Fluorescence Wavelength Research Articles

Significant loophole-free test of Kochen-Specker contextuality using two species of atomic ions.

Quantum measurements cannot be thought of as revealing preexisting results, even when they do not disturb any other measurement in the same trial. This feature is called contextuality and is crucial for the quantum advantage in computing. Here, we report the observation of quantum contextuality simultaneously free of the detection, sharpness, and compatibility loopholes. The detection and sharpness loopholes are closed by adopting a hybrid two-ion system and highly efficient fluorescence measurements offering a detection efficiency of 100% and a measurement repeatability of >98%. The compatibility loophole is closed by targeting correlations between observables for two different ions in a Paul trap, a 171Yb+ ion and a 138Ba+ ion, chosen so measurements on each ion use different operation laser wavelengths, fluorescence wavelengths, and detectors. The experimental results show a violation of the bound for the most adversarial noncontextual models and open a way to certify quantum systems.

Dynamic Timing Control over Multicolor Molecular Emission by Temporal Chemical Locking

AbstractDynamic control over molecular emission, especially in a time‐dependent manner, holds great promise for the development of smart luminescent materials. Here we report a series of dynamic multicolor fluorescent systems based on the time‐encoded locking and unlocking of individual vibrational emissive units. The intramolecular cyclization reaction driven by adding chemical fuel acts as a chemical lock to decrease the conformational freedom of the emissive units, thus varying the fluorescence wavelength, while the resulting chemically locked state can be automatically unlocked by the hydrolysis reaction with water molecules. The dynamic molecular system can be driven by adding chemical fuels for multiple times. The emission wavelength and lifetime of the locking states can be readily controlled by elaborating the molecular structures, indicating this strategy as a robust and versatile way to modulate multi‐color molecular emission in a time‐encoded manner.

Dynamic Timing Control over Multicolor Molecular Emission by Temporal Chemical Locking

Dynamic control over molecular emission, especially in a time-dependent manner, holds great promise for the development of smart luminescent materials. Here we report a series of dynamic multicolor fluorescent systems based on the time-encoded locking and unlocking of individual vibrational emissive units. The intramolecular cyclization reaction driven by adding chemical fuel acts as a chemical lock to decrease the conformational freedom of the emissive units, thus varying the fluorescence wavelength, while the resulting chemically locked state can be automatically unlocked by the hydrolysis reaction with water molecules. The dynamic molecular system can be driven by adding chemical fuels for multiple times. The emission wavelength and lifetime of the locking states can be readily controlled by elaborating the molecular structures, indicating this strategy as a robust and versatile way to modulate multi-color molecular emission in a time-encoded manner.

Hybrid device of hexagonal boron nitride nanoflakes with defect centres and a nano-fibre Bragg cavity

Solid-state quantum emitters coupled with a single mode fibre are of interest for photonic and quantum applications. In this context, nanofibre Bragg cavities (NFBCs), which are microcavities fabricated in an optical nanofibre, are promising devices because they can efficiently couple photons emitted from the quantum emitters to the single mode fibre. Recently, we have realized a hybrid device of an NFBC and a single colloidal CdSe/ZnS quantum dot. However, colloidal quantum dots exhibit inherent photo-bleaching. Thus, it is desired to couple an NFBC with hexagonal boron nitride (hBN) as stable quantum emitters. In this work, we realize a hybrid system of an NFBC and ensemble defect centres in hBN nanoflakes. In this experiment, we fabricate NFBCs with a quality factor of 807 and a resonant wavelength at around 573 nm, which matches well with the fluorescent wavelength of the hBN, using helium-focused ion beam (FIB) system. We also develop a manipulation system to place hBN nanoflakes on a cavity region of the NFBCs and realize a hybrid device with an NFBC. By exciting the nanoflakes via an objective lens and collecting the fluorescence through the NFBC, we observe a sharp emission peak at the resonant wavelength of the NFBC.

