Short-wavelength Emission Research Articles

Glare at Night-Time Driving: Effect of Correlated Color Temperature of Led Lamps.

This study aims to analyze the effect of correlated color temperature from LED glare sources on driving performance. The evaluation includes assessing the effect of disability glare on visual reaction time and rating discomfort glare using a standardized scale. LED technology is widely incorporated into various lighting systems; however, the impact of glare from oncoming car headlamps on driving performance at night-time is crucial for road safety. Twenty-three healthy young subjects participated in a laboratory-based experiment simulating night driving using a two-channel Maxwellian view optical system. Two LED lamps with correlated color temperature of 2800K and 6500K were used to generate a glare of 52 lx. Disability glare was quantified in terms of foveal reaction time and discomfort glare was rated using the de Boer scale. The results show that glare-induced effect is mitigated by an increase in background luminance. The correlated color temperature of the LED lamp does not affect either reaction time or discomfort glare rating. The greater short-wavelength emission of 6500K lamp does not intensify the effect of disability or discomfort glare, probably due to the macular pigment absorption on foveal vision and the transparency of ocular media, coupled with the involvement of other contributing factors. The correlated color temperature of the lamp is not the best descriptive parameter to identify its effect on glare. It is important to consider the impact of LED technology on visual performance to enhance road safety in critical glare situations during night driving.

Turn-On NIR-II Polymer Dots with Large Stokes Shift for In Vivo Visualizing Dynamical Brain Zinc in Alzheimer's Disease Mouse.

It is a critical and broad prospect to evaluate ion levels and monitor their dynamic changes in the brain for early diagnosis, in-depth mechanism investigation, and accurate staging of neurodegenerative diseases including Alzheimer's disease (AD). It is still a great challenge to in vivo track Zn2+ levels in the brain by fluorescence imaging due to the drawbacks including short emission wavelength, poor selectivity and sensitivity, and unfavorable penetration across the blood-brain barrier (BBB) for currently developed fluorescent probes. We herein engineer a fluorescent probe with a large Stokes shift of 256 nm, NNDPTQ Pdots, which display substantial Zn2+-specific turn-on response in the NIR II region with the longest emission of 1064 nm up to now. The probe shows a fast response within seconds, high selectivity, low-nanomolar affinity of 6 nM, low detection limit of 3.4 nM, and efficient BBB-permeability efficacy of 37%. The results of brain imaging demonstrate that brain Zn2+ level in AD mice is substantially higher than normal mice and also is elevated with the prolonging of AD-bearing time. This study may provide a promising fluorescent indicator for in vivo tracing of brain Zn2+ levels to reveal AD pathogenesis.

Redox-switchable multicolor luminescent polymers for theragnosis of osteoarthritis

Nonaromatic and nonconjugated fluorescent materials have garnered increasing attention in recent years. However, most non-classical chromophores are derived from electro-rich nitrogen and oxygen atoms, which suffer from short emission wavelengths, low efficiency, limited responsiveness, and obscure luminescence mechanisms. Here we present an emission mechanism in bioactive polycysteine, an aliphatic polymer that displays polymerization- and aggregation-induced emission, high quantum yield, and multicolor emission properties. We show that the hydrogen atoms bonded to the sulfur atoms play a crucial role in luminescence. This enables reversible modulation of polymer fluorescence under reducing and oxidizing conditions, facilitating specific imaging and quantitative detection of redox species in cells and in vivo. Furthermore, the polymer exhibits better anti-inflammatory and antioxidative activities compared to first-line clinical antioxidants, offering a promising platform for in vivo theragnosis of diseases such as osteoarthritis.

A Novel Fluorescent Chemosensor for Sensitive and Rapid Determination of Pb(II) Ions in Aqueous Environments.

