Near-infrared Region Research Articles

Expanding the Toolbox of Oxidants: Controllable Etching of Ultrasmall Au Nanoparticles toward Tailorable NIR-II Luminescence and Ligand-Mediated Biodistribution and Clearance.

Oxidant-driven and controllable etching of small-sized nanoparticles (NPs, d < 3 nm) and tailorable modulation of their optical properties are challenging due to the high reactivity and complicated surface chemistry. Herein, we present a facile strategy for highly controllable oxidative etching of ultrasmall AuNPs and tailorable modulation of luminescence. The proper choice of a moderate oxidant, ClO-, could not only selectively etch the Au(I)-thiolate motifs from the nanoparticle surface at the subnanometer scale but also retained a stable metallic core structure without aggregation, which impressively prompted the wide-range luminescent switching from the visible to second near-infrared (NIR-II) region. The resultant oxidized AuNPs displayed highly luminescent NIR-II emission with a quantum yield of 3.0%, excellent monodispersed stability, ideal biocompatibility, and tunable shielding effects against protein adsorption. With those outstanding features, oxidized AuNPs could be utilized as nanoprobes for long-lasting and in vivo bioimaging of associated metabolic behaviors with distinguishable organ-specific targeting capabilities and ligand-mediated kinetics in nanoparticle clearance. These findings expand the toolbox of oxidants for the controllable synthesis of NIR-II nanoprobes and open up a path for exploring diverse ligand interactions on ultrasmall AuNPs with organs or tissues that might advance their monitoring applications for a wide range of clinically important diseases.

Tailored Environment-Friendly Reverse Type-I Colloidal Quantum Dots for a Near-Infrared Optical Synapse and Artificial Vision System.

Colloidal quantum dots (QDs) are emerging as potential candidates for constructing near-infrared (NIR) photodetectors (PDs) and artificial optoelectronic synapses due to solution processability and a tunable bandgap. However, most of the current NIR QDs-optoelectronic devices are still fabricated using QDs with incorporated harmful heavy metals of lead (Pb) and mercury (Hg), showing potential health and environment risks. In this work, we tailored eco-friendly reverse type-I ZnSe/InP QDs by copper (Cu) doping and extended the photoresponse from the visible to NIR region. Transient absorption spectroscopy analysis revealed the presence of Cu dopant states in ZnSe/InP:Cu QDs that facilitated the extraction of photogenerated charge carriers, leading to an enhanced photodetection performance. Specifically, under 400 nm illumination, the Cu-doped ZnSe/InP QDs-based PDs presented a broadband photodetection ranging from ultraviolet (UV) to NIR, with a responsivity of 70.5 A W-1 and detectivity of 2.8 × 1011 Jones, surpassing those of the undoped ZnSe/InP QDs-based PDs (49.4 A W-1 and 1.9 × 1011 Jones, respectively). More importantly, the ZnSe/InP:Cu QDs-PDs demonstrated various synapse-like characteristics of short-term plasticity (STP), long-term plasticity (LTP), and learning-forging-relearning under NIR light illumination, which were further used to construct PD array devices for simulating the artificial visual system that is available in prospective optical neuromorphic applications.

High Fluorescence of Phytochromes Does Not Require Chromophore Protonation

Fluorescing proteins emitting in the near-infrared region are of high importance in various fields of biomedicine and applied life sciences. Promising candidates are phytochromes that can be engineered to a small size and genetically attached to a target system for in vivo monitoring. Here, we have investigated two of these minimal single-domain phytochromes, miRFP670nano3 and miRFP718nano, aiming at a better understanding of the structural parameters that control the fluorescence properties of the covalently bound biliverdin (BV) chromophore. On the basis of resonance Raman and time-resolved fluorescence spectroscopy, it is shown that in both proteins, BV is deprotonated at one of the inner pyrrole rings (B or C). This protonation pattern, which is unusual for tetrapyrroles in proteins, implies an equilibrium between a B- and C-protonated tautomer. The dynamics of the equilibrium are slow compared to the fluorescence lifetime in miRFP670nano3 but much faster in miRFP718nano, both in the ground and excited states. The different rates of proton exchange are most likely due to the different structural dynamics of the more rigid and more flexible chromophore in miRFP670nano3 and miRFP718nano, respectively. We suggest that these structural properties account for the quite different fluorescent quantum yields of both proteins.

