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Keywords = aggregation-caused quenching

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18 pages, 5815 KB  
Article
Solvent-Responsive Luminescence of an 8-Hydroxyquinoline-Modified 1H-Imidazo[4,5-f][1,10]phenanthroline Ligand and Its Cu(I) Complexes: Excited-State Mechanisms and Structural Effects
by Zhenqin Zhao, Siyuan Liu, Shu Cui, Yichi Zhang, Ziqi Jiang and Xiuling Li
Molecules 2025, 30(19), 3973; https://doi.org/10.3390/molecules30193973 - 3 Oct 2025
Abstract
Understanding how solvents influence the luminescence behavior of Cu(I) complexes is crucial for designing advanced optical sensors. This study reports the synthesis, structures and photophysical investigation of an 8-hydroxyquinoline-functionalized 1H-imidazo[4,5-f][1,10]phenanthroline ligand, ipqH2, and its four Cu(I) complexes [...] Read more.
Understanding how solvents influence the luminescence behavior of Cu(I) complexes is crucial for designing advanced optical sensors. This study reports the synthesis, structures and photophysical investigation of an 8-hydroxyquinoline-functionalized 1H-imidazo[4,5-f][1,10]phenanthroline ligand, ipqH2, and its four Cu(I) complexes with diphosphine co-ligands. Photoluminescence studies demonstrated distinct solvent-dependent excited-state mechanisms. In DMSO/alcohol mixtures, free ipqH2 exhibited excited-state proton transfer (ESPT) and enol-keto tautomerization, producing dual emission at about 447 and 560 nm, while the complexes resisted ESPT due to hydrogen bond blocking by PF6 anions and Cu(I) coordination. In DMSO/H2O, aggregation-caused quenching (ACQ) and high-energy O–H vibrational quenching dominated, but complexes 1 and 2 showed a significant red-shifted emission (569–574 nm) with high water content due to solvent-stabilized intra-ligand charge transfer and metal-to-ligand charge transfer ((IL+ML)CT) states. In DMSO/DMF, hydrogen bond competition and solvation-shell reorganization led to distinct responses: complexes 1 and 3, with flexible bis[(2-diphenylphosphino)phenyl]ether (POP) ligands, displayed peak splitting and (IL + ML)CT redshift emission (501 ⟶ 530 nm), whereas complexes 2 and 4, with rigid 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene (xantphos), showed weaker responses. The flexibility of the diphosphine ligand dictated DMF sensitivity, while the coordination, the hydrogen bonds between PF6 anions and ipqH2, and water solubility governed the alcohol/water responses. This work elucidates the multifaceted solvent-responsive mechanisms in Cu(I) complexes, facilitating the design of solvent-discriminative luminescent sensors. Full article
(This article belongs to the Special Issue Influence of Solvent Molecules in Coordination Chemistry)
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13 pages, 2130 KB  
Article
Controllable Structure and Fluorescence Enhancement of ACQ Dye Nanoparticles Based on the FNP Process
by Yue Wu, Yutao Zhang, Zhiqian Guo and Yisheng Xu
Polymers 2025, 17(15), 2152; https://doi.org/10.3390/polym17152152 - 6 Aug 2025
Viewed by 493
Abstract
Fluorescent dyes, such as cyanine dyes, are widely used in fluorescence-imaging-guided tumor therapy due to their high absorbance and fluorescence quantum yield. However, challenges persist in optimizing the performance of fluorescent nanoparticles, particularly due to the aggregation-caused quenching (ACQ) effect of cyanine dyes. [...] Read more.
