Fluorescence Emission Mechanism Research Articles

Unraveling two yellow fluorescence emission mechanisms and color-changing afterglow characteristics of Dy-doped Mg2SnO4 luminescent materials

In this work, Dy ion doped Mg2SnO4 (Mg2SnO4:Dy3+) with monochromatic yellow fluorescence and color-changing long afterglow properties are prepared by the high-temperature solid-phase method. Mg2SnO4:Dy3+ shows the best luminescence performance under the preparation conditions of 1550 °C and 0.02 Dy3+ concentration. The samples are able to achieve yellow fluorescence emission (λem = 575 nm) under 350 nm and 291 nm excitation, and the emission intensity of the samples under 350 nm excitation is much higher than that of 291 nm excitation. Under 254 nm excitation, the sample not only emits bright white fluorescence but also has the ability of obvious afterglow after excitation. Moreover, the afterglow also has the color change function of transition from bright white to yellow. The luminescence mechanism study shows that Mg2SnO4:Dy3+ contains two emission centers, Dy3+ and lattice defects. Combining the results of spectroscopic measurements with the Dy3+ energy level distribution data, two different fluorescence emission processes under 291 and 350 nm excitation as well as the afterglow discoloration mechanism due to 254 nm excitation are discussed in detail.

Photophysical Properties of (E)-1-(4-(Diethyla-mino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide Compound and Its Triple Fluorescence Emission Mechanism: A Theoretical Perspective.

In view of the application prospects in biomedicine of (E)-1-(4-(diethyla-mino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide (DAHTS), the behavior of excited-state dynamics and photophysical properties were studied using the density functional theory/time-dependent density functional theory method. A series of studies indicated that the intramolecular hydrogen-bond (IHB) intensity of DAHTS was enhanced after photoexcitation. This was conducive to promoting the excited-state intramolecular proton-transfer (ESIPT) process. Combining the analysis of the IHB and hole-electron, it revealed that the molecule underwent both the ESIPT process and the twisted charge-transfer (TICT) process. Relying on exploration of the potential energy surface, it was proposed that the different competitive mechanisms between the ESIPT and TICT processes were regulated by solvent polarity. In acetonitrile (ACN) solvent, the ESIPT process occurred first, and the TICT process occurred later. In contrast, in the CYH solvent, the molecule first underwent the TICT process and then the ESIPT process. Furthermore, we raised the possibility that the TICT behavior was the cause of weak fluorescence emission for the DAHTS in CYH and ACN solvents. By the dimer correlation analysis, the corresponding components of triple fluorescence emission were clearly assigned, corresponding to the monomer, dimer, and ESIPT isomer in turn. Our work precisely elucidated the photophysical mechanism of DAHTS and the attribution of the triple fluorescence emission components, which provided valuable guidance for the development and regulation of bioactive fluorescence probes with multiband and multicolor emission characteristics.

Study on the Tunable Fluorescence Emission Mechanism of Nitrogen-Doped Carbon Dots and Ion Sensing Potential Applications

Study on the Tunable Fluorescence Emission Mechanism of Nitrogen-Doped Carbon Dots and Ion Sensing Potential Applications

Nitrogen fluorescence emission induced by femtosecond vortex beams in air

Fluorescence emission is a typical nonlinear phenomenon occurring during the femtosecond laser filamentation in air. The characteristics of nitrogen fluorescence emission induced by femtosecond vortex beams in air are experimentally studied. It is found that the topological charge has a great influence on the nitrogen fluorescence emission induced by a femtosecond filament: the fluorescence signals from nitrogen molecules (e.g., 337, 357 and 380 nm spectral lines) and molecular nitrogen ions (e.g., 391 and 428 nm spectral lines) differ much in the intensity distribution along the propagation direction. The discrepancy is explained by revisiting the generation mechanisms for nitrogen fluorescence, and it is found that the intersystem crossing scheme can account for it, indicating that the intersystem crossing scheme plays the main role in the formation of This work is helpful to the understanding of the physical mechanism of fluorescence emission induced by the filamentation of femtosecond vortex beams in air.

