Excitation Wavelength Research Articles

ElectroFluor Voltage-Sensitive Dyes: Comprehensive Analysis of Wavelength-Dependent Sensitivity and Cross-Channel Bleed-Through.

New voltage-sensitive ElectroFluor (EF) dyes that emit across the visible and near-infrared spectrum (e.g., 730 nm) were recently developed. We evaluated EF-530, EF-630, and EF-730p-dyes spectrally orthogonal to green fluorescent protein (GFP)-at excitation wavelengths outside the conventional 470 nm range used for GFP-based indicators. Although previously applied in cardiac voltage imaging, their performance in neuronal tissue remains untested. We performed side-by-side comparisons using population voltage imaging in mouse cerebral cortex slices at optimal excitation wavelengths (530, 630, and 730 nm) and assessed cross-channel signal bleed-through across four excitation wavelengths (475, 530, 630, and 730 nm). All dyes produced robust optical signals at their optimal wavelengths, though non-preferred channels exhibited bleed-through with distinct amplitudes, polarities, and photobleaching patterns. These results provide detailed quantifications of EF dye performance for neuronal population imaging.

Environmentally Friendlier Development of Latent Prints on Porous Surfaces Using 1,8-Diazafluoren-9-one (DFO) and iPhone 11

A novel method for the development of fingerprints in environmentally friendlier conditions and on porous surfaces with 1,8-diazafluoren-9-one (DFO) is reported herein. DFO, a fluorescent dye was formulated in glacial acetic acid, methanol, and a minimum amount of methylene chloride. The DFO reacted with amino acid components of latent prints, resulting in a fluorescent species that was visualized under daylight, UV light at 254 nm, 365 nm, and LED at 395–405 nm. The developed prints were photographed using iPhone 11 and IOS 17.4.1. The fluorescent spectra of the species resulting from DFO’s reaction with the amino acid glycine and the wavelengths of maximum excitation (λex = 470 nm) and emission (λem = 585 nm) were also reported. The method is suitable for forensic laboratories.

Multi-wavelength emission nitrogen-doped carbon dots as fluorescent nanosensing platform for the detection of ascorbic acid and their application in bioimaging tracking.

Multi-wavelength emission nitrogen-doped carbon dots as fluorescent nanosensing platform for the detection of ascorbic acid and their application in bioimaging tracking.

Intercalation of Transition-Metal Complexes into 2D Hybrid Perovskites for Tailored Dual-Band Emission.

The recently emerging two-dimensional (2D) hybrid lead-halide perovskites are mostly templated by "inert" organic cations, limiting their light emission solely from the inorganic components. Using "optically active" organic cations can grant access to the coupling between two luminescent components, potentially leading to new excitation and emission pathways. However, employing optically active organic cations requires delicate design and complicated synthesis. To circumvent these problems, transition-metal complexes (Cu2+ and Ni2+) were intercalated in 2D perovskites and reported, for the first time, the photoluminescence (PL) profiles. 2D perovskites incorporating transition-metal complexes can be considered a molecular "type II" heterostructure where"conduction band" is localized on the complexes and"valence band" on the haloplumbate layers. As evident in the absorption and PL spectra of the materials, the "type II" configuration allows inter-band transitions to occur in addition to intraband within 2D Pb-Br layers. This makes the material's PL excitation wavelength dependent, allowing activation of only inter-band or inter-band plus intraband transitions by certain wavelengths. As the transition-metal complexes are highly tunable, this extra variable renders 2D hybrid perovskites a fertile playground for PL engineering as desired outcome can be targeted through fine-tailoring of inorganic lattice structures and selection of complexes with specific electronic configuration.

Dual-mode thermochromic afterglow in phosphorus-doped carbon dot composites for visible light-activated information encryption.

Dual-mode thermochromic afterglow in phosphorus-doped carbon dot composites for visible light-activated information encryption.

4D Encryption System: Hydrophilic–Hydrophobic Polyurethane Actuators with Smart Color Switching for High‐Capacity Data Storage

AbstractNatural communication methods have influenced the creation of sophisticated artificial materials capable of coherent and abundant responses to stimuli, a crucial necessity for developing applications such as dynamic encryption systems and high‐density information storage. However, existing materials for encryption and information storage are limited by predictable, single‐stimulus responses and lack the capacity for dynamic, continuous, and programmable changes. To address this gap, a bioinspired multicolor fluorescent polyurethane actuator is developed that combines dynamic color and shape adaptability within a single material platform. This smart actuator mimics the turgor‐driven movements of Oxalis corniculata through a hydrophilic/hydrophobic network that enables water diffusion, hydrogen bonding, and dynamic bond exchange. It responds to multiple stimuli, including temperature, pH, and excitation wavelength, exhibiting reversible multi‐state deformations and programmable fluorescence across red, green, blue, and even white light. The deformation behavior is supported by finite element simulations, ensuring precise control and predictability. Additionally, the tunable trichromatic fluorescence of the actuator underpins a 3D and 4D information encoding system, demonstrating increased information storage capacity and encryption security. The employment of micro‐processing technology in the fabrication of micro‐hidden optical encryption chips has been demonstrated, thus paving the way for underwater communication encryption technologies and adaptive materials.