Fluorescent dyes, such as cyanine dyes, are widely used in fluorescence-imaging-guided tumor therapy due to their high absorbance and fluorescence quantum yield. However, challenges persist in optimizing the performance of fluorescent nanoparticles, particularly due to the aggregation-caused quenching (ACQ) effect of cyanine dyes. Here, a novel counterion construction strategy is introduced using cyanine dye as a model ACQ dye. Through dynamic-controlled flash nanoprecipitation, fluorescent nanoparticles (CyINPs) with tunable structures are developed, investigating the effects of various factors, including counterions, block copolymers, and dye concentrations, on CyINPs’ stability and fluorescence enhancement. The optimized CyINPs with good water solubility show a 21-fold increase in fluorescence intensity and a 3.5-fold increase in encapsulation efficiency compared to CyINPs prepared by a thermodynamic-driven method. Under the efforts of polymers and counterions, dyes are separated, which reduces the impact of the ACQ effect and results in stronger fluorescence intensity, providing insights into improving nanoparticle biocompatibility and energy utilization efficiency. Full article
(This article belongs to the Section Polymer Applications)
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13 pages, 1573 KB  
Review
Recent Progress of Carbon Dots in Fluorescence Sensing
by Xiao-Tian Lou, Lei Zhan and Bin-Bin Chen
Inorganics 2025, 13(8), 256; https://doi.org/10.3390/inorganics13080256 - 31 Jul 2025
Cited by 1 | Viewed by 797
Abstract
Carbon dots (CDs) have attracted much attention as new types of luminescent carbon nanomaterials in recent years because of their tunable fluorescence, good biocompatibility, high stability, and low cost. In this review, the classification of CDs is overviewed based on their differences in [...] Read more.
Carbon dots (CDs) have attracted much attention as new types of luminescent carbon nanomaterials in recent years because of their tunable fluorescence, good biocompatibility, high stability, and low cost. In this review, the classification of CDs is overviewed based on their differences in structure. Subsequently, the latest research progress of CDs in fluorescence sensing is systematically summarized and various sensing principles are elucidated in detail, including fluorescence resonance energy transfer, aggregation-induced emission, aggregation-caused quenching, electron transfer, and the inner filter effect. Finally, the challenges and future direction of CD fluorescent probes are discussed in detail. The purpose of this review is to stimulate the design of advanced CD fluorescent probes and achieve the accurate and reliable measurement of analytes in complex samples. Full article
(This article belongs to the Special Issue Synthesis and Application of Luminescent Materials, 2nd Edition)
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15 pages, 3934 KB  
Article
Methyl Viologen@β-Zeolite with Absorption/Fluorescence Dual-Mode and Photo/Chemical Synergistic Stimuli-Responsive Chromism
by Jingxuan Han, Shaoning Li, Huihui Li, Yu Li, Jiaqiao Qin, Fuxiang Wang and Qinhe Pan
Molecules 2025, 30(13), 2872; https://doi.org/10.3390/molecules30132872 - 6 Jul 2025
Cited by 1 | Viewed by 581
Abstract
In this work, methyl viologen (MV) was adsorbed into the nanopores of Si/Al H-β-zeolite via cation exchange. The resulting MV@β-zeolite possessed absorption/fluorescence dual-mode and photo/chemical synergistic stimuli-responsive chromism. Owing to the acidic surrounding provided by β-zeolite, the chromism of MV required the synergistic [...] Read more.
In this work, methyl viologen (MV) was adsorbed into the nanopores of Si/Al H-β-zeolite via cation exchange. The resulting MV@β-zeolite possessed absorption/fluorescence dual-mode and photo/chemical synergistic stimuli-responsive chromism. Owing to the acidic surrounding provided by β-zeolite, the chromism of MV required the synergistic stimuli of UV irradiation and a chemical reductant (such as Na2SO3). UV irradiation induced single electron transfer from the chemical reductant to MV@β-zeolite, leading to enhanced absorption at 610 nm together with a daylight color change from pale yellow to blue. Meanwhile, the nanopores of β-zeolite inhibited aggregation-caused quenching of MV, enabling MV to emit cyan fluorescence at 500 nm. After the single electron transfer of the chemical reductant under UV irradiation, the cyan fluorescence of MV@β-zeolite was quenched. Additionally, MV@β-zeolite exhibited a short stimulus response time (250 s) and good color change reversibility. These findings in this work provide valuable insights into the design of multi-mode and synergistic stimuli-responsive viologen-based chromic materials, particularly for applications in secure high-throughput information storage, high-level anti-counterfeiting and multi-target multi-mode sensing. Full article
(This article belongs to the Special Issue Novel Organic-Inorganic Hybrid Porous Photochromic Materials)
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19 pages, 3942 KB  
Article
Boundary Between Amorphously and Molecularly Dispersed Curcumin of Its Amorphous Solid Dispersions Determined by Fluorescence Spectroscopy
by Shixin Fan, Wenling Zheng, Shizhao Ren, Wangchuan Xiao, Fenghua Chen and Rongrong Xue
Crystals 2025, 15(6), 512; https://doi.org/10.3390/cryst15060512 - 27 May 2025
Cited by 1 | Viewed by 652
Abstract
Amorphous solid dispersion (ASD) technology is popularly used for enhancing the solubility of poorly water-soluble drugs. Drug molecules in ASDs can be dispersed in the form of either amorphous (AASD) or molecular (MASD) forms. The boundary between AASDs and MASDs (A–M boundary) is [...] Read more.