Exploring the highly selective Fe(III) and Al(III) triggered “OFF-ON” ellagic acid based fluorescent sensor: Spectroscopic, structural elucidations and dual-response mechanism

Owing to the favorable efficiency and low cost, dual-response fluorescent sensors play critical roles in the development of fluorescence assay systems. In this paper, the dual-response fluorescent of ellagic acid was reported both turn-off to Fe3+ and turn-on to Al3+, as well as the effects of pH by UV–vis absorption and fluorescence emission spectroscopy. The addition of Fe3+ changed the color of the ellagic acid solution from colorless to grey-green, and the fluorescence emission was quenched. In contrast, the addition of Al3+ changed the colorless solution to light yellow, and the fluorescence emission was significantly enhanced. The coordination constants of EA to Fe3+ and Al3+ were determined to be 3.42 × 104 M−1 and 2.83 × 105 M−1, respectively, according to Job's plot. By comparing the reaction with urolithin and its derivatives, the fluorescence emission mechanism of the ellagic acid reaction with Fe3+ and Al3+ was elucidated. The detection limits of EA for Fe3+ and Al3+ were 9.80 × 10−7 and 1.90 × 10−7 M, respectively.

β-Cyclodextrin derived full-spectrum fluorescent carbon dots: The formation process investigation and biological applications

Carbon dots (CDs), a new building unit, have been revolutionizing the fields of biomedicine, bioimaging, and optoelectronics with their excellent physical, chemical, and biological properties. However, the difficulty of preparing excitation-dependent full-spectrum fluorescent CDs has seriously hindered their further research in fluorescence emission mechanisms and biomedicine. Here, we report full-spectrum fluorescent CDs that exhibit controlled emission changes from purple (380 nm) to red (613 nm) at room temperature by changing the excitation wavelength, and the excitation dependence was closely related to the regulation of sp2 and sp3 hybrid carbon structures by β-cyclodextrin-related groups. In addition, by regulating the content of β-cyclodextrin, the optimal quantum yields of full-spectrum fluorescent CDs were 8.97%, 8.35%, 7.90%, 9.69% and 17.4% at the excitation wavelengths of 340, 350, 390, 410 and 540 nm, respectively. Due to their excellent biocompatibility and color tunability, full-spectrum fluorescent CDs emitted bright and steady purple, blue, green, yellow, and red fluorescence in MCF-7 cells. Moreover, we optimized the imaging conditions of CDs and mitochondrial-specific dyes; and realized the mitochondrial-targeted co-localization imaging of purple, blue and green fluorescence. After that, we also explored the effect of full-spectrum fluorescent CDs in vivo fluorescence imaging through the intratumorally, subcutaneously, and caudal vein, and found that full-spectrum fluorescent CDs had good fluorescence imaging ability in vivo.

A novel phenanthroline[9,10-d] imidazole-based fluorescent sensor for Hg2+ with “turn-on” fluorescence response

Herein, a phenanthro[9,10-d] imidazole Schiff based “turn-on” fluorescence sensor (compound 1) was synthesized by 4-hydroxy-3-nitrobenzaldehyde and 9,10-phenanthrenequinone. In DMF/PBS buffer solution (1:4, v/v, pH 7.4), compound 1 responsed to Hg2+ with high sensitivity (detection limit was 45.76 nM) and rapid response (completed within 5 s), accompanied by the fluorescence change from null to blue. The binding ratio of compound 1 to Hg2+ was 1:1, and the binding constant was 2.933 × 106 M−1. Through detailed analysis of 1H–1H COSY and 1H–13C HSQC spectra, we proposed the possible fluorescence emission mechanism of compound 1 and Hg2+, and verified the recognition mechanism of compound 1 through density functional theory (DFT) calculation. Compound 1 was successfully used to detect Hg2+ in actual water samples, the recovery was 91 %–106 %, and the relative standard deviation (R.S.D.) was less than 2.5 %, which provided possibility for compound 1 to be used as a sensor in environmental research.

Design of ZnO/Ag dimer/porous silicon sandwich structures and theoretical investigation on its fluorescence emission mechanism

Design of ZnO/Ag dimer/porous silicon sandwich structures and theoretical investigation on its fluorescence emission mechanism

Smart probes for optical imaging of T cells and screening of anti-cancer immunotherapies.

T cells are an essential part of the immune system with crucial roles in adaptive response and the maintenance of tissue homeostasis. Depending on their microenvironment, T cells can be differentiated into multiple states with distinct functions. This myriad of cellular activities have prompted the development of numerous smart probes, ranging from small molecule fluorophores to nanoconstructs with variable molecular architectures and fluorescence emission mechanisms. In this Tutorial Review, we summarize recent efforts in the design, synthesis and application of smart probes for imaging T cells in tumors and inflammation sites by targeting metabolic and enzymatic biomarkers as well as specific surface receptors. Finally, we briefly review current strategies for how smart probes are employed to monitor the response of T cells to anti-cancer immunotherapies. We hope that this Review may help chemists, biologists and immunologists to design the next generation of molecular imaging probes for T cells and anti-cancer immunotherapies.