Synthesis and fluorescence property modulation of α-cyano-1,4-diphenylbutadiene derivatives containing triphenylamine structure

In this paper, a series of α-cyano-1,4-diphenylbutadiene derivatives containing triphenylamine structure were designed and synthesized. By changing the connection mode of the terminal diphenylamine, the angle between the donor and the acceptor was adjusted to further regulate the fluorescent wavelengths of 1a–1h from 456 nm to 621 nm in solution and 515 nm–614 nm in solid states.

Fluorescence thermometers: intermediation of fundamental temperature and light.

The rapid advancement of thermal materials and fluorescence spectroscopy has extensively promoted the development of micro-scale fluorescence thermometry in recent years. Based on their advantages of fast response, high sensitivity, simple operation, high spatial resolution, and non-destructive detection, fluorescence thermometers have become powerful analysis tools used to sense temperature fluctuations through fluorescent signals, especially to accurately capture living cells via fluorescent signals and local temperature variations in living bodies, thus providing the most direct means for the in-depth understanding of biological processes in cells. Herein, we systematically categorize the currently reported fluorescence thermometers based on the aspects of fluorescence intensity and wavelength, reveal the intrinsic relationship between fluorescence (intensity and wavelength) and temperature response, expound the applications of fluorescence thermometers in the fields of chemical sensing and biomedicine, and analyze the challenges faced by current fluorescence thermometers based on fundamental problems and practical applications simultaneously, thus highlighting the future directions of fluorescence thermometers.

Determination of the critical micelle concentration of surfactants using fluorescence strategies.

The increasing importance of surfactants in various fields has led to growing interest in the comprehensive characterization of surfactants. The critical micelle concentration (CMC), the most fundamental property of surfactants, is a parameter that must be measured. In particular, with the continuous expansion of the molecular structure of surfactants, numerous novel amphiphilic molecules have been developed that are capable of forming ordered aggregates in various solvent systems. Fluorescence spectroscopy, based on the differences in fluorescence intensity and wavelength of the fluorescent probe in the solvent phase and micellar phase, can sensitively detect the CMC of surfactants. This review aims to summarize the various fluorescence methods used to determine the CMC, including aggregation-induced emission (AIE), excimer formation, intramolecular charge transfer (ICT), and other miscellaneous strategies. The difficulties and limitations in the CMC determination process are also described. Further suggestions are provided to guide the existing fluorescence probes and the corresponding fluorescence methods to detect critical aggregation concentrations of amphiphilic molecules.

A Fast Detection Method for Pesticide Residues by Spectrometry Technique

In this paper, a fast detection method for pesticide residues was proposed, and the qualitative and quantitative detection of the pesticide could be got at once by the method of solution of multiple linear regression equations which were obtained by dual wavelength absorbance and fluorescence spectrometry with least squares method. Moreover, it could detect two kinds of mixed pesticides. Four selected pesticides, aldicarb, fenitrothion, fenvalerate, and chlorothalonil were detected by the method. The results shown that there were good linear relationship in the range of 0.01-1 ppm, and R2 ＞ 0.90. And the method could 100% discriminate the four pesticide residues, the limit of detection was below 8 ppb both single one and mixed one. The recoveries of the pesticides in cabbage samples were observed 92.12%-107.50%. And the recoveries of the mixed pesticides in mineral water samples were observed 86.44%-114.10%. The preliminary study demonstrates that the proposed method has excellent potential application for the safety inspection of food.

Petroleum hydrocarbons in Brazilian Northeast continental shelf waters: baseline values