Amorphous solid dispersion (ASD) technology is popularly used for enhancing the solubility of poorly water-soluble drugs. Drug molecules in ASDs can be dispersed in the form of either amorphous (AASD) or molecular (MASD) forms. The boundary between AASDs and MASDs (A–M boundary) is defined as the drug concentration at which the existence of MASDs obviously influences the physicochemical properties of ASDs. In this work, fluorescence spectroscopy based on the aggregation-caused quenching (ACQ) phenomenon was used to determine the A–M boundary of curcumin (CUR) ASDs prepared via neat ball milling. The relationship between the fluorescence intensity and the loading of CUR in the sample is consistent with the Stern–Volmer equation. For the CUR ASDs with PVP, the samples with CUR loading below 10% show significantly increased fluorescence and have a higher solubility (~178 μg·mL−1), suggesting the A–M boundary is around 10%. Similar A–M boundaries around 10% were also observed for CUR ASDs with PVPVA, Soluplus, HPMC, and HPMCAS. It is of great significance to define the A–M boundary of ASDs for guiding pharmaceutical ASD formulas by balancing drug loading, stability, and solubility. Full article
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15 pages, 2652 KB  
Article
Construction of Triphenylamine-Based Aggregation-Induced Emission Luminogens for Lysosomes Imaging and Its Application in the Photodynamic Therapy of Cancer Cells
by Zhanguo Sun, Bin Liu and Huijun Liu
Molecules 2025, 30(11), 2272; https://doi.org/10.3390/molecules30112272 - 22 May 2025
Viewed by 671
Abstract
Lysosomes are important acidic subcellular organelles whose dysfunction can lead to some related diseases. The development of new lysosome-imaging-guided AIEgens for the photodynamic therapy of cancer cells is important. In this work, two novel organic compounds with AIE characteristics, namely, TPAB-CF3 and [...] Read more.
Lysosomes are important acidic subcellular organelles whose dysfunction can lead to some related diseases. The development of new lysosome-imaging-guided AIEgens for the photodynamic therapy of cancer cells is important. In this work, two novel organic compounds with AIE characteristics, namely, TPAB-CF3 and TPAB-diCF3, were designed and synthesized by introducing the weakly basic morpholinyl moiety with lysosome-targeting ability into a triphenylamine-based luminogen. The distorted spatial feature of TPA and the D1-D2-π-A structure of these AIEgens prevented the aggregation-caused quenching of traditional fluorescent molecules and efficiently promoted the separation of the HOMO and LUMO. The outcomes were AIE features and a narrow single-triplet energy gap. Furthermore, TPAB-CF3 and TPAB-diCF3 showed bright yellow fluorescence emission peaks at 577 and 601 nm; large Stokes shifts of 234 and 256 nm, respectively; and excellent lysosome-targeted imaging of HeLa cells (Pearson’s coefficient = 0.90). In addition to the good 1O2-generation ability under light irradiation, these AIEgens achieved the high-efficiency bright lysosome imaging-guided photodynamic killing of cancer cells under white-light irradiation. Full article
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37 pages, 6833 KB  
Review
Recent Advances in Aggregation-Induced Emission (AIE) Fluorescent Sensors for Biomolecule Detection
by Kavya S. Keremane, M. Gururaj Acharya, Praveen Naik, Chandi C. Malakar, Kai Wang and Bed Poudel
Chemosensors 2025, 13(5), 174; https://doi.org/10.3390/chemosensors13050174 - 9 May 2025
Cited by 3 | Viewed by 2254
Abstract
Fluorescent sensors are indispensable tools in fields such as molecular biology, clinical diagnostics, biotechnology, and environmental monitoring, due to their high sensitivity, selectivity, biocompatibility, rapid response, and ease of use. However, conventional fluorophores often suffer from aggregation-caused quenching (ACQ), leading to diminished fluorescence [...] Read more.