This investigation devised an eco-friendly spectrofluorometric Pb(II) ion measurement approach. To determine Pb(II) ions, a polymeric fluorescence sensor membrane with excellent selectivity has been developed. It contains photoinitiators, functional monomers that can be cured under UV radiation, and cross-linking agents. After the characterization of the membrane, the most suitable parameters for the measurement of Pb(II) ions were determined. The measurement was performed in a short time-roughly 40s-at emission and excitation wavelengths of 488nm and 277nm, respectively, at pH 6.0. The developed method's detection limit was calculated as 1.42 × 10- 9 mol L- 1, and its calibration range was recorded as 4.83 × 10- 9 to 9.66 × 10- 8 mol L- 1. Recovery studies and the sensor's stability, lifetime, and repeatability have been evaluated. Real sample applications have been implemented using wastewater samples. The suggested approach may be used to quickly and accurately determine Pb(II) ions at low concentrations with good selectivity and sensitivity.

A Paradox of LED Road Lighting: Reducing Light Pollution Is Not Always Linked to Energy Savings

A variety of LED types can be employed for street and road lighting purposes. White phosphor-converted LEDs represent the most widely used option. However, amber LEDs are increasingly being used to reduce some negative effects associated with light pollution. These LEDs can be manufactured using both phosphor-converted and monochromatic direct chip technologies. This paper addresses the link between the reduction in short-wavelength light emissions which contribute to sky glow and the energy efficiency of LED-based road lighting. This paper focuses on an example illustrating the common misconception that reducing light pollution also means saving energy. Through the consideration of how spectral power distribution influences both mesopic vision and the amount of emitted blue light, it has been concluded that while monochromatic direct amber LEDs consume more energy than their white or amber phosphor-converted counterparts, their use in outdoor lighting is justifiable due to their potential effects of reducing sky brightness.

Bivariate tracking of NIR phototherapeutic probe that illuminates the deterioration process of NAFLD-HCC

Non-alcoholic fatty liver disease (NAFLD) has evolved to become a major cause of hepatocellular carcinoma (HCC). Visualization of NAFLD-HCC deterioration process imaging is essential to understand the underlying pathophysiological processes. However, currently relevant probes with short emission wavelengths, univariate and the inability to achieve theranostics functionality have encountered obstacles in further evaluating the NAFLD-HCC process. Here, we present a carboxylesterase (CE)-activated NIR fluorescent probe (BODJ) which has lipid droplets (LDs)-targeting ability and emits at a wavelength of 858 nm with a fluorescence quantum yield of 19.06%. CE-activated BODJ was used as a visual tool to successfully visualize both NAFLD deterioration processes and HCC in situ based on changes in the average number of LDs and the associated fluorescence intensity fluctuations. Imaging results showed that changes associated with CE and LDs in the modelled cells varied during the transition from nonalcoholic fatty liver to nonalcoholic steatohepatitis and later progression to HCC, highlighting the close association between bivariate and disease. We also demonstrate that BODJ has photodynamic (PDT) and photothermal therapy (PTT) capabilities, allowing image-guided dual phototherapy to damage HCC in situ. This NIR probe, which takes advantage of bivariate to track the deterioration process that illuminates NAFLD-HCC and has dual phototherapy capabilities, provides new ideas for the design of probes related to the diagnosis and treatment of hepatic metabolic diseases.

Near-infrared xanthene fluorescence probe for frequency upconversion fluorescence detection of HSO3− in evaluation of drug-induced hepatotoxicity

Bisulfite (HSO3−) plays an important role in life activities. Abnormal content of HSO3− may cause cardiovascular, cancer and other diseases. Frequency upconverted luminescent (FUCL) probes are a class of anti-Stokes luminescent materials with long-wavelength excitation and short-wavelength emission properties, which offer advantages in a range of applications due to their higher sensitivity and photostability. In addition, FUCL imaging has the advantages of high tissue penetration depth and low photo-damage, thus, it is more suitable for fluorescence imaging. In this work, a FUCL probe based on an xanthene fluorophore was designed and synthesised to detect HSO3−. The Probe PT-1 could respond to HSO3− and had high selectivity and sensitivity. It also exhibited a quenched FUCL signal. The detection limit of FUCL concerning HSO3− was 43 nM (λex = 730 nm), which is half the detection limit achieved under traditional excitation (93 nM, λex = 643 nm). Cell fluorescence imaging showed that PT-1 could effectively target mitochondria and monitor endogenous/exogenous HSO3− in living cells. More importantly, PT-1 was successfully used to monitor the level of HSO3− in mice with drug-induced liver injury through FUCL imaging.

