Design of a Temperature-Independent Luminescent Probe for Visualization of Ice-to-Liquid Transition at −129 °C

The temperature-dependent nature and intense emission in solution of fluorescence molecules prevent them from visualizing various processes accompanying temperature changes (e.g., the liquid–ice transition at ultralow temperatures). To overcome the intrinsic difficulty, we synthesized a custom-designed fluorescent probe to exhibit the temperature-independent negligible fluorescence in the solution state but emit bright light in the icing state. The ice-to-liquid transition of four hydrocarbons, whose freezing points are between −27 and −129 °C, can be sensitively visualized using the proposed temperature-independent fluorescent probe. More interestingly, we have built a homemade platform to enable the real-time imaging of the freezing points of these four hydrocarbons within 3 min. For the first time, we designed a liquid–ice transition-sensitive probe at ultralow temperatures, different from the conventional temperature-dependent systems. This success will not only help to gain insights into the icing mechanisms but may also contribute to the development of portable visualization devices for monitoring phase transition

Rapid Discrimination of Adsorbed Oxygen and Lattice Oxygen in Catalysts by the Cataluminescence Method

Adsorbed oxygen and lattice oxygen are crucial parameters for catalyst characterization and catalytic oxidation mechanism. Therefore, rapid discrimination of adsorbed oxygen and lattice oxygen is highly desired. Herein, a direct correlation between cataluminescence (CTL) kinetic curve and oxygen species was discovered. The adsorbed oxygen-catalyzed CTL only lasted for a few minutes, whereas the lattice oxygen-catalyzed CTL could exhibit hours of continuous luminescence. The long-term CTL was attributed to the slow migration of lattice oxygen in a slow and continuous catalytic oxidation reaction. In addition to the discrimination between the adsorbed oxygen and lattice oxygen by the CTL kinetic processes, the corresponding CTL intensity was positively proportional to their amounts. Accordingly, the developed catalytic oxidation-related CTL can be used as an indicator for rapid discrimination and determination of adsorbed oxygen and lattice oxygen in catalysts. Oxygen species detected by the proposed CTL method not only matched well with those obtained by conventional X-ray photoelectron spectroscopy and O2-temperature programmed methods but also offered some distinguished advantages, such as convenient operation, fast response, and low cost. It can be expected that the established oxygen-responsive CTL probe has great potential in distinguishing adsorbed oxygen and lattice oxygen in various catalysts

Vesicles as a Multifunctional Microenvironment for Electrochemiluminescence Signal Amplification

Vesicles as a typical interface-rich microenvironment can promote the reaction rate and the intermediate stability, which are promising for introduction in electrochemiluminescence (ECL) signal amplification. In this work, a kind of multilamellar vesicle obtained from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was used to modify the electrode surface. The AOT vesicle-modified microenvironment could significantly enhance the ECL performances for the luminol/O2 system in a neutral medium. The mechanism study demonstrated that the nanoscale multilamellar vesicles could maintain the vesicle structure on the electrode surface, which substantially improved the electron transfer and reaction rate, luminescence efficiency of the excited-state 3-aminophthalate anion, and stability of the superoxide anion radical. Alternatively, such a multifunctional microenvironment was also able to enhance the ECL signals from the tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+)/tripropylamine (TPrA) system. Moreover, another dodecyl dimethyl(3-sulfopropyl) ammonium hydroxide inner salt (DSB)-based vesicle was constructed to further verify the versatility of the vesicle-modified microenvironment for ECL signal amplification. Our work not only provides a versatile microenvironment for improving the efficiency of various ECL systems but also offers new insights for the microenvironment construction using the ordered assemblies in ECL fields

Real-Time Imaging of Stress in Single Spherulites and Its Relaxation at the Single-Particle Level in Semicrystalline Polymers

