Emission Wavelength Research Articles

Computational chemistry facilitates the development of second near-infrared xanthene-based dyes.

The dyes in the second near-infrared (NIR-II) region play a crucial role in advancing imaging technology. However, developing small-molecule dyes in NIR-II poses a significant bottleneck to meet the substantial demands in biological fields, which may be attributed to the lack of a rational design strategy. Herein, we designed a series of rhodamine analogs with more red-shifted emission by replacing the oxygen-bridge atom in xanthene-based dyes with -C(CH3)2, -Si(CH3)2, -SO2, and -P(O)Ph. We investigated the frontier molecular orbital, electrostatic potential surfaces, the interaction region indicator, electron-hole distribution, and absorption and emission spectrum of xanthene-based dyes using (time-dependent) density functional theory. Our results demonstrated that these designed small molecular dyes exhibit long emission wavelengths covering 1377-1809nm. We expected these findings to enable the targeted design of long-wavelength rhodamines. Geometry optimization of dyes in the ground and excited states was carried out at ω-B97XD/Def2SVP level using Gaussian 16 A03. The absorption and emission wavelengths were evaluated using 13 functional, including TPSSH, O3LYP, B3LYP*, B3LYP, PBE0, MPW1B95, PBE-1/3, PBE38, MPWB1K, MN15, BHandHLYP, ω-B97XD, and CAM-B3LYP.

Strength in Numbers: A Giant NIR-II AIEgen with One-for-All Phototheranostic Features for Exceptional Orthotopic Bladder Cancer Treatment.

One-for-all phototheranostics that allows the simultaneous implementations of multiple optical imaging and therapeutic modalities by utilizing a single component, is growing into a sparkling frontier in cancer treatment. Of particular interest is phototheranostic agent with emission in the second near-infrared (NIR-II) window. Nevertheless, the practical uses of those conventional NIR-II agents are severely impeded by their unsatisfactory features including insufficient stability, low synthetic yield, to be extended absorption/ emission wavelengths, and inefficient phototheranostic outcomes. Developing exceptional phototheranostic agents is thus highly desirable yet remains formidably challenging. Herein, we synthesized two novel N-heteroacenes-based NIR-II luminogens, namely 2TT-PPT and 4TT-PBPT, by respectively employing pyrene-fused phenaziothiadiazoles and pyrene-fused bisphenaziothiadiazoles as acceptor skeletons. There is strength in numbers by increasing the fusing rings in N-heteroacenes moieties and numbers of appended donors. Compared to less ring-fused 2TT-PPT, the giant molecule 4TT-PBPT shows improved photophysical characteristics, such as enhanced light absorbance, red-shifted wavelengths, higher brightness, favorable reactive oxygen species (ROS) generation, and elevated photothermal conversion efficiency, which render 4TT-PBPT nanoparticles excellent fluorescence-photoacoustic-photothermal trimodal imaging guided photodynamic-photothermal synergistic therapy for orthotopic bladder cancer.

Recent Advances of Organic-Inorganic Hybrid Fluorescent Hyperbranched Polymer: Synthesis, Performance Regulation Strategies and Applications.

The organic-inorganic hybrid fluorescent hyperbranched polymer, including hyperbranched polysiloxane and hyperbranched polyborate, have attracted much attention due to their excellent optical properties and wide range of applications. Hyperbranched polysiloxane and polyborates, prepared by introducing Si or B elements into organic polymer chains at the molecular level through rational molecular design and novel synthesis methods, exhibit outstanding photophysical properties as an indispensable branch of organic-inorganic hybrid fluorescent materials. Herein, this review highlights the recent research progress on hyperbranched polysiloxanes and hyperbranched polyborates, including strategies for regulating their emission wavelengths, quantum yields, and fluorescence lifetimes, potential emission mechanisms, and various applications. Finally, some challenges and promising future directions in the field of organic-inorganic hybrid fluorescent polymers are summarized.