Carbazole-Based Dual-Band Electrochromic Polymers: The Effect of Linkage Sites on Electrochromic Performance.

Dual-band electrochromic (EC) materials are expected to be utilized as building materials for energy saving, but their cycle stability is still an obstacle. Here, two D-A conjugated polymers, PDPPCz36 and PDPPCz27, based on diketopyrrolopyrrole and carbazole linked with different sites, are synthesized. Both of them exhibit dual-band EC behaviors with a dark blue color in the neutral state and high absorption in the near-infrared (NIR) region when oxidized. However, PDPPCz36 exhibits better cycle stability and a shorter response time than PDPPCz27. In the visible (VIS) region, the PDPPCz36 film exhibits an initial light modulation range (ΔT) of 43.0% and that of the PDPPCz27 film is 41.3%. After 100 cycles of redox, the ΔT of the PDPPCz36 film declines by 32%, while that of PDPPCz27 attenuates by more than 50%. A similar tendency is evident in the NIR region. Moreover, PDPPCz36 shows subsecond colored switch times both in the VIS (0.4 s) and NIR (0.7 s) regions, while those of PDPPCz27 are 2.1 and 1.6 s, respectively. Further research suggests that 3,6-linked carbazoles in PDPPCz36 simultaneously inhibit the side reaction and film aggregation, which leads to better redox stability and shorter response time in both EC tests and devices.

Selective Chromogenic Chemosensors for Arsenite Anion: A Facile Approach to Analyzing Arsenite in Honey, Milk, and Water Samples.

In this study, two chemosensors, N5R1 and N5R2, based on 5-(4-nitrophenyl)-2-furaldehyde, with varying electron-withdrawing groups, were synthesized and effectively employed for the colorimetric selective detection of arsenite anions in a DMSO/H2O solvent mixture (8 : 2, v/v). Chemosensors N5R1 and N5R2 exhibited a distinct color change upon binding with arsenite, accompanied by a spectral shift toward the near-infrared region (Δλmax exceeding 200 nm). These chemosensors established stability between a pH range 6-12. Among them, N5R2 displayed the lowest detection limit of 17.63 ppb with a high binding constant of 2.6163×105 M-1 for arsenite. The binding mechanism involved initial hydrogen bonding between the NH binding site and the arsenite anion, followed by deprotonation and an intramolecular charge transfer (ICT) mechanism. The mechanism was confirmed through UV and 1H NMR titrations, cyclic voltammetric studies, and theoretical calculations. The interactions between the sensor and arsenite anions were further analyzed using global reactivity parameters (GRPs). Practical applications were demonstrated through the utilization of test strips and molecular logic gates. Real water samples, honey, and milk samples were successfully analyzed by both chemosensors for the sensing of arsenite.

Room-temperature infrared photoluminescence and broadband photodetection characteristics of Ge/GeSi islands on silicon-on-insulator.

