit of detection (LOD) of 0.126 µM. Using Job's plot for determining the binding stoichiometry, it was found that probe could form a more stable complex (1:1) with carnitine. The binding constant (K) between probe and carnitine was calculated as 8 × 107  M-1 using the Benesi-Hildebrand plot. The binding interaction of the probe with l-carnitine was confirmed by nuclear magnetic resonance titrations, Fourier-transform infrared spectroscopy, photo physical studies and density functional theory calculations. Meanwhile, the probe can be used to quantitatively detect carnitine in food samples.

Highly Sensitive and Selective Detection of Melatonin in Biofluids by Antipyrine Based Fluorophore.

A simple fluorescent based organic fluorophore was synthesized and it shows significant fluorescent intensity with melatonin (MLN). Hence, it was applicable to the detection of MLN by colorimetric and fluorimetric techniques at neutral pH. Under optimized experimental condition, the synthesized organic fluorophore detects MLN selectively in the presence of other interfering biomolecules through ICT mechanism. The melatonin sensing mechanism is supported by DFT and 1H-NMR titration. Based on the findings, this method can be applied to design a simple clinical diagnostic tool for MLN.

When telecommuters are willing to be good soldiers during COVID-19.

COVID-19 pandemic can be regarded as a game changer, it has changed the way people work or live. How has the telecommuter's psychology changed under coronavirus? Accordingly, this study contributes to clarify the relationships among telecommuter's organizational citizenship behavior, happiness, work-family conflict, and job performance under COVID-19. The first purpose of present study is to evaluate the impacts of telecommuter's organizational citizenship behavior. To explore the roles of happiness and work-family conflict, the second purpose is to explore the relationships among the organizational citizenship behavior, happiness, and work-family conflict. In addition, the influences of telecommuter's happiness and work-family conflict on job performance deserve further consideration. To assess the applicability of this conceptual model, this study develops a questionnaire and distributed it to a sample consisted of telecommuters of firms. The statistical techniques adopt contain descriptive statistics, factor analysis, reliability analysis, structural equation modeling (SEM), and fuzzy set qualitative comparative analysis (fsQCA). Based on the empirical analyses, telecommuter's extra-role organizational citizenship behavior enhances in-role job performance, telecommuter's organizational citizenship also associates with happiness and work-family conflict. Both happiness and work-family conflict associate with the job performance. In addition, there are three causal configurations found to be sufficient for high job performance.

Pyrene-Based AIEE Active Nanoprobe for Zn2+ and Tyrosine Detection Demonstrated by DFT, Bioimaging, and Organic Thin-Film Transistor.

The development of aggregation-induced emission enhancement (AIEE) active nanoprobes without any synthetic complication for solution-state and organic thin-film transistor (OTFT)-based sensory applications is still a challenging task. In this study, the novel pyrene-incorporated Schiff base (5-phenyl-4-((pyren-1-ylmethylene)amino)-4H-1,2,4-triazole-3-thiol; PT2) with an AIEE property was synthesized via a one-pot reaction and was reported for detecting Zn2+ and tyrosine in the solution state and OTFT. In the AIEE studies of PT2 (in CH3CN) at various water fractions (fw: 0-97.5%), the existence of J-aggregation, crystalline changes, and nanofibers formation was confirmed by ultraviolet absorption/photoluminescence (UV/PL) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and dynamic-light scattering (DLS) techniques. Similarly, PT2-based Zn2+ detection and sensory reversibility with tyrosine were demonstrated by UV/PL studies with evidence related to crystalline/nanolevel changes in PXRD, SEM, TEM, AFM, and DLS data. Distinct decay profiles associated with the AIEE and sensory responses of PT2 were observed in time-resolved photoluminescence spectra. From the standard deviation and linear fittings of PL titrations, detection limits (LODs) of the Zn2+ with PT2 and the tyrosine with PT2-Zn2+ were estimated as 0.79 and 45 nM, respectively. High-resolution mass and 1H NMR results confirmed 2:1 and 1:1 stoichiometry and binding sites of PT2-Zn2+-PT2* and tyrosine-Zn2+ complexes. Moreover, the values of association constants determined by linear fittings were 4.205 × 10-7 and 1.73 × 10-8 M-2, correspondingly. Optimization via the density functional theory disclosed the binding sites and suppression of twisted intramolecular charge transfer/photoinduced electron transfer (TICT/PET) as well as the involvement of restricted intramolecular rotation in the AIEE and PET "ON-OFF-ON" mechanisms in the Zn2+ and tyrosine sensors. Results from the B16-F10 cellular and zebrafish imaging of AIEE, Zn2+, and tyrosine sensors further attested the applicability of PT2 in biological samples. Finally, the PT2 and pentacene-incorporated OTFT devices were fabricated. The devices displayed more than 90% change in drain-source current when reacted with Zn2+ with an LOD of 5.46 µM but showed no response to tyrosine, thereby confirming the reversibility. Moreover, the OTFT devices also demonstrated Zn2+ ion detection in tap water and lake water samples.