Water quality on the continental shelf off the eastern Brazilian Northeast region was investigated in two oceanographic campaigns during winter and summer, when vertical profiles of salinity, temperature, turbidity, chlorophyll and dissolved oxygen were recorded. Dissolved / dispersed petroleum hydrocarbons (DDPH) were also analyzed in sub-superficial water samples using fixed wavelength fluorescence spectroscopy methods. Shelf waters are dominated by Tropical Waters, with high salinity (> 36.5 g kg-1) and temperature (> 26 °C) and little continental influence. Turbidity was higher during winter, which may be due to the higher continental contribution and/or higher wave action. Chlorophyll was mostly < 1 µg L-1 and dissolved oxygen saturation was predominantly high (> 90%), but innermost costal stations were influenced by the Capibaribe estuary. Median DDPH concentrations were as low as 0.07 and 0.04 µg L-1 Carmópolis oil equivalents during winter and summer respectively, and 0.02 µg L-1 chrysene equivalent for both periods. An exception was observed off Suape Harbor (0.35 µg L-1 Carmópolis oil equiv. and 0.13 µg L-1 chysene equiv.), suggesting navigation activities as the main local source. The overall DDPH median of 0.06 μg L-1 Carmópolis oil equivalents and 0.02 μg L-1 chrysene equivalents are proposed as the baseline concentration for non-polluted coastal water for the tropical western Atlantic Ocean margin.

Solvatofluorochromic Contrast with Supramolecular Stereoisomers Using Linked Rotaxane Structures to Investigate Local Solvation in Excited Donor-Bridge-Acceptor Systems

Abstract To optimize the photophysical properties of donor-bridge-acceptor (D-B-A) systems, the elucidation of the excited state of each component (i.e., D, B, and A) plays a crucial role in controlling the forward and back electron transfer rates. However, the direct evaluation of solvation spheres and their rearrangement on the excited bridge is still challenging. In this work, we report a method that exploits a linked rotaxane structure to uncover the solvation effects on an excited bridge by leveraging solvatofluorochromic contrast. We synthesize a D-insB-A system, in which a diphenylacetylene-based bridging moiety is insulated by a covalently linked permethylated α-cyclodextrin (PM α-CD), as a structural isomer of the uninsulated counterpart (D-uninsB-A). In the D-insB-A system, PM α-CD selectively covers the bridge while the donor and acceptor remain exposed. In this way, a comparison of the fluorescence wavelengths of D-insB-A and D-uninsB-A can reveal the local solvation effects on the excited bridge moiety. The investigation of the fluorescence properties in various solvents highlights a weak solvent interaction with the excited bridge in protic solvents and strong one in chlorinated polar solvents. These results provide crucial insight into the properties of excited D-B-A systems from the perspective of external environments, including solvent interactions.

New rhodamines with changeable π-conjugation for lengthening fluorescence wavelengths and imaging peroxynitrite

<h2>Summary</h2> Rhodamines, a group of excellent fluorophores, have been widely used to design various fluorescent probes; however, their maximum emission wavelengths are relatively short for bioimaging. Herein, we report a new kind of rhodamine derivatives characterized by the dibenzo[1,4]oxazepine core, which can selectively react with peroxynitrite (ONOO⁻), generating oxazines with much longer analytical wavelengths. These derivatives are readily synthesized in one step via a similar Stieglitz rearrangement; the presence of the 1,4-oxazepine ring is confirmed by single-crystal X-ray. Most importantly, the derivative (ON-RB) from rhodamine B, upon reaction with ONOO⁻, releases the oxazine moiety that emits in the near-infrared wavelength region. Using ON-RB, we have monitored the generation of ONOO⁻ in macrophage-derived foam cells, revealing that ONOO⁻ might be formed mainly in lipid droplets. The new chemistry of the dibenzo[1,4]oxazepine ring formation, together with its specific reaction with ONOO⁻, may provide a convenient strategy to develop rhodamine-based probes with longer wavelengths.