In this study, molecular beam epitaxial growth of strain-driven three-dimensional self-assembled Ge/GeSi islands on silicon-on-insulator (SOI) substrates, along with their optical and photodetection characteristics, have been demonstrated. The as-grown islands exhibit a bimodal size distribution, consisting of both Ge and GeSi alloy islands, and show significant photoluminescence (PL) emission at room temperature, specifically near optical communication wavelengths. Additionally, these samples were used to fabricate a Ge/GeSi islands/Si nanowire (NW) based phototransistor using a typical e-beam lithography process. The fabricated device exhibited broadband photoresponse characteristics, spanning a wide wavelength range (300-1600 nm) coupled with superior photodetection characteristics and relatively low dark current (~ tens of pA). The remarkable photoresponsivity of the fabricated device, with a peak value of ~11.4 A/W (λ ~ 900 nm) in the near-infrared (NIR) region and ~ 1.36 A/W (λ ~ 1500 nm) in the short-wave infrared (SWIR) region, is a direct result of the photoconductive gain exceeding unity. The room-temperature optical emission and outstanding photodetection performance, covering a wide spectral range from the visible to the SWIR region, showcased by the single layer of Ge/GeSi islands on SOI substrate, highlight their potential towards advanced applications in broadband infrared Si-photonics and imaging. These capabilities make them highly promising for cutting-edge applications compatible with complementary metal-oxide-semiconductor (CMOS) technology.

Early Detection of Dendroctonus valens Infestation with UAV-Based Thermal and Hyperspectral Images

Dendroctonus valens is one of the main invasive pests in China, causing serious economic and ecological damage. Early detection and control of D. valens can help prevent further outbreaks. Based on unmanned aerial vehicle (UAV) thermal infrared and hyperspectral data, we compared the spectral characteristics of Pinus sylvestris var. mongolica in three states (healthy, early-infested, and dead), and constructed a classification model based on the random forest algorithm using four spectral datasets (reflectance, first derivative, second derivative, and spectral vegetation index) and one temperature parameter dataset. Our results indicated that the spectral differences between healthy and early-infested trees mainly occur in the near-infrared region, with dead trees showing different characteristics. While it was effective to distinguish healthy from early-infested trees using spectral data alone, the addition of a temperature parameter further improved classification accuracy across all datasets. The combination of the spectral vegetation index and temperature parameter achieved the highest accuracy at 93.75%, which is 3.13% higher than using the spectral vegetation index alone. This combination also significantly improved early detection precision by 13.89%. Our findings demonstrated the applicability of UAV-based thermal infrared and combined hyperspectral datasets in monitoring D. valens early-infested trees, providing important technical support for the scientific prevention and control of D. valens.

Recent Advances in DNA-Based Nanoprobes for In vivo MiRNA Imaging.

As a post transcriptional regulator of gene expression, microRNAs (miRNA) is closely related to many major human diseases, especially cancer. Therefore, its precise detection is very important for disease diagnosis and treatment. With the advancement of fluorescent dye and imaging technology, the focus has shifted from in vitro miRNA detection to in vivo miRNA imaging. This concept review summarizes signal amplification strategies including DNAzyme catalytic reaction, hybrid chain reaction (HCR), catalytic hairpin assembly (CHA) to enhance detection signal of lowly expressed miRNAs; external stimuli of ultraviolet (UV) light or near-infrared region (NIR) light, and internal stimuli such as adenosine triphosphate (ATP), glutathione (GSH), protease and cell membrane protein to prevent nonspecific activation for the avoidance of false positive signal; and the development of fluorescent probes with emission in NIR for in vivo miRNA imaging; as well as rare earth nanoparticle based the second near-infrared window (NIR-II) nanoprobes with excellent tissue penetration and depth for in vivo miRNA imaging. The concept review also indicated current challenges for in vivo miRNA imaging including the dynamic monitoring of miRNA expression change and simultaneous in vivo imaging of multiple miRNAs.

Diaminonaphthalene Boronic Acid (DANBA): New Approach for Peroxynitrite Sensing Site.