A Computational Study on the Redox Reactions of Ammonia and Methylamine with Nitrogen Tetroxide.

The redox reactions of NH3 and CH3NH2 with N2O4 (NTO) have been studied by ab initio molecular orbital (MO) calculations at the UCCSD(T)∥UB3LYP/6-311+G(3df,2p) level of theory. These reactions are related to the well-known NTO-hydrazine(s) propellant systems. On the basis of the predicted potential energy surfaces, the mechanisms for these reactions were found to be similar to the hydrolysis of NTO and the hypergolic initiation reaction of the NTO-N2H4 mixture, primarily controlled by the conversion of NTO to ONONO2 via very loose transition states (with NH3 and CH3NH2 as spectators in the collision complexes) followed by the rapid attack of ONONO2 at the spectating molecules producing HNO3 and RNO (R = NH2 and CH3NH). The predicted mechanism for the NH3 reaction compares closely with its isoelectronic process NTO + H2O; similarly, the mechanism for the NTO + CH3NH2 reaction also compares closely with its isoelectronic NTO + NH2NH2 reaction. The kinetics for the formation of the final products, HNO3 + RNO (R = NH2, OH, CH3NH, and N2H3), were found to be weakly pressure-dependent at low temperatures and affected by the strengths of H-NH2 and H-OH but not in the RNH2 case. We have also compared the predicted rate constant for the oxidation of NH3 by N2O4 with that for the analogous NH3 + N2O5 recently reported by Sarkar and Bandyopadhyay [J. Phys. Chem. A. 2020, 124, 3564-3572] under troposphere conditions. The rate of the latter reaction was estimated to be 2 orders of magnitude slower than that of the N2O4 reaction under troposphere conditions.

Development of Compound Fault Diagnosis System for Gearbox Based on Convolutional Neural Network.

Gear transmission is widely used in mechanical equipment. In practice, if the gearbox is damaged, it not only affects the yield rate but also damages other parts of machines; thus, increases the cost and difficulty of maintenance. With the advancement of technology, the concept of unmanned factories has been proposed; an automatic diagnosis system for the health management of gearboxes becomes necessary. In this paper, a compound fault diagnosis system for the gearbox based on convolutional neural network (CNN) is developed. Specifically, three-axis vibration signals measured by accelerometers are used as the input of the one-dimensional CNN; the detection of the existence and type of the fault is directly output. In testing, the model achieved nearly 100% accuracy on the fault samples we captured. Experimental evidence also shows that the frequency-domain data can provide better diagnostic results than the time-domain data due to the stable characteristics in the frequency spectrum. For practical usage, we demonstrated a remote fault diagnosis system through a local area network on an embedded platform. Furthermore, optimization of convolution kernels was also investigated. When moderately reducing the number of convolution kernels, it does not affect the diagnostic accuracy but greatly reduces the training time of the model.

