Achieving broadband near-infrared luminescence in Cr^(3+)-Activated Y_(2)Mg_(2)Al_(2)Si_(2)O_(12)phosphors via multi-site occupancy

Cr^(3+)-activated near-infrared(NIR)phosphors are key for NIR phosphor-converted light emitting diodes(NIR pc-LED).While,the site occupancy of Cr^(3+)is one of the debates that have plagued researchers.Herein,Y2Mg2Al2-Si_(2)O1_(2)(YMAS)with multiple cationic sites is chosen as host of Cr^(3+)to synthesize YMAS:xCr^(3+)phosphors.In YMAS,Cr^(3+)ions occupy simultaneously Al/SiO4 tetrahedral,Mg/AlO6 octahedral,and Y/MgO8 dodecahedral sites which form three luminescent centers named as Cr1,Cr2,and Cr3,respectively.Cr1 and Cr2 relate to an intermediate crystal field,with transitions of^(2)E→^(4)A_(2)and^(4)T_(2)→^(4)A_(2)occurring simultaneously.As Cr^(3+)concentration increases,the^(4)T_(2)→^(4)A_(2)transition becomes more pronounced in Cr1 and Cr2,resulting in a red-shift and broadband emission.Cr3 consistently behaves a weak crystal field and exhibits the broad and long-wavelength emission.Wide-range NIR emission centering at 745 nm is realized in YMAS:0.03Cr^(3+)phosphor.This phosphor has high internal quantum efficiency(IQE?86%)and satisfying luminescence thermal stability(I423 K?70.2%).Using this phosphor,NIR pc-LEDs with 56.6 mW@320 mA optical output power is packaged and applied.Present study not only demonstrates the Cr^(3+)multi-site occupancy in a certain oxide but also provides a reliable approach via choosing a host with diverse cationic sites and local environments for Cr^(3+)to achieve broadband NIR phosphors.

Recent developments of fluorescence imaging technology in the second near-infrared window

Background:Fluorescence bio-imaging in the second near-infrared window(NIR-II FL,1000-1700nm)has great potential in clinical theranostics,which is of great importance providing precise locations of lesions and molecular dynamic actions simultaneously in a single nanoprobe.Methods:T here has been an upsurge of multidisciplinary research focusing on developing functional types of inorganic and organic nanoprobes that can be used for NIR-II FL with the high spatiotemporal resolution,deep tissue penetration,and negligible auto-fluorescence.Results:In this mini-review,we summarize recent progress in inorganic/organic NIR-II FL nanoprobes.We introduce the design and properties of inorganic and organic nanoprobes,in the order of single-walled carbon nanotubes,quantum dots,rare-earth-doped nanoparticles,metal nanoclusters and organic fluorophores,expect to realize precise diagnosis and efficient image-guided therapy.Conclusion:Meanwhile,to elucidate the problems and perspectives,we aim to offer diverse biological applications of inorganic/organic NIR-II FL nanoprobes and accelerate the clinical transformation progress.

Furan-modified thiadiazolo quinoxaline as an electron acceptor for constructing second near-infrared aggregation-induced emission fluorophores for beyond 1300 nm fluorescence/photoacoustic imaging and photothermal therapy

Creation of new fluorophores is important for understanding the structure-property relationship,by which the required optical properties are likely to be attained.Herein,through theory calculation,it is found that furan-modified thiadiazolo quinoxaline acting as an electron acceptor can endow donor-acceptor-donor(D-A-D)type second near-infrared(NIR-Ⅱ)fluorophores with longer emission wavelength than the other thiadiazolo quinoxaline-based acceptors containing pyridine,pyrrole,thiophene,and phenyl groups,respectively.On the basis of this theoretical prediction,a D-A-D type NIR-Ⅱ fluorophore with 6,7-di(furan-2-yl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline(DFTQ)as the acceptor and dithieno[3,2-b:2′,3′-d]pyrrole(DTP)as the donor is designed and synthesized,and the aggregation-induced emission(AIE)function is further achieved by introducing the AIE units of tetraphenylethylene(TPE)and triphenylamine(TPA),respectively,totally forming three NIR-Ⅱ fluorophores DFTQ-DTP,DFTQ-DTPE,and DFTQ-DTPA.For biological applications,the fluorophores are encapsulated by amphiphilic DSPE-PEG2000 to generate water-dispersible nanoparticles(NPs).Almost the whole emission of each of the NPs falls into the NIR-Ⅱ spectral range,with part emission beyond 1300 nm.By using DFTQ-DTPA NPs as the contrast and photothermal therapy(PTT)agent,high-resolution in vivo fluorescence imaging is achieved in the greater than 1300 nm window,and their good performance in photoacoustic imaging and high tumor PTT efficacy in tumor-bearing mice are also demonstrated.Taken together,this work mainly provides a strong electron acceptor for constructing longemitting fluorophores,and by using the electron acceptor,a AIE fluorophore with desirable quantum yield(QY)and photothermal conversion efficienciy(PCE)is synthesized and demonstrated to be promising in fluorescence/photoacoustic imaging and PTT.