Crystallization-induced microscopic stress and its relaxation play a vital role in understanding crystallization behavior and mechanism. However, the real-time measurements for stress and its relaxation seem to be an unachievable task due to difficulties in simultaneous labeling, spatiotemporal discrimination, and continuous quantification. We designed a micron-sized fluorescent probe, whose fluorescence can respond to stress-induced environmental rigidity and whose three-dimensional (3D) flow can respond to stress relaxation. Using the as-prepared fluorescent probe, we established a versatile strategy to realize the real-time 3D imaging of stress and its relaxation in the crystallization process. The rigidity-responsive fluorescence clearly indicated the stress, while the 3D flow movement could quantify the stress relaxation. It is revealed that stress in spherulites increased dramatically as a result of the suppression of stress relaxation in polymer melts. The developed method provides a novel avenue to simultaneously detect stress and its relaxation in various semicrystalline polymers at the single-particle level. This success would achieve the microscopic ways to guide the development of advanced crystallization-dependent materials

Chemiluminescence as a Novel Indicator for Interactions of Surfactant–Polymer Mixtures at the Surface of Layered Double Hydroxides

Chemiluminescence (CL) has been employed as a novel technique to monitor the interactions between poly­(ethylene glycol) (PEG) and sodium dodecyl benzenesulfonate (SDBS) at the surface of CO₃-layered double hydroxides (LDHs). The CL data demonstrated that the interactions of PEG and SDBS at the LDH surfaces were dependent on the SDBS concentration, the PEG molecular weight, and the PEG concentration. Furthermore, powder X-ray diffraction (XRD), zeta-potential measurements, thermogravimetric analysis (TGA), CL spectrum, and radical scavenging methods clarified the relationship between the CL intensity and the interactions of PEG with SDBS at the LDH surfaces. At low concentrations of SDBS, few interactions between PEG and SDBS took place. The aggregation of the LDH colloidal solution occurred as a result of SDBS hydrophobic tails pointed to the aqueous environment. As the concentration of SDBS increased, the PEG chains were bound onto the SDBS bilayers to reduce the electrostatic repulsion between anionic head groups of SDBS due to the structural transformation of SDBS at the surface of LDHs from monolayers to bilayers. This work would provide an attractive route to manipulate the adsorption and composition of polymer–surfactant mixtures at the particle surface by tuning the CL signals

Superoxide-Triggered Luminol Electrochemiluminescence for Detection of Oxygen Vacancy in Oxides

Oxygen vacancy is known to act as a reactive center in oxides to produce radicals. Currently, X-ray photoelectron spectra (XPS) become a unique spectral tool for analyzing oxygen vacancy based on the differences in atomic number ratios between metal ions and lattice oxygen. In this work, it was found that the superoxide radical (O2•–)-luminol electrochemiluminescence (ECL) intensity linearly increases with increasing the oxygen vacancy concentrations of TiO2 samples coated on the electrodes. An experimental study of the mechanism demonstrates that an increase in oxygen vacancy concentrations could lead to an increase in the generation of O2•–, resulting in an increase in the O2•–-related luminol ECL signals. Accordingly, we have developed a rapid and simple O2•–-luminol ECL platform to detect oxygen vacancy in TiO2 samples, based on the relationship between O2•– generation and oxygen vacancy. The proposed ECL platform exhibits good reproducibility and stability through the parallel ECL measurements. Moreover, the feasibility is verified by analyzing the oxygen vacancy concentrations in different TiO2 samples with varying the Co, Cr, Fe, and N doping concentrations. The oxygen vacancy concentrations obtained by the proposed ECL method could match well with those obtained by conventional XPS measurements. Our successful construction of the ECL platform will significantly promote the development of the oxygen vacancy detection in oxides and deepen the understanding of the relationship between oxygen vacancy and radicals

Micelle-Mediated Chemiluminescence as an Indicator for Micellar Transitions

The structural phase of micelles plays an important role in controlling the micellar performance. Despite the great developments of some advanced characterization techniques, it remains challenging to achieve fast and sensitive determination of micellar transitions in solution. Herein, a novel indicator system for micellar transitions was developed based on the micelle-mediated peroxyoxalate chemiluminescence that showed a sensitive response toward the changes of micellar morphologies. A peroxyoxalate derivative and a fluorophore were first coassembled into the hydrophobic cavities of micelles of the typical cationic surfactant cetyltrimethylammonium bromide (CTAB). A strong and rapidly falling chemiluminescence response was exhibited in spherical micelles as a result of the loose arrangement of CTAB molecules. By contrast, rodlike or wormlike micelles transformed from spherical micelles could induce a compact arrangement of CTAB molecules, leading to a weak chemiluminescence emission with a slow decay rate. The practicability and universality of the chemiluminescent indicator were demonstrated by determining the micellar transitions in a variety of surfactant solutions (ionic, nonionic, and polymeric). These findings open attractive perspectives for the practice of chemiluminescence technique in micelle characterization