Electron-acceptor density adjustments for preparation conjugated polymers with NIR-II absorption and brighter NIR-II fluorescence and 1064 nm active photothermal/gas therapy

Designing conjugated polymers (CPs) with both efficient second near-infrared wavelength (NIR-II) fluorescence and NIR-II photothermal therapy performance remains a huge challenge, as the introduction of excessively strong electron donor and acceptor units significantly increase non-radiative decay. Herein, we describe an “electron acceptor density adjustment” strategy to address this problem, since a lower electron acceptor density in the conjugated polymer backbone can enhance the radiative rate constant and improve NIR-II fluorescence brightness. We used quaterthiophene (4T) with four repeated thiophene chain units and bithiophene (2 TC) modified with long alkyl side chains to reduce the electron acceptor density in the conjugated polymer backbone. The resultant 1064 nm absorption polymer, TTQ-2TC-4T displayed approximately 7.30-folds enhancement in NIR-II emission intensity compared to that of undoped TTQ-1T at the same mass concentration in toluene solution. Furthermore nanoparticles (TTQ-MnCO NPs) based on TTQ-2TC-4T and CO donors (Mn2(CO)10) were developed to realize NIR-II FI-guided 1064 nm laser-triggered NIR-II PTT/Gas synergistic therapy. The TTQ-MnCO NPs nanoparticles exhibited high photothermal conversion efficiency (η) of 44.43% at 1064 nm and high specific NIR-II fluorescence imaging of the cerebral vasculature of live mice. The in vivo results demonstrate that TTQ-MnCO NPs nanoparticles have excellent PTT/Gas synergistic therapeutic effects in MCF-7 tumor-bearing mice under 1064 nm laser irradiation. This study provides a new approach for optimizing both NIR-II fluorescence and NIR-II photothermal performance of NIR-II absorption conjugated polymers.

Aggregation-induced emission with large redshift in 2,7-diphenyl-fluorenone: Reality or artifact?

The luminescence property of 2,7-diphenyl-fluorenone (DPFO) was previously reported to be very unusual with a large aggregation-induced effect associated with a fluorescence redshift of 150 nm. The phenomenon is reexamined in this work. It is found that the abnormal observations are caused by the presence of a trace amount of impurity 2,7-diphenyl-fluorene (DPF) in the as-synthesized DPFO. The pure DPFO molecule does have an intense fluorescence (FL) in solid (528 nm), about 4–5 times larger than in its dilute dichloromethane solutions (542 nm), but with a blueshifted rather than redshifted FL wavelength in solid. The enormous FL enhancement and redshifted FL wavelength of the as-synthesized DPFO solid are due to the presence of impurity DPF. The FL of DPF is much stronger than that of DPFO in dilute solutions and it also has shorter FL wave-lengths. In a dilute solution of DPFO with a trace amount of DPF (~1%), the dominant FL peaks are from DPF. Because the electronic absorption peaks of DPF overlaps with DPFO, the electronic energy of DPF can transfer to DPFO. The energy transfer is faster with the increase of concentration because DPF and surrounding DPFO molecules become closer, which quenches the FL of DPF (356 and 372 nm) and enhances the FL of DPFO (542 nm in solution and 528 nm in solid). Therefore, at high concentrations or in solids, only peak at about 542 or 528 nm shows up, and peaks at 356 and 372 nm disappear.

Preparation and Fluorescent Wavelength Control of Multi-Color Nitrogen-Doped Carbon Nano-Dots.

It is known that, by taking advantage of heteroatom doping, the electronic states and transition channels in carbon nano-dots (CNDs) can be effectively modulated. Thus, the photoluminescence (PL) properties of CNDs can be changed. For potential applications of CNDs as advanced materials for optoelectronic devices, it is important and significant to develop the practical techniques for doping heteroatoms into CNDs. In this work, we synthesize the multi-color fluorescent by using a fast and effective microwave method where the CNDs are nitrogen-doped. We examine the influence of different ratios of the raw materials on the structure and optical properties of N-CNDs. The results show that the prepared N-CNDs can generate blue (445 nm), green (546 nm), and orange (617 nm) fluorescence or PL with the mass ratio of the raw materials at 1:1, 1:2 and 1:3, respectively. We find that the N content in N-CNDs leads to different surface/edge states in domain. Thus, the wavelength of the PL emission from N-CNDs can be tuned via controlling the N concentration doped into the CNDs. Moreover, it is shown that the intensity of the PL from N-CNDs is mainly positively related to the content of C-O groups attached on the surface/edges of the N-CNDs. This study provides an effective experimental method and technical way to improve the fluorescent emission, and to modulate the color of the PL emission from CNDs.