A PEGylated conjugated-BODIPY oligomer for NIR-II imaging-guided photothermal therapy.

The integration of second near-infrared (NIR-II) fluorescence imaging and photothermal therapy (PTT) achieved precise and efficient tumor treatment. BODIPY, a promising fluorescent dye, is widely used in biological fluorescence imaging due to its excellent optical properties and chemical stability. However, the excitation wavelengths of BODIPY typically range from 530 nm to 650 nm within the visible spectrum, which significantly limits tissue penetration. In this work, a self-assembled nanoparticle (BODIPY4-PEG NP) was fabricated with a BODIPY-conjugated oligomer (BODIPY4) bearing a hydrophilic polyethylene glycol (PEG) chain. BODIPY4-PEG NPs exhibit excellent NIR-II emission, with a maximum fluorescence emission peak of 1123 nm. The outstanding imaging performance of BODIPY4-PEG NPs has been evaluated in the imaging of lymph nodes and the vascular system in mice, demonstrating excellent spatial resolution. Based on the excellent imaging performance and photothermal conversion efficiency (35%) of the BODIPY4-PEG NPs, they can be further utilized in NIR-II imaging-guided photothermal therapy. In a 4T1 tumor-bearing mouse model, BODIPY4-PEG NPs exhibited strong fluorescence under 980 nm laser irradiation and successfully induced heat generation to eliminate the tumor. To summarize, BODIPY4-PEG NPs contribute to the ongoing progress in the field of NIR-II fluorescence imaging-guided PTT.

Raman-Polarization-Fluorescence Spectroscopic Lidar for Real-Time Detection of Humic-like Substance Profiles.

Humic-like substances (HULIS) widely exist in the atmosphere and may strongly affect human health, environment, and climate. However, there are still no accurate methods for detecting the vertical distribution of HULIS. Here, a Raman-Polarization-Fluorescence Spectroscopic Lidar (RPFSL) was developed to simultaneously measure 64-channel broad fluorescence spectra (370-710 nm) of atmospheric aerosols at an excitation wavelength of 355 nm. The study revealed that dust could be coated by abundant fluorescent substances, with a maximum fluorescence efficiency reaching 0.15. Moreover, the fluorescent spectra of air pollutants exhibited a unimodal structure, while the spectra of dust exhibited three peaks, suggesting that they may be useful for highly accurate identification of dust aerosols from other aerosols. The findings in this study were confirmed by near-ground air sampling analysis based on fluorescence excitation-emission matrix-parallel factor (EEM-PARAFAC) methods; we demonstrated that HULIS and protein-like organic matter (PLOM) were the main components of fluorescent aerosols during the study period. During air pollution events, the number concentration of HULIS reached up to 9699 particles·m-3. For the first time, this study proposes a real-time, high-resolution method for detecting height-resolved HULIS, significantly helping to evaluate the environmental and health implications of HULIS.

Multicolor Upconversion Luminescence from Single Materials

Upconversion (UC) luminescence (UCL) from single materials has garnered significant attention in recent years due to its potential applications in bioimaging, anti‐counterfeiting, and display technologies. This review explores the most recent developments in achieving multicolor UCL using single materials. We provide a detailed discussion of the strategies used to obtain multicolor UCL from single materials, including structural design, modifications to excitation power density, control of excitation pulse width, changes in excitation wavelength, temperature adjustments, and the use of time‐resolved techniques for dynamic UCL color tuning. The review examines the basic mechanisms behind parameter manipulation and their direct impact on the UC process, highlighting their adaptability for a broad spectrum of applications. Moreover, we examine current challenges and outline potential future directions for the progress of multicolor UCL based on single materials.