Optical Performance of Quantum Dots and Their Applications in Biomedical Imaging

Quantum dots are nanomaterials which have attracted significant focus over the past few years because of their singular optical features. They have shown great potential in the field of bioimaging. This study delves into the photonic properties of quantum dots which include good luminescence stability and broad excitation spectra. Besides, the emission wavelength can be precisely controlled. These properties make them an excellent choice for bio-imaging. The usage of quantum dots in live organism imaging, such as pinpointing cell boundaries, tracking intracellular molecular dynamics, and early disease diagnosis, indicate the immense potential of quantum dots in biomedical realm. Through modifications on the surface of quantum dots, targeted imaging can be realized, which greatly improves the specificity and sensitivity of imaging. Nonetheless, the biosafety and long-term in vivo behavior of quantum dots still need to be further investigated. Overall, the light-based attributes of quantum dots have brought breakthroughs in bio-imaging technology. In addiiton, it would foretell a bright future for quantum dots in the biomedical field.

Lantern-Shaped Structure Induced by Racemic Ligands in Red-Light-Emitting Metal Halide with Near 100 % Quantum Yield and Multiple-Stimulus Response.

Organic-inorganic metal halides (OIMHs) have become a research hotspot in recent years due to their excellent luminescent properties and tunable emission wavelengths. However, the development of efficient red-light-emitting OIMHs remains a significant challenge. This work reports three Mn-based OIMHs derived from 1-methyl-1,2,3,4-tetrahydroisoquinoline hydrobromide: racemic one (Rac-TBM) and chiral ones (R-TBM and S-TBM). As a result of the synergism of chiral organic ligands inducing a unique lantern-shaped hybrid structure containing both tetrahedra and octahedra, Rac-TBM exhibits red-light emission with near-unity luminescence quantum yield. In comparison, the chiral counterparts R/S-TBM display strong green emission and circularly polarized luminescence (CPL) with a glum value up to ±2.5×10-2. Interestingly, a mixture of R- and S-TBM can transform into Rac-TBM, successfully achieving a sensitive and reversible switch between red light of octahedra and green light of tetrahedra under external stimuli. The outstanding luminescent properties allow Rac-TBM to be utilized not only for X-ray radioluminescence with a detection limit down to 46.29 nGys-1, but also for advanced information encryption systems to achieve leak-proof decryption.

Studies of Quantum Dots in Light-Emitting Diodes

Quantum dots are regarded as a revolutionary material especially in display and lighting applications due to their excellent optical properties. Their high quantum efficiency, high color purity, low-cost solution processability, and tunable emission wavelength, facilitate the realization of their potential for display applications. Therefore, researchers have made a lot of effort in the development and characterization of quantum dot light-emitting diodes (QD-LEDs) to achieve high color purity and brightness in light-emitting devices. Meanwhile, with the aim of commercialization, inefficiency, instability, and cost seem to be inevitable challenges that need to be faced. Progression and challenges of using quantum dots in light-emitting diodes are two aspects that are concentrated on in this review. It also affords methods to tackle these challenges. Lastly, the potential applications of QD-LEDs in displays and lighting are investigated. Their potential to revolutionize various industries are also highlighted. By overcoming current limitations and capitalizing on emerging opportunities, QD-LEDs technology will have further applications. This work will help promote in-depth research on QD-LEDs.

Synthesis, Structure, and Optical Property of Tris(biaryldiyl)metal Complexes Consisting of Group 9 Elements.

