Near-infrared Region Research Articles

Feasibility of spectro-polarimetric measurement in separating reflection components for improving water contaminant determination

Water bodies are critical to the environment, providing numerous ecological benefits; however, human activities increasingly threaten their quality. Natural water systems exhibit regional variability, dominated by organic and inorganic species, rendering in-situ measurements insufficient. Current remote sensing methods often overlook the impact of surface light components, which vary with solar radiation and wave intensity. This study demonstrates an approach for water quality monitoring utilizing spectral reflectance and polarization in the visible and near-infrared regions. A line spectrometer with a polarization filter was employed for hyperspectral measurements under simulated wave conditions. Chlorophyll (Chl) and suspended sediment (SS) pollution were simulated using locally sourced products at various concentrations. The contaminant reflectance was computed, and the polarization components were analyzed using the Pickering method and Stokes vectors. Normalization and continuum removal techniques ensured reliable comparisons across the spectra. The spectral angle mapper (SAM) algorithm quantified the similarity between unpolarized wave conditions and total reflectance spectra under calm conditions, while spectral entropy quantified wave effects compared to calm water. The results indicated that the polarized components of Chl and SS reflectance were minimal in calm water but increased under wave conditions, particularly at lower wavelengths. Higher contaminant concentrations exhibited greater spectral similarity, with lower SAM values indicating reduced specular reflections. The raw and normalized unpolarized reflectance spectra displayed characteristic features; however, the reflectance at high concentrations was lower than anticipated, likely due to spectrometer sensitivity and strong water absorption. The degree of Linear Polarization (DoLP) analysis revealed distinct scattering behaviors: Chl exhibited a lower DoLP than SS. Wave conditions enhanced the DoLP due to increased specular reflections. Overall, the method effectively separates reflection components but is sensitive to measurement conditions, emphasizing the necessity to account for angles and water conditions when estimating contaminants.

Biodiversity from the Sky: Testing the Spectral Variation Hypothesis in the Brazilian Atlantic Forest

Tropical forests have high species richness, being considered the most diverse and complex ecosystems in the world. Research on the variation and maintenance of biodiversity in these ecosystems is important for establishing conservation strategies. The main objective of this study was to test the Spectral Variation Hypothesis through associations between species diversity and richness measured in the field and hyperspectral data collected by a Remotely Piloted Aircraft (RPA) in areas with secondary tropical forest in the Brazilian Atlantic Forest biome. Specific objectives were to determine which dispersion measurements, standard deviation (SD) or coefficient of variation (CV), estimated for the n pixels occurring within each sampling unit, better explains species diversity; the effects of pixel size on the direction and intensity of this relationship; and the effects of shaded pixels within each sampling unit. The spectral variability hypothesis was confirmed for the Atlantic Forest biome, with R2 of 0.83 for species richness and 0.76 and 0.69 for the Shannon and Simpson diversity indices, respectively, using 1.0 m illuminated pixels. The dispersion (CV and SD) of hyperspectral bands were most strongly correlated with taxonomic diversity and richness in the red-edge and near-infrared (NIR) regions of the electromagnetic spectrum. Pixel size affected R2 values, which were higher for 1.0 m pixels (0.83) and lower for 10.0 m pixels (0.71). Additionally, illuminated pixels had higher R2 values than those under shadow effects. The main dispersion variables selected as metrics for regression models were mean CV, CV for the 726.7 nm band, and SD for the 742.3 and 933.4 nm bands. Our results suggest that spectral diversity can serve as a proxy for species diversity in the Atlantic Forest. However, factors that can affect this relationship, such as taxonomic and spectral diversity metrics used, pixel size, and shadow effects in images, should be considered.

One-dimensional C60 arrays in noncovalent benzidine networks

Face-centered cubic packing is typically observed for pristine C60 in the solid state, and one-dimensional alignment structures of pristine C60 in the solid state are extremely rare. This study presents the synthesis of novel one-dimensional aligned C60 in single-cocrystal nanosheets, formed from C60 and N,N,N′,N′-tetraphenylbenzidine (TPB). In C60/TPB, which exhibits ambipolar charge transport characteristics, TPB serves as a molecular receptor to facilitate the formation of noncovalent networks wherein C60 organizes into one-dimensional arrays. The resulting C60/TPB nanosheets give rise to a distinct absorption band in the near-infrared region, suggesting the occurrence of charge-transfer interactions between the C60 and TPB frameworks within the cocrystals.

Quasi-point NIR light source based on laser-driven photoluminescence for eye-safe imaging applications

Near-infrared (NIR) imaging, as a newly emerged technique, demonstrates immense potential in various imaging applications such as biological detection, night vision, and anti-counterfeiting. The imaging quality of the currently available NIR light sources is limited by their low radiant exitance and poor beam quality. Herein, a quasi-point NIR light source based on a laser-driven photoluminescence technique was successfully developed. A single blue laser diode (LD) with a power of ∼2250 mW and a minimum spot size of ≈ 0.13 mm-2 is employed as the pumping source. A Cr-doped MgO ceramic displaying strong luminescence in the NIR region is used as the emitter. Interestingly, the prepared MgO:Cr ceramic is able to withstand the blue laser irradiation density of > 5600 mW·mm-2, and therefore, the fabricated NIR light source demonstrates a high radiant flux of ∼234 mW with a high radiant exitance of ∼139 mW·mm-2. Furthermore, the emitting area is as small as ∼1.6 mm2, which is highly beneficial for optical design and device miniaturization. The overall performance of the quasi-point NIR light source in blood vessel imaging and night vision applications is evaluated.

The Quenching of Long-Wavelength Fluorescence by the Closed Reaction Center in Photosystem I in Thermostichus vulcanus at 77 K.

Photosystem I in most organisms contains long-wavelength or "Red" chlorophylls (Chls) absorbing light beyond 700 nm. At cryogenic temperatures, the Red Chls become quasi-traps for excitations as uphill energy transfer is blocked. One pathway for de-excitation of the Red Chls is via transfer to the oxidized RC (P700+), which has broad absorption in the near-infrared region. This study investigates the excitation dynamics of Red Chls in Photosystem I from the cyanobacterium Thermostichus vulcanus at cryogenic temperatures (77 K) and examines the role of the oxidized RC in modulating their fluorescence kinetics. Using time-resolved fluorescence spectroscopy, the kinetics of Red Chls were recorded for samples with open (neutral P700) and closed (P700+) RCs. We found that emission lifetimes in the range of 710-720 nm remained unaffected by the RC state, while more red-shifted emissions (>730 nm) decayed significantly faster when the RC was closed. A kinetic model describing the quenching by the oxidized RC was constructed based on simultaneous fitting to the recorded fluorescence emission in Photosystem I with open and closed RCs. The analysis resolved multiple Red Chl forms and variable quenching efficiencies correlated with their spectral properties. Only the most red-shifted Chls, with emission beyond 730 nm, are efficiently quenched by P700+, with rate constants of up to 6 ns-1. The modeling results support the notion that structural and energetic disorder in Photosystem I can have a comparable or larger effect on the excitation dynamics than the geometric arrangement of Chls.

Photothermal and colorimetric detection of cholesterol using hollow ruthenium nanoparticles

Nanozyme, an artificial enzyme with some advantages that compensate for the inherent shortcomings of natural enzymes have been explored. Among the various nanoparticles, those with a hollow structure have the advantage of enabling facile transfer of reactants and exhibiting a high surface-to-volume ratio. Herein, we synthesized hollow ruthenium nanoