Multimode Luminescence with Temperature and Energy Level Synergistic Dependence in Rare Earth Halide DPs for Advanced Multifunctional Applications.

Rare-earth halide double perovskites (DPs) have attracted extensive attention due to their excellent optoelectronic performance. However, the correlation between luminescence performance, crystal structure, and temperature, as well as the inherent energy transfer mechanism, is not well understood. Herein, Lanthanide ions (Ln3+: Nd3+ or Dy3+) as the co-dopants are incorporated into Sb3+ doped Cs2NaYbCl6 DPs to construct energy transfer (ET) models to reveal the effects of temperature and energy levels of rare earth on luminescence and ET. The different excited state structures of Sb3+-Ln3+ doped Cs2NaYbCl6 DPs at different temperatures and relative positions of energy levels of rare earth synergistically determine the physical processes of luminescence. These multi-mode luminescent materials exhibit good performance in anti-counterfeiting, NIR imaging, and temperature sensing. This work provides new physical insights into the effects of temperature and energy levels of rare earth on the energy transfer mechanism and related photophysical process.

Osmapentalenofurans Constructed by Reacting Os≡C1 of Osmapentalyne with Phenols.

Over the past decade, significant research efforts have focused on osmapentalyne, characterized by the more reactive Os≡C7 (Carbon atoms numbered in a clockwise direction on the osmapentalyne skeleton), across areas encompassing electrophilic, nucleophilic, and addition reactions. Nevertheless, the reactivity of osmapentalyne featuring Os≡C1 remains ripe for further exploration. In this investigation, we effectively synthesized a lineage of osmapentalenofurans through the nucleophilic reaction of osmapentalyne incorporating Os≡C1 with phenols. These resulting complexes demonstrate near-infrared luminescence traits in both solid and liquid states. Particularly noteworthy is the osmapentalenofuran derived from tetraphenylethane (TPE) unit, which showcases remarkable aggregation-induced emission ( AIE) property in the aggregated state. These osmapentalenofurans are also able to further extend their range of reactions, including reactions with base and isonitrile. This study not only broadens the scope of applications for metal aromatics but also furnishes valuable insights into the realm of specialized functional materials.

In Vivo High-Contrast Biomedical Imaging in the Second Near-Infrared Window Using Ultrabright Rare-Earth Nanoparticles.

Intravital luminescence imaging in the second near-infrared window (NIR-II) enables noninvasive deep-tissue imaging with high spatiotemporal resolution of live mammals because of the properties of suppressed light scattering and diminished autofluorescence in the long-wavelength region. Herein, we present the synthesis of a downconversion luminescence rare-earth nanocrystal with a core-shell-shell structure (NaYF4@NaYbF4:Er,Ce@NaYF4:Ca). The structure efficiently maximized the doping concentration of the sensitizers and increased Er3+ luminescence while preventing cross relaxation. Furthermore, Ce3+ doping in the middle layer efficiently limited the upconversion pathway and increased downconversion by 24-fold to produce bright 1550 nm luminescence under 975 nm excitation. Finally, optimizing the inert shell coating of NaYF4:Ca and liposome encapsulation reduced the luminescence quenching impact by water and improved biological metabolism. Thus, our synthesized biocompatible, ultrabright NIR-II probes provide high contrast and resolution for through-scalp and through-skull luminescence imaging of mice cerebral vasculature without craniotomy as well as imaging of mouse hindlimb microvessels.

Chiral Canoe-Like Pd0 or Pt0 Alloyed Copper Alkynyl Nanoclusters Display Near-Infrared Luminescence.

