Modulation of Heterotypic and Homotypic Interactions to Visualize the Evolution of Organic Aggregates in a Fluorescence Turn-on Manner.

The abnormal evolution of membrane-less organelles into amyloid fibrils is a causative factor in many neurodegenerative diseases. Fundamental research on evolving organic aggregates is thus instructive for understanding the root causes of these diseases. In-situ monitoring of evolving molecular aggregates with built-in fluorescence properties is a reliable approach to reflect their subtle structural variation. To increase the sensitivity of real-time monitoring, we presented organic aggregates assembled by TPAN-2MeO, which is a triphenyl acrylonitrile derivative. TPAN-2MeO showed a morphological evolution with distinct turn-on emission. Upon rapid nanoaggregation, it formed non-emissive spherical aggregates in the kinetically metastable state. Experimental and simulation results revealed that the weak homotypic interactions between the TPAN-2MeO molecules liberated their molecular motion for efficient non-radiative decay, and the strong heterotypic interactions between TPAN-2MeO and water stabilized the molecular geometry favorable for the non-fluorescent state. After ultrasonication, the decreased heterotypic interactions and increased homotypic interactions acted synergistically to allow access to the emissive thermodynamic equilibrium state with a decent photoluminescence quantum yield (PLQY). The spherical aggregates were eventually transformed into micrometer-sized blocklike particles. Under mechanical stirring, the co-assembly of TPAN-2MeO and Pluronic F-127 formed uniform fluorescent platelets, inducing a significant enhancement in PLQY. These results decipher the stimuli-triggered structural variation of organic aggregates with concurrent sensitive fluorescence response and pave the way for a deep understanding of the evolutionary events of biogenic aggregates.

Enhanced Light-Harvesting and Energy Transfer in Carbon Dots Embedded Thylakoids for Photonic Hybrid Capacitor Applications.

Nanohybrid photosystems have advantages in converting solar energy into electricity, while natural photosystems based solar-powered energy-storage device is still under developed. Here, we fabricate a new kind of photo-rechargeable zinc-ion hybrid capacitor (ZHC) benefiting from light-harvesting carbon dots (CDs) and natural thylakoids for realizing solar energy harvesting and storage simultaneously. Under solar light irradiation, the embedded CDs in thylakoids (CDs/Thy) can convert the less absorbed green light into highly absorbed red light for thylakoids, besides, Förster resonance energy transfer (FRET) between CDs and Thy also occurs, which facilitates the photoelectrons generation during thylakoids photosynthesis, thereby resulting in 6-fold photocurrent output in CDs/Thy hybrid photosystem, compared to pristine thylakoids. Using CDs/Thy as the photocathode in ZHCs, the photonic hybrid capacitor shows photoelectric conversion and storage features. CDs can improve the photo-charging voltage response of ZHCs to ≈1.2 V with a remarkable capacitance enhancement of 144 % under solar light. This study provides a promising strategy for designing plant-based photonic and electric device for solar energy harvesting and storage.

Assignment of Core and Surface States in Multicolor-Emissive Carbon Dots.

It is important to reveal the luminescence mechanisms of carbon dots (CDs). Herein, CDs with two types of optical centers are synthesized from citric acid in formamide by a solvothermal method, and show high photoluminescence quantum yield reaching 42%. Their green/yellow emission exhibits pronounced vibrational structure and high resistance toward photobleaching, while broad red photoluminescence is sensitive to solvents, temperature, and UV-IR. Under UV-IR, the red emission is gradually bleached due to the photoinduced dehydration of the deprotonated surface of CDs in dimethyl sulfoxide, while this process is hindered in water. From the analysis of steady-state and time-resolved photoluminescence and transient absorption data together with density functional theory calculations, the green/ yellow emission is assigned to conjugated sp2 -domains (core state) similar to organic dye derivatives stacked within disk-shaped CDs; and the broad red emission-to oxygen-containing groups bound to sp2 -domains (surface state), whereas energy transfer from the core to the surface state can happen.