Effect of <i>γ</i>-Valerolactone Blending on Engine Performance, Combustion Characteristics and Exhaust Emissions in a Diesel Engine

γ-valerolactone (GVL) is a C5-cyclic ester that can be produced from biomass providing a potentially renewable fuel for transportation and feedstock for the chemical industry. Experiments were performed with fossil diesel (D), D + biodiesel (BD) and D + BD + GVL blends. A four-cylinder, turbocharged direct injection diesel engine was used for the tests. The engine was coupled to a dynamometer to vary the load. CO, NOx, THC and smoke emissions were measured by using a multi-channel gas analyzer. Combustion characteristics were assessed by in-cylinder pressure data with respect to crank angle and the derived heat release rates. Compared with D, and D + BD blends, addition of GVL had relatively little effect on engine performance and NOx emission, but reduced the exhaust concentration of CO, unburned fuel and smoke significantly. The smoke reduction is particularly notable in view of the very recent suggestion that black carbon is the second most important greenhouse gas in the atmosphere next to carbon dioxide. No diesel engine study with GVL has been reported so far.

Deep-red and near-infrared organic lasers based on centrosymmetric molecules with excited-state intramolecular double proton transfer activity

Organic lasers that emit light in the deep-red and near-infrared(NIR)region are of essential importance in laser communication,night vision,bioimaging,and information-secured displays but are still challenging because of the lack of proper gain materials.Herein,a new molecular design strategy that operates by merging two excited-state intramolecular proton transfer-active molecules into one excited-state double proton transfer(ESDPT)-active molecule was demonstrated.Based on this new strategy,three new materials were designed and synthesized with two groups of intramolecular resonance-assisted hydrogen bonds,in which the ESDPT process was proven to proceed smoothly based on theoretical calculations and experimental results of steady-state and transient spectra.Benefiting from the effective six-level system constructed by the ESDPT process,all newly designed materials showed low threshold laser emissions at approximately 720 nm when doped in PS microspheres,which in turn proved the existence of the second proton transfer process.More importantly,our well-developed NIR organic lasers showed high laser stability,which can maintain high laser intensity after 12000 pulse lasing,which is essential in practical applications.This work provides a simple and effective method for the development of NIR organic gain materials and demonstrates the ESDPT mechanism for NIR lasing.

Positron-emission tomography/computed tomography imaging in head and neck oncology:An update

Cancers of the head and neck account for more than half a million cases worldwide annually, with a significant majority diagnosed as squamous cell carcinoma(HNSCC). Imaging studies such as contrast-enhanced computed tomography(CT), magnetic resonance imaging(MRI) and ^(18)F-2-fluoro-2-deoxy-D-glucose positron-emission tomography/computed tomography(^(18)F-FDG PET/CT) are widely used to determine the presence and extent of tumors and metastatic disease, both before and after treatment. Advances in PET/CT imaging have allowed it to emerge as a superior imaging modality compared to both CT and MRI, especially in detection of carcinoma of unknown primary, cervical lymph node metastasis, distant metastasis, residual/recurrent cancer and second primary tumors, often leading to alteration in management. PET/CT biomarker may further provide an overall assessment of tumor aggressiveness with prognostic implications. As new developments emerged leading to better understanding and use of PET/CT in head and neck oncology, the aim of this article is to review the roles of PET/CT in both pre- and post-treatment management of HNSCC and PET-derived parameters as prognostic indicators.