Two‐Photon Clusteroluminescence Enabled by Through‐Space Conjugation for In Vivo Bioimaging

AbstractClusteroluminescence (CL) materials without largely conjugated structures have gained significant attention due to their unique photophysical properties and potential in bioimaging. However, low luminescence efficiency and short emission wavelength limit their development. This work designs three luminogens with CL properties (CLgens) by introducing n‐electron‐involved through‐space conjugation (TSC) into diarylmethane. Apart from single‐photon excited long‐wavelength (686 nm) and high‐efficiency (29 %) CL, two‐photon clusteroluminescence (TPCL) is successfully achieved in such small luminogens with only two isolated heteroatomic units. TSC stabilized in the aggregate state has been proven to realize efficient spatial electron delocalization similar to conventionally conjugated compounds. Encouraged by the excellent TPCL properties, two‐photon imaging of blood vessels in vivo and biocompatibility verification utilizing CLgens are also achieved. This work illustrates the essential role of TSC in promoting nonlinear optical properties of CLgens and may facilitate further design and development of the next generation of bioprobes with excellent biocompatibility.

Visualization of Mitochondrial DNA G-Quadruplexes with Isaindigotone Derived Near-Infrared Fluorogenic Probe.

Mitochondrial DNA G-quadruplexes (mtDNA G4s) play potential regulatory roles in mitochondrial functions. Fluorescent probes for imaging mtDNA G4s may provide useful information to unveil their regulating dynamics and functions. However, the existing probes for mtDNA G4s still exhibit short absorption and emission wavelengths and limited sensitivity. Here, we develop a new isaindigotone-derived near-infrared (NIR) fluorogenic probe for imaging mtDNA G4s in live cells and in vivo. Different fluorescent probes are engineered by conjugating the isaindigotone scaffold with varying electron-donating groups. It is shown that the probe ISAP using dimethylaminophenyl as the electron-donating group exhibits near-infrared absorption/emission and a high fluorescence activation fold in response to G4s. Molecular docking simulations reveal that ISAP binds to c-Myc G4 via multiple π-π stacking and hydrogen-bond interaction. Cellular studies show that ISAP exhibits an excellent mitochondrial targeting ability and allows specific imaging of mtDNA G4s. We further employed ISAP to image the dynamics of mtDNA G4s under glycolysis and oxidative stresses in live cells. Its capability to mtDNA G4s in vivo is showcased using a tumor-bearing mice model. This probe may serve as a useful tool to image mtDNA G4s and interrogate their biological roles in living systems.

Universal sulfatase-based chemiluminescence biosensing platform: Validation via AFP detection in clinical blood samples

Enzyme-catalyzed chemiluminescence has been widely used in the field of biomedicine, especially in the test kit for various biomarkers. However, the currently reported enzyme-catalyzed chemiluminescence systems suffered from the addition of oxidizing substances, short emission wavelength, and susceptibility to interference by autofluorescence. In this paper, a universal sulfatase-based chemiluminescence system with NIR was developed, in which the designed substrate QM-CF could be transformed into 1,2-dioxetane derivate in the presence of sulfatase and oxygen. This system exhibited long emission wavelengths and CL half-time, a high signal-noise ratio, and without other additives. Importantly, the sulfatase-based chemiluminescence enzyme-linked immunoassay platform was successfully constructed and could be generally applied to detect biomarkers. As a proof of concept, the sulfatase-labeled AFP antibody and substate QM-CF were conveniently suitable for commercial AFP test kits, leading to satisfactory detection results of AFP in clinical blood samples.

Achieving Ultrasound-Excited Emission with Organic Mechanoluminescent Materials.