Persistent Charging of CsPbBr3 Perovskite Nanocrystals Confined in Glass Matrix.

Manipulation of persistent charges in semiconductor nanostructure is the key point to obtain quantum bits towards the application of quantum memory and information devices. However, realizing persistent charge storage in semiconductor nano-systems is still very challenge due to the disturbance from crystal defects and environment conditions. Herein, the two-photon persistent charging induced long-lasting afterglow and charged exciton formation are observed in CsPbBr3 perovskite nanocrystals (NCs) confined in glass host with effective lifetime surpassing one second, where the glass inclosure provides effective protection. A method combining the femtosecond and second time-resolved transient absorption spectroscopy is explored to determine the persistent charging possibility of perovskite NCs unambiguously. Meanwhile, with temperature-dependent spectroscopy, the underlying mechanism of this persistent charging is elucidated. A two-channel carrier transfer model is proposed involving athermal quantum tunneling and slower thermal-assisted channel. On this basis, two different information storage devices are demonstrated with the memory time exceeding two hours under low-temperature condition. These results provide a new strategy to realize persistent charging in perovskite NCs and deepen the understanding of the underlying carrier kinetics, which may pave an alternative way towards novel information memory and optical data storage applications.

L-Arginine-Functionalized Carbon Dots with Enhanced Red Emission and Upregulated Intracellular L-Arginine Intake for Obesity Inhibition.

Obesity is a major global health problem that significantly increases the risk of many other diseases. Herein, a facile method of suppressing lipogenesis and obesity using L-arginine-functionalized carbon dots (L-Arg@CDots) is reported. The prepared CDots with a negative surface charge form stronger bonds than D-arginine and lysine with L-Arg in water. The L-Arg@CDots in the aqueous solution offer a high photoluminescence quantum yield of 23.6% in the red wavelength region. The proposed L-Arg functionalization strategy not only protects the red emission of the CDots from quenching by water molecules but also enhances the intracellular uptake of L-Arg to reduce lipogenesis. Injection of L-Arg@CDots can reduce the body weight increase in ob/ob mice by suppressing their food intake and shrinking the white adipose tissue cells, thereby significantly inhibiting obesity.

Triplet Homoleptic Iridium(III) Complex as a Potential Donor Material for Organic Solar Cells.

Triplet photovoltaic materials have been rarely investigated in organic solar cells (OSCs) because the role and mechanism of triplet excitons are still unclear. Cyclometalated heavy metal complexes with triplet features are expected to increase exciton diffusion lengths and improve exciton dissociation in OSCs, while the power conversion efficiencies (PCEs) of their bulk-heterojunction (BHJ) OSCs are still limited to <4%. We herein report an octahedral homoleptic tris-Ir(III) complex TBz3Ir as a donor material for BHJ OSCs with a PCE of over 11%. In comparison with the planar organic TBz ligand and heteroleptic TBzIr, TBz3Ir demonstrates the highest PCE and best device stability in both fullerene- and non-fullerene-based devices, owing to the long triplet lifetime, enhanced optical absorption, increased charge transport, and improved film morphology. From transient absorption, triplet excitons were deduced to participate in the photoelectric conversion process. In particular, the more significant 3D structure of TBz3Ir induces an unusual film morphology in TBz3Ir:Y6 blends, showing obviously large domain sizes suitable for triplet excitons. Thus, a high PCE of 11.35% with a high circuit current density of 24.17 mA cm-2 and a fill factor of 0.63 is achieved for small-molecular Ir complex-based BHJ OSCs.

Passivating Defects at the Bottom Interface of Perovskite by Ethylammonium to Improve the Performance of Perovskite Solar Cells.