We report the synthesis and characterization of tris(biphenyl-2,2'-diyl)metal complexes of trivalent group 9 elements (1M, M = Co, Rh, Ir) and their nonplanarly π-extended analogs, tris(1,1'-binaphthyl-2,2'-diyl)metal complexes (2M, M = Rh, Ir). Single crystal X-ray crystallography reveals the distorted octahedral geometry with an approximate C3 symmetry of trianionic complexes 1M (M = Co, Rh, Ir) and 2M (M = Rh, Ir), which are contacted by three Li+ ions in the crystal. Complex 1Ir exhibits yellow luminescence in THF with a photoluminescence quantum yield (ΦPL) of up to 0.73, along with a distinctive photophysical property, namely, a concentration dependence of the emission wavelength from 530 to 580 nm. This is a characteristic property of 1Ir and has not been observed in its isoelectronic analog, tris(2-phenylpyridinato)iridium(III) (Ir(ppy)3). The concentration-dependent optical properties originate from the dissociation equilibria of Li+ ions from the anionic chromophore. Complex 2Ir also exhibits luminescence at 715 nm in THF, with a notable bathochromic shift from 1Ir through the π-extension. The findings offer insights into the photophysical properties of homoleptic organo-transition metal complexes, providing the foundation for the design of related transition metal complexes.

Achieving Flat Ultra‐Broadband NIR Emission in Cr3+ Doped Garnet‐Type Phosphors Enabled by Structural Regulation Toward Multi‐Functional Spectroscopy Applications

AbstractCr3+‐activated near‐infrared (NIR) emitting phosphors are considered as one of the most potential light‐conversion materials for NIR phosphor converted light‐emitting diodes (NIR pc‐LEDs). However, it is still a challenge for a single Cr3+ ion to achieve a flat ultra‐broadband emission toward multi‐functional spectroscopy applications. Herein, a chemical unit co‐substituting strategy is utilized to regulate the crystallographic occupancy of Cr3+ ions, and a flat ultra‐broadband NIR emission is successfully realized with a record emission wavelength of 915 nm in garnet‐type phosphors Ca3Sc2‐xHfxAlxSi3‐xO12: yCr3+ (0 ≤ x ≤ 1, 0.02 ≤ y ≤ 0.06), together with a large full width at half maximum (FWHM) regulation from 130 to 250 nm. The relation between the site occupation of Cr3+ ions in disordered [CaO8], [(Sc, Hf)O6] and [(Si, Al)O4] polyhedrons and the corresponding NIR emission are clarified by carefully evaluating the structural evolution, Raman spectra, electron paramagnetic resonance and time‐resolved emission lifetime spectra of Cr3+ ions. The corresponding crystal field strength of Cr3+ ions is investigated to further clarify the multi‐sites induced flat broadband NIR emission. Finally, a blue light pumped NIR pc‐LED is fabricated with a total output power of 37.58 mW and photoelectric conversion efficiency (PCE) of 13.67%@100 mA, which realizes the multi‐functional applications in night vision imaging, non‐destructive detection and palmprint vein recognition for assistant medical treatment.

Spectrally narrowband simultaneous dual-wavelength emission from Y-branch DBR diode lasers at 785 nm

Y-branch distributed Bragg reflector (DBR) diode lasers with a stable narrowband emission in simultaneous dual-wavelength operation with spectral distances below 3.2 nm are presented. The Y-branch laser consists of two laser branches with different DBR gratings serving as wavelength-selective rear-side mirrors. Therefore, two emission wavelengths with a spectral distance defined by the DBR grating periods can be generated simultaneously. A Y-coupler combines the two ridge waveguide (RW) branches into a single straight output RW. Devices with a spectral distance of 0.6 nm and 2.0 nm emitting around 785 nm are manufactured. Selecting the operation parameters carefully, stable narrowband emission for both wavelengths is obtained. Resistors serving as heaters implemented next to the DBR gratings allow for wavelength adjustment and a tuning of the spectral distance. At an optical output power of 100 mW, the spectral distance can be shifted from 0 to 1.55 nm (0–0.76 THz) for the former device or from 1.00 to 3.15 nm (0.49–1.54 THz) for the latter device, respectively. This makes the Y-branch DBR diode laser particularly interesting for the generation of THz beat-note signals, needed to generate THz radiation via photo-mixing.