Atomic emission spectra and field non-classical properties

This paper studies the interaction of a A-type three-level atom with a single mode field. It discusses the emission spectrum characteristics of the A-type three-level atom driven by the photon-added coherent field. By means of the second-order degree of coherence, it shows some nonclassical properties of the cavity field, such as sub-Poissonian photon- number distribution and the two-time intensity-intensity correlation which violates the Cauchy Schwarz inequality.

Near-infrared aggregation-induced emission materials:Bibliometric analysis and their application in biomedicalfield

Aggregation-induced emission(AIE)is an intriguing photophysical phenomenon,where specific materials exhibit a remarkable surge in luminescence when brought together in non-ideal solvents or within a solid matrix.Since the concept of AIE wasfirst introduced in 2001,numerous advanced applications have been gradually explored across various domains,including optics,electronics,energy,and the life sciences.Of particular note is the growing interest in the application of AIE systems with near-infrared(NIR)emissive feature in thefield of biomedicine,encompass-ing detection,imaging,and therapeutic interventions.Notably,bibliometric analysis serves as a valuable tool to provide researchers with a comprehensive understand-ing of research achievements and developmental trends in specificfields,which is crucial for academic research.Herein,we present a general bibliometric overview spanning two decades of NIR-AIE development.With the assistance of core scien-tific databases and various bibliometric software tools,we conducted a systematic analysis of annual publications and citations,the most influential countries/regions,leading authors,journals,and institutions,as well as the hot topics related to NIR applications and forward-looking predictions.Furthermore,the application of AIE with NIR properties in the biomedicalfield is also systematically reviewed.

Efficient tunable visible and near-infrared emission in Sb^(3+)/Sm^(3+)-codoped Cs_(2)NaLuCl_6 for near-infrared light-emitting diode,triple-mode fluorescence anti-counterfeiting and information encryption

Rare earth ions(RE^(3+))-doped double perovskites have attracted tremendous attention for its fascinating optical properties.Nevertheless,RE^(3+)generally exhibits poor photoluminescence quantum yield(PLQY)for their parity-forbidden 4f-4f transition and the low doping concentration.Herein,we reported Sb^(3+)/Sm^(3+)-codoped rare earth-based double perovskite Cs_(2)Na Lu Cl_(6)that enables efficient visible and nearinfrared(NIR)emission,which stems from self-trapped exciton(STE)and Sm^(3+),respectively.Benefit from up to 72.89%energy transfer efficiency from STE to Sm^(3+)and high doping concentrations due to similar ionic activity between Sm^(3+)and Lu^(3+),thus eruptive PLQY of 74.58%in the visible light region and 23.12%in the NIR light region can be obtained.Moreover,Sb^(3+)/Sm^(3+)-codoped Cs_(2)Na Lu Cl_(6)exhibits tunable emission characteristic in the visible light region under different excitation wavelengths,which can change from blue emission(254 nm excitation)to white emission(365 nm excitation).More particularly,only the NIR emission can be captured by the NIR camera when a 700 nm cutoff filter is added.The excellent stability and unique optical properties of Sb^(3+)/Sm^(3+)-codoped Cs_(2)Na Lu Cl_(6)enable us to demonstrate its applications in NIR light-emitting diode,triple-mode fluorescence anti-counterfeiting and information encryption.These findings provide new inspiration for the application of rare earth-based double perovskite in optoelectronic devices.

Near-infrared organic lasers with ultra-broad emission bands by simultaneously harnessing four-level and six-level systems

Organic lasers with broad emission bands in near-infrared(NIR)region are crucial for their applications in laser communication,night-vision as well as bioimaging owing to the abundance of selectable lasing wavelengths.However,for most organic gain materials,gain regions are limited in a small wavelength range because of the fixed energy level systems.Herein,we design a strategy to realize NIR organic lasers with broad emission bands based on tunable energy level systems induced by cascaded excited-state intramolecular proton transfer(ESIPT).A novel gain material named DHNN was developed,which can undergo a cascaded double-ESIPT process supporting four-level and six-level systems simultaneously.By doping DHNN into polystyrene microspheres,NIR lasers with tunable emission bands can be achieved based on the careful modulation of microcavities.Finally,organic lasers with an ultra-broad emission band ranging from 700 nm to 900 nm was successfully achieved by harnessing four-level and six-level systems simultaneously.

In situ instant generation of an ultrabroadband near-infrared emission center in bismuth-doped borosilicate glasses via a femtosecond laser

Bismuth(Bi)-doped photonic materials, which exhibit broadband near-infrared(NIR) luminescence(1000–1600 nm), are evolving into interesting gain media. However, the traditional methods have shown their limitations in enhancing Bi NIR emission, especially in the microregion. Consequently, the typical NIR emission has seldom been achieved in Bi-doped waveguides, which highly restricts the application of Bi-activated materials.Here, superbroadband Bi NIR emission is induced in situ instantly in the grating region by a femtosecond(fs)laser inside borosilicate glasses. A series of structural and spectroscopic characterizations are summoned to probe the generation mechanism. And we show how this novel NIR emission in the grating region can be enhanced significantly and erased reversibly. Furthermore, we successfully demonstrate Bi-activated optical waveguides.These results present new insights into Bi-doped materials and push the development of broadband waveguide amplification.

Rational Design and Application of an Indolium-Derived Heptamethine Cyanine with Record-Long Second Near-Infrared Emission

Heptamethine cyanine dyes,typified by indocyanine green,have been extensively employed as bioimaging indicators and theranostic agents.Significant efforts have been made to develop functional heptamethine cyanine dyes with outstanding bioimaging and theranostic utilities.In this work,we rationally designed and successfully developed a novel indolium-like heptamethine cyanine dye by installing indolium-derived polycyclic aromatic hydrocarbons on the terminal ends of a conjugated polyene backbone.This dye showed excellent photostability and showed bright fluorescent emission in the second near-infrared(NIR-Ⅱ)window with a peak at approximately 1120 nm.Such long wavelength emission prompted a superior bioimaging resolution in vivo.In particular,this NIR-Ⅱ dye had the remarkable capability of marking the blood vessels of the hindlimbs,abdomens,and brains of mice.More significantly,this dye involved a typical indolium-like heptamethine skeleton and exhibited two strong absorption bands in the 700–1300 nm NIR range,which endowed it with an intrinsic tumor-targeting capability and a high photothermal conversion efficiency(up to 68.2%),serving for the photothermal therapy of tumors under the guidance of NIR-Ⅱ fluorescence imaging.This work provides an efficient design strategy for achieving indolium-like heptamethine cyanine dyes with further NIR-Ⅱ emission.

High-entropy rare earth stannate ceramics:Acid corrosion resistant radiative cooling materials with high atmospheric transparency window emissivity and high near-infrared solar reflectivity

In response to the development of the concepts of“carbon neutrality”and“carbon peak”,it is critical to developing materials with high near-infrared(NIR)solar reflectivity and high emissivity in the atmospheric transparency window(ATW;8–13μm)to advance zero energy consumption radiative cooling technology.To regulate emission and reflection properties,a series of high-entropy rare earth stannate ceramics(HE-RE_(2)Sn_(2)O_(7):(Y_(0.2)La_(0.2)Nd_(0.2)Eu_(0.2)Gd_(0.2))_(2)Sn_(2)O_(7),(Y_(0.2)La_(0.2)Sm_(0.2)Eu_(0.2)Lu_(0.2))_(2)Sn_(2)O_(7),and(Y_(0.2)La_(0.2)Gd_(0.2)Yb_(0.2)Lu_(0.2))_(2)Sn_(2)O_(7))with severe lattice distortion were prepared using a solid phase reaction followed by a pressureless sintering method for the first time.Lattice distortion is accomplished by introducing rare earth elements with different cation radii and mass.The as-synthesized HE-RE_(2)Sn_(2)O_(7)ceramics possess high ATW emissivity(91.38%–95.41%),high NIR solar reflectivity(92.74%–97.62%),low thermal conductivity(1.080–1.619 W·m^(−1)·K^(−1)),and excellent chemical stability.On the one hand,the lattice distortion intensifies the asymmetry of the structural unit to cause a notable alteration in the electric dipole moment,ultimately enlarging the ATW emissivity.On the other hand,by selecting difficult excitation elements,HE-RE_(2)Sn_(2)O_(7),which has a wide band gap(Eg),exhibits high NIR solar reflectivity.Hence,the multi-component design can effectively enhance radiative cooling ability of HE-RE_(2)Sn_(2)O_(7)and provide a novel strategy for developing radiative cooling materials.