Fluorescence Behavior and Emission Mechanisms of Poly(ethylene succinamide) and Its Applications in Fe3+ Detection and Data Encryption

Fluorescence Behavior and Emission Mechanisms of Poly(ethylene succinamide) and Its Applications in Fe3+ Detection and Data Encryption

Efficient Exciton Dislocation and Ultrafast Charge Extraction in CsPbI3 Perovskite Quantum Dots by Using Fullerene Derivative as Semiconductor Ligand.

CsPbI3 quantum dots (QDs) are of great interest in new-generation photovoltaics (PVs) due to their excellent optoelectronic properties. The long and insulative ligands protect their phase stability and enable superior photoluminescence quantum yield, however, limiting charge transportation and extraction in PV devices. In this work, we use a fullerene derivative with the carboxylic anchor group ([SAM]C60) as the semiconductor ligand and build the type II heterojunction system of CsPbI3 QDs and [SAM]C60 molecules. We find their combination enables obvious exciton dislocation and highly efficient photogenerated charge extraction. After the introduction of [SAM]C60, the exciton-binding energy of CsPbI3 decreases from 30 meV to 7 meV and the fluorescence emission mechanism also exhibits obvious changes. Transient absorption spectroscopy visualizes a ~5 ps electron extraction rate in this system. The findings gained here may guide the development of perovskite QD devices.

The crosstalk fluorescence spectroscopy analysis principle and an accurate fluorescence quantitative method for multi-composition fluorescence substances

Fluorescence quantitative analysis methods are extensively used in biomedicine inspection, petrochemical industry, environmental monitoring, and many other fields in the past decades. When the analyte is composed of multiple compositions, the accuracy of the conventional method declines significantly due to the fluorescence spectral crosstalk. In this research, the interactions between the light and the multiple compositions are comprehensively analyzed. The concepts of the quenching due to mutual absorption and the fluorescence overlapping are considered, and the mechanism of multi-composition fluorescence emission under single-wavelength excitation light is analyzed theoretically. The mixture experiment and the dilution experiment are designed to illustrate that the quenching due to mutual absorption has a significant nonlinear impact on fluorescence quantitative analysis and the mechanism of fluorescence spectral crosstalk gives a good explanation for these experiments. Through the in-depth theoretical analysis, the computer simulation, and the experiments, a novel principle named the Crosstalk Fluorescence Spectroscopy Analysis (CFSA) is proposed and verified, which has much higher quantitative analysis accuracy (R2>0.99 and RMSE≤0.2) than the conventional methods when analyzing the multi-composition samples. Unlike many correction approaches to fluorescence spectroscopy, the novel CFSA can serve as a complete analysis method rather than a correction method. These concepts and the principle are expected to be applied in many practical analysis fields.

One-pot alkali cutting-assisted synthesis of fluorescence tunable amino-functionalized graphene quantum dots as a multifunctional nanosensor for sensing of pH and tannic acid

Herein, a one-pot alkali cutting-assisted synthesis approach has been developed to gain fluorescence (FL) tunable amino functionalized GQDs (NH2-GQDs), which exhibit concentration- and excitation-dependent FL behaviors, due to the self-assembled J-type aggregation effect and different electronic transitions governed by graphene basal plane and functional groups. While NH2-GQDs possess brighter FL emission than pristine GQDs, owning to the functionalization of amino groups with strong electron withdrawing ability. Particularly, the pH-dependent FL behavior of NH2-GQDs further reflects the FL emission mechanism originated from the intrinsic zigzag sites and introduced amino and carboxylic groups, which is available for pH sensing. Moreover, the NH2-GQDs also show a FL quenching upon reaction with tannic acid (TA), resulting in the construction of a FL turn-off TA sensing platform. A good linear relationship is obtained between logarithm of FL intensity (log F) and TA concentration in a linear dynamic range of 1–40 μM and a limit of detection of 43.3 nM (3σ/s, n = 9) is achieved, with a precision of 0.08% RSD at a concentration level of 5 μM (n = 9). This work features a simple and direct approach to acquire multifunctional nanosensor, providing great potential for further applications in chem/biosensing.

Structural Features of a Family of Coumarin-Enamine Fluorescent Chemodosimeters for Ion Pairs.