Full-color tuning in multi-layer core-shell nanoparticles from single-wavelength excitation

Lanthanide-based luminescent materials have shown great capabilities in addressing scientific problems encountered in diverse fields. However, achieving full-color switchable output under single-wavelength irradiation has remained a daunting challenge. Here we report a conceptual model to realize this aim by the temporal control of full upconversion evolution in a multi-layer core-shell nanostructure upon a single commercial 980-nm laser, instead of two or more excitation wavelengths as reported previously. We show that it is able to realize the red-to-green color change (from Er3+) under non-steady state excitation by constructing the cooperative modulation effect in the Er-Tm-Yb triple system, and single out the blue light (from Tm3+) by filtering out the short-decay emissions via a time-gating technique. The key role of Tm3+ in manipulating up-transition dynamics of Er3+ is further demonstrated. Our results present a deep insight into the photophysics of lanthanides, and help develop new generation of smart luminescent materials toward emerging photonic applications.

MetaMax: an objective-sized instrument for advanced light microscope characterization and performance metadata collection

MetaMax is a device designed to replace the objective lens in light microscopes and provide a wide range of performance metadata that characterize microscope hardware behavior. MetaMax includes a large-area photodiode that is referenced against calibrated power meters to measure excitation light power and source stability; a broadband LED to quantify detector system responsivity and signal-dependent noise; a spectrometer to identify excitation wavelengths; an adjustable iris to simulate an objective’s back aperture; and a quadrant photodiode to assess beam alignment and aperture overfill. MetaMax enables users to collect performance metadata for quality control, image provenance, and comprehensive acquisition parameter delineation. It simplifies access to performance data that typically requires expert knowledge and expensive equipment to obtain, lowering the access barrier for users. Such performance data is crucial metadata for improving the reliability and reproducibility of microscopy images. The MetaMax aims to facilitate collaboration through data reusability and promote a more rigorous, transparent approach to scientific inquiry using light microscopy techniques. This work presents a detailed evaluation and comparison of several MetaMax prototypes.

Quantitation of adulterated honey by three-dimensional fluorescence

Abstract Honey products adulterated with syrup need to be availably distinguished from the true ones and quantified by modern method, for instance three-dimensional fluorescence spectroscopy. The spectra from eight types of honey showed that a linear relationship existed between fluorescence intensity and honey solution concentration in two excitation wavelength ranges of 240–320 nm and 320–360 nm when honey was diluted to 1 % (V:V) or less. Based on the linearity, a way was proposed to estimate the purity of adulterated honey by employing the least squares model to compare the spectra of adulterated honey with honey and syrup on a computer, after they were properly diluted. Honey artificially mixed with syrup in a ratio of 3:7 (V:V) was evaluate to be 31.6 % and the error was only 1.6 %. The method of quantitation on adulterated honey has the characteristics of convenience and accuracy.

Green Carbon Dots from Pinecones and Pine Bark for Amoxicillin and Tetracycline Detection: A Circular Economy Approach

Over the years, the abuse of antibiotics has increased, leading to their presence in the environment. Therefore, a sustainable method for detecting these substances is crucial. Researchers have explored biomass-based carbon dots (CDs) to detect various contaminants, due to their low cost, environmental friendliness, and support of a circular economy. In our study, we reported the synthesis of CDs using pinecones (PCs) and pinebark (PB) through a sustainable microwave method. We characterized the PCCDs and PBCDs using X-ray diffraction, Raman spectroscopy, Transmission Electron Microscope, and Fourier transform infrared, Ultraviolet-visible, and photoluminescence (PL) spectroscopy. The PCCDs and PBCDs were tested for the detection of amoxicillin (AMX) and tetracycline (TC). The results indicated that the sizes of the PCCDs and PBCDs were 19.2 nm and 18.39 nm, respectively, and confirmed the presence of the 002 plane of the graphitic carbon structure. They exhibited excitation wavelength dependence, good stability, and quantum yields ranging from 6% to 11%. PCCDs and PBCDs demonstrated “turn-off” detection for TC and AMX. The limits of detection (LOD) for TC across a broader concentration range were found to be 0.062 µM for PCCDs and 0.2237 µM for PBCDs. For AMX detection, PBCDs presented an LOD of 0.49 µM.

LIFSim, a modular laser-induced fluorescence code for concentration and temperature analysis of diatomic molecules

Laser-induced fluorescence (LIF) is a non-invasive optical diagnostics technique frequently used in reactive media to measure physical properties such as gas-phase species concentrations and temperature. It provides important information for understanding reaction and transport processes. For deriving detection schemes that provide selective and quantitative information, fluorescence spectra of the species of interest as well as potential interference sources must be simulated. LIFSim 4.0 is a modular software for simulating absorption, LIF excitation, and LIF emission spectra of NO, SiO, OH, and O2 that also can be extended by the user to include other species. Line positions, line broadening, and collisional quenching are calculated based on spectroscopic data from literature. The code provides spectral analysis tools to interrogate and analyze sensitive spectral regions suitable for derivation of temperature from multi-line LIF measurements. The library includes fitting functions optimized for enhancing and accelerating the post-processing of stacked LIF images with varied excitation wavelength for temperature imaging and separation of the target LIF signal from broad-band or scattering background as well as tools for assessing the validity of results in non-ideal measurement situations.