PbS quantum dots and Ba F_(2):Tm^(3+) nanocrystals co-doped glass for ultra-broadband near-infrared emission [Invited]

With the rapid growth of optical communications traffic,the demand for broadband optical amplifiers continues to increase.It is necessary to develop a gain medium that covers more optical communication bands.We precipitated PbS quantum dots(QDs) and Ba F_(2):Tm^(3+) nanocrystals (NCs) in the same glass to form two independent emission centers.The Ba F_(2)NCs in the glass can provide a crystal field environment with low phonon energy for rare earth (RE) ions and prevent the energy transfer between RE ions and PbS QDs.By adjusting the heat treatment schedule,the emission of the two luminescence centers from PbS QDs and Tm^(3+) ions perfectly splices and covers the ultra-broadband near-infrared emission from 1200 nm to 2000 nm with bandwidth over 430 nm.Therefore,it is expected to be a promising broadband gain medium for fiber amplifiers.

Six-and five-coordinated Cr^(3+)in Ga_(2)GeO_(5) invokes tunable broadband near-infrared emission toward night-vision applications

Broadband near-infrared(NIR)light sources play a critical role in widespread applications such as advanced spectroscopy analysis and nondestructive testing.One of the most promising techniques is the fabrication of broadband NIR phosphor-converted light emitting diode(pc-LED).However,the purposeful design of a tunable ultra-broadband NIR-emitting phosphor in a single host is still a challenge.In this work,Ga_(2)GeO_(5) with two sites of six-coordinated[Ga1O_(6)]and five-coordinated[Ga2O_(5)]is chosen to host Cr^(3+),successfully producing tunable broadband NIR luminescence(680-1350 nm).It can be tuned largely from 828 to 970 nm with the full-width at half maximum(FWHM)varied from 208 to 258 nm just by simply adjusting the Cr^(3+)-doping content.The tailoring of the Cr^(3+)NIR spectral emission is ascertained to the site occupation preference and competition.The encapsulation of a prototype of NIR pc-LED with an output power of 29.5mW@390 mA is conducted for the implementation of night-vision application.This work provides a novel broadband NIR phosphor by Cr^(3+)-doping in both the sixand five-coordination field,meanwhile,further demonstrating the feasibility of discovering new host material with more than one crystallographic site for Cr^(3+)to trigger tunable broadband NIR emission.

Naphthalene diimide based near-infrared luminogens with aggregation-induced emission characteristics for biological imaging and high mobility ambipolar transistors

Organic conjugated materials combining high conductivity with strong solid-state emission are highly desired for organic electronic applications,yet still rather rare.Herein,a novel luminogen(TEN)comprised by linking naphthalene diimides and triphenyl ethylene with vinyl bridges is reported.TEN exhibits aggregation-induced emission(AIE)behavior of a strong nearinfrared fluorescence over 700 nm and the efficiency above 60.5%in the solid state,while also shows promising application in vivo bio-imaging with good permeability and extremely low background.Single crystal of TEN reveals intra-and intermolecular C–H…O hydrogen bonds,contributing to an inclined molecular stacking along the a-axis of the cell,creating a 1 D charge carrier transporting channel under a shortπ-πinteraction distance of 3.42?,which might benefit the solid emission and charge transport ability simultaneously.Solution processed bottom contact,top gate organic field effect transistors based on TEN reveal a high ambipolar charge transport ability with the hole mobility up to 0.13 cm2 V-1 s-1 and electron mobility up to0.010 cm2 V-1 s-1.Further atomic force microscopy and X-ray diffraction analysis on TEN thin film confirm the existence of the1 Dπ-πstacking channel,suggesting the stacking geometry revealed in crystal crucial for facilitating high charge carrier mobility while preserving the strong solid emission at the same time.