Alloying nanoclusters (NCs) has emerged as a widely explored and versatile strategy for tailoring tunable properties, facilitating in-depth atomic-level investigations of structure-property correlations. In this study, we have successfully synthesized six atomically precise copper NCs alloyed with Group 10 metals (Pd or Pt). Notably, the Pd0 or Pt0 atom situated at the center of the distorted hexagonal antiprism Pd0/Pt0@Cu12 cage, coordinated with twelve Cu+ and two tBuC≡C- ligands. Moreover, ligand exchange strategies demonstrated the potential for Cl- and Br- to replace one or two alkynyl ligands positioned at the top or side of the NCs. The chirality exhibited by these racemic NCs is primarily attributed to the involvement of halogens and a chiral (Pd/Pt)@Cu18 skeleton. Furthermore, all the NCs exhibit near-infrared (NIR) luminescence, characterized by emission peaks at 705-755 nm, lifetimes ranging from 6.630 to 9.662 µs, and absolute photoluminescence quantum yields (PLQYs) of 1.75 %-2.52 % in their crystalline state. The experimental optical properties of these NCs are found to be in excellent agreement with the results of theoretical calculations. These alloy NCs not only offer valuable insights into the synthesis of Pd0/Pt0-Cu alloy NCs, but also bridge the gap in understanding the structure-luminescence relationships of Pd0/Pt0-Cu molecules.

Comparison of Performance between Single- and Multiparameter Luminescence Thermometry Methods Based on the Mn5+ Near-Infrared Emission.

Herein, we investigate the performance of single- and multiparametric luminescence thermometry founded on the temperature-dependent spectral features of Ca6BaP4O17:Mn5+ near-infrared emission. The material was prepared by a conventional steady-state synthesis, and its photoluminescence emission was measured from 7500 to 10,000 cm-1 over the 293-373 K temperature range in 5 K increments. The spectra are composed of the emissions from 1E → 3A2 and 3T2 → 3A2 electronic transitions and Stokes and anti-Stokes vibronic sidebands at 320 cm-1 and 800 cm-1 from the maximum of 1E → 3A2 emission. Upon temperature increase, the 3T2 and Stokes bands gained in intensity while the maximum of 1E emission band is redshifted. We introduced the procedure for the linearization and feature scaling of input variables for linear multiparametric regression. Then, we experimentally determined accuracies and precisions of the luminescence thermometry based on luminescence intensity ratios between emissions from the 1E and 3T2 states, between Stokes and anti-Stokes emission sidebands, and at the 1E energy maximum. The multiparametric luminescence thermometry involving the same spectral features showed similar performance, comparable to the best single-parameter thermometry.

A Novel Near-Infrared Ytterbium Complex [Yb(DPPDA)2](DIPEA) with Φ = 0.46% and τobs = 105 µs.

The luminescent performances of near-infrared (NIR) lanthanide (Ln) complexes were restricted greatly by vibration quenching of X-H (X = C, N, O) oscillators, which are usually contained in ligands and solvents. Encapsulating Ln3+ into a cavity of coordination atoms is a feasible method of alleviating this quenching effect. In this work, a novel ytterbium complex [Yb(DPPDA)2](DIPEA) coordinated with 4,7-diphenyl-1,10-phenanthroline-2,9-dicarboxylic acid (DPPDA) was synthesized and characterized by FT-IR, ESI-MS and elemental analysis. Under the excitation of 335 nm light, [Yb(DPPDA)2](DIPEA) showed two emission peaks at 975 and 1011 nm, respectively, which were assigned to the characteristic 2F5/2 → 2F7/2 transition of Yb3+. Meanwhile, this ytterbium complex exhibited a plausible absolute quantum yield of 0.46% and a luminescent lifetime of 105 µs in CD3OD solution. In particular, its intrinsic quantum yield was calculated to be 12.5%, and this considerably high value was attributed to the near-zero solvent molecules bound to Yb3+ and the absence of X-H oscillators in the first coordination sphere. Based on experimental results, we further proposed that the sensitized luminescence of [Yb(DPPDA)2](DIPEA) occurred via an internal redox mechanism instead of an energy transfer process.

NIR Clusteroluminescence of Non-conjugated Phenolic Resins Enabled by Through-Space Interactions.