A Novel Near-Infrared Tricyanofuran-Based Fluorophore Probe for Polarity Detection and LD Imaging

In this paper, LD-TCF, a targeting probe for lipid droplets (LDs) with a near-infrared emission wavelength and large Stokes shift, was fabricated for polarity detection by assembling a donor–π–acceptor (D–π–A) molecule with typical twisted intramolecular charge transfer (TICT) characteristics. Surprisingly, the fluorescence emission wavelength of the newly constructed probe LD-TCF was stretched to 703 nm, and the Stokes shift was amplified to 126 nm. Furthermore, LD-TCF could specifically answer the change in polarity efficiently and did not experience interference from other biologically active materials. Importantly, LD-TCF exhibited the ability to target lipid droplets, providing valuable insights for the early diagnosis and tracking of pathophysiological processes underlying LD polarity.

All‐Optical Imaging Using Perovskite Nanocrystals Based on Spectro‐Spatial Correlation

AbstractThe exponential growth of data from sensors and internet‐connected devices has challenged traditional electronic computing, particularly in processing speed and power efficiency. Optical information processing, with its inherent high speed and parallelism, offers a promising solution. Moreover, optical processing is vital for developing all‐optical networks, where all‐optical imaging is essential. In this paper, a novel all‐optical imaging technique that leverages in situ anion exchange reactions between perovskite nanocrystals to create an array of pixels with tunable emission wavelengths is proposed. This method enables the conversion of UV light, whether transmitted or reflected by an object, into the visible spectrum, thereby establishing a direct correlation between spectral and spatial information. By employing wavelength division multiplexing (WDM), the approach reduces the dimensionality of information acquisition from two dimensions to one, enhancing imaging speed. This innovation paves the way for significant advancements in all‐optical imaging and image processing, offering new possibilities for faster and more efficient imaging technologies.

High-Efficiency and Stable Emission Wavelength Red InGaN Light-Emitting Diodes with Porous Distributed Bragg Reflectors on Si Substrates

High-Efficiency and Stable Emission Wavelength Red InGaN Light-Emitting Diodes with Porous Distributed Bragg Reflectors on Si Substrates

Sensing the Small Change of Intermolecular Distance in Supramolecular Assembly by Using the Tunable Emission Wavelength of AIE-Active Luminogens.

The distinct molecular states - single molecule, assembly, and aggregate - of two ionic macromolecules, TPPE-APOSS and TPE-APOSS, are easily distinguishable through their tunable fluorescence emission wavelengths, which reflect variations in intermolecular distances. Both ionic macromolecules contain aggregation-induced emission (AIE) active moieties whose emission wavelengths are directly correlated to their mutual distances in solution: far away from each other as individual molecules, maintaining a tunable and relatively long distance in electrostatic interactions-controlled blackberry-type assemblies (microphase separation), or approaching van der Waals close distance in aggregates (macrophase separation). Furthermore, within the blackberry assemblies, the emission wavelength decreases monotonically with increasing assembly size, indicative of shorter intermolecular distances at nanoscale. The emission changes of TPPE-APOSS blackberry assemblies can even be visually distinguishable by eyes when their sizes and intermolecular distances are tuned. Molecular dynamics simulations further revealed that macromolecules are confined in various conformations by controllable intermolecular distances within the blackberry structure, thereby resulting in fluorescence emission with tunable wavelength.