Selective detection of reactive oxygen species (ROS) is vital for studying their role in brain diseases. Fluorescence probes can distinguish ONOO- species from other ROS; however, their selectivity toward ONOO- species depends on the ONOO- recognition group. Aryl-boronic acids and esters, which are common ONOO- recognition groups, are not selective for ONOO- over H2O2. In this study, we developed a diaminonaphthalene (DAN)-protected boronic acid as a new ONOO- recognition group that selectively reacts with ONOO- over H2O2 and other ROS. Three DAN-protected boronic acid (DANBA)-based fluorophores that emit fluorescence over visible to near-infrared (NIR) regions, Cou-BN, BVP-BN, and HDM-BN, and their aryl-boronic acid-based counterparts (Cou-BO, BVP-BO, and HDM-BO), were developed. The DANBA-based probes exhibited enhanced selectivity toward ONOO- over that of their control group, as well as universality in solution assays and in vitro experiments with PC12 cells. The NIR-emissive HDM-BN was optimized to delineate in vivo ONOO- levels in mouse brains with Parkinson's disease. This DAN-protected boronic acid belongs to a new generation of recognition groups for developing ONOO- probes, and this strategy could be extended to other common hydroxyl-containing dyes to detect ONOO- levels in complex biological systems and processes.

Improving broadband absorption of carbon dot conjugated melanin via pre-doping strategy as interfacial photothermal evaporator

Photothermal seawater desalination harnesses solar energy to induce heat and expediates seawater evaporation and purification. The desalination efficacy heavily relies on the light absorption capability and microstructure of the solar evaporator. Polydopamine (PDA) represents a typical synthetic melanin with broad spectral absorption characteristics. However, its absorption capacity within the near-infrared (NIR) region is limited, leading to inadequate photothermal conversion efficiency. To overcome this challenge, we adopt a straightforward approach involving the pre-doping of N,S-doped carbon quantum dots (N,S-CQDs) with dopamine through covalent interaction to fabricate CQDs-loaded mesoporous polydopamine (MPDA-8). This strategy effectively reduces the band gap of PDA by fostering additional donor–acceptor pairs and π-stacking structures, thereby broadening the absorption capacity across the UV–Vis-NIR spectrum through nonradiative transitions. The MPDA-8 coated Balsa wood and cellulose evaporator achieved high evaporation rates of 1.82 kg m−2 h−1 and 2.10 kg m−2 h−1, respectively, overcoming the limit of 2D interfacial evaporator. The small pores and fiber channels within the wood, coupled with the hydrophilicity of MPDA-8, facilitates efficient water transportation and reduces evaporation enthalpy. Outdoor evaporation experiments conducted under sunlight corroborated the practical viability of this material. This study introduces a new perspective for advancing synthetic melanins in photothermal applications through the nanoparticle pre-doping strategy.

Advanced Palladium Nanosheet-Enhanced Phototherapy for Treating Wound Infection Caused by Multidrug-Resistant Bacteria.

With the increasing spread of multidrug-resistant (MDR) bacteria worldwide, it is needed to develop antibiotics-alternative strategies for the treatment of bacterial infections. This work develops a multifunctional single-component palladium nanosheet (PdNS) with broad-spectrum and highly effective bactericidal activity against MDR bacteria. PdNS exerts its endogenous nanoknife (mechanical cutting) effect and peroxidase-like activity independent of light. Under near-infrared region (NIR) light irradiation, PdNS exhibits photothermal effect to produce local heat and meanwhile possesses photodynamic effect to generate 1O2; notably, PdNS has catalase-like activity-dependent extra photodynamic effect upon H2O2 addition. PdNS+H2O2+NIR employs a collectively synergistic mechanism of nanoknife effect, peroxidase/catalase-like catalytic activity, photothermal effect, and photodynamic effect for bacterial killing. PdNS+H2O2+NIR causes compensatory elevated phospholipid biosynthesis, disordered energy metabolism, increased cellular ROS levels and excessive oxidative stress, and inhibited nucleic acid synthesis in bacteria. In mice, PdNS+H2O2+NIR gives >92.7% bactericidal rates at infected wounds and almost the full recovery of infected wounds, and it leads to extensive down-regulation of proinflammatory pathways and comprehensive up-regulation of wound healing pathways, conferring elevated inflammation resolution and meanwhile accelerated wound repair. PdNS+H2O2+NIR represents a highly efficient nanoplatform for photoenhanced treatment of superficial infections.