Diversiform Nanostructures Constructed from Tetraphenylethene and Pyrene-Based Acid/Base Controllable Molecular Switching Amphiphilic [2]Rotaxanes with Tunable Aggregation-Induced Static Excimers.

Dual-emissive tetraphenylethene (TPE) and pyrene-containing amphiphilic molecules are of great interest because they can be integrated to form stimuli responsive materials with various biological applications. Herein, we report the study of mechanically interlocked molecules (MIMs) with aggregation-induced static excimer emission (AISEE) property through a series of TPE and pyrene-based amphiphilic [2]rotaxanes, where t-butylcalix[4]arene with hydrophobic nature was used as the macrocycle. Evidently, by adorning TPE and pyrene units in [2]rotaxanes P1, P2, P1-b, and P2-b, they display remarkable emission bands in 70% of water fraction (fw) in tetrahydrofuran (THF)/water mixture, which could be attributed to the restricted intramolecular rotation of phenyl groups, whereas prominent blue-shifted excimer emission of pyrene started to appear as fw reached 80% for P1 and 90% for P1-b, P2, and P2-b, which was ascribed to the favorable π-π stacking and hydrophobic interactions of the pyrene rings that enabled their static excimer formation. The well-defined distinct amphiphilic nanostructures of [2]rotaxanes including hollowspheres, mesoporous nanostructures, spheres, and network linkages can be driven smoothly depending on the molecular structures and their aggregated states in THF/water mixture. These fascinating diversiform nanostructures were mainly controlled by the skillful manner of reversible molecular shuttling of t-butylcalix[4]arene macrocycle and also the interplay of multinoncovalent interactions. To further understand the aggregation capabilities of [2]rotaxanes, the human lung fibroblasts (MRC-5) living cell incubated with either P1, P2, P1-b, or P2-b was studied and monitored by confocal laser scanning microscopy. The AISEE property was achieved at an astonishing level by integrating TPE and pyrene to MIM-based reversible molecular switching [2]rotaxanes; furthermore, distinct nanostructures, especially hollowspheres and mesoporous nanostructures, were observed, which are rarely reported in the literature but are highly desirable for future applications.

Novel rhodamine probe for colorimetric and fluorescent detection of Fe3+ ions in aqueous media with cellular imaging.

A novel rhodamine-pyridine conjugated spectroscopic probe RhP was synthesized and its X-ray single crystalline properties were revealed with tabulation. The RhP displayed a distinct pale-pink colorimetric and "turn-on" fluorescent response to Fe3+ in aqueous media [H2O:DMSO (95:5, v/v)] than that of other interfering ions. During the Fe3+ recognition, the absorption (UV-Vis) and photoluminescence (PL) spectral studies revealed new peaks at 561 and 592 nm, respectively. The 1:1 stoichiometry and binding sites were verified by Job's plot, ESI-mass, and 1H NMR titrations. Subsequently, LOD and binding constant for RhP + Fe3+ complex were estimated as 102.3 nM and 6.265 × 104 M-1 from linear fitting and Benesi-Hildebrand plots, correspondingly. Sensor reversibility of RhP + Fe3+ by EDTA was demonstrated by UV/PL and TRPL investigations. Moreover, the photoinduced energy transfer mechanism and band gap changes were established from the DFT interrogations. Lastly, cellular imaging studies were carried out to authenticate the real applicability of RhP in Fe3+ detection.

Controlled Sol-Gel and Diversiform Nanostructure Transitions by Photoresponsive Molecular Switching of Tetraphenylethene- and Azobenzene-Functionalized Organogelators.