Aggregation-induced emission:Red and near-infrared organic light-emitting diodes

Red and near-infrared(NIR)organic light-emitting diodes(OLED)have gained remarkable interest due to their numerous applications.However,the construction of highly emissive emitters is hampered by the energy-gap law and aggregation-caused quenching(ACQ)effect.Whereas,aggregationinduced emission(AIE)materials could avoid the undesirable ACQ effect and emit bright light in aggregated state,which is one class of the most promising materials to fabricate high-performance OLED with a high external quantum efficiency and low efficiency roll-off.This review summarizes recent advances in red and NIR OLED with AIE property,including the traditional fluorescence,thermally activated delayed fluorescence,and hybridized local and charge transfer compounds.Meanwhile,the emphasis attention is paid to the molecular design principles,as well as the molecular structure-photophysical characteristics.We also briefly further outlook the challenges and perspective of red and NIR AIE luminogens.

Rational Design of a Near-infrared Fluorescent Material with High Solid-state Efficiency,Aggregation-induced Emission and Live Cell Imaging Property

Near-infrared(NIR)fluorescent materials with high photoluminescent quantum yields(PLQYs)have wide application prospects.Therefore,we design and synthesize a D-A type NIR organic molecule,TPATHCNE,in which triphenylamine and thiophene are utilized as the donors and fumaronitrile is applied as the acceptor.We systematically investigate its molecular structure and photophysical property.TPATHCNE shows high T_(g) of 110℃ and T_(d) of 385℃ and displays an aggregation-induced emission(AIE)property.A narrow optical bandgap of 1.65 eV is obtained.The non-doped film of TPATHCNE exhibits a high PLQY of 40.3%with an emission peak at 732 nm,which is among the best values of NIR emitters.When TPATHCNE is applied in organic light-emitting diode(OLED),the electroluminescent peak is located at 716 nm with a maximum external quantum efficiency of 0.83%.With the potential in cell imaging,the polystyrene maleic anhydride(PMSA)modified TPATHCNE nanoparticles(NPs)emit strong fluorescence when labeling HeLa cancer cells,suggesting that TPATHCNE can be used as a fluorescent carrier for specific staining or drug delivery for cellular imaging.TPATHCNE NPs fabricated by bovine serum protein(BSA)are cultivated with mononuclear yeast cells,and the intense intracellular red fluorescence indicates that it can be adopted as a specific stain for imaging.

Donor-Acceptor Typed AIE Luminogens with Near-infrared Emission for Super-resolution Imaging

Aggregation-induced emission(AIE)luminogens(AIEgens)with high brightness in aggregates exhibit great potentials in biological imaging,but these AIEgens are seldom applied in super-resolution biological imaging,especially in the imaging by using the structural illumination microscope(SIM).Based on this consideration,we synthesized the donor-acceptor typed AIEgen of DTPA-BTN,which not only owns high brightness in the near-infrared(NIR)emission region from 600 nm to 1000 nm(photoluminescence quantum yield,PLQYs=11.35%),but also displays excellent photo-stability.In addition,AIE nanoparticles based on 4,7-ditriphenylamine-[1,2,5]-thiadiazolo[3,4-c]pyridine(DTPA-BTN)were also prepared with highly emissive features and excellent biocompatibility.Finally,the developed DTPA-BTN-based AIE nanoparticles were applied in the super-resolution cellular imaging via SIM,where much smaller full width at half-maximum values and high signal to noise ratios were obtained,indicating the superior imaging resolution.The results here imply that highly emissive AIEgens or AIE nanoparticles can be promising imaging agents for super-resolution imaging via SIM.

Stimuli-responsive organic chromic materials with near-infrared emission

Organic chromic materials that respond to external stimuli, especially in the solid state, have sparked extensive interest owing to their potential use as smart materials. In particular, the availability of chromic materials, which emit fluorescence or phosphorescence in the deep penetrating, near-infrared（NIR）region, has led to great improvements in imaging. Various methods that were commonly applied to construct chromic materials, have been reformed to develop the novel type of compounds, and some have received rewards with excellent fingdings. Relevant research achievements of practical applications have showed their potential with the changes that locate in the NIR region, while further in-depth explorations about the inherent chromic chromism are underway. In this review, several representative studies, which have led the development of responsive organic chromic materials with near-infrared emission, will be discussed.