A family of coumarin-enamine chemodosimeters is evaluated for their potential use as fluorescent molecular probes for multiple analytes [cadmium(II), cobalt(II), copper(II), iron(II), nickel(II), lead(II), and zinc(II)], as their chloride and acetate salts. These fluorophores displayed excellent optical spectroscopic modulation when exposed to ion pairs with different Lewis acidic and basic properties in dimethyl sulfoxide (DMSO). The chemodosimeters were designed to undergo excited-state intramolecular proton transfer (ESIPT), which leads to significant Stokes shifts (ca. 225 nm) and lower-energy fluorescence emission (ca. 575 nm). A more basic anion, e.g., acetate, inhibited the ESIPT mechanism by deprotonation of the enol, producing a binding pocket (N^O- chelate) that can coordinate to an appropriate metal ion. Coordination of the metal ions enhances the fluorescent intensity via the chelation-enhanced fluorescence emission mechanism. Subjecting the spectroscopic data to linear discriminant analysis provided insights into the source of these systems' markedly different behavior toward ion pairs, despite the subtle structural differences in the organic framework. These compounds are examples of versatile, low-molecular-weight, dual-channel fluorescent sensors for ion-pair recognition. This study paves the way for using these probes as practical components of a sensing array for different metal ions and their respective anions.

Advances, opportunities, and challenge for full-color emissive carbon dots

Carbon dots (CDs), novel luminescent zero-dimensional carbon nanomaterials, have been widely applied due to their low toxicity, optimal optical properties, and easy modification. However, the current controllable equipment and mechanism explanation of CDs are relatively vague and require urgent resolution. Full-color emission CDs, an essential CDs category, have attracted people's attention given their light and color-tunable properties. In addition to a wider range of biological and optoelectronic device applications, full-color emission CDs have similar structures and significantly affected the fluorescence mechanism of CDs. At present, few studies have reported on the summary research of CDs emitted by its full color, which greatly limits the development of CDs mechanisms and applications. As such, the present review detailed the full-color CDs development status, to which a suitable method for preparing full-color CDs was presented and the existing fluorescence emission mechanism of full-color CDs was summarized. Herein, we comprehensively introduced full-color CDs applications in biology and optoelectronics. Finally, we made an outlook on the development and potential applications of full-color CDs. The present review aims to contribute novel insights and methods for understanding full-color CDs.

Femtosecond laser-induced nitrogen fluorescence emission at different air pressures

In this paper, we experimentally investigate femtosecond laser-induced nitrogen fluorescence emission at different air pressures (0.1 Pa–100 kPa). The variation of nitrogen molecule (N2) and molecular nitrogen ion (N2+) characteristic fluorescence spectral lines' intensity as a function of air pressure is observed. When the air pressure is between 10 Pa and 100 kPa, the intensity of fluorescence signals from N2+ and N2 shows opposite variation as a function of air pressure. We deduce that dissociative recombination is the main pathway for the production of the C3∏u state of N2. This research helps elucidate the physical emission mechanism of femtosecond laser-induced nitrogen fluorescence emission.

Application of graphene quantum dots in the detection of Hg2+ and ClO− and analysis of detection mechanism

Graphene quantum dots (GQDs) are a new type of carbon material that have received widespread attention in recent years. However, due to their complex structure, it is difficult to explore their fluorescence emission mechanism and application mechanism. In this work, GQDs with simple structure were prepared using citric acid as a single precursor. The fluorescence properties and structure of GQDs were characterized, and the results confirmed that their luminescence originated from the n → π* electronic transition produced by the oxygen-containing functional groups in the edge state. Significantly, GQDs can be used as excellent probes to detect Hg2+ and ClO− in aqueous solution. Hg2+ combines with the carboxyl groups of the edge states of GQDs to form a complex, and then reduces the fluorescence emission through non-radiative electron transfer. ClO− can oxidize the hydroxyl groups in the edge states of GQDs to make them positively charged, which prevents electron transfer related to the luminescent center and reduces fluorescence emission.

Conjugated Polymers with Aggregation-Induced Emission Characteristics for Fluorescence Imaging and Photodynamic Therapy.

Accurate diagnosis and treatment have been extensively developed in the field of biomedicine, which put forward higher requirements for the development of biomedical materials with high efficiency and selectivity. Among them, conjugated polymers featuring aggregation-induced emission (AIE) characteristics (AIE conjugated polymers) have stood out in recent years owing to their unique properties, such as intense solid emission, high light-harvesting ability, efficient energy transfer, and high 1 O2 generation ability, which empower them with effective biomedical functions in fluorescence imaging (FLI), photodynamic therapy (PDT), FLI-guided PDT, two-photon excited photodynamic therapy (2PE-PDT), etc. In this review, we highlight recent progress in AIE conjugated polymers and their applications in anticancer and antibacterial areas based on FLI and PDT, and summarize the mechanism of color-tuned fluorescence emission and efficient 1 O2 generation ability. The challenges and perspectives for the future development of AIE conjugated polymers are also discussed.