Emerging class of SrZrS3 chalcogenide perovskite solar cells: Conductive MOFs as HTLs - A game changer?

The emerging SrZrS3 chalcogenide perovskite has been suggested as a potential alternative to lead halide perovskites, offering unique optoelectronic properties while addressing concerns such as lead toxicity and instability. Our research explored its potential, demonstrating the use of conductive metal-organic frameworks (c-MOFs) Cu-MOF ({[Cu2(6-mercapto nicotinate)]·NH4}n), NTU-9, Fe2(DSBDC), Sr-MOF ({[Sr(ntca)(H2O)2]·H2O}n), Mn2(DSBDC), and Cu3(HHTP)2 as promising substitutes for traditional HTLs via SCAPS-1D. By systematically optimizing the absorber and HTL properties, maximum PCEs of 30.60 %, 29.78 %, 28.29 %, 28.44 %, 28.80 %, and 28.62 % were accomplished for solar cell devices based on the aforementioned MOFs, respectively. Comparative analysis of initial and optimized solar cells using energy band diagrams, Nyquist plots, and quantum efficiency revealed that optimized devices consistently raised quasi-Fermi levels, significantly enhanced conductivity, and boosted solar cell performance. Additionally, the high recombination resistance of 1.4 × 107 Ω cm2, improved spectral response of 35 % in the NIR region, and heightened built-in potential (∼0.99 V) resulted in the highest efficiency of 30.60 % for Cu-MOF solar cells. This research highlights the promising potential of novel SrZrS3 absorbers and the utilization of c-MOFs as HTLs in solar cells, positioning them as a game changer in the PV field.

Generating Immunological Memory Against Cancer by Camouflaging Gold-Based Photothermal Nanoparticles in NIR-II Biowindow for Mimicking T-Cells.

Photothermal therapy (PTT) against cancer not only directly ablates tumors but also induces tumor immunogenic cell death (ICD). However, the antitumor immune response elicited by ICD is insufficient to prevent relapse and metastasis because of the immunosuppressive tumor microenvironment (TME). A biomimetic nanoplatform (bmNP) mimicking cytotoxic lymphocytes (CTLs) for combinational photothermal-immunotherapy to effectively regulate the immunosuppressive TME is reported here. The bmNP is constructed by wrapping the T-cell membrane onto a new type of photothermal agents, spherical Au-based PNCs (sAuPNCs). Similar to T-cells, the bmNP enhanced accumulation at the tumor site by targeting the tumor via adhesion proteins on T-cell membrane. The obtained sAuPNCs have a wide absorption band in the second near-infrared (NIR-II) region with a high photothermal conversion efficiency (PCE) up to about 75% and excellent photostability. The bmNP with a smaller size is more superior compete with T-cells to bond with tumor cells via PD-1/PD-L1 interaction to effectively block the PD-1 checkpoint of T-cells for preventing T-cell exhaustion. Furthermore, in vivo studies reveal the immunological memory effect is significantly elicited in mice received bmNPs therapy. Collectively, bmNPs show great potential in photothermal-enhanced immunotherapy.

Enhanced broadband perfect absorption in visible and near-infrared regimes

ABSTRACT It is still a challenge to achieve perfect ((near-unity)) absorption across a wide wavelength range with a three-layer structure. This paper presents a metamaterial absorber (MA) based on MXene that can achieve broadband and perfect absorption in the near-infrared and visible regions. The MA with a simple three-layer structure consists of a top Ti3C2T x layer, an intermediate dielectric layer and a bottom gold layer. It can achieve perfect absorption (the absorptivity over 99%) in the wavelength range of 730–900 nm. The electric field distribution reveals that the localized surface plasmon resonance occurring at the interface of Ti3C2T x and SiO2 leads to strong absorption over the wide wavelength range. Furthermore, the MA exhibits excellent angular stability. This work provides a method to construct MAs with broadband perfect absorption in the near-infrared and visible band.

Investigating the impact of acetylenic linkage in C20 fullerene: Utilization in optoelectronic devices and as anode material

This study delves into the diverse characteristics of C80 fulleryne, derived from the incorporation of acetylenic linkages into each chain of the smallest fullerene, C20. Utilizing advanced theoretical computations, we confirm the stability of C80 fulleryne. Notably, its possession of a finite energy gap (0.743 eV) categorizes it as a semiconductor. Further enlightenment into its structural stability, bonding and reactivity stems from an exploration of different energy components, topological descriptors of electron density and chemical reactivity parameters. C80 fulleryne can act as radical scavenger owing to its higher electron affinity (5.5 eV). Spectral analysis revealed the C80 fulleryne’s absorption within the near-infrared region and its intriguing optical transparency with negligible loss in specific regions of the electromagnetic spectrum. Additionally, our investigation scrutinized the viability of C80 fulleryne as an anode material in Lithium-ion batteries. The presence of low adsorption energy (−1.693 eV) and significant amount of Bader charge transfer (0.917 e) between Li-ion and C atoms of C80 fulleryne confirms that Li-ion gets chemisorbed on the C80 fulleryne. Remarkably, this cage acts as a storehouse to host 12 Li ions, precisely one for each of its constituent pentagons within the C80 fulleryne structure, bearing a theoretical capacitance of 335 mAhg−1.

A synergetic effect of light and anion: near-infrared colorimetric monitoring of nitric oxide (NO) release from fluoride/cyanide anions and a water responsive ruthenium nitrosyl complex.

Near-infrared (NIR) spectral-responsive multitasking chemical systems are always advantageous in biological and environmental systems. Although ruthenium complexes are highly attractive compounds for many applications, studies on NIR optical responsive sensors are very limited because of their synthetic difficulties. The sensing of fluoride and cyanide ions using ruthenium nitrosyl complexes is not known. In this study, we report the synthesis and characterization of a new terpyridine-based ruthenium nitrosyl complex [Ru(Cl)2NO(terpy-C6H4OH)] 1·Ru-OH. The complex exhibited distinct NIR absorptions at 680 nm, as well as a visible color change with the fluoride ion in DMSO-CH3CN medium. However, when the solvent is changed to DMSO-H2O, it responds only with a cyanide ion with a distinct colorimetric change. Binding of the F- ion leads to deprotonation of 1·Ru-OH; the deprotonated complex is also used for the colorimetric detection of a trace amount of water in DMSO and acetonitrile with a limit of detection (LOD) of 0.034 wt% and 0.007 wt%, respectively. Ruthenium nitrosyl complexes have appeared as promising platforms for light-controlled release of nitric oxide (NO), which can be beneficial for therapeutic application. NO release studies of 1·Ru-OH by UV-vis and FT-IR spectroscopy confirm that it can release NO in a light-controlled manner. In addition, the NO release could be monitored by the naked eye with a color change and spectral change in the NIR region. Importantly, NO release studies revealed that the rate of NO release could be modulated in the presence of the F- ion. Here, the fluoride ion acts as an allosteric regulator. These results demonstrate that 1·Ru-OH is both a promising multitasking colorimetric and NIR sensor and a colorimetric responsive NO-releasing agent.

Hydrogen Sulfide (H2S)activatable Photodynamic Therapy Against Colon Cancer by tunable FRET Effect.

