Aromatic Alcohol-Based pH-Sensitive Chromophore with a Unique Near-Infrared Dual-Band Solvatochromic Property and Its Application as a Ratiometric Fluorescent Sensor for G-Quadruplexes.

Solvatochromes have gained great attention because of their unique roles in monitoring biomolecular location, interaction, and dynamics. Particularly, solvatochromes presenting both red-shifting excitation and dual-band switchable emission are in great demand yet significantly difficult to come true. In this article, we disclose an aromatic alcohol-based pH-sensitive chromophore NIR-HBT that not only presents red-shifting excitation and solvent-dependent dual-band emission but also shows high photostability and excellent brightness. To the best of our knowledge, this is the first solvatochrome to simultaneously display these optical properties. Especially, in contrast to the reported dual-band solvatochromes whose solvatochromism is achieved by affecting their excited state behaviors, the solvatochromism of NIR-HBT is realized by modulating its ground state proton dissociation, which is a new solvatochromic mechanism that has not been reported. Furthermore, based on the dual-band solvatochromism of NIR-HBT and its intrinsic binding ability to GQs, near-infrared ratiometric detection of GQs is achieved. These results indicate that NIR-HBT is an attractive solvatochrome that can be used to develop near-infrared ratiometric biosensors for biological research. More broadly, the discovered solvatochromic mechanism can also open new horizons for exploring the solvatochrome.

Fluorine-Nitrogen-Codoped Carbon Dots as Fluorescent Switch Probes for Selective Fe(III) and Ascorbic Acid Sensing in Living Cells.

High-quality fluorescent probes based on carbon dots (CDs) have promising applications in many fields owing to their good stability, low toxicity, high quantum yield, and low raw material price. The fluorine- and nitrogen-doped fluorescent CDs (NFCDs) with blue fluorescence was successfully synthesized using 3-aminophenol and 2,4-difluorobenzoic acid as the raw material by the hydrothermal method. The NFCDs as probe can be used to directly and indirectly detect Fe3+ (detection range: 0.1-150 µM and detection limit: 0.14 µM) and ascorbic acid (AA) (detection range: 10-80 µM and detection limit: 0.11 µM). The NFCDs-based probe shows exceptional selectivity and strong anti-interference for Fe3+ and ascorbic acid (AA). In addition, we examined the response of NFCDs to Fe3+ and AA in living cells, which showed that the timely use of AA can reduce the effects of iron poisoning. This has important biological significance. This means that using NFCDs as fluorescent probes is beneficial for Fe3+ and AA detection and observing their dynamic changes in living cells. Thus, this work may contribute to the study of Fe3+- and AA-related diseases.

Nitrogen-doped carbon dots with high selectivity for hydrosulfide sensing and their living cells imaging.

Hydrosulfuric acid is an aqueous solution of hydrogen sulfide (H2S). At physiological pH, approximately 80% of the total amount of H2S exists in the form of monoanionic HS-. Because HS- is both widely distributed and highly toxic to humans, it is necessary to design an efficient method to detect HS- with high sensitivity and selectivity. So, the nitrogen-doped carbon dots (NCDs) with green fluorescence are synthesized using a one-step hydrothermal method. The as-prepared NCDs show it can be effectively used as an indicator for monitoring HS-. And the NCD fluorescence intensity exhibits a linear relationship with HS- concentration. In addition, NCDs as a probe can be applied for fluorescence imaging in living cells to detect the presence of trace exogenous HS-.

NIR-II J-Aggregated Pt(II)-Porphyrin-Based Phosphorescent Probe for Tumor-Hypoxia Imaging.

The luminescence of traditional phosphorescence-based hypoxia probes is limited to the visible and first near-infrared wavelength regions (<1000 nm), which has defects of higher light scattering and lower penetration depth in contrast with the second near-infrared wavelength window (NIR-II, 1000-1700 nm) for optical bioimaging. Herein, 5,15-bis(2,6-bis(dodecyloxy)phenyl)-porphyrin platinum(II) (PpyPt) with J-aggregation induced NIR-II phosphorescence is reported. J-aggregates of PpyPt are confirmed by the X-ray diffraction data in the crystalline state. Moreover, the emission and excitation spectra of PpyPt in the solid states reveal NIR-II luminescence feature of PpyPt in J-aggregates. More importantly, by preparation of water-soluble PpyPt nanoparticles (PpyPt NPs4.76 ) with J-aggregates, it has NIR-II phosphorescent lifetime of microseconds and good oxygen-sensitivity in water. Moreover, the good biological hypoxia-sensing potential of PpyPt NPs4.76 is demonstrated in cells and 4T1-tumor-bearing mice. This study provides an efficient strategy to design NIR-II phosphorescent probe for sensitive tumor-hypoxia detection through the construction of J-aggregates.