Unlike traditional photoluminescence (PL), mechanoluminescence (ML) achieved under mechanical excitation demonstrates unique characteristics such as high penetrability, spatial resolution, and signal-to-background ratio (SBR) for bioimaging applications. However, bioimaging with organic mechanoluminescent materials remains challenging because of the shallow penetration depth of ML with short emission wavelengths and the absence of a suitable mechanical force to generate ML in vivo. To resolve these issues, the present paper reports the achievement of ultrasound (US)-excited fluorescence and phosphorescence from purely organic luminogens for the first time with emission wavelengths extending to the red/NIR region, with the penetrability of the US-excited emission being considerably higher than that of PL. Consequently, US-excited subcutaneous phosphorescence imaging can be achieved using a mechanoluminescent-luminogen-based capsule device with a quantified intensity of 9.15 ± 1.32 × 104 p s-1 cm-2 sr-1 and an SBR of 24. Moreover, the US-excited emission can be adequately tuned using the packing modes of the conjugated skeletons, dipole orientation of mechanoluminescent luminogens, and strength and direction of intermolecular interactions. Overall, this study innovatively expands the kind of excitation sources and the emission wavelengths of organic mechanoluminescent materials, paving the way for practical biological applications based on US-excited emission.

Two-photon Clusteroluminescence Enabled by Through-Space Conjugation for In Vivo Bioimaging.

Clusteroluminescence (CL) materials without largely conjugated structures have gained significant attention due to their unique photophysical properties and potential in bioimaging. However, low luminescence efficiency and short emission wavelength limit their development. This work designs three luminogens with CL properties (CLgens) by introducing n-electron-involved through-space conjugation (TSC) into diarylmethane. Apart from single-photon excited long-wavelength (688 nm) and high-efficiency (29%) CL, two-photon clusteroluminescence (TPCL) is successfully achieved in such small luminogens with only two isolated heteroatomic units. TSC stabilized in the aggregate state has been proven to realize efficient spatial electron delocalization similar to conventionally conjugated compounds. Encouraged by the excellent TPCL properties, two-photon imaging of blood vessels in vivo and biocompatibility verification utilizing CLgens are also achieved. This work illustrates the essential role of TSC in promoting nonlinear optical properties of CLgens and may facilitate further design and development of the next generation of bioprobes with excellent biocompatibility.

Tunable multi-peak emission solid-state fluorescent carbon dots: Luminescence regulation mechanism and application in single-component-based LEDs

The design of solid-state fluorescent carbon dots (CDs) with multi-peak emission has become an urgent challenge to be solved with the in-depth research of CDs in LEDs. Here, one- and two-component solid-state white light CDs are synthesized by microwave-assisted hydrothermal method using the biological pollutant cyanobacteria, respectively. The solid-state fluorescence quantum yield of the one-component CDs was as high as 41.8 %, and the solid-state fluorescence mechanism of CDs is discussed to be mainly attributed to the self-quenching-resistant feature of “core-shell” structure and the reabsorption/RET-induced long-wavelength red light emission, and attenuation of the short emission wavelength. For two-component white light CDs, blue- and red-light CDs are obtained by simple dialysis separation, realizing the fluorescence tunability. The different origins of their multi-peak emission are discussed: core, edge and surface states. The synthesis yields of CDs are up to 62 %, enabling stable gram-scale production. The white- and red-light CDs are used as phosphors to fabricate fluorescent films and cold, pure, and warm white- and red-light LEDs with good resistance to photobleaching and temperature stability and CRI of 84.4, 85.7 and 61.5.

Short-Wavelength Emission from a Hot Dense Plasma

Short-Wavelength Emission from a Hot Dense Plasma

Red Fluorescence from Organic Microdots: Leveraging Foldamer-Linked Azobenzene for Enhanced Stability and Intensity in Bioimaging Applications.