Clusteroluminescence (CL) and through-space interactions (TSIs) of non-conjugated molecules have drawn more attention due to their unique photophysical behaviors that are different from largely conjugated luminogens. However, achieving red and even near-infrared (NIR) emission from such systems is still challenging due to the intrinsic drawbacks of non-conjugated molecules and the lack of theories for structure-property relationships. In this work, six phenolic resins are designed and synthesized based on two molecule-engineering strategies: increasing the number of TSIs units and introducing electron-donating/-withdrawing groups. All phenolic resins are verified as luminogens with CL property (CLgens), and the first example of CLgens with NIR emission (maximum emission wavelength ≥680 nm) and high absolute quantum yield (47 %) is reported. Experiments and theoretical analysis reveal that two TSIs types, through-space locally excited state and through-space charge transfer state, play essential roles in achieving CL from these non-conjugated polymers, which could be manipulated via changing structural conformation and electron density or altering electron transition behaviors. This work not only provides an approach to manipulate TSIs and CL of non-conjugated polymers but also endows commercially available phenolic resins with high practical value as luminescence materials.

Wide-coverage and Efficient NIR Emission from Single-component Nanophosphors through Shaping Multiple Metal-halide Packages.

Wide-coverage near infrared (NIR) phosphor-converted LEDs possess promising potential for practical applications, but little is developed towards the efficient and wide-coverage NIR phosphors. Here, we report the single-component lanthanide (Ln3+ ) ions doped Cs2 M(In0.95 Sb0.05 )Cl6 (M=alkali metal) nanocrystals (NCs), exhibiting emission from 850 to 1650 nm with high photoluminescence quantum yield of 20.3 %, which is accomplished by shaping the multiple metal halide octahedra of double perovskite via the simple alkali metal substitution. From Judd-Ofelt theoretical calculation and spectroscopic investigations, the shaping of metal halide octahedra in Cs2 M(In1-x Sbx )Cl6 NCs can break the forbidden of f-f transition of Ln3+ , thus increasing their radiative transition rates and simultaneously boosting the energy transfer efficiency from host to Ln3+ . Finally, the wide-coverage NIR LEDs based on Sm3+ , Nd3+ , Er3+ -tridoped Cs2 K0.5 Rb0.5 (In0.95 Sb0.05 )Cl6 NCs are fabricated and employed in the multiplex gas sensing and night-vision application.

Pentacyclic and Hexacyclic Osmaarynes and Their Derivatives.

Although osmabenzyne, osmanaphthalyne, osmaphenanthryne, and osmaanthracyne have been previously reported, the synthesis of polycyclic osmaarynes is still a challenge. Herein, we report the successful synthesis of the first pentacyclic osmaarynes (pyreno[b]osmabenzynes 1 a and 2 a) and hexacyclic osmaaryne (peryleno[b]osmabenzyne 3 a). Nucleophilic reaction of osmaarynes was used to obtain the corresponding pyreno[b]osmium complexes (1 and 2) and peryleno[b] osmium complex (3), which exhibited near-infrared luminescence and aggregation-induced emission (AIE) properties. Complexes 2 and 3 are resistant to photodegradation, and complex 2 has better photothermal conversion properties than 3.

Efficient Near-Infrared Luminescence in Lanthanide-Doped Vacancy-Ordered Double Perovskite Cs2 ZrCl6 Phosphors via Te4+ Sensitization.

All-inorganic lead-free perovskite-derivative metal halides have shown great promise in optoelectronics, however, it remains challenging to realize efficient near-infrared (NIR) luminescence in these materials. Herein, we report a novel strategy based on Te4+ /Ln3+ (Ln=Er, Nd, and Yb) co-doping to achieve efficient NIR luminescence in vacancy-ordered double perovskite Cs2 ZrCl6 phosphors, which are excitable by a low-cost near-ultraviolet light-emitting diode (LED) chip. Through sensitization by the spin-orbital allowed 1 S0 →3 P1 transition of Te4+ , intense and multi-wavelength NIR luminescence originating from the 4f→4f transitions of Er3+ , Nd3+ , and Yb3+ was acquired, with a quantum yield of 6.1 % for the Er3+ emission. These findings provide a general approach to achieve efficient NIR emission in lead-free metal halides through ns2 -metal and lanthanide ion co-doping, thereby opening up a new avenue for exploring NIR-emitting perovskite derivatives towards versatile applications such as NIR-LEDs and bioimaging.