Preface

The 2021 2nd International Conference on Geology, Mapping and Remote Sensing (ICGMRS 2021) was be held virtually online on April 23-25, 2021 due to the precaution taken to minimizing the COVID-19 risk. The safety and well-being of all conference participants was our first and top priority, while we strived to offer many scholars and researchers this long-awaited conference to conduct academic exchanges with their peers.ICGMRS 2021 is to bring together innovative academics and industrial experts in the field of geology, mapping and remote sensing to a common conference. The primary goal of the conference is to promote research and developmental activities in geology, mapping and remote sensing and another goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working all around the world.The COVID-19 virus has made our life very challenging, but we want to reiterate that there are no barriers to science, as we continue to do our research works via modern technical means. The ICGMRS 2021 has selected Zoom as the virtual platform. Each presenter will be given a 15-minute talk and followed by a short discussion afterward. Before the conference, all of the authors were encouraged to submit a video as a backup in case of unexpected technical problems. There were 140 individuals who attended this on-line conference, represented many countries including China, Canada, South Korea, Singapore and UK.During the conference, we invited three professors as our keynote speakers. A. Prof. Chao Chen, from Zhejiang Ocean University, performed a speech: Spatio-temporal pattern evolution of coastlines for archipelagic regions. His research area is Marine Environment Remote Sensing. And then we had A. Prof. Heng Dong, from Wuhan University of Technology. He delivered a speech: Estimation of Global Terrestrial Gross Primary Productivity based on Solar-Induced Chlorophyll Fluorescence. In this study, after analyzing the fluorescence emission mechanism at different spatial scales, and the GPP-SIF empirical linear estimation model, some factors affecting the photosynthetic capacity of the vegetation and the canopy SIF emission were introduced to construct a new GPP estimation method. Lastly, we were glad to invite A. Prof. Xuemin Xing, from Changsha University of Science & Technology as our finale keynote speakers. She shared a speech: Measuring subsidence over soft clay highway based on a novel time-series InSAR deformation model: with emphasis on rheological properties and seasonal factors. Their insightful speeches had triggered heated discussion of the conference. Every participant praised this conference for disseminating useful and insightful knowledge.The proceedings are a compilation of the accepted papers and represent an interesting outcome of the conference. Topics include but are not limited to the following areas: Geography & Geology, Surveying & Mapping, Remote Sensing, Application of Remote Sensing Technology and other related topics. All the papers have been through rigorous review and process to meet the requirements of International publication standard.We would like to acknowledge all of those who supported ICGMRS 2021. The help and contribution of each individual and institution was instrumental in the success of the conference. In particular, we would like to thank the organizing committee for its valuable inputs in shaping the conference program and reviewing the submitted papers.The Committee of ICGMRS 2021Committee member, Conference Chair, Program Committees, Technical Program Committees and this titles are available in this pdf.

An "off-on-off" fluorescence chemosensor for the sensitive detection of Cu2+ in aqueous solution based on multiple fluorescence emission mechanisms.

A new organosiloxane precursor ((E)-3-hydroxy-4-((2-(2-hydroxy-4-(3-(3-(triethoxysilyl)propyl)ureido)benzoyl)hydrazono)methyl)phenyl(3-(triethoxysilyl)propyl)carbamate, hereinafter referred to as AHBH-Si) and tetraethylorthosilicate (TEOS) were mixed as the mixed Si source, and bridged periodic mesoporous organic silica (AHBH-PMOs) nanoparticles were obtained through the co-condensation reaction. AHBH-PMO nanoparticles possess mechanisms of "Aggregation Induced Emission" (AIE) and "Intramolecular Charge Transfer" (ICT), which originate from the molecular structure of AHBH having "C[double bond, length as m-dash]N" bond, ortho hydroxyl groups, etc.. Therefore, the optical properties of AHBH are excellent with respect to the solvent effect and enhanced fluorescence. For hybrid materials, the silica framework provides a rigid environment that restricts the rotation of AHBH, thereby turning on the fluorescence of AHBH due to the regulation by the AIE effect. In particular, AHBH-PMOs are no longer restricted by organic solvents and could really achieve the response to Cu2+ with high sensitivity and selectivity in aqueous solutions of a wide pH range. In addition, the detection limit is as low as 3.26 × 10-9 M. Methods such as Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and high-resolution mass spectrometry have shown the coordination interaction between AHBH and Cu2+. The Gaussian 09 software of density functional theory to calculate the reducing changes of energy gaps among AHBH and AHBH-Si before and after the addition of Cu2+ showed that coordination interaction exists in the system. These results indicate that AHBH-PMO hybrid materials have potential applications in the field of environmental monitoring.