Azobenzene, while relevant, has faced constraints in biological system applications due to its suboptimal quantum yield and short-wavelength emission. This study presents a pioneering strategy for fabricating organic microdots by coupling foldamer-linked azobenzene, resulting in robust fluorescence intensity and stability, especially in aggregated states, thereby showing promise for bioimaging applications. Comprehensive experimental and computational examinations elucidate the mechanisms underpinning enhanced photostability and fluorescence efficacy. In vitro and in vivo evaluations disclose that the external layer of cis-azo-foldamer microdots performs a self-sacrificial function during photo-bleaching. Consequently, these red-fluorescent microdots demonstrate extraordinary structural and photochemical stabilities over extended periods. The conjugation of a β-peptide foldamer to the azobenzene chromophore through a glycine linker instigates a blue-shifted and amplified π*-n transition. Molecular dynamics simulations reveal that the aggregated state of cis-azo-foldamers fortifies the stability of cis isomers, thereby augmenting fluorescence efficiency. This investigation furnishes crucial insights into conceptualizing novel, biologically inspired materials, promising stable and enduring imaging applications, and carries implications for diverse arenas such as medical diagnostics, drug delivery, and sensing technologies.

NHC-derived carbon-centered luminescent radicals with short-wavelength emission via suppression of Kasha’s rule

NHC-derived carbon-centered luminescent radicals with short-wavelength emission via suppression of Kasha’s rule

Novel pyrrolidine-alkylamino-substituted dicyanoisophorone derivatives as near-infrared fluorescence probe for imaging β-amyloid in vitro and in vivo

BackgroundThe formation of amyloid-β (Aβ) plaques is one of the key neuropathological hallmarks of Alzheimer's disease (AD). Near-infrared (NIR) probes show great potential for imaging of Aβ plaques in vivo and in vitro. Dicyanoisophorone (DCIP) based Aβ probes have attracted considerable attention due to their exceptional properties. However, DCIP probes still has some drawbacks, such as short emission wavelength (<650 nm) and low fluorescence intensity after binding to Aβ. It is clear that further modification is needed to improve their luminescence efficiency and sensitivity. ResultsWe designed and synthesize four novel pyrrolidine-alkylamino-substituted DCIP derivatives (6a-d) as imaging agents for β-amyloid (Aβ) aggregates. Compound 6c responds better to Aβ aggregates than the other three compounds (6a, 6b and 6d) and its precursor DCIP. The calculated detection limit is to be as low as 0.23 μM. Compound 6c shows no cytotoxicity in the tested concentration for SH-SY5Y and HL-7702 cells. Additionally, compound 6c is successfully applied to monitor Aβ aggregates in live SH-SY5Y cells and APP/PS1 transgenic mice. The retention time in the transgenic mice brain is much longer than that of age-matched wild-type mice. SignificanceThe results indicates that compound 6c had an excellent ability to penetrate the blood-brain barrier and it could effectively distinguish APP/PS1 transgenic mice and wide-type mice. This represents its promising applications for Aβ detection in basic and biomedical research.

Glutathione-activated biotin-targeted dual-modal imaging probe with improved PDT/PTT synergistic therapy

BackgroundGlutathione (GSH), a highly abundant thiol compound within cells, plays a critical role in physiological processes and exhibits close correlation with cancer. Among molecular imaging technologies, most probes have relatively short emission wavelengths and lack photoacoustic imaging (PA) capability, resulting in the inability to obtain tissue images with high penetration depth. The presence of GSH in the tumor microenvironment neutralizes ROS, diminishing the therapeutic effect of PDT, thus resulting in often unsatisfactory therapeutic efficacy. Therefore, it is imperative to develop a dual-modal probe for the detection of GSH and the diagnosis and treatment of cancer. ResultsIn this study, we synthesized a novel dual-modal probe, Cy-Bio-GSH, utilizing near-infrared fluorescence (NIRF) and photoacoustic (PA) imaging techniques for GSH detection. The probe integrates cyanine dye as the fluorophore, nitroazobenzene as the recognition moiety, and biotin as the tumor-targeting moiety. Upon reacting with GSH, the probe emits NIR fluorescence at 820 nm and generates a PA signal. Significantly, this reaction activates the photodynamic and photothermal properties of the probe. By depleting GSH and employing a synergistic photothermal therapy (PTT) treatment, the therapeutic efficacy of photodynamic therapy (PDT) is remarkably enhanced. In-vivo experiments confirm the capability of the probe to detect GSH via NIRF and PA imaging. Notably, the combined tumor-targeting ability and PDT/PTT synergistic therapy enhance therapeutic outcomes for tumors and facilitate their ablation. SignificanceA novel tumor-targeting and dual-modal imaging probe (Cy-Bio-GSH) is synthesized, exhibiting remarkable sensitivity and selectivity to GSH, enabling the visualization of GSH in cells and the differentiation between normal and cancer cells. Cy-Bio-GSH enhances PDT/PTT with effective killing of cancer cells and makes the ablation of tumors in mice. This work represents the first tumor-targeting probe for GSH detection, and provides crucial tool for cancer diagnosis and treatment by dual-modal imaging with improved PDT/PTT synergistic therapy.

