Heating and cooling can induce reversible solid‐to‐liquid transitions of matter. In contrast, athermal photochemical processes can induce reversible solid‐to‐liquid transitions of some newly ...developed azobenzene compounds. Azobenzene is photoswitchable. UV light induces trans‐to‐cis isomerization; visible light or heat induces cis‐to‐trans isomerization. Trans and cis isomers usually have different melting points (Tm) or glass transition temperatures (Tg). If Tm or Tg of an azobenzene compound in trans and cis forms are above and below room temperature, respectively, light may induce reversible solid‐to‐liquid transitions. In this Review, we introduce azobenzene compounds that exhibit photoinduced reversible solid‐to‐liquid transitions, discuss the mechanisms and design principles, and show their potential applications in healable coatings, adhesives, transfer printing, lithography, actuators, fuels, and gas separation. Finally, we discuss remaining challenges in this field.
Light switch: Azobenzene‐containing materials that show photoinduced reversible solid‐to‐liquid transitions are reviewed. These materials show trans‐to‐cis and cis‐to‐trans isomerization under UV and visible light irradiation. The trans isomers are solid and cis isomers are liquid. Thus, light can induce reversible solid‐to‐liquid transitions. Photoinduced reversible solid‐to‐liquid transitions are promising for many applications.
The overexpressed glutathione peroxidase4 (GPX4) and insufficient H2O2 in tumor cells weaken ferroptosis therapy and the elicited anticancer immune response. Herein, a rigid metal‐polyphenol shell ...decorated nanodevice ssPPELap@Fe‐TA is constructed to successfully overcome the drawbacks of ferroptosis therapy. The ssPPELap@Fe‐TA consists of a rigid Fe‐TA network‐based shell and disulfide‐containing polyphosphoester (ssPPE) core with β‐lapachone loading. The rigid Fe‐TA network‐based shell of ssPPELap@Fe‐TA enables its efficient internalization by tumor cell and then disintegrates in the acidic endosome/lysosome to initiate Fe3+/Fe2+ conversion‐driven ferroptosis. The ssPPE core will deplete glutathione (GSH) via the disulfide‐thiol exchange reaction to inactivate GPX4, and also trigger the release of β‐lapachone to significantly increase intracellular H2O2 and then promote Fe3+‐mediated Fenton reaction, eventually achieving strong inhibition of tumor progression. Moreover, ssPPELap@Fe‐TA elicites a robust systemic antitumor immune response by promoting dendritic cells (DCs) maturation and T cell infiltration, and synergizes with anti‐PD‐L1 antibody (a‐PD‐L1) to strikingly suppress 4T1 tumor growth and lung metastasis.
Rigid Fe‐TA network‐based shell and disulfide‐containing polyphosphoester (ssPPE) core with β‐lapachone loading is introduced to construct nanodevices (ssPPELap@Fe‐TA). The nanodevices with the ability of intracellular GSH consumption and Fe/H2O2 self‐supply are used to improve ferroptosis of tumor cells and synergized immunotherapy.
We report a photodynamic therapy driven by electrochemiluminescence (ECL). The luminescence generated by Ru(bpy)32+ and co‐reactant tripropylamine (TPA) pair acts as both optical readout for ECL ...imaging, and light source for the excitation of photosensitizer to produce reactive oxygen species (ROS) in photodynamic therapy (PDT) system. The ECL‐driven PDT (ECL‐PDT) relies on the effective energy transfer from ECL emission to photosensitizer chlorin e6 (Ce6), which sensitizes the surrounding O2 into ROS. The dynamic process of gradual morphological changes, the variation of cell‐matrix adhesions, as well as the increase of cell membrane permeability in the process of ECL‐PDT were monitored under ECL microscopy (ECLM) with good spatiotemporal resolution. Combining real‐time imaging with ECL‐PDT, this new strategy provides not only new insights into dynamic cellular processes, but also promising potential of ECL in clinical applications.
A system for photodynamic therapy driven by electrochemiluminescence (ECL) is reported. The ECL generated by the Ru(bpy)32+/TPA pair acts as both the optical readout for the monitoring of the dynamic cellular processes and the light source for the excitation of a photosensitizer to produce cytotoxic ROS.
Oxygen electrochemistry plays a critical role in clean energy technologies such as fuel cells and electrolyzers, but the oxygen evolution reaction (OER) severely restricts the efficiency of these ...devices due to its slow kinetics. Here, we show that via incorporation of lithium ion into iridium oxide, the thus obtained amorphous iridium oxide (Li–IrO x ) demonstrates outstanding water oxidation activity with an OER current density of 10 mA/cm2 at 270 mV overpotential for 10 h of continuous operation in acidic electrolyte. DFT calculations show that lithium incorporation into iridium oxide is able to lower the activation barrier for OER. X-ray absorption characterizations indicate that both amorphous Li–IrO x and rutile IrO2 own similar IrO6 octahedron units but have different IrO6 octahedron connection modes. Oxidation of iridium to higher oxidation states along with shrinkage in the Ir–O bond was observed by in situ X-ray absorption spectroscopy on amorphous Li–IrO x , but not on rutile IrO2 under OER operando conditions. The much more “flexible” disordered IrO6 octahedrons with higher oxidation states in amorphous Li–IrO x as compared to the periodically interconnected “rigid” IrO6 octahedrons in crystalline IrO2 are able to act as more electrophilic centers and thus effectively promote the fast turnover of water oxidation.
A look at the uses of trifluoromethyltrimethylsilan is presented. Topics discussed include trifluoromethyltrimethylsilane as a difluorocarbene precursor and trifluoromethylation involving transition ...metal complexes.