The interface of perovskite solar cells (PSCs) plays a significant role in influencing their performance, yet there is still scarce research focusing on their difficult-to-expose bottom interfaces. Herein, ethylammonium bromide (EABr) is introduced into the bottom interface and its passivation effects are studied directly. First, EABr can improve substrate wettability, which is beneficial for the perovskite-film deposition. By lifting off the perovskite film spontaneously from the substrate, it is found that EABr can significantly reduce the amount of unreacted PbI2 at the bottom interface. These PbI2 crystals have been recently identified as a major defect source and degradation site for perovskite film. Meanwhile, EABr also lifts the valence band maximum at the bottom side of perovskite from -5.38 to -5.09 eV, facilitating better hole transfer. Such a improvement is also verified by the study of charge carrier dynamics. Through introducing EABr, all photovoltaic parameters of the inverted PSCs are improved, and their power conversion efficiency (PCE) increases from 20.41% to 21.06%. The study highlights the importance of direct characterization of the bottom interface for a better passivation effect.

Enhanced solar water splitting using plasmon-induced resonance energy transfer and unidirectional charge carrier transport.

Solar water splitting by photoelectrochemical (PEC) reactions is promising for hydrogen production. The gold nanoparticles (AuNPs) are often applied to promote the visible response of wideband photocatalysts. However, in a typical TiO2/AuNPs structure, the opposite transfer direction of excited electrons between AuNPs and TiO2 under visible light and UV light severely limits the solar PEC performance. Here we present a unique Pt/TiO2/Cu2O/NiO/AuNPs photocathode, in which the NiO hole transport layer (HTL) is inserted between AuNPs and Cu2O to achieve unidirectional transport of charge carriers and prominent plasmon-induced resonance energy transfer (PIRET) between AuNPs and Cu2O. The measured applied bias photon-to-current efficiency and the hydrogen production rate under AM 1.5G illumination can reach 1.5% and 16.4 µmol·cm-2·h-1, respectively. This work is original in using the NiO film as the PIRET spacer and provides a promising photoelectrode for energy-efficient solar water splitting.

Supramolecular Fullerene Tetramers Concocted with Porphyrin Boxes Enable Efficient Charge Separation and Delocalization.

Herein, we report a novel porphyrin/fullerene supramolecular cocrystal using a shape-persistent zinc-metalated porphyrin box (Zn-PB) and C60/C70. An unprecedented arrangement of a tightly packed square-planar core of four C60 or C70 surrounded by six cube-shaped Zn-PBs was observed. This unique packing promotes strong charge transfer (CT) interactions between the two components in the ground state and formation of charge-separated states with very long lifetimes in the excited state and enables unusually high photoconductivity. Quantum chemical calculations show that these features are enabled by delocalized orbitals that promote the CT, on one hand, and that are spatially separated from each other, on the other hand. This work may open a new avenue to design novel electron donor/acceptor architectures for artificial photosynthesis.

Oxygen-Embedded Pentacene Based Near-Infrared Chemiluminescent Nanoprobe for Highly Selective and Sensitive Visualization of Peroxynitrite In Vivo.

Peroxynitrite (ONOO-) is involved in neurodegenerative, inflammatory, cardiovascular disorders, cancers, and other pathological progress. However, current imaging methods for sensing ONOO- usually suffer from high background/autofluorescence for fluorescent probes and poor selectivity/short emission wavelength for chemiluminescent probes. Herein, we present a novel chemiluminescent molecule (oxygen-embedded quinoidal pentacene) responsive to ONOO- for the first time, on the basis of which we rationally construct a near-infrared nanoprobe for detecting ONOO- via chemiluminescence resonance energy transfer (CRET) mechanism. Notably, our nanoprobe exhibits good selectivity, ultrahigh sensitivity (nanomole level), low background noise, fast response, and high water solubility. Moreover, the near-infrared emission from CRET offers higher tissue penetration of the chemiluminescent signal. Finally, our nanoprobe is further successfully applied to detecting endogenous ONOO- in mice with abdominal inflammation, drug-induced hepatotoxicity, or tumor models in vivo. In summary, the self-luminescing nanoprobes can act as an alternative visualizable tool for illuminating the mechanism of ONOO- involved in the specific pathological process.