Highly Distorted Antimony(III) Chloride [Sb2 Cl8 ]2- Dimers for Near-Infrared Luminescence up to 1070†nm.

Zero-dimensional (0D) hybrid metal halides with unique compositional and structural tunability appear as an emerging class of luminescent materials, but near-infrared (NIR) emitters therein are largely unexplored to date. This study presents three novel 0D hybrid antimony chlorines with edge-sharing [Sb2 Cl8 ]2- dimers, showing unusual room-temperature broadband NIR emission with the maximum emission wavelength up to 1070 nm. Photoluminescence studies and density functional theory calculation demonstrate that the emissions originate from the highly localized excitons, and that the confined [Sb2 Cl8 ]2- dimers in these structures show low symmetry and a large degree of structural freedom. These hybrid antimony chlorines with [Sb2 Cl8 ]2- dimers expand the range of new NIR materials in 0D metal halides.

Boosting Near-Infrared Luminescence of Lanthanide in Cs2 AgBiCl6 Double Perovskites via Breakdown of the Local Site Symmetry.

Currently, lanthanide (Ln3+ )-doped near-infrared (NIR)-emitting double perovskites (DPs) suffer from low photoluminescence quantum yield (PLQY). Herein, we develop a new class of NIR-emitting DPs based on Ln3+ -doped Cs2 (Na/Ag)BiCl6 . Benefiting from the Na+ -induced breakdown of local site symmetry in the Cs2 AgBiCl6 DPs, effective NIR emissions of Ln3+ are realized through Bi3+ sensitization. Specifically, 7.3-fold and 362.9-fold enhanced NIR emissions of Yb3+ and Er3+ are achieved in Cs2 Ag0.2 Na0.8 BiCl6 DPs relative to those in Na-free Cs2 AgBiCl6 counterparts, respectively. The optimal absolute NIR PLQYs for Yb3+ and Er3+ in Cs2 Ag0.2 Na0.8 BiCl6 DPs are determined to be 19.0 % and 4.3 %, respectively. Raman spectroscopy and first-principles density functional theory calculations verify the sublattice distortion in Cs2 (Na/Ag)BiCl6 DPs via Na+ doping. These findings provide fundamental insights into the design of efficient NIR-emitting Ln3+ -doped DPs for versatile optoelectronic applications.

[Cu15 (PPh3 )6 (PET)13 ]2+ : a Copper Nanocluster with Crystallization Enhanced Photoluminescence.

Due to their atomically precise structure, photoluminescent copper nanoclusters (Cu NCs) have emerged as promising materials in both fundamental studies and technological applications, such as bio-imaging, cell labeling, phototherapy, and photo-activated catalysis. In this work, a facile strategy is reported for the synthesis of a novel Cu NCs coprotected by thiolate and phosphine ligands, formulated as [Cu15 (PPh3 )6 (PET)13 ]2+ , which exhibits bright emission in the near-infrared (NIR) region (≈720 nm) and crystallization-induced emission enhancement (CIEE) phenomenon. Single crystal X-ray crystallography shows that the NC possesses an extraordinary distorted trigonal antiprismatic Cu6 core and a, unique among metal clusters, "tri-blade fan"-like structure. An in-depth structural investigation of the ligand shell combined with density functional theory calculations reveal that the extended CH···π and π-π intermolecular ligand interactions significantly restrict the intramolecular rotations and vibrations and, thus, are a major reason for the CIEE phenomena. This study provides a strategy for the controllable synthesis of structurally defined Cu NCs with NIR luminescence, which enables essential insights into the origins of their optical properties.

Optical Properties of Carbon Dots in the Deep-Red to Near-Infrared Region Are Attractive for Biomedical Applications.