Study on the chiroptical properties of carbon dots based on citric acid and formamide with the addition of various chiral molecules

Subject of study. The study focuses on luminescent carbon nanoparticles, specifically carbon dots, based on citric acid, formamide, and various chiral molecules. Aim of study. The aim is to assess the influence of chiral molecules used in the synthesis of carbon dots on optical transitions in the long-wavelength spectral region and to investigate the mechanism underlying the circular dichroism signal of these nanoparticles. Method. Carbon dot samples were synthesized using two methods: (i) a one-step solvothermal synthesis of carbon dots from citric acid, formamide, and various chiral molecules and (ii) a two-step method involving the solvothermal synthesis of achiral carbon dots from citric acid and formamide, followed by surface treatment with L-cysteine. Absorption and luminescence spectroscopy methods were employed to study the chemical structure and optical properties of the carbon dots. The chiroptical properties of the obtained samples were analyzed using circular dichroism spectroscopy. Main results. The addition of various chiral molecules to a mixture of precursors during one-step synthesis enabled the fabrication of carbon dots with different chemical compositions, including variations in surface groups and types of emission centers in the spectral region of 350–700 nm. The use of L-phenylglycine and L-tryptophan in the one-step synthesis was shown to lead to the formation of nanoparticles with optical transitions in both short- and long-wavelength regions of the spectrum. The addition of L-glutathione during the one-step synthesis resulted in the formation of carbon dots with short-wavelength emission, while the addition of L-cysteine did not alter the emission characteristics of achiral carbon dots based on citric acid and formamide. The optical properties of the chiral carbon dots obtained using the two-step synthesis method with L-cysteine remained unchanged compared with those of the achiral carbon dots synthesized from citric acid and formamide. The circular dichroism spectra of all the samples showed a signal at ∼250nm, which was attributed to the derivatives of the chiral precursors attached to the surface of the nanoparticles, irrespective of the preparation method. Practical significance. Chiral carbon dots hold promise in biomedicine as sensors, luminescent biomarkers, and other applications due to their biocompatibility and non-toxicity. The results obtained in this work will serve as a foundation for the further fabrication and investigation of chiral carbon nanoparticles with long-wavelength luminescence.

Neutral Cyanine: Ultra-Stable NIR-II Merocyanines for Highly Efficient Bioimaging and Tumor-Targeted Phototheranostics.

Fluorescence imaging (FLI)-guided phototheranostics using emission from the second near-infrared (NIR-II) window show significant potential for cancer diagnosis and treatment. Clinical imaging-used polymethine ionic indocyanine green (ICG) dye is widely adopted for NIR fluorescence imaging-guided photothermal therapy (PTT) research due to its exceptional photophysical properties. However, ICG has limitations such as poor photostability, low photothermal conversion efficiency (PCE), short-wavelength emission peak, and liver-targeting issues, which restrict its wider use. In this study, two ionic ICG derivatives are transformed into neutral merocyanines (mCy) to achieve much-enhanced performance for NIR-II cancer phototheranostics. Initial designs of two ionic dyes show similar drawbacks as ICG in terms of poor photostability and low photothermal performance. One of the modified neutral molecules, mCy890, shows significantly improved stability, an emission peak over 1000nm, and a high photothermal PCE of 51%, all considerably outperform ICG. In vivo studies demonstrate that nanoparticles of the mCy890 can effectively accumulate at the tumor sites for cancer photothermal therapy guided by NIR-II fluorescence imaging. This research provides valuable insights into the development of neutral merocyanines for enhanced cancer phototheranostics.