Fluorescent sensors are indispensable tools in fields such as molecular biology, clinical diagnostics, biotechnology, and environmental monitoring, due to their high sensitivity, selectivity, biocompatibility, rapid response, and ease of use. However, conventional fluorophores often suffer from aggregation-caused quenching (ACQ), leading to diminished fluorescence in the aggregated state. The advent of aggregation-induced emission (AIE) luminogens, which exhibit enhanced fluorescence upon aggregation, offers a powerful solution to this limitation. Their unique photophysical properties have made AIE-based materials highly valuable for diverse applications, including biomedical imaging, optoelectronics, stimuli-responsive systems, drug delivery, and chemical sensing. Notably, AIE-based fluorescent probes are emerging as attractive alternatives to traditional analytical methods owing to their low cost, fast detection, and high selectivity. Over the past two decades, considerable progress has been made in the rational design and development of AIE-active small-molecule fluorescent probes for detecting a wide variety of analytes, such as biologically relevant molecules, drug compounds, volatile organic compounds (VOCs), explosives, and contaminants associated with forensic and food safety analysis. This review highlights recent advances in organic AIE-based fluorescent probes, beginning with the fundamentals of AIE and typical “turn-on” sensing mechanisms, and concluding with a discussion of current challenges and future opportunities in this rapidly evolving research area. Full article
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14 pages, 5415 KB  
Article
Amphiphilic Styrene-Based Pyrene Derivatives: Tunable Aggregation Luminescence and Their Photo-Induced Dimerization Behavior
by Junying Zhang, Xingwei Luo and Juan Qiu
Molecules 2025, 30(8), 1719; https://doi.org/10.3390/molecules30081719 - 11 Apr 2025
Viewed by 663
Abstract
Since the discovery of the aggregation-induced emission (AIE) phenomenon, various stimuli-responsive materials have been rapidly developed. However, how to achieve the transition between aggregation-caused quenching (ACQ) and AIE through molecular design is an urgent problem to be solved. In this work, we synthesized [...] Read more.
Since the discovery of the aggregation-induced emission (AIE) phenomenon, various stimuli-responsive materials have been rapidly developed. However, how to achieve the transition between aggregation-caused quenching (ACQ) and AIE through molecular design is an urgent problem to be solved. In this work, we synthesized and studied the aggregation luminescence behavior and photochromism of two different substituted pyrene ethylene derivatives, 1-H and 1-CN. Due to the different substituents attached to the ethylene unit, 1-H exhibits ACQ luminescence behavior. When the substituent is a cyanide group, it exhibits AIE behavior. In addition, the ordered nanoparticles formed by self-assembly in aqueous solution exhibit interesting photo-induced cyclization behavior, which leads to fluorescence quenching under ultraviolet light irradiation (λ = 365 nm). Therefore, due to their amphiphilicity and photo-responsiveness, these compounds can be used as anticounterfeiting inks in information encryption. This work contributes new members to the family of amphiphilic photo-responsive materials and demonstrates their potential applications in optical information storage and multi-color luminescence. Full article
(This article belongs to the Special Issue Advances in Functional Organic Dye Chemistry)
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19 pages, 3794 KB  
Article
Generalized Solvent Effect on the Fluorescence Performance of Spiropyran for Advanced Quick Response Code Dynamic Anti-Counterfeiting Sensing
by Junji Xuan, Lingjie Chen and Jintao Tian
Int. J. Mol. Sci. 2025, 26(4), 1531; https://doi.org/10.3390/ijms26041531 - 12 Feb 2025
Cited by 2 | Viewed by 1130
Abstract
Spiropyran has an attractive and mysterious fluorescence switch and dual-color conversion characteristics, as it exhibits both aggregation-caused quenching (ACQ) in solvents and fluorescence enhancement in polymer matrices. The explanation for this phenomenon has always been of great controversy. Hence, the solvent effect on [...] Read more.