Carbon dots (CDs) represent a recently emerged class of luminescent materials with a great potential for biomedical theranostics, and there are a lot of efforts to shift their absorption and emission toward deep-red (DR) to near-infrared (NIR) region falling in the biological transparency window. This review offers comprehensive insights into the synthesis strategies aimed to achieve this goal, and the current approaches of modulating the optical properties of CDs over the DR to NIR region. The underlying mechanisms of their absorption, photoluminescence, and chemiluminescence, as well as the related photophysical processes of photothermal conversion and formation of reactive oxygen species are considered. The already available biomedical applications of CDs, such as in the photoacoustic imaging and photothermal therapy, photodynamic therapy, and their use as bioimaging agents and drug carriers are then shortly summarized.

808 nm-Light-Excited Near-Infrared Luminescent Lanthanide Metal-Organic Frameworks for Highly Sensitive Physiological Temperature Sensing.

Ongoing demand for accurate self-calibrated noninvasive thermometers for micro-/nano-scale applications, particular biomedical diagnosis, is driving the development of temperature sensors. Here a new type of lanthanide metal-organic framework having near-infrared absorption and near-infrared emission features is presented, and it is based on efficient Nd3+ -to-Yb3+ energy transfer in 808 nm photoexcitation. The results show that the ratiometric parameter of Nd0.5 Yb0.5 TPTC (TPTC= 1,1':4',1''-terphenyl]-3,3'',5,5''-tetracarboxylic acid) can deliver good exponential-type luminescence response to temperature in the physiological regime (293-328 K) with high relative sensitivity and accurate temperature resolution, as well as good biocompatibility and chemical stability. Such lanthanide-based materials are especially useful in biomedical applications.

Determination and analysis of singlet oxygen quantum yields of talaporfin sodium, protoporphyrin IX, and lipidated protoporphyrin IX using near-infrared luminescence spectroscopy.

In photodynamic therapy (PDT), singlet oxygen ([Formula: see text]) is the main species responsible for promoting tumor cell death. The determination of the quantum yield (ΦΔ) of a photosensitizer (PS) is important for dosimetry. The purpose of this paper is to quantify the [Formula: see text] generated by the PS by near-infrared spectroscopy (NIRS). The ΦΔ of different PS species were measured by the detection of near-infrared [Formula: see text] luminescence. From the measurement results, the ΦΔ of talaporfin sodium, protoporphyrin IX (PpIX), and lipidated PpIX (PpIX lipid) were measured as 0.53, 0.77, and 0.87, respectively. In addition, the ΦΔ values of PpIX in a hypoxic and oxic solution were evaluated, since tumors are associated with regions of hypoxia. The measured ΦΔ indicated a same value at high (DO: 20%) and low (DO: 1%) oxygen concentrations. Using the measured ΦΔ, the amount of [Formula: see text] generated by the PSs was estimated using [[Formula: see text]] = D*ΦΔ, where D* is the total excited PS concentration. The generated [Formula: see text] amounts were little different at the high and the low oxygen concentrations, and the generated [Formula: see text] amount for each PS was different depending on each ΦΔ. The NIRS measurement determined the ΦΔ of talaporfin sodium, PpIX, and PpIX lipid. The quantitative evaluation based on the measured ΦΔ will support the development of PDT treatment monitoring and design.

Near-Infrared Electroluminescence beyond 800†nm with High Efficiency and Radiance from Anthracene Cored Emitters.

Derivatives based on anthryleno[1,2-b]pyrazine-2,3-dicarbonitrile (DCPA) are used as luminescent materials, to realize near-infrared (NIR) electroluminescence. By functionalizing DCPA with aromatic amine donors, two emitters named DCPA-TPA and DCPA-BBPA are designed and synthesized. Both molecules have large dipole moments owing to the strong intramolecular charge transfer interactions between the amine donors and the DCPA acceptor. Thus, compared with doped films, the emission of neat films of DCPA-TPA and DCPA-BBPA can fully fall into the NIR region (>700 nm) with increasing surrounding polarity by increasing doping ratio. Moreover, the non-doped devices based on DCPA-TPA and DCPA-BBPA provide NIR emission with peaks at 838 and 916 nm, respectively. A maximum radiance of 20707 mW Sr-1 m-2 was realized for the further optimized device based on DCPA-TPA. This work provides a simple and efficient strategy of molecular design for developing NIR emitting materials.

