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High specific detectivity (D*) is one of the key performance metrics for near‐infrared (NIR) organic photodetectors (OPDs), which however is always limited by the high dark current density (Jd). Herein, high‐performance NIR‐OPDs with ultralow Jd are successfully achieved by developing new conjugated pyrrolic polysquaraines as photoactive materials. By changing the linkage sites of the carbazole bridge, two low‐bandgap pyrrolic polysquaraines, i.e., PSQ‐3,6‐Cz and PSQ‐2,7‐Cz, are prepared via a facile synthetic route, both showing strong absorption in the visible and NIR region (600–1000 nm), respectable hole mobility, and enhanced compatibility with the PC61BM acceptor. The fabricated polysquaraine‐based NIR‐OPDs deliver impressive Jd values as low as ≈2.0 × 10−11 A cm−2 in a photovoltaic mode, which to the best of the knowledge is among the lowest values for NIR‐OPDs so far, and thus enables a high shot‐noise‐limited specific detectivity (Dsh*) over 1013 Jones in 650–950 nm. With a more accurate noise spectral current measurement, the PSQ‐2,7‐Cz‐based OPDs show lower noise currents and better detection performance than the PSQ‐3,6‐Cz‐based OPDs, which is attributed to the lower energetic disorder degree and fewer traps of the former, both resulting in suppressed trap‐assisted recombination. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

One type of seepage water that is difficult to plug by grouting is the water exuding through the pores of sandstone in deep underground engineering. Aiming at this problem, this paper collected deep-mine sandstone samples from the Southwest Shandong coalfield, studied the sandstone pore structure and its influential factors by casting thin slices, scanning electron microscopy, mercury intrusion and physical property tests, and selected five representative permeability classification indicators: permeability, porosity, average pore throat radius, comprehensive diagenetic coefficient and sorting coefficient. According to these five indicators, the pore permeability of all the sandstone samples was divided into four subcategories (I1, I2, II1, and II2) from the perspective of grouting. I1 has medium pores and medium pore throats that can be filled with ultrafine cement-based slurries; I2 has medium-small pores and fine pore throats; II1 has medium-small pores and fine pore throats or small pores and microthroats; both I2 and II1 can be filled with chemical slurries; and II2 has micropores and microthroats that cannot be grouted. This case study provides a reference for the classification and evaluation of the pore permeability of sandstone for grouting and lays a foundation for classified permeation grouting and subsequent pore-expanding permeation grouting. [ABSTRACT FROM AUTHOR]

Seepage from the pores of sandstone exposed in deep mines is difficult to block by grouting. In this paper, the permeability evolution of four subcategories of sandstone with different pore structures under different confining pressures, pore water pressures and temperatures is analyzed by experiments. (1) With increasing confining pressure, the permeabilities of the four tested subcategories of sandstone all decrease, but at different rates and to different extents. (2) With increasing pore water pressure, the permeability of subcategory I1, I2 and II1 sandstones increases linearly, while that of subcategory II2 sandstone decreases following a power function under low confining pressures and tends to be stable under high confining pressures. (3) With increasing temperature, the permeabilities of the four sandstone subcategories decrease at different rates. (4) The orthogonal experimental results show that the confining pressure has the greatest influence on the permeability, followed by the water pressure and temperature. (5) The confining pressure, pore water pressure and temperature produce stress-strain in sandstone and thus change the sandstone pore structure and permeability. The permeability evolution of sandstones varies with pore structure. The findings of this study can inform the classified grouting of deep sandstone and optimize grouting parameters. [ABSTRACT FROM AUTHOR]