Defect Assisted Multicolor Luminescence in Borosilicate Photonic Glass for High‐Level Anticounterfeiting and X‐Ray Imaging

AbstractRare earth‐doped glasses have attracted extensive attention due to their excellent luminescent property. It is of great significance for the development of optical functional glass to obtain unique luminescent properties through glass structural regulation. Here, via structural optimization, multicolor luminescent borosilicate glasses with dual luminescence centers (Ce3⁺ ions and oxygen vacancy defect) are obtained. Leveraging the distinct luminescent traits of these two centers, tunable luminescence colors ranging from purple to orange–red are achieved by varying the excitation wavelength and temperature. Under X‐ray excitation, the glasses exhibit one of the highest scintillation luminescence intensities (85.69% of Bi4Ge3O12 crystal) among the Ce3+‐doped glasses reported in recent years, and the imaging resolution (11 LP mm−1) is comparable to CsI:Tl crystal. Capitalizing on their multicolor luminescence characteristics and excellent scintillation performance, a 3D optical anti‐counterfeiting scheme and an X‐ray imaging model are developed, demonstrating promising practical applications. After being stored under ambient conditions for two years, the luminescent intensity retains more than 98% of its initial value, underscoring the exceptional luminescence stability of the glass. This work not only presents a multifunctional material for high‐level anti‐counterfeiting and X‐ray imaging but also provides insights into borosilicate glass design.

Influence of Measurement Geometry and Blank on Absolute Measurements of Photoluminescence Quantum Yields of Scattering Luminescent Films.

For a series of 500 μm-thick polyurethane films containing different concentrations of luminescent and scattering YAG:Ce microparticles, we systematically explored and quantified pitfalls of absolute measurements of photoluminescence quantum yields (Φf) for often employed integrating sphere (IS) geometries, where the sample is placed either on a sample holder at the bottom of the IS surface or mounted in the IS center. Thereby, the influence of detection and illumination geometry and sample position was examined using blanks with various scattering properties for measuring the number of photons absorbed by the sample. Our results reveal that (i) setup configurations where the scattering sample is mounted in the IS center and (ii) transparent blanks can introduce systematic errors in absolute Φf measurements. For strongly scattering, luminescent samples, this can result in either an under- or overestimation of the absorbed photon flux and hence an under- or overestimation of Φf. The size of these uncertainties depends on the scattering properties of the sample and instrument parameters, such as sample position, IS size, wavelength-dependent reflectivity of the IS surface coating, and port configuration. For accurate and reliable absolute Φf measurements, we recommend (i) a blank with scattering properties closely matching those of the sample to realize similar distributions of the diffusely scattered excitation photons within the IS, and (ii) a sufficiently high sample absorption at the excitation wavelength. For IS setups with center-mounted samples, measurement geometries should be utilized that prevent the loss of excitation photons by reflections from the sample out of the IS.

Photochemical Pathways and Light-Enhanced Radical Scavenging Activity of 1,8-Dihydroxynaphthalene Allomelanin.

Melanins play important roles in nature, particularly in coloration and photoprotection, where interaction with light is essential. Biomimetic melanins represent an advantageous alternative to natural melanin for technological applications, sharing the same unique biocompatibility, as well as optoelectronic properties. Allomelanin, derived from 1,8-dihydroxynaphthalene, has been reported to exhibit even better photoprotective and antioxidant properties than the most studied example of biomimetic melanin, polydopamine. However, the interaction of allomelanin with light remains largely unexplored. Here we report the excited state dynamics of allomelanin in a wide range of time windows from femtoseconds to microseconds to minutes, using different experimental techniques, i.e., ultrafast transient absorption, nanosecond transient absorption, X-band electron paramagnetic resonance and radical quenching assays. We find that the photophysics of allomelanin starkly differs from that of the widely studied polydopamine, with broadband excitonically coupled states funneling the absorbed energy to a lower energy species in less than 1 ps. Independent of the excitation wavelength, a long-lived (>450 μs) photoproduct is populated in ≈24 ps. Quantum chemistry calculations suggest that the photoproduct primarily exhibits the character of localized 1,8-naphthoquinone radical anions. This light-driven increase in the anionic semiquinone-like radical concentration enhances the antioxidant activity of allomelanin. These results suggest that the two mechanisms considered at the basis of photoprotection, light-extinction and antioxidant action, are indeed synergistic in allomelanin and not independent, paving the way for new applications of allomelanin in nanomedicine, photocatalysis, energy conversion and environmental remediation.