Suppressing Strong Exciton-Phonon Coupling in Blue Perovskite Nanoplatelet Solids by Binary Systems.

Quasi-two-dimensional (2D) perovskites are promising candidates for light generation owing to their high radiative rates. However, strong exciton-phonon interactions caused by mechanical softening of the surface act as a bottleneck in improving their suitability for a wide range of lighting and display applications. Moreover, it is not easily available to tune the phonon interactions in bulk films. Here, we adopt bottom-up fabricated blue emissive perovskite nanoplatelets (NPLs) as model systems to elucidate and as well as tune the phonon interactions via engineering of binary NPL solids. By optimizing component domains, the phonon coupling strength can be reduced by a factor of 2 driven by the delocalization of 2D excitons in out-of-plane orientations. It shows the picosecond energy transfer originated from the Förster resonance energy transfer (FRET) efficiently competes with the exciton-phonon interactions in the binary system.

Designing Cascades of Electron Transfer Processes in Multicomponent Graphene Conjugates.

A novel family of nanocarbon-based materials was designed, synthesized, and probed within the context of charge-transfer cascades. We integrated electron-donating ferrocenes with light-harvesting/electron-donating (metallo)porphyrins and electron-accepting graphene nanoplates (GNP) into multicomponent conjugates. To control the rate of charge flow between the individual building blocks, we bridged them via oligo-p-phenyleneethynylenes of variable lengths by ß-linkages and the Prato-Maggini reaction. With steady-state absorption, fluorescence, Raman, and XPS measurements we realized the basic physico-chemical characterization of the photo- and redox-active components and the multicomponent conjugates. Going beyond this, we performed transient absorption measurements and corroborated by single wavelength and target analyses that the selective (metallo)porphyrin photoexcitation triggers a cascade of charge transfer events, that is, charge separation, charge shift, and charge recombination, to enable the directed charge flow. The net result is a few nanosecond-lived charge-separated state featuring a GNP-delocalized electron and a one-electron oxidized ferrocenium.

NIR-II Driven Plasmon-Enhanced Catalysis for a Timely Supply of Oxygen to Overcome Hypoxia-Induced Radiotherapy Tolerance.

Hypoxia, as a characteristic feature of solid tumor, can significantly adversely affect the outcomes of cancer radiotherapy (RT), photodynamic therapy, or chemotherapy. In this study, a strategy is developed to overcome tumor hypoxia-induced radiotherapy tolerance. Specifically, a novel two-dimensional Pd@Au bimetallic core-shell nanostructure (TPAN) was employed for the sustainable and robust production of O2 in long-term via the catalysis of endogenous H2 O2 . Notably, the catalytic activity of TPAN could be enhanced via surface plasmon resonance (SPR) effect triggered by NIR-II laser irradiation, to enhance the O2 production and thereby relieve tumor hypoxia. Thus, TPAN could enhance radiotherapy outcomes by three aspects: 1) NIR-II laser triggered SPR enhanced the catalysis of TPAN to produce O2 for relieving tumor hypoxia; 2) high-Z element effect arising from Au and Pd to capture X-ray energy within the tumor; and 3) TPAN affording X-ray, photoacoustic, and NIR-II laser derived photothermal imaging, for precisely guiding cancer therapy, so as to reduce the side effects from irradiation.

Concave-Convex π-π Template Approach Enables the Synthesis of [10]Cycloparaphenylene-Fullerene [2]Rotaxanes.