Water electrolysis offers a promising energy conversion and storage technology for mitigating the global energy and environmental crisis, but there still lack highly efficient and pH-universal ...electrocatalysts to boost the sluggish kinetics for both cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER). Herein, we report uniformly dispersed iridium nanoclusters embedded on nitrogen and sulfur co-doped graphene as an efficient and robust electrocatalyst for both HER and OER at all pH conditions, reaching a current density of 10 mA cm
with only 300, 190 and 220 mV overpotential for overall water splitting in neutral, acidic and alkaline electrolyte, respectively. Based on probing experiments, operando X-ray absorption spectroscopy and theoretical calculations, we attribute the high catalytic activities to the optimum bindings to hydrogen (for HER) and oxygenated intermediate species (for OER) derived from the tunable and favorable electronic state of the iridium sites coordinated with both nitrogen and sulfur.
Ionic current rectification (ICR) based nanopipettes allow accurate monitoring of cellular behavior in single living cells. Herein, we proposed a 30 nm nanopipette functionalized with G‐quadruplex ...DNAzyme as an efficient biomimetic recognizer for ROS generation at subcellular level via the changes of current–voltage relationship. Taking advantages of the ultra‐small tip, the nanopipette could penetrate into a single living cell repeatedly or keep measuring for a long time without compromising the cellular functions. Coupled with precision nanopositioning system, generation of ROS in mitochondria in response to cell inflammation was determined with high spatial resolution. Meanwhile, the changes of aerobic metabolism in different cell lines under drug‐induced oxidative stress were monitored continuously. We believe that the ICR‐nanopipette could be developed as a powerful approach for the study of cellular activities via electrochemical imaging in living cells.
Electrochemical imaging: An ionic current rectification (ICR) based nanopipette with a 30 nm nanotip was fabricated for continuous monitoring of aerobic metabolism processes in single living cells at subcellular level. The cells produced reactive oxygen species (ROS) in mitochondria. The inner surface of the nanopipette was functionalized with G‐quadruplex DNAzyme.
Azobenzene is a switchable compound that exhibits reversible
trans
-
cis
photoisomerization. Photoresponsive polymers have been prepared by incorporating azobenzene groups into polymers. Most of the ...reported azobenzene-containing polymers (azopolymers) have only one azobenzene group in the repeat unit of the polymers (mono-azopolymers). To improve photoresponsiveness, multi-azobenzene groups have been covalently or non-covalently introduced into the repeat units of azopolymers (multi-azopolymers). In this Perspective, we introduce photoresponsive multi-azopolymers. We summarize the preparation of such polymers and highlight their potential applications in photoactuation, photo-patterning, and photoinduced birefringence. The innovative potential, open questions, and remaining challenges in this field are also discussed.
Photoresponsive polymers with multi-azobenzene groups are reviewed and their potential applications in photoactuation, photo-patterning, and photoinduced birefringence are introduced.
Ligand‐induced surface restructuring with heteroatomic doping is used to precisely modify the surface of a prototypical Au25(SR1)18− cluster (1) while maintaining its icosahedral Au13 core for the ...synthesis of a new bimetallic Au19Cd3(SR2)18− cluster (2). Single‐crystal X‐ray diffraction studies reveal that six bidentate Au2(SR1)3 motifs (L2) attached to the Au13 core of 1 were replaced by three quadridentate Au2Cd(SR2)6 motifs (L4) to create a bimetallic cluster 2. Experimental and theoretical results demonstrate a stronger electronic interaction between the surface motifs (Au2Cd(SR2)6) and the Au13 core, attributed to a more compact cluster structure and a larger energy gap of 2 compared to that of 1. These factors dramatically enhance the photoluminescence quantum efficiency and lifetime of crystal of the cluster 2. This work provides a new route for the design of a wide range of bimetallic/alloy metal nanoclusters with superior optoelectronic properties and functionality.
On the surface of it: Ligand‐induced surface restructuring with heteroatomic doping is used to precisely modify the surface of a prototypical Au25(SR1)18− cluster while maintaining its icosahedral Au13 core for the synthesis of a new bimetallic Au19Cd3(SR2)18− cluster.
The fabrication of dual‐mode patterns in the same region of a material is a promising approach for high‐density information storage, new anti‐counterfeiting technologies, and highly secure ...encryption. However, dual‐mode patterns are difficult to achieve because the two patterns in one material may interfere with each other during fabrication and usage. The development of noninterfering dual‐mode patterns requires new materials and patterning techniques. Herein, a novel orthogonal photopatterning technique is reported for the fabrication of noninterfering dual‐mode patterns on an azopolymer P1. P1 is a unique material that exhibits both photoinduced reversible solid‐to‐liquid transitions and good stretchability. In the first step of orthogonal photopatterning, patterned photonic structures are fabricated on a P1 film via masked nanoimprinting controlled by photoinduced reversible solid‐to‐liquid transitions. In the second step, the P1 film is stretched and irradiated with polarized light through a photomask, which generates a chromatic polarization pattern. In particular, the photonic structures and chromatic polarization in the dual‐mode pattern are noninterfering. Another feature of dual‐mode patterns is that they are rewritable via photo‐, thermal, or solution reprocessing, which are useful for recycling and reprogramming. This study opens an avenue for the development of novel materials and techniques for photopatterning.
Two patterns are observed in one film! Orthogonal photopatterning is developed to fabricate dual‐mode patterns in stretchable azopolymers that exhibit photoinduced reversible solid‐to‐liquid transitions. The dual‐mode pattern contains photonic and chromatic polarization patterns, which do not interfere with each other. The dual‐mode patterns are rewritable and reprocessable. They are promising materials for anti‐counterfeiting, information storage, and encryption applications.
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