Layered Double Hydroxide-Supported Carbon Dots as an Efficient Heterogeneous Fenton-Like Catalyst for Generation of Hydroxyl Radicals

The development of a new heterogeneous Fenton-like catalyst is highly desired. Herein, we reported a simple and efficient method for the preparation of colloidal nanocomposites consisting of carbon dots and dodecylbenzenesulfonate (DBS)-layered double hydroxides (LDHs). The resulting nanocatalyst can function as an effective heterogeneous Fenton-like catalyst for the decomposition of acidified H2O2 to generate abundant hydroxyl radicals (·OH). With the aid of chemiluminescence (CL) technique, electron spin resonance (ESR) measurements and ion chromatography (IC) separation technique, we demonstrated that the unique structural configuration of the carbon dot-DBS-LDH nanocomposites was responsible for the highly efficient catalytic activities toward H2O2 decomposition. The fabricated material introduced a novel family of Fenton-like nanocatalysts with environmental friendliness, cost effectivity, and superior efficiency for the decomposition of H2O2 to ·OH radicals. Such heterogeneous Fenton-like catalyst could realize the degradation of DBS without any external energy input, showing a promising application for the oxidative degradation of organic contaminants in wastewater treatment applications

Screening of Photosensitizers by Chemiluminescence Monitoring of Formation Dynamics of Singlet Oxygen during Photodynamic Therapy

Finding an efficient photosensitizer is crucial in ensuring a therapeutic effect of photodynamic treatment. Currently, screening of photosensitizers during photodynamic therapy is achieved by evaluating the total yield of singlet oxygen (¹O₂), rather than monitoring the formation dynamics of ¹O₂. ¹O₂-based chemiluminescence (CL) is a suitable method to directly monitor the generated amount of ¹O₂. Herein, the tetraphenylethene-sodium dodecyl sulfonate surfactant with aggregation-induced emission characteristics can remarkably amplify the intrinsic CL emission from ¹O₂ by integrating its micellar microenvironment with a CL energy acceptor effect in a cage-like structure. We present a new luminescence platform for the rapid screening of photosensitizers by monitoring the formation dynamics of ¹O₂ during photodynamic therapy. This study will not only be critical in optimizing the irradiation time during photodynamic therapy but also open a new door to the discovery of efficient photosensitizers

Ag–O–Co Interface Modulation-Amplified Luminol Cathodic Electrogenerated Chemiluminescence

It remains a great challenge to develop effective strategies for improving the weak cathodic electrogenerated chemiluminescence (ECL) of the luminol-dissolved O2 system. Interface modulation between metal and supports is an attractive strategy to improve oxygen reduction reaction (ORR) activity. Therefore, the design of electrocatalysts via interface modulation would provide new opportunities for the ECL amplification involving reactive oxygen species (ROSs). Herein, we have fabricated an Ag single-atom catalyst with an oxygen-bridged interface (Ag–O–Co) through the electrodeposition of Ag on a CoAl layered double hydroxide (LDH) modified indium tin oxide (ITO) electrode (Ags/LDH/ITO). Interestingly, it was found that the cathodic ECL intensity of the luminol-dissolved O2 system at the Ags/LDH/ITO electrode was extraordinarily enhanced in comparison with those at bare ITO and other Ag nanoparticle-based electrodes. The enhanced ECL performances of the Ags/LDH/ITO electrode were attributed to the increasing amounts of ROSs by electrocatalytic ORR in the Ag–O–Co interface. The electron redistribution of Ag and Co bimetallic sites could accelerate electron transfer, promote the adsorption of O2, and sufficiently activate O2 through a four-electron reaction pathway. Finally, the luminol cathodic ECL intensity was greatly improved. Our findings can provide inspiration for revealing the interface effects between metal and supports, and open up a new avenue to improve the luminol cathodic ECL