Developing activatable photodynamic agents is becoming a promising mode for realizing selective photodynamic therapy (PDT) in cancer treatment. However, till now only a few H2S-activatable photodynamic agents have been involved in this field. Here, we fabricated H2S-activatable nano-assemblies (P@TPPCY) for the treatment of colon cancer containing high concentration H2S. The H2S-activatable photosensitizer (TPPCY) was synthesized by covalent conjugation between tetraphenylporphyrin (TPP) and heptamethine cyanine (Cy7), and then TPPCY was encapsulated by an amphiphilic polymer DSPE-mPEG to form P@TPPCY nano-assemblies. We demonstrated that the photosensitizing effect of TPP was efficiently quenched by Cy7 with strong absorption in the NIR region via fluorescence resonance energy transfer (FRET) effect. Interestingly, the FRET effect between Cy7 and TPP was attenuated by the decrease of absorption of Cy7 in the NIR region after the Cy7 reacted with H2S, and then the photosensitizing effect of TPP in P@TPPCY was activated. Strikingly, the P@TPPCY showed efficient H2S-activatable photodynamic therapy (PDT) in vitro against HCT116 cells (human colon carcinoma cell line), thus this work provides a new method for realizing accurate treatment of colon cancer in virtue of high H2S concentration microenvironment.

Photothermal performance of carbon nanotubes in the visible and near-infrared regions: applications in water evaporation and destroying cancer cells

Photothermal performance of carbon nanotubes in the visible and near-infrared regions: applications in water evaporation and destroying cancer cells

Water-Soluble Lipophilic Near-Infrared Region II Fluorophores for High-Brightness Lipid Layer and Lipid Droplets Imaging Applications.

Fluorescence imaging in the second near-infrared region (NIR-II, 1000-1700nm) has garnered considerable attention for displaying the biological information of deep tissues. However, the lack of biocompatible contrast agents with bright NIR-II emission has hampered the precise clinical application of deep tissue imaging. Here, a lipophilic enhancement strategy employing donor-acceptor-donor (D-A-D) molecules, introducing long alkoxy chains and quaternary ammonium salts for the development of highly bright water-soluble NIR-II fluorophores (BBTD-2C-N), is described. Notably, liposome-encapsulated BBTD-2C-N nanoparticles (B-2C-N/DMPC) in aqueous solution exhibit a 1.8-fold increase in NIR-II fluorescence brightness compared to free BBTD-2C-N in methanol. Avoidance of the aggregation-caused quenching effect and enhanced NIR-II fluorescence are attributed to significantly attenuated π-π stacking interactions and maintained monodisperses in the hydrophobic liposome shell. Moreover, BBTD-2C-N demonstrates superior performance in visualizing lipid droplet-rich HeLa cells in vitro, as well as precise monitoring of adipose tissue and fatty liver in vivo. This study reveals a new avenue for the development of bright NIR-II fluorophores and precise in vivo imaging.

Au25 Cluster-Based Atomically Precise Coordination Frameworks and Emission Engineering through Lattice Symmetry.

The atomically precise metal nanoclusters (NCs) have attracted significant attention due to their superatomic behavior originating from the quantum confinement effect. This behavior makes these materials suitable for various photoluminescence-based applications, including chemical sensing, bioimaging, and phototherapy, owing to their intriguing optical properties. Especially, the manipulation of inter- or intracluster interaction through cluster-assembled materials (CAMs) presents significant pathways for modifying the photophysical properties of NCs. Herein, two distinct CAMs, Au25-Zn-Hex and Au25-Zn-Rod, were synthesized via forming a coordination bond between [Au25(p-HMBA)18]- (p-H2MBA = 4-mercaptobenzoic acid) and Zn2+. Au25-Zn-Rod exhibited a 6-fold higher luminescence intensity in the near-infrared region compared to Au25-Zn-Hex, attributed to synergistic inter- and intracluster interactions that induce exciton delocalization and structure rigidification at the atomic scale. This study highlights the potential of diverse lattice symmetries in cluster-based frameworks for tuning the photophysical properties, contributing to a deeper understanding of the structure-property relationship in Au NCs.