The groundwater in nonkarst areas can be divided into two categories: pore water and fracture water. Unlike fracture seepage, sandstone pore seepage in deep mines manifests as a large area of "sweating," rather than an area of local "spray," and is difficult to plug via conventional grouting methods. This study focused on pore seepage in deep mine sandstone to improve the grouting effect. Taking the deep mine sandstone in the southwest Shandong coal field, where "large-area sweating" seepage occurs, as the study object, this study examined the pore structure, petrological characteristics, physical properties, and grain sizes of the sandstone by analyzing experimental data from thin sections and scanning electron microscopy samples. The formation mechanism of the "large-area sweating" seepage was then analyzed. The range of permeability in which "large-area sweating" seepage may occur in the sandstone was discussed. The results indicate that the process of "large-area sweating" seepage in deep mine sandstone can be divided into a matrix softening stage, a matrix erosion stage, and a "large-area sweating" water seepage formation stage. According to the case analysis on the "large-area sweating" seepage in the Tangkou coal mine of the Southwest Shandong coalfield, the lower limit of permeability of the "large-area sweating" sandstone is approximately 0.25 mD. Thus, this type of seepage can occur in deep mine sandstone with a permeability of greater than 0.25 mD and affect typical mining production. The results of this study provide information about the formation mechanism of "large-area sweating" water seepage from sandstone pores and can theoretically inform the development of a new permeation grouting technique. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Squaraines (SQs) are unusual cyanine dyes with a unique resonance-stabilized zwitterionic structure. These dyes have attracted significant attention in the fields of organic electronics and organic photonics, due to their facile synthesis, intense and narrow visible and near-infrared absorption/emission, high photostability, low biotoxicity, etc. In this review, we summarize the recent progress of SQ-based fluorescent materials and their biomedical applications. After a brief introduction to SQs, general synthetic routes and design principles of SQ-based fluorescent materials, as well as their aggregation-induced luminescence behaviors, are discussed. Subsequently, their biomedical applications for cell imaging and as fluorescent sensors and therapeutic agents are introduced. Finally, a summary and perspective are given for promoting the development of SQs-based fluorescent materials. [ABSTRACT FROM AUTHOR]

Development of ratiometric fluorescent hypochlorite probes with strong long wavelength fluorescence in aqueous medium, high resistance to photobleaching, high sensitivity and selectivity, and low biological toxicity remains a challenge. In this work, a molecular design strategy is proposed that can transform the traditional squaraine dyes (SQs) with aggregation‐caused quenching character into aggregation‐induced emission (AIE)‐active luminogens by functionalizing the end‐groups with tetraphenylethylene units and further introducing hydrophilic sulfonate group as the side chains. The resulting TPE‐SQ5 not only emits strong deep‐red fluorescence with a high quantum yield of 11.0% and high photostability, but more encouragingly can serve as a ratiometric fluorescent hypochlorite probe with high selectivity and sensitivity (detection limit: 5.6 nm), which indeed is the first report for SQs. The detailed sensing mechanism study demonstrates that the oxindole product with sulfonate substitution is responsible for the ratiometric fluorescent response. Furthermore, TPE‐SQ5 nanoparticles with high biocompatibility and low cytotoxicity are successfully used for ratiometrically imaging exogenous and endogenous hypochlorite in living cells. [ABSTRACT FROM AUTHOR]

Aggregation-induced emission (AIE) has attracted great attention during the past two decades, and preventing strong π–π interactions in the aggregate state has been widely accepted as a strategy that brings an AIE effect. However, the relationship among the molecular structure, molecular packing, and emission properties of AIE-active molecules remains unclear. Herein, we have systematically investigated the emission properties of four fluorenone derivatives and have found that changing the substituents and substitution positions results in significantly different emission characteristics. 27-DPA exhibits a nearly quenched emission in both the solution and the aggregated states, while its regioisomer, 36-DPA, is a typical AIE molecule. In addition, two-color polymorph-dependent emission can be found for 36-TPA. X-ray single-crystal analysis was then conducted to understand these distinct emission properties. Our results emphasize the importance of molecular packing modes on the AIE effect, in particular for molecules containing molecular rotors, and further show that the formation of a three-dimensional molecular packing network is an effective way to suppress molecular motions to achieve AIE properties. [ABSTRACT FROM AUTHOR]

Squaraine dyes (SQs) are an important class of polymethine dyes with a unique reasonable‐stabilized zwitterionic structure, in which electrons are highly delocalized over the conjugated bridge. These dyes can not only be easily synthesized via a condensation, but also exhibit intense absorption and emission in the visible and near‐infrared region with excellent photochemical stability, making them attractive material candidates for many photoelectric and biomedical applications. Thus, in this review, after an introduction of SQs, the recent advances of SQs in the photovoltaic field are comprehensively summarized including dye‐sensitized solar cells, organic solar cells, and perovskite solar cells. Then, the important advances in the use of SQs as the biosensors, biological imaging, and photodynamic/photothermal therapy reagents in the biomedical field are also discussed. Finally, a summary and outlook will be provided with some new perspectives for the future design of SQs. [ABSTRACT FROM AUTHOR]

Enhancement of the fluidity and mechanical performance of grouting materials has proven to be an effective method of seepage prevention in geotechnical engineering. In this research, a microfine-cement-based grout mixed with microfine fly ash (MFA), nano-CaCO3 (NC), and superplasticizer (SP) was designed to improve the rheological and mechanical properties of grouting materials, and the particle size distribution, fluidity, spreading ability, bleed capacity, setting time, and mechanical properties were studied. A water/solid (W/S) ratio of 1.2 was selected, and the contents of MFA, NC, and SP by mass of microfine cement (MC) were 0–40%, 0–2.0%, and 1.5%, respectively. The results showed that MFA and 1.5% SP improved the fluidity and spreading ability of fresh grouts, while prolonging the setting time. The addition of NC can increase the yield stress and plastic viscosity and decrease the fluidity and spreading ability; nevertheless, it obviously enhances the stability and shortens the setting time of grouts. The addition of MFA and 1.5% SP reduced the compressive strength of hardened grouts; however, the addition of NC improved the mechanical properties. [ABSTRACT FROM AUTHOR]

The energy evolution behaviour and mesodamage mechanism of CRC (crumb rubber concrete) were investigated by laboratory experiments and numerical simulations. The mesoscopic physical and mechanical parameters of CRC (crumb rubber concrete) materials were analyzed and determined by the discrete element method and trial-and-error method, and the mechanism and evolution of microcracks propagation during CRC failure were studied based on the parallel-bond model. The relationship among dissipation energy, damage threshold, and rubber content during CRC damage was studied by adopting the method of microscopic energy tracking. The energy release ratio was proposed to analyze the degree of "brittleness" of CRC after reaching its peak strength. The essential mechanism of different failure characteristics of CRC and NC (normal concrete) was analyzed and discussed by referring to their correlation between the microenergy evolution rule and the constitutive curve. The results show that (1) the calibrated mesoscopic physical and mechanical parameters can better reflect the mechanical characteristics of CRC materials, (2) there is a strong correlation between the mesoscopic damage threshold of CRC with different rubber contents and the proportion of dissipation energy at the peak strength, and the damage threshold of the CRC with 25% rubber mass is the largest, (3) the relationship between elastic strain energy release ratio of CRC and rubber particle contents can be fitted by the negative exponential function, and (4) the essential reasons for the different destruction characteristics of CRC and NC is that the addition of rubber particles makes more external input energy to be converted into dissipative energy required for microcracks propagation and sliding friction between particles and released step by step. [ABSTRACT FROM AUTHOR]

Based on the results of the test among the joint roughness coefficient (JRC) of rock fracture, mechanical aperture, and hydraulic aperture proposed by Barton, this paper deduces and proposes a permeability coefficient formula of single fracture stress-seepage coupling considering microroughness by the introduction of effect variables considering the microparticle size and structural morphology of facture surface. Quasi-sandstone fracture of different particle size is made by the laboratory test, and the respective modification is made on the coupled shear-seepage test system of JAW-600 rock. Under this condition, the laboratory test of stress-seepage coupling of fracture of different particle size is carried out. The test results show that, for the different particle-sized fracture surface of the same JRC, the permeability coefficient is different, which means the smaller particle size, the smaller permeability coefficient, and the larger particle size, the larger permeability coefficient; with the increase of cranny hydraulic pressure, the permeability coefficient increases exponentially, and under the same cranny hydraulic pressure, there is relation of power function between the permeability coefficient and normal stress. Meanwhile, according to the theoretical formula, the microroughness coefficient of the fractures with different particle size is obtained by the calculation, and its accuracy and validity are verified by experiments. The theoretical verification values are in good agreement with the measured values. [ABSTRACT FROM AUTHOR]

In article number 2008201, Tae-il Kim, Zhong'an Li, and co-workers discuss molecular design principles that allow SQs to be applied in photovoltaic devices and as biosensors, bioimaging, and phototherapy reagents. Biological imaging, biosensors, donor materials, hole transporting materials, light sensitizers, photodynamic/photothermal therapy, squaraine dyes Squaraine Dyes: Squaraine Dyes for Photovoltaic and Biomedical Applications (Adv. Funct. [Extracted from the article]

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. [ABSTRACT FROM AUTHOR]