Synthesis of a conjugated polymer film via interfacial Knoevenagel polymerization and conversion to covalent triazine polymer for photocatalysis

The Knoevenagel condensation was applied to the interfacial polymerization of difunctional aldehyde and trifunctional acetonitrile monomers for the first time. The polymerization was conducted at the interface between water containing a base and an organic phase containing the monomers at room temperature for periods ranging from a day to several weeks. The structural and morphological changes of the polymer were investigated to complete the Knoevenagel condensation and, interestingly, the morphological shape of the polymer was significantly changed from particles to film. Specifically, the polymer showed a particle-type product (about 400 nm) at the early stage of polymerization and was transformed to a film-like structure after a prolonged polymerization time. Scanning electron microscope images revealed that the polymer particles were aggregated and connected to each other to form a film, in which each particle was linked by covalent self-assembly. As one of the proofs of the covalent self-assembly, as a result of the increase in the conjugation length, the polymer's fluorescence wavelength was red-shifted after the film formation. Such a red-shift was also observed across the polymer film from the edge (particle) to the central region (film). To improve the photocatalytic performance under visible light irradiation, a triazine group was introduced using the vinylic nitrile group. Using the triazine-containing polymer, almost 100% photodegradation of rhodamine B dye was attained within 30 min.

Horseradish peroxidase-triggered direct in situ fluorescent immunoassay platform for sensing cardiac troponin I and SARS-CoV-2 nucleocapsid protein in serum

Direct in situ fluorescent enzyme-linked immunosorbent assay (ELISA) is rarely investigated and reported. Herein, a direct in situ high-performance HRP-labeled fluorescent immunoassay platform was constructed. The platform was developed based on a rapid in situ fluorogenic reaction between Polyethyleneimine (PEI) and p-Phenylenediamine (PPD) analogues to generate fluorescent copolymer nanoparticles (FCNPs). The formation mechanism of FCNPs was found to be the oxidation of •OH radicals, which was further proved by nitrogen protection and scavenger of •OH radicals. Meantime, the fluorescence wavelength of FCNPs could be adjusted from 471 to 512 nm by introducing various substitution groups into the PPD structure. Using cardiac troponin I (cTnI) and SARS-CoV-2 nucleocapsid protein (N-protein) as the model antigens, the proposed fluorescent ELISA exhibited a wide dynamic range of 5–180 ng/mL and a low limit of detection (LOD) of 0.19 ng/mL for cTnI, and dynamic range of 0–120 ng/mL and a LOD of 0.33 ng/mL for SARS-CoV-2 N protein, respectively. Noteworthy, the proposed method was successful applied to evaluate the cTnI and SARS-CoV-2 N protein levels in serum with satisfied results. Therefore, the proposed platform paved ways for developing novel fluorescence-based HRP-labeled ELISA technologies and broadening biomarker related clinical diagnostics.

Colorimetric Sensing of Benzoyl Peroxide Based on the Emission Wavelength-Shift of CsPbBr3 Perovskite Nanocrystals

Using the ionic salt characteristics of CsPbBr3 perovskite nanocrystals (CsPbBr3 NCs), the fluorescence wavelength of CsPbBr3−xIx NCs could be changed by the halogen exchange reaction between CsPbBr3 NCs and oleylammonium iodide (OLAM-I). Under the excitation of a 365 nm UV lamp and the increase of OLAM-I concentration, the content of iodine in CsPbBr3−xIx NCs increased, and the fluorescence emission wavelength showed a redshift from 511.6 nm to 593.4 nm, resulting in the fluorescence color change of CsPbBr3 NCs from green to orange-red. Since OLAM-I is a mild reducing agent and easily oxidized by benzoyl peroxide (BPO), a novel colorimetric sensing approach for BPO based on the fluorescence wavelength shift was established in this study. The linear relationship between the different wavelength shifts (Δλ) and the concentration of BPO (CBPO) is found to be in the range of 0 to 120 μmol L−1. The coefficient of alteration (R2) and the detection limit are 0.9933 and 0.13 μmol L−1 BPO, respectively. With this approach, the determination procedure of BPO in flour and noodle samples can be achieved in only a few minutes and exhibit high sensitivity and selectivity.