The significance of measuring cosmological time dilation in the Dark Energy Survey Supernova Program

In the context of the dispersion relation c=λν and considering an expanding universe where the observed wavelength today is redshifted from the emitted wavelength by λ0=λemit(1+z), to keep c constant, it must be that ν0=νemit/(1+z). However, although the theory for wavelength in the RW metric includes the cosmological redshift, the same is not simply deduced for frequency (the inverse of time). Instead, cosmological time dilation T0=Temit(1+z) is an additional assumption made to uphold the hypothesis of constant speed of light rather than a relation directly derived from the RW metric. Therefore, verifying cosmological time dilation observationally is crucial. The most recent data employing supernovae for this purpose was released recently by the Dark Energy Survey. Results from the i-band specifically support variations in the speed of light within 1-σ. We used these observations to investigate variations in various physical quantities, including c and G, using the minimally extended varying speed of light model. The speed of light was 0.4% to 2.2% slower, and Newton’s constant may have decreased by 1.7% to 8.4% compared to their current values at redshift 2. These findings, consistent with previous studies, hint at resolving tensions between different ΛCDM cosmological backgrounds but are not yet conclusive evidence of a varying speed of light, as the full-band data aligns with standard model cosmology. However, the data remains valuable for testing variations in fundamental constants over cosmic time. Future analyses, particularly with more refined redshift data, may provide clearer insights into these potential changes.

Solvent mediated synthesis of multicolor narrow bandwidth emissive carbon quantum dots and their potential in white light emitting diodes

The development of efficient and environmentally sustainable materials for white light-emitting diodes (WLEDs) is of paramount importance in the field of lighting technology. In this study, we present a solvent-modulated synthesis approach for the fabrication of multicolor narrow-bandwidth emissive carbon quantum dots (CQDs) as a promising solution for constructing WLEDs. The synthesis method involves the controlled reaction of organic precursors in different solvent environments, leading to the formation of CQDs with distinct emission wavelengths with a relatively small full width at half maximum, ranging from 28 to 42 nm. Moreover, these synthesized multicolor CQDs demonstrate a remarkably high fluorescence quantum yield of up to 65%, indicating their potential for constructing efficient WLED when incorporated in polymer matrix and coated on the surface of blue light-emitting diode (LED).

Near-Infrared Room-Temperature Phosphorescence from Monocyclic Luminophores.

Compact luminophores with long emission wavelengths have aroused considerable theoretical and practical interest. Organics with room-temperature phosphorescence (RTP) are also desirable for their longer lifetimes and larger Stokes shifts than fluorescence. Utilizing the low electronic transition energy intrinsic to thiocarbonyl compounds, electron-withdrawing groups were attached to the 4H-pyran-4-thione core to further lower the excited state energies. The resulting mini-phosphors were doped into suitable polymer matrices. These purely organic, amorphous materials emitted near-infrared (NIR) RTP. Having a molar mass of only 162 g·mol-1, one of the phosphors emitted RTP that peaked at 750 nm, with a very large Stokes shift of 15485 cm-1 (403 nm). Thanks to the good processability of the polymer film, light-emitting diodes (LEDs) with NIR emission were easily fabricated by coating doped polymer on ultraviolet LEDs. This work provides an intriguing strategy to achieve NIR RTP using compact luminophores.

Near‐Infrared Room‐Temperature Phosphorescence from Monocyclic Luminophores

Compact luminophores with long emission wavelengths have aroused considerable theoretical and practical interest. Organics with room‐temperature phosphorescence (RTP) are also desirable for their longer lifetimes and larger Stokes shifts than fluorescence. Utilizing the low electronic transition energy intrinsic to thiocarbonyl compounds, electron‐withdrawing groups were attached to the 4H‐pyran‐4‐thione core to further lower the excited state energies. The resulting mini‐phosphors were doped into suitable polymer matrices. These purely organic, amorphous materials emitted near‐infrared (NIR) RTP. Having a molar mass of only 162 g·mol‐1, one of the phosphors emitted RTP that peaked at 750 nm, with a very large Stokes shift of 15485 cm‐1 (403 nm). Thanks to the good processability of the polymer film, light‐emitting diodes (LEDs) with NIR emission were easily fabricated by coating doped polymer on ultraviolet LEDs. This work provides an intriguing strategy to achieve NIR RTP using compact luminophores.

Short-Wave Infrared Upconverting Nanoparticles.