Facile Synthesis of Green Fluorescent Carbon Dots and Their Application to Fe3+ Detection in Aqueous Solutions.

Carbon dots (CDs), a class of fluorescent nanomaterials, have attracted widespread attention from researchers. Because of their unique chemical properties, these high-quality fluorescent probes are widely used for ion and molecule detection. Excess intake of many ions or molecules can cause harm to the human body. Although iron (in the form of Fe3+ ions) is essential for the human body, excess iron in the human body can cause many diseases, such as iron poisoning. In this study, we have synthesized fluorine and nitrogen co-doped carbon dots (FNCDs) by a hydrothermal method. These FNCDs exhibited good stability, selectivity, and anti-interference ability for Fe3+. Fe3+ could be detected in the range of 0.2-300 µM, and their detection limit is up to 0.08 µM. In addition, the recovery and relative standard deviation measured by the standard addition recovery method were not higher than 107.5% and 1.1%, respectively, indicating that FNCDs have good recovery and accuracy for Fe3+ detection.

Enhancing Performance of Fused-Ring Electron Acceptor Using Pyrrole Instead of Thiophene.

Selecting suitable outermost aromatic rings of the central cores is of particular importance for the design of fused-ring electron acceptors (FREAs) because the direct electronic communication between the outermost aromatic rings and termini exerts a strong impact on the optoelectronic properties of FREAs. In most cases, the outermost rings of the FREA cores are thiophene. This work reported the first example of using pyrrole as the outermost rings of the core. Fused hexacyclic electron acceptor, P6IC, using pyrrole in place of the often-used thiophene as the outermost rings of the central core was synthesized. Compared with its structural analogue F6IC with thiophene as the outermost rings, P6IC exhibits a remarkably upshifted highest occupied molecular orbital energy level (P6IC: -5.43 eV, F6IC: -5.71 eV), a slightly upshifted lowest unoccupied molecular orbital energy level (P6IC: -3.94 eV, F6IC: -4.00 eV), 54 nm red-shifted absorption, a narrower band gap (P6IC: 1.30 eV, F6IC: 1.37 eV), and an enhanced mobility (P6IC: 8.8 × 10-4 cm2 V-1 s-1, F6IC: 7.4 × 10-4 cm2 V-1 s-1). Organic photovoltaic cells using PTB7-Th/P6IC as a photoactive layer exhibit an efficiency of 12.2%, far surpassing that based on PTB7-Th/F6IC active layer (5.57%). The semitransparent devices using PTB7-Th/P6IC as the active layer yield efficiency of 10.2% with an average visible transmittance (AVT) of 17.0%, far surpassing that based on PTB7-Th/F6IC (5.26% with an AVT of 18.4%).

Z-Shaped Fused-Chrysene Electron Acceptors for Organic Photovoltaics.

A new fused-chrysene electron-donating core is synthesized, where chrysene is condensed with two thiophenes via two dihydrobenzene rings. Based on this building block coupled with two electron-accepting end groups of 1,1-dicyanomethylene-3-indanone, a new Z-shaped fused-ring electron acceptor, FCIC, is designed and synthesized. FCIC shows intense absorption in the 500-850 nm region, with a maximum molar absorptivity of 1.5 × 105 M-1 cm-1, a bandgap of 1.50 eV, and a charge mobility of 2.5 × 10-4 cm2 V-1 s-1. The ternary organic photovoltaic cells based on PTB7-Th/F8IC/FCIC yield an efficiency of 12.6%, higher than that of the binary cells of PTB7-Th/F8IC (10.7%) and PTB7-Th/FCIC (7.21%). Relative to the PTB7-Th/F8IC binary blend, the addition of FCIC leads to improvement in the open-circuit voltage, short-circuit current, and fill factor.

Semimetal-Semiconductor Transitions for Monolayer Antimonene Nanosheets and Their Application in Perovskite Solar Cells.

Antimonene-based 2D materials are attracting increasing research interest due to their superior physicochemical properties and promising applications in next-generation electronics and optoelectronics devices. However, the semiconductor properties of antimonene are still at the theoretical simulation stage and are not experimentally verified, significantly restricting its applications in specific areas. In this study, the semiconductor properties of monolayer antimonene nanosheets are experimentally verified. It is found that the obtained semiconductive antimonene nanosheets (SANs) exhibit indirect bandgap properties, with photoluminescence (PL) bandgap at about 2.33 eV and PL lifetime of 4.3 ns. Moreover, the obtained SANs are ideal for the hole extraction layer in planar inverted perovskite solar cells (PVSCs) and significantly enhance the device performance due to fast hole extraction and efficient hole transfer at the perovskite/hole transport layer interface. Overall, these findings look promising for the future prospects of antimonene in electronics and optoelectronics.