Spiropyran has an attractive and mysterious fluorescence switch and dual-color conversion characteristics, as it exhibits both aggregation-caused quenching (ACQ) in solvents and fluorescence enhancement in polymer matrices. The explanation for this phenomenon has always been of great controversy. Hence, the solvent effect on the emission of spiropyran (SP) was investigated in 16 solvents. By means of molecular orbital theory and the Jablonski diagram, several special parameters (e.g., Hansen solubility parameters and viscosity) were selected for this analysis, with excellent goodness of fit. Subsequently, the main factors that affected the blue shift, red shift, and luminescence efficiency of the emission of the ring-opened form merocyanine (MC) were found to be the hydrogen bonding and polarity, aggregation effect, and viscosity, respectively. A newly modified Jablonski diagram was proposed to clarify the emission behaviors of spiropyran influenced by solvent polarity and isomerization. Meanwhile, the solvent effect could also be extended to a solid polymer matrix (six kinds of polyethylene glycol (PEG) with different molecular weights), which is proposed to be defined as the generalized solvent effect. Accordingly, we have demonstrated that the unique fluorescence properties of spiropyran are dominated by the generalized solvent effect. The security information storage capacity of the simulated quick response (QR) code sensor combined with SP for anti-counterfeiting was significantly improved to six dimensions in taking advantage of the former theoretical analysis. Full article
(This article belongs to the Special Issue Recent Advances in Luminescence: From Mechanisms to Applications)
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13 pages, 6535 KB  
Article
An Eight-Membered Ring Molecular Framework Based on Carbazole for the Development of Electroluminescent Materials
by An Yan, Shipan Xu, Xuyang Du, Chengyun Zhu, Shengli Li, Xiaolong Yang, Guijiang Zhou and Yuanhui Sun
Molecules 2025, 30(3), 716; https://doi.org/10.3390/molecules30030716 - 5 Feb 2025
Viewed by 1088
Abstract
The organic light-emitting diode (OLED) has been regarded as the most prominent product in the current market of organic electronics, which has attracted growing attention because of their applications in full-color displays and solid-state lighting. Organic materials that exhibit strong luminescence in the [...] Read more.
The organic light-emitting diode (OLED) has been regarded as the most prominent product in the current market of organic electronics, which has attracted growing attention because of their applications in full-color displays and solid-state lighting. Organic materials that exhibit strong luminescence in the solid state constitute the core position of OLED. Extensive research efforts to probe the structure of organic luminescent materials have attracted considerable attention to the conjugated fusion ring architecture. This is because it can confer molecular rigidity and helps to inhibit intermolecular interactions and non-radiative transitions, thus enhancing the performance of luminescent materials. Here, we use an efficient and simple method to construct an eight-membered ring molecular framework based on carbazole. Moreover, we have introduced groups with different electron-withdrawing abilities to develop a series of luminescent molecules. The results show that the nonplanar structure based on the eight-membered ring suppresses fluorescence quenching caused by molecular aggregation. As the doping concentration increases, the electroluminescence spectrum remains basically unchanged, indicating that the eight-membered ring structure can effectively suppress the intermolecular interaction. Notably, DCBz-pm exhibits deep blue emission with a Commission Internationale de l’Eclairage (CIE) coordinate of (0.158, 0.046), which nearly meets the BT. 2020 standards. The DCBz-CN device reaches a maximum external quantum efficiency (EQE) of 4.36%. These results offer a new design strategy for improving the performance of OLEDs. Full article
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16 pages, 2445 KB  
Review
Aggregation-Caused Quenching Dyes as Potent Tools to Track the Integrity of Antitumor Nanocarriers: A Mini-Review
by Xiye Wang, Jiayue Huang, Mengqin Guo, Yiling Zhong and Zhengwei Huang
Pharmaceuticals 2025, 18(2), 176; https://doi.org/10.3390/ph18020176 - 27 Jan 2025
Cited by 3 | Viewed by 1318
Abstract
Cancer has become one of the major causes of death worldwide. Chemotherapy remains a cornerstone of cancer treatment. To enhance the tumor-targeting efficiency of chemotherapy agents, pharmaceutical scientists have developed nanocarriers. However, the in vivo structural integrity and dynamic changes in nanocarriers after [...] Read more.
Cancer has become one of the major causes of death worldwide. Chemotherapy remains a cornerstone of cancer treatment. To enhance the tumor-targeting efficiency of chemotherapy agents, pharmaceutical scientists have developed nanocarriers. However, the in vivo structural integrity and dynamic changes in nanocarriers after administration are not well understood, which may significantly impact their tumor-targeting abilities. In this paper, we propose the use of environmentally responsive fluorescent probes to track the integrity of antitumor nanocarriers. We compare three main types of dyes: fluorescence resonance energy transfer (FRET) dyes, aggregation-induced emission (AIE) dyes, and aggregation-caused quenching (ACQ) dyes. Among them, ACQ dyes, possessing sensitive water-quenching properties and easily detected “on–off” switching behavior, are regarded as the most promising choice. We believe that ACQ dyes are suitable for investigating the in vivo fate of antitumor nanocarriers and can aid in designing improved nanoformulations for chemotherapy agents. Full article
(This article belongs to the Section Pharmaceutical Technology)
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18 pages, 6815 KB  
Review
Engineered Strategies for Lipid Droplets-Targeted AIEgens Based on Tetraphenylethene
by Fei Zhang, Yao Zhang, Zhuoxia Li, Xiaoxiao Wu, Dong Wang, Youling He, Hong Cheng, Baolei Fan, Dan Zhu, Min Li and Ben Zhong Tang
Molecules 2024, 29(24), 5904; https://doi.org/10.3390/molecules29245904 - 13 Dec 2024
Cited by 3 | Viewed by 1815
Abstract
Lipid droplets (LDs), once regarded as inert fat particles, have been ignored by scientific researchers for a long time. Now, studies have shown that LDs are dynamic organelles used to store neutral lipids in cells and maintain cell stability. The abnormality of intracellular [...] Read more.
