Naphthyl Substituted Impurities Induce Efficient Room Temperature Phosphorescence.

Accidentally, it was found that triphenylamine (TPA) from commercial sources shows ultralong yellow-green room temperature phosphorescence (RTP) like commercial carbazole, which however disappears for lab-synthesized TPA with high purity. Herein, we for the first time identify the impurity types that cause RTP of commercial TPA, which are two N, N-diphenyl-naphthylamine isomers. Due to similar molecular polarity and very trace amount (≈0.8 ‰, molar ratio), these naphthyl substituted impurities can be easily overlooked. We further show that even at an extremely low amount (1000000 : 1, mass ratio) of impurities, RTP emission is still generated, attributed to the triplet-to-triplet energy transfer mechanism. Notably, this doping strategy is also applicable to the triphenylphosphine and benzophenone host systems, of which strong RTP emission can be activated by simply doping the corresponding naphthyl substituted analogues into them. This work therefore provides a general and efficient host/guest strategy toward high performance and diverse organic RTP materials.

Deep-Red Emissive Squaraine-AIEgen in Elastomer Enabling High Contrast and Fast Thermoresponse for Anti-Counterfeiting and Temperature Sensing.

Two challenges remain for organic thermoresponsive materials; one is to develop high-performance red-emissive thermoresponsive materials, while another is to simultaneously achieve high contrast ratio (CR), fast and reversible thermoresponse in a single element. Herein, we not only develop a new deep-red emissive squaraine-based AIEgen (TPE-SQ12) based on a pyrylium end group, which is suitable for fabricating high-performance thermoresponsive materials, but also show an effective approach to improve both CR (∼ten times increase) and response time (less than 3 seconds), that is, molecularly dispersing AIEgen into an elastomer, attributed to the significantly expanded free volume of elastomer upon increasing the temperature that can activate the AIEgen intramolecular movements more pronouncedly. Double encryption and temperature mapping systems have been separately established by using our designed elastomer/TPE-SQ12 film, showing the great potential for anti-counterfeiting and temperature sensing. Finally, white emission is further achieved by co-doping TPE-SQ12 with cyan dye into elastomer, which enables fluorescent thermochromism for improving the temperature mapping ability.

Supramolecular H-Aggregates of Squaraines with Enhanced Type I Photosensitization for Combined Photodynamic and Photothermal Therapy.

Combined photodynamic and photothermal therapy (PDT and PTT) can achieve more superior therapeutic effects than the sole mode by maximizing the photon utilization, but there remains a significant challenge in the development of related single-molecule photosensitizers (PSs), particularly those with type I photosensitization. In this study, self-assembly of squaraine dyes (SQs) is shown to be a promising strategy for designing PSs for combined type I PDT and PTT, and a supramolecular PS (TPE-SQ7) has been successfully developed through subtle molecular design of an indolenine SQ, which can self-assemble into highly ordered H-aggregates in aqueous solution as well as nanoparticles (NPs). In contrast to the typical quenching effect of H-aggregates on reactive oxygen species (ROS) generation, our results encouragingly manifest that H-aggregates can enhance type I ROS (•OH) generation by facilitating the intersystem crossing process while maintaining a high PTT performance. Consequently, TPE-SQ7 NPs with ordered H-aggregates not only exhibit superior combined therapeutic efficacy than the well-known PS (Ce6) under both normoxic and hypoxic conditions but also have excellent biosafety, making them have important application prospects in tumor phototherapy and antibacterial fields. This study not only proves that the supramolecular self-assembly of SQs is an effective strategy toward high-performance PSs for combined type I PDT and PTT but also provides a different understanding of the effect of H-aggregates on the PDT performance.

Research on Cement Slurry Using Silica Fume Instead of Fly Ash.

Ordinary cement is not environmentally friendly, has high cost and lacks superior performance. Many scholars use various admixtures to adjust the properties of cement slurry, but admixtures are usually not environmentally friendly, and it is difficult to ensure that the properties after deployment meet engineering requirements. In this study, a variety of admixtures were obtained using the environmental protection method, and the optimal mixing ratio was analyzed by combining the entropy weight method and the Taguchi grey relational analysis method. The developed cement slurry was compared with conventional slurry from both macroscopic and microscopic aspects. Aiming at the problem that previous scholars lacked the engineering feasibility verification of the developed slurry, this study combined the constitutive equation regression analysis method, discrete element numerical simulation and other methods to study various actual engineering conditions. The results show that the optimal mix ratio of silica fume cement slurry has good permeability characteristics under the conditions of different roughness, grouting pressure and confining pressure. At the same time, under different geological temperatures and different erosive liquid states, the cement slurry stone body shows good properties of reinforcement materials.

Experimental study on seepage characteristics of microfracture with different aperture.

Exploring the flow mechanism of fluid in rock mass is important in solving the water inrush problems during tunnel excavation. However, it is difficult to obtain an undisturbed rock mass from the actual site conditions and study the flow mechanism of fluid through a fracture network composed of multiple single fractures. Therefore, a solution to simulate rock seepage using rock-like samples with single microfracture was presented in this paper. Water flow through microfracture was tested and the deformation of microfracture was recorded by quasi-distributed fiber Bragg grating (FBG) technology. Experimental data showed that Forchheimer's law and Izbash's law could well describe the nonlinear relationship between flow velocity and hydraulic gradient. The coefficient b in Forchheimer's equation decreased with the increase of microfracture aperture. A critical value of E = 0.8 was proposed to classify the nonlinear flow regime: weak turbulence (E < 0.8) and fully developed turbulence (E > 0.8).

Multi-Response Optimization of Ultrafine Cement-Based Slurry Using the Taguchi-Grey Relational Analysis Method.

The grouting technique is an important method in underground engineering that prevents water seepage and reinforces fractured rock mass. In this research, ultrafine cement-based grouting material, including ultrafine cement (UC), ultrafine fly ash (UFA), polycarboxylate superplasticizer (SP), colloidal nanosilica (CNS), sodium sulfate solution (SS) and water, was developed. The flow time, viscosity, bleeding, setting time and uniaxial compressive strength of the UC-based slurry were measured by orthogonal experiments, and the optimal mix proportion of the UC-based slurry was obtained based on the Taguchi-Grey relational analysis method. Microstructure analysis of the UC-based slurry was conducted using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests. The results showed that the Bingham model could provide a satisfactory description of the rheological properties of the UC-based slurry. The addition of CNS and SS could promote the hydration of the UC-based slurry and improve the microstructure of the hardened slurry, thereby increasing the strength of the hardened slurry. The optimum ratio for the UC-based slurry was water/solid (W/S) ratio of 1.0, and the contents of UFA, SP, CNS and SS by mass of UC were 40%, 0.2%, 4% and 4%, respectively.

Evidence for Aggregation-Induced Emission from Free Rotation Restriction of Double Bond at Excited State.

This paper reports that cis-TPE dicycles emit strong fluorescence, while the gem dicycles show almost no emission in solution, demonstrating that the free rotation restriction of the double bond at the excited state is the key factor for AIE effects.