π-Bridge Effect on Symmetric Carbazole-Based Small Molecules for Realizing Ultraviolet Fluorescent Emission.

A series of symmetric carbazole derivatives (CzP-H, CzP-CN, CzP-Me, and CzP-OMe), which comprise electron-donating and electron-drawing groups appending on a phenyl core, was synthesized and characterized in detail. These compounds exhibit excellent thermal stabilities, with thermal decomposition temperatures exceeding 400 °C. From the fluorescent spectra in film, CzP-H, CzP-Me, and CzP-OMe showed UV to blue-violet emission, with peaks at 396 nm, 402 nm, and 392 nm, respectively. The E00 energies of CzP-H, CzP-CN, CzP-Me, and CzP-OMe were 3.39 eV, 2.83 eV, 3.50 eV, and 3.35 eV, respectively. From the electrochemical measurements, the highest occupied molecular orbital (HOMOs) energy levels were −5.30 eV, −5.64 eV, −5.46 eV, and −5.24 eV for CzP-H, CzP-CN, CzP-Me, and CzP-OMe, respectively. Through calculations from HOMO energy levels and E00 energies, the lowest unoccupied molecular orbital (LUMOs) energy levels of CzP-H, CzP-CN, CzP-Me, and CzP-OMe were −1.91 eV, −2.81 eV, −1.96 eV, and −1.89 eV, respectively. Therefore, the introduction of different substitutes in phenyl cores would distinctly affect the photophysical properties. These results indicate that the prepared carbazole derivatives could be potential candidates for realizing ultraviolet or blue-violet emission.

Interfacial Passivation of the p-Doped Hole-Transporting Layer Using General Insulating Polymers for High-Performance Inverted Perovskite Solar Cells.

Organic-inorganic lead halide perovskite solar cells (PVSCs), as a competing technology with traditional inorganic solar cells, have now realized a high power conversion efficiency (PCE) of 22.1%. In PVSCs, interfacial carrier recombination is one of the dominant energy-loss mechanisms, which also results in the simultaneous loss of potential efficiency. In this work, for planar inverted PVSCs, the carrier recombination is dominated by the dopant concentration in the p-doped hole transport layers (HTLs), since the F4-TCNQ dopant induces more charge traps and electronic transmission channels, thus leading to a decrease in open-circuit voltages (VOC ). This issue is efficiently overcome by inserting a thin insulating polymer layer (poly(methyl methacrylate) or polystyrene) as a passivation layer with an appropriate thickness, which allows for increases in the VOC without significantly sacrificing the fill factor. It is believed that the passivation layer attributes to the passivation of interfacial recombination and the suppression of current leakage at the perovskite/HTL interface. By manipulating this interfacial passivation technique, a high PCE of 20.3% is achieved without hysteresis. Consequently, this versatile interfacial passivation methodology is highly useful for further improving the performance of planar inverted PVSCs.

Enhanced perovskite morphology and crystallinity for high performance perovskite solar cells using a porous hole transport layer from polystyrene nanospheres.

Organic-inorganic metal halide perovskites have led to remarkable advancements in emerging photovoltaics. The rapid increase in the power conversion efficiency (PCE) of PSCs has been mainly achieved by improving perovskite morphology and crystallinity. Herein, we report a simple and effective means to improve perovskite grain sizes using a porous hole transport layer (i.e. , PEDOT: PSS in this work). We used polystyrene nanospheres as a sacrificial template to fabricate the porous-PEDOT:PSS. The growth of the CH3NH3PbI3 perovskite film on the porous-PEDOT:PSS substrate yields a dramatic improvement in crystallinity and an enhancement in perovskite grain sizes. When the porous structure was applied as a hole transport layer in PSCs with planar heterojunction structures, the efficiency was significantly enhanced from 15.33% for the planar device to 17.32%. This simple method for enhancing perovskite morphology and crystallinity paves the way for its application to other device architectures for enhanced photovoltaic performance.

[Performance dependence of organic light-emitting devices on the thickness of Alq3 emitting layer].

The dependence of opto-electronical characteristics in organic light-emitting devices on the thickness of Alq3 emitter layer was studied, where MoO3, NPB, and Alq3 were used as hole injector, hole transporter, and emitter/electron transporter, respectively. By increasing the thickness of Alq3 layer from 20 to 100 nm, the device current decreased gradually, and the EL spectra of devices performed a little red shift with an obvious broadening in long wavelength range but a little decrease in intensity of short wavelength range. The authors simulated the EL spectra using the photoluminescence (PL) spectra of Alq3 as Alq3 intrinsic emission, which coincided with the experimental EL spectra well. The simulated results suggested that the effect of interference takes the major role in broadening the long wavelength range of EL spectra, and the distribution of emission zone largely affects the profile of EL spectra in short wavelength range.