Lipid droplets (LDs), once regarded as inert fat particles, have been ignored by scientific researchers for a long time. Now, studies have shown that LDs are dynamic organelles used to store neutral lipids in cells and maintain cell stability. The abnormality of intracellular LDs usually causes metabolic disorders in the body, such as obesity, atherosclerosis, diabetes, and cancer, so the LDs have attracted wide attention. The traditional small molecules used for LDs recognition seriously affect the imaging effect due to their poor photo-stability, low signal-to-noise ratios, and aggregation-induced quenching (ACQ). In contrast to ACQ, aggregation-induced emission (AIE) materials, with structural modifiability, can make up for the aforementioned deficiencies in the field of fluorescence imaging and have attracted much attention. In this review, the importance of LDs in vivo, the design principles for LDs recognition, and the recent research progress of AIE compounds with tetraphenylethene (TPE) structure in LDs targets are reviewed. We expect this review to further provide researchers with feasible methods and protocols for expanding LDs identification, imaging, and other applications. Full article
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14 pages, 23122 KB  
Article
Construction of Heterogeneous Aggregation-Induced Emission Microspheres with Enhanced Multi-Mode Information Encryption
by Zhiwei Wu, Weiqin Yu, Fenghao Luo, Yue Jin, Ligou Pan, Qianjun Deng, Qing Wang and Mingguang Yu
Molecules 2024, 29(24), 5852; https://doi.org/10.3390/molecules29245852 - 11 Dec 2024
Cited by 1 | Viewed by 1139
Abstract
Traditional organic light-emitting materials hinder their anti-counterfeiting application in solid state due to their aggregation-caused quenching effect. A facile and straightforward method was reported to introduce AIE molecules into microspheres and manipulate different reaction parameters to prepare AIE microspheres with different morphologies. In [...] Read more.
Traditional organic light-emitting materials hinder their anti-counterfeiting application in solid state due to their aggregation-caused quenching effect. A facile and straightforward method was reported to introduce AIE molecules into microspheres and manipulate different reaction parameters to prepare AIE microspheres with different morphologies. In this strategy, fluorescent microspheres with spherical, apple-shaped, and hemoglobin-like types were synthesized. Driven by the photocyclization and oxidation of tetraphenylethene, microspheres can be used as an aqueous fluorescence ink with erasable properties. The fluorescent patterns printed by microsphere ink on paper can be irreversibly erased by prolonged exposure to ultraviolet light (365 nm, 60 mw/cm2). Moreover, the multi-morphology microspheres can be further arranged for multiple-information encryption and anti-counterfeiting of barcodes and two-dimensional codes, in which double validation was carried out through fluorescence spectroscopy and laser confocal microscopy. This approach provides a new method for more reliable anti-counterfeiting and information encryption. Full article
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13 pages, 9609 KB  
Article
Effect of Heat Treatment on Microstructure and Properties of Powder Metallurgy High-Speed Steel Prepared by Hot Isostatic Pressing
by Deyin Zhang, Tianyu Lu, Xu Hao, Yixiao Wu, Jiaxun Zhang, Mingming Sun, Baorui Jia, Haoyang Wu, Mingli Qin and Xuanhui Qu
Metals 2024, 14(10), 1160; https://doi.org/10.3390/met14101160 - 11 Oct 2024
Cited by 2 | Viewed by 1810
Abstract
The microstructure and properties of powder metallurgy high-speed steel prepared by hot isostatic pressing with different heat treatments have been studied. The microstructure, phase composition, effect of quenching and tempering parameters, fracture morphology, and mechanical properties of the sample are discussed in detail. [...] Read more.