The cycloparaphenylenes (CPPs) are a class of strained macrocycles that until 2008 were considered beyond the reach of organic synthesis. With its cyclic array of ten para-substituted phenylene rings, [10]CPP possesses a concave π-system that is perfectly preorganized for the strong supramolecular association of convex fullerenes such as C60. Although mechanically interlocked CPP architectures have been observed in the gas phase, the rational synthesis of bulk quantities has not been achieved yet, which is likely due to the fact that conventional template strategies are not amenable to CPP rings that lack heteroatoms. Here, we report the synthesis of two [2]rotaxanes in which a [10]CPP ring binds to a central fullerene bis-adduct and is prevented from dethreading by the presence of two bulky fullerene hexakis-adduct stoppers. The final step in the rotaxane synthesis is surprisingly efficient (up to ca. 40% yield) and regioselective because the fullerene acts as an efficient convex template, while [10]CPP acts as a supramolecular directing group, steering the reaction at the central fullerene exclusively toward two trans regioisomers. Comprehensive physicochemical studies confirmed the interlocked structure, shed light on the dynamic nature of the CPP-fullerene interaction, and revealed intriguing consequences of the mechanical bond on charge transfer processes. In light of recent advances in the synthesis of nanohoops and nanobelts, our concave-convex π-π templating strategy may be broadly useful and enable applications in molecular electronics or complex molecular machinery.

A Supramolecular [10]CPP Junction Enables Efficient Electron Transfer in Modular Porphyrin-[10]CPP⊃Fullerene Complexes.

Efficient photoinduced electron transfer was observed across a [10]cycloparaphenylene ([10]CPP) moiety that serves as a rigid non-covalent bridge between a zinc porphyrin and a range of fullerenes. The preparation of iodo-[10]CPP is the key to the synthesis of a porphyrin-[10]CPP conjugate, which binds C60 , C70 , (C60 )2 , and other fullerenes (KA >105 m-1 ). Fluorescence and pump-probe spectroscopy revealed intramolecular energy transfer between CPP and porphyrin and also efficient charge separation between porphyrin and fullerenes, affording up to 0.5 µs lifetime charge-separated states. The advantage of this approach towards electron donor-acceptor dyads is evident in the case of dumbbell-shaped (C60 )2 , which gave intricate charge-transfer behavior in 1:1 and 2:1 complexes. These results suggest that [10]CPP and its cross-coupled derivatives could act as supramolecular mediators of charge transport in organic electronic devices.

Understanding Charge-Transfer Characteristics in Crystalline Nanosheets of Fullerene/(Metallo)porphyrin Cocrystals.

Cocrystals in the form of crystalline nanosheets comprised of C70 and (metallo)porphyrins were prepared by using the liquid-liquid interfacial precipitation (LLIP) method where full control over the morphologies in the C70/(metallo)porphyrins nanosheets has been accomplished by changing the solvent and the relative molar ratio of fullerene to (metallo)porphyrin. Importantly, the synergy of integrating C70 and (metallo)porphyrins as electron acceptors and donors, respectively, into nanosheets is substantiated in the form of a near-infrared charge-transfer absorption. The presence of the latter, as reflection of ground-state electron donor-acceptor interactions in the nanosheets, in which a sizable redistribution of charge density from the electron-donating (metallo)porphyrins to the electron-accepting C70 occurs, leads to a quantitative quenching of the localized (metallo)porphyrin fluorescence. Going beyond the ground-state characterization, excited-state electron donor-acceptor interactions are the preclusion to a full charge transfer featuring formation of a radical ion pair state, that is, the one-electron reduced fullerene and the one-electron oxidized (metallo)porphyrin.

The combination use of 1-O-acetylbritannilactone (ABL) and gemcitabine inhibits cell growth and induces cell apoptosis in lung adenocarcinoma cells.

1-O-acetylbritannilactone (ABL), a natural chemical component obtained from Chinese traditional medicine, Inula britannica, has been demonstrated to have anticancer activities. In the present study, we evaluated the anti-proliferative and the pro-apoptotic abilities of ABL alone or in combination with gemcitabine in human NSCLC cell line. A549 cells were treated, in vitro, with ABL, gemcitabine, and the combination of ABL and gemcitabine for 72 h. Our results showed ABL and gemcitabine inhibited cell growth and induced apoptosis of A549 cells. These effects after the combination of ABL and gemcitabine were superior to those of each alone. Furthermore, signal transduction analysis revealed NF-κB expression was significantly decreased by ABL and the combination treatment. IκBα and Bax levels were up regulated whereas Bcl-2 was substantially downregulated after all treatments. Our findings suggest that ABL combined with gemcitabine elicits a potent apoptosis of lung cancer cell and hence ABL has the potential to be developed as a chemotherapeutic agent.