Synthesis of heteroatom doped polymer coated nanomaterials for slow and controlled drug release in the physiological microenvironment.

This study aimed to develop doped carbon dots and coat them with carboxyl-polymer to explore their applications in imaging living tissue cells and achieving targeted drug release, particularly for tumor therapy. The synthesis of NP-CDs involved a one-pot hydrothermal reaction of seaweed powder, ethylene diamine, and phosphoric acid at atmospheric pressure. Subsequently, the NP-CDs were coated with carboxyl-mounted PEG to create PEG@NP-CDs, serving as a nano carrier for delivering the anti-cancer drug Doxorubicin (DOX). The drug delivery capabilities of PEG@NP-CDs were assessed, and their sensitivity to variations in pH value was studied. The hydrothermal reaction successfully yielded NP-CDs with distinctive fluorescence properties, exhibiting green fluorescence at 430 nm and varying emission peaks depending on the excitation wavelength used. The subsequent coating of NP-CDs with carboxyl-mounted PEG resulted in PEG@NP-CDs, which demonstrated biocompatibility and potential for drug delivery applications. The MTT assay confirmed the high biocompatibility of PEG@NP-CDs, rendering them suitable for biomedical applications. The study successfully developed a straightforward method to synthesize CDs doped with nitrogen and phosphorus, which exhibited green fluorescence and sensitivity to excitation wavelengths. These nanomaterials have potential for imaging living tissue cells and achieving slow drug release. Their drug delivery capabilities, especially pH sensitivity, make them promising for targeted therapy, particularly in tumors. The biocompatibility of PEG@NP-CDs further supports their safe biomedical use. Overall, PEG@NP-CDs offer a valuable tool for simultaneous imaging and drug delivery, with promising applications in tumor detection and therapy.

Energy transfer up-conversion of Tm,Yb-codoped ZnO grown on ZnO nanowires by sputtering-assisted metalorganic chemical vapor deposition

Abstract We report on the optical characteristics of Tm,Yb-codoped ZnO (ZnO:Tm,Yb) films on ZnO nanowires (NWs). ZnO:Tm,Yb films with controlled concentration ratios of Tm3+ and Yb3+ are grown on the ZnO NWs by sputtering-assisted metalorganic chemical vapor deposition. Characteristic luminescence due to intra-4f shell transitions of Tm3+ and Yb3+ in the ZnO host is observed at 5 K via photoluminescence (PL) characterization. The PL characterization under both indirect and direct excitation of rare earth ions reveals the occurrence of energy transfer up-conversion from Yb3+ to Tm3+. Phonon-assisted energy transfer is identified as the dominant process for up-conversion in the ZnO:Tm,Yb by performing detailed optical characterization including the dependence of excitation wavelength and power.

Comprehensive Raman Fingerprinting and Machine Learning-Based Classification of 14 Pesticides Using a 785 nm Custom Raman Instrument

Raman spectroscopy enables fast, label-free, qualitative, and quantitative observation of the physical and chemical properties of various substances. Here, we present a 785 nm custom-built Raman spectroscopy instrument designed for sensing applications in the 400–1700 cm−1 spectral range. We demonstrate the performance of the instrument by fingerprinting 14 pesticide reference samples with over twenty technical repeats per sample. We present molecular Raman fingerprints of the pesticides comprehensively and distinguish similarities and differences among them using multivariate analysis and machine learning techniques. The same pesticides were additionally investigated using a commercial 532 nm Raman instrument to see the potential variations in peak shifts and intensities. We developed a unique Raman fingerprint library for 14 reference pesticides, which is comprehensively documented in this study for the first time. The comparison shows the importance of selecting an appropriate excitation wavelength based on the target analyte. While 532 nm may be advantageous for certain compounds due to resonance enhancement, 785 nm is generally more effective for reducing fluorescence and achieving clearer Raman spectra. By employing machine learning techniques like the Random Forest Classifier, the study automates the classification of 14 different pesticides, streamlining data interpretation for non-experts. Applying such combined techniques to a wider range of agricultural chemicals, clinical biomarkers, or pollutants could provide an impetus to develop monitoring technologies in food safety, diagnostics, and cross-industry quality control applications.