The microstructure and properties of powder metallurgy high-speed steel prepared by hot isostatic pressing with different heat treatments have been studied. The microstructure, phase composition, effect of quenching and tempering parameters, fracture morphology, and mechanical properties of the sample are discussed in detail. The H-HSS sample presents the characteristics of the powder prior to the particle boundary and consists of carbide and ferrite, in which the carbides are fine and evenly dispersed without segregation. The bending strength and hardness of the H-HSS sample are 3112 MPa and 56.3 HRC, respectively. The Q-HSS sample is mainly composed of martensite, residual austenite, and carbides. With the increase in quenching temperature, the grain size of the matrix gradually grows, and the small carbide particles dissolve into the matrix, causing an increase in carbide size and a decrease in quantity. The bending strength and hardness of the Q-HSS sample quenched at 1210 °C achieve the maximum values of 3114 MPa and 68.8 HRC, respectively. After tempering, the martensite is transformed from a quenched lath shape to a needle shape, the residual austenite content decreases, and secondary carbides precipitate from the matrix, resulting in a secondary hardening. The T-HSS sample that is quenched at 1120 °C followed by tempering at 550 °C for 20 min has the best bending strength of 4355 MPa. However, the T-HSS sample that is quenched at 1240 °C followed by tempering at 550 °C for 120 min has a maximum hardness value of 69.5 HRC. The fracture mode of Q-HSS sample is brittle fracture, and the fracture mechanism is cleavage fracture. After tempering, the fracture mechanism of the T-HSS sample presents a transitional fracture mode between the cleavage fracture and micropore aggregation fracture. Full article
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15 pages, 3580 KB  
Article
NIR-Sensitive Squaraine Dye—Peptide Conjugate for Trypsin Fluorogenic Detection
by Priyanka Balyan, Shekhar Gupta, Sai Kiran Mavileti, Shyam S. Pandey and Tamaki Kato
Biosensors 2024, 14(10), 458; https://doi.org/10.3390/bios14100458 - 25 Sep 2024
Cited by 4 | Viewed by 1741
Abstract
Trypsin enzyme has gained recognition as a potential biomarker in several tumors, such as colorectal, gastric, and pancreatic cancer, highlighting its importance in disease diagnosis. In response to the demand for rapid, cost-effective, and real-time detection methods, we present an innovative strategy utilizing [...] Read more.
Trypsin enzyme has gained recognition as a potential biomarker in several tumors, such as colorectal, gastric, and pancreatic cancer, highlighting its importance in disease diagnosis. In response to the demand for rapid, cost-effective, and real-time detection methods, we present an innovative strategy utilizing the design and synthesis of NIR-sensitive dye–peptide conjugate (SQ-3 PC) for the sensitive and selective monitoring of trypsin activity by fluorescence ON/OFF sensing. The current research deals with the design and synthesis of three unsymmetrical squaraine dyes SQ-1, SQ-2, and SQ-3 along with a dye–peptide conjugate SQ-3-PC as a trypsin-specific probe followed by their photophysical characterizations. The absorption spectral investigation conducted on both the dye alone and its corresponding dye–peptide conjugates in water, utilizing SQ-3 and SQ-3 PC respectively, reveals enhanced dye aggregation and pronounced fluorescence quenching compared to observations in DMSO solution. The absorption spectral investigation conducted on dye only and corresponding dye–peptide conjugates in water utilizing SQ-3 and SQ-3 PC, respectively, reveals not only the enhanced dye aggregation but also pronounced fluorescence quenching compared to that observed in the DMSO solution. The trypsin-specific probe SQ-3 PC demonstrated a fluorescence quenching efficiency of 61.8% in water attributed to the combined effect of aggregation-induced quenching (AIQ) and fluorescence resonance energy transfer (FRET). FRET was found to be dominant over AIQ. The trypsin-mediated hydrolysis of SQ-3 PC led to a rapid and efficient recovery of quenched fluorescence (5-fold increase in 30 min). Concentration-dependent changes in the fluorescence at the emission maximum of the dyes reveal that SQ-3 PC works as a trypsin enzyme-specific fluorescence biosensor with linearity up to 30 nM along with the limit of detection and limit of quantification of 1.07 nM and 3.25 nM, respectively. Full article
(This article belongs to the Special Issue Photonics for Bioapplications: Sensors and Technology)
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