Polylysine-modified near-infrared-emitting carbon dots assemblies: Amplification of tumor accumulation for enhanced tumor photothermal therapy.

A key challenge to enhance the therapeutic outcome of photothermal therapy (PTT) is to improve the efficiency of passive targeted accumulation of photothermal agents at tumor sites. Carbon dots (CDs) are an ideal choice for application as photothermal agents because of their advantages such as adjustable fluorescence, high photothermal conversion efficiency, and excellent biocompatibility. Here, we synthesized polylysine-modified near-infrared (NIR)-emitting CDs assemblies (plys-CDs) through post-solvothermal reaction of NIR-emitting CDs with polylysine. The encapsulated structure of plys-CDs was confirmed by determining morphological, chemical, and luminescent properties. The particle size of CDs increased to approximately 40 ± 8 nm after polylysine modification and was within the size range appropriate for achieving superior enhanced permeability and retention effect. Plys-CDs maintained a high photothermal conversion efficiency of 54.9 %, coupled with increased tumor site accumulation, leading to a high efficacy in tumor PTT. Thus, plys-CDs have a great potential for application in photothermal ablation therapy of tumors.

Carbon Dots-Inked Paper with Single/Two-Photon Excited Dual-Mode Thermochromic Afterglow for Advanced Dynamic Information Encryption.

Achieving thermochromic afterglow (TCAG) in a single material for advanced information encryption remains a significant challenge. Herein, TCAG in carbon dots (CDs)-inked paper (CDs@Paper) is achieved by tuning the temperature-dependent dual-mode afterglow of room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF). The CDs are synthesized through thermal treatment of levofloxacin in melting boric acid with postpurification via dialysis. CDs@Paper exhibit both TCAG and excitation-dependent afterglow color properties. The TCAG of CDs@Paper exhibits dynamic color changes from blue at high temperatures to yellow at low temperatures by adjusting the proportion of the temperature-dependent TADF and phosphorescence. Notably, two-photon afterglow in CDs-based afterglow materials and time-dependent two-photon afterglow colors are achieved for the first time. Moreover, leveraging the opposite emission responses of phosphorescence and TADF to temperature, CDs@Paper demonstrate TCAG with temperature-sensing capabilities across a wide temperature range. Furthermore, a CDs@Paper-based 3D code containing color and temperature information is successfully developed for advanced dynamic information encryption.

Metallopolymer strategy to explore hypoxic active narrow-bandgap photosensitizers for effective cancer photodynamic therapy.

Practical photodynamic therapy calls for high-performance, less O2-dependent, long-wavelength-light-activated photosensitizers to suit the hypoxic tumor microenvironment. Iridium-based photosensitizers exhibit excellent photocatalytic performance, but the in vivo applications are hindered by conventional O2-dependent Type-II photochemistry and poor absorption. Here we show a general metallopolymerization strategy for engineering iridium complexes exhibiting Type-I photochemistry and enhancing absorption intensity in the blue to near-infrared region. Reactive oxygen species generation of metallopolymer Ir-P1, where the iridium atom is covalently coupled to the polymer backbone, is over 80 times higher than that of its mother polymer without iridium under 680 nm irradiation. This strategy also works effectively when the iridium atom is directly included (Ir-P2) in the polymer backbones, exhibiting wide generality. The metallopolymer nanoparticles exhibiting efficient O2•- generation are conjugated with integrin αvß3 binding cRGD to achieve targeted photodynamic therapy.