Optical technologies enable real-time, noninvasive analysis of complex systems but are limited to discrete regions of the optical spectrum. While wavelengths in the short-wave infrared (SWIR) window (typically, 1700-3000 nm) should enable deep subsurface penetration and reduced photodamage, there are few luminescent probes that can be excited in this region. Here, we report the discovery of lanthanide-based upconverting nanoparticles (UCNPs) that efficiently convert 1740 or 1950 nm excitation to wavelengths compatible with conventional silicon detectors. Screening of Ln3+ ion combinations by differential rate equation modeling identifies Ho3+/Tm3+ or Tm3+ dopants with strong visible or NIR-I emission following SWIR excitation. Experimental upconverted photoluminescence excitation (U-PLE) spectra find that 10% Tm3+-doped NaYF4 core/shell UCNPs have the strongest 800 nm emission from SWIR wavelengths, while UCNPs with an added 2% or 10% Ho3+ show the strongest red emission when excited at 1740 or 1950 nm. Mechanistic modeling shows that addition of a low percentage of Ho3+ to Tm3+-doped UCNPs shifts their emission from 800 to 652 nm by acting as a hub of efficient SWIR energy acceptance and redistribution up to visible emission manifolds. Parallel experimental and computational analysis shows rate equation models are able to predict compositions for specific wavelengths of both excitation and emission. These SWIR-responsive probes open a new IR bioimaging window, and are responsive at wavelengths important for vision technologies.

Efficient and Scalable Radiative Cooling for Photovoltaics Using Solution‐Processable and Solar‐Transparent Mesoporous Nanoparticles

AbstractContinuous heat generation in perovskite solar cells (PSCs), caused by solar radiation, poses a significant challenge to their lifespan. Existing active cooling methods require extra energy input and might not be effective at high temperatures. Most reported passive radiative cooling materials either lack solar transparency or require complex fabrication processes. Here, mesoporous silica nanoparticles are designed, synthesized, and assembled into multilayered stacks with a graded refractive index (GRI) by spray coating them on top of PSCs made from methylammonium lead iodide (MAPbI3) over a large scale (15.6 × 15.6 cm2). This coating offers both high transparency in the visible wavelength and high emissivity in the mid‐infrared region, leading to an average temperature reduction of 6.65 ± 1.48 °C in GRI‐coated MAPbI3 PSCs under outdoor conditions compared to non‐coated references. After 50 d, the GRI‐coated PSCs maintain 80.9 ± 8.7% of their initial photoconversion efficiency, in contrast to 6.1 ± 5.9% for the noncoated ones. The calculated cooling power of the GRI‐coated PSCs is 28.9% higher than that of the reference cells.

High color rendering index WLEDs enabled by multi-band tuning of InP quantum dots

Quantum dots (QDs) represent a significant class of fluorescent materials, offering the potential to reduce power consumption and enhance the color rendering index (CRI) of white light-emitting diode (WLED) devices. However, the presence of toxic elements such as Cd and Pb in traditional fluorescent QDs limits their widespread commercial application. Compared to the broad emission characteristics of environmentally friendly AgInS2 and CuInS2 QDs, the narrower linewidth of InP-based core-shell QDs is advantageous for developing WLED devices with a higher CRI. In this study, we employed a multistage heating method to synthesize a series of amino-phosphine-based InP/ZnSe core-shell QDs, which exhibited emission wavelengths ranging from 535 to 650 nm, narrow emission linewidths of 43-47 nm, and high photoluminescence quantum yields of 60%-80%. Subsequently, six different color QDs are used to fabricate a WLED device. The best WLEDs show not only bright warm light (correlated color temperature = 3323 K) with a maximum luminous efficacy of 74.1 lm W-1, but also excellent color quality (CRI Ra = 93, as well as R9 = 94.8, and R13 = 97.1). These results indicate remarkable progress in InP-based WLEDs for high-quality lighting applications.