Indium nanoparticle-based surface enhanced fluorescence from deep ultraviolet to near-infrared: A theoretical study

Herein, for the first time, we report a theoretical investigation on Indium nanoparticle-based surface enhanced fluorescence (SEF) from deep ultraviolet (UV) to near-infrared (NIR). In the beginning, the far- and near-field plasmonic properties of the Indium nanospheres of different sizes are studied to extract the wavelengths of lower and higher-order localized surface plasmon modes and the corresponding local electric field enhancement (EFE) values. Later, the dependence of the SEF enhancement with the separation between the fluorophore and nanoparticle (d), fluorescence, and excitation wavelengths is studied systematically. The role of the surrounding medium on plasmon mode wavelength and the SEF enhancement is also shown. Moreover, the effect of d and fluorescence wavelength on the average SEF enhancement is investigated. Finally, the variation in the plasmonic properties after thin dielectric coating on the surface of single Indium nanospheres is studied.

N-quaternization of heterocyclic compound extended the emission to NIR with large Stokes shift and its application in constructing fluorescent probe

This is great significant to establish a method that extends the small molecules fluorescence emission wavelength to the near-infrared region (NIR) for in vivo imaging. Hence, we firstly reported a novel fluorogenic scaffold QOH that could extend its fluorescence wavelength from (λem = 555 nm) to NIR (λem = 720 nm) with a large Stokes shift (120 nm) by forming its N-quaternization product (QMOH). In addition, the effect of the introduction of substituent at different modification sites and the properties of substituent on the optical properties of QOH were fully discussed by theoretical calculation. To investigate the possibility of QOH as probe construction, the compound Q-SH and QM-R were synthesized and applied to detect H2S and H2O2 in vitro and in vivo, respectively. This study provided an efficient strategy to extend fluorescence emission to NIR and design fluorescence probes with large ratio variation for accurately imaging biomarkers in biological system.

Effect of donor and acceptor on optoelectronic properties of benzo[1,2-b:4,5-b′]dithiophene

A series of acceptor and donor groups anchored to benzo[1,2-b:4,5-b′]dithiophene (BDT) molecule have been systematically investigated at the density functional theory (DFT) and time-dependent density functional theory (TDDFT) level to reveal structure–property relationships, charge transfer, and fluorescence lifetimes. The DFT optimization shows that the hetero atom in the ring induces the polarity from central ring to both ends of the thiophene ring, participating in the conjugation. The donor and acceptor groups were anchored at the terminals of the BDT at two different positions to fine-tune the properties according to the requirement and study the push–pull effect. All the models studied in this work retain their aromaticity as estimated from NICS(0) and NICS(1) aromaticity index in ground and excited states. The results show that the hardness, softness, HOMO–LUMO gaps, ionization potentials (IP), and electron affinities (EA) of the BDTs are significantly affected by the electron-withdrawing and electron-donating groups. The 1H and 13C NMR chemical shift values have been computed to quantify the push–pull effect. Further, the charge transfer properties in these BDTs were explored based on reorganization energies and diagnostic descriptors derived from hole–electron theory that present different electron excitation behavior. The relationship between the computed variables such as highest occupied molecular orbital, lowest unoccupied molecular orbital, oscillator strength, dipole moment, absorption, and fluorescence energy correlates the system with one another and also to extend the possible applications of the system in optical devices. Structure–property relationship of various BDTs reveal that, upon optical excitation, the resonance effect plays an important role changing the bonding character between the substituent and BDT unit, enabling efficient electron delocalization. The examination of TDDFT results indicates that among the various models studied in this work, nitro-substituted model is better candidate for optoelectronic properties with relatively large absorption wavelength and long fluorescence lifetime.