The implementation of stimuli-responsive materials with dynamically controllable features has long been an important objective that challenges chemists in the materials science field. We report here the synthesis and characterization of [2]rotaxanes (R1 and R1-b) with a molecular shuttle and photoresponsive properties. Axles T1 and T1-b were found to be highly efficient and versatile organogelators toward various nonpolar organic solvents, especially p-xylene, with critical gelation concentrations as low as 0.67 and 0.38 w/v %, respectively. The two molecular stations of switchable [2]rotaxanes (R1 and R1-b) can be revealed or concealed by t-butylcalix[4]arene macrocycle, thus inhibiting the gelation processes of the respective axles T1 and T1-b through the control of intermolecular hydrogen-bonding interactions. The sol-gel transition of axles T1 and T1-b could be achieved by the irradiation of UV-visible light, which interconverted between the extended and contracted forms. Interestingly, the morphologies of organogels in p-xylene, including flakes, nanobelts, fibers, and vesicles depending on the molecular structures of axles T1 and T1-b, were induced by UV-visible light irradiation. Further studies revealed that acid-base-controllable and reversible self-assembled nanostructures of these axle molecules were mainly constructed by the interplay of multi-noncovalent interactions, such as intermolecular π-π stacking, CH-π, and intermolecular hydrogen-bonding interactions. Surprisingly, our TPE molecular systems (R1, R1-b, T1, and T1-b) are nonemissive in their aggregated states, suggesting that not only fluorescence resonance energy transfer but also aggregation-caused quenching may have been functioning. Finally, the mechanical strength of these organogels in various solvents was monitored by rheological experiments.

Development of Hybrid Pseudohalide Tin Perovskites for Highly Stable Carbon-Electrode Solar Cells.

Tin-based perovskites degrade rapidly upon interaction with water and oxygen in air because Sn-I bonds are weak. To address this issue, we developed novel tin perovskites, FASnI(3-x)(SCN)x (x = 0, 1, 2, or 3), by employing a pseudohalide, thiocyanate (SCN-), as a replacement for halides and as an inhibitor to suppress the Sn2+/Sn4+ oxidation. The structural and electronic properties of pseudohalide tin perovskites in this series were explored with quantum-chemical calculations by employing the plane-wave density functional theory (DFT) method; the corresponding results are consistent with the experimental results. Carbon-based perovskite devices fabricated with tin perovskite FASnI(SCN)2 showed about a threefold enhancement of the device efficiency (2.4%) relative to that of the best FASnI3-based device (0.9%), which we attribute to the improved suppression of the formation of Sn4+, retarded charge recombination, enhanced hydrophobicity, and stronger interactions between Sn and thiocyanate for FASnI(SCN)2 than those for FASnI3. After the incorporation of phenylethyleneammonium iodide (PEAI, 10%) and ethylenediammonium diiodide (EDAI2, 5%) as coadditives, the FASnI(SCN)2 device gave the best photovoltaic performance with JSC = 20.17 mA cm-2, VOC = 322 mV, fill factor (FF) = 0.574, and overall efficiency of power conversion PCE = 3.7%. Moreover, these pseudohalide-containing devices display negligible photocurrent-voltage hysteresis and great stability in ambient air conditions.

Development of Novel Mixed Halide/Superhalide Tin-Based Perovskites for Mesoscopic Carbon-Based Solar Cells.

Tin perovskites suffer from poor stability and a self-doping effect. To solve this problem, we synthesized novel tin perovskites based on superhalide with varied ratios of tetrafluoroborate to iodide and implemented them into solar cells based on a mesoscopic carbon-electrode architecture because film formation was an issue in applying this material for a planar heterojunction device structure. We undertook quantum-chemical calculations based on plane-wave density functional theory (DFT) methods and explored the structural and electronic properties of tin perovskites FASnI3-x(BF4)x in the series x = 0, 1, 2, and 3. We found that only the x = 2 case, FASnI(BF4)2, was successfully produced, beyond the standard FASnI3. The electrochemical impedance and X-ray photoelectron spectra indicate that the addition of tin tetrafluoroborate instead of SnI2 suppressed trap-assisted recombination by decreasing the Sn4+ content. The power conversion efficiency of the FASnI(BF4)2 device with FAI and Sn(BF4)2 in an equimolar ratio improved 72% relative to that of a standard FASnI3 solar cell, with satisfactory photostability under ambient air conditions.