Synthesis and Near Infrared Luminescence Properties of a Series of Lanthanide Complexes with POSS Modified Ligands.

A polyhedral oligomeric silsesquioxanes (POSS) modified 8-hydroxyquinoline derivative (denoted as Q-POSS) was synthesized and used as a ligand to coordinate with lanthanide ions to obtain a series of lanthanide complexes Ln(Q-POSS)3 (Ln = Er3+, Yb3+, Nd3+). The as-prepared lanthanide complexes have been characterized by FT-IR, UV⁻Vis, and elemental analysis. All these complexes showed the characteristic near-infrared (NIR) luminescence originated from the corresponding lanthanide ions under excitation. Compared with the unmodified counterparts LnQ3 (HQ = 8-hydroxyquinoline), the Ln(Q-POSS)3 complexes showed obviously increased emission intensity, which was ascribed mainly to the steric-hindrance effects of the POSS moiety in the ligands. It is believed that the POSS group could suppress undesired excimer formation and intermolecular aggregation, thus decreasing the concentration quenching effect of the corresponding lanthanide complexes.

Highly Efficient Near-Infrared Delayed Fluorescence Organic Light Emitting Diodes Using a Phenanthrene-Based Charge-Transfer Compound.

Significant efforts have been made to develop high-efficiency organic light-emitting diodes (OLEDs) employing thermally activated delayed fluorescence (TADF) emitters with blue, green, yellow, and orange-red colors. However, efficient TADF materials with colors ranging from red, to deep-red, to near-infrared (NIR) have been rarely reported owing to the difficulty in molecular design. Herein, we report the first NIR TADF molecule TPA-DCPP (TPA=triphenylamine; DCPP=2,3-dicyanopyrazino phenanthrene) which has a small singlet-triplet splitting (ΔEST ) of 0.13 eV. Its nondoped OLED device exhibits a maximum external quantum efficiency (EQE) of 2.1 % with a Commission International de L'Éclairage (CIE) coordinate of (0.70, 0.29). Moreover, an extremely high EQE of nearly 10 % with an emission band at λ=668 nm has been achieved in the doped device, which is comparable to the most-efficient deep-red/NIR phosphorescent OLEDs with similar electroluminescent spectra.

Size-independent boosting of near-infrared persistent luminescence in nano-phosphors via a magnesium doping strategy.

Near-infrared (NIR)-emitting persistent luminescence nanoparticles (PLNPs) are ideal optical imaging contrast reagents characterized by autofluorescence-free optical imaging for their frontier applications in long-term bioimaging. Preparation of uniform small-sized PLNPs with excellent luminescence performance is crucial for biomedical applications, but challenging. Here, we report a facile magnesium doping strategy to achieve size-independent boost of NIR persistent luminescence in typical and most concerned ZnGa2O4:Cr3+ PLNPs. This strategy relies on the doping of Mg2+ ions that with similar size of Zn2+ ions in the host lattice matrix, and concomitant to the electron traps tailoring tuned by varying the feed ratio of Mg2+. The optimum Mg2+-doped PLNPs give a long afterglow time (signal-to-noise ratio (SNR) = 31.6 at 30 d) without changing the desirable uniform sub-10 nm size of the original nanocrystals. The appropriate increase of the depth and concentration of electron trap contribute jointly to the enhancement of lifetime (488 % longer, 20.57 s) and afterglow time for 700 nm persistent luminescence. Meanwhile, these PLNPs keep the original excellent rechargeability and promote over 60 times increase of SNR in renewable in vivo imaging. This simple strategy provides a basis for new opportunities to address the critical challenge of effective optical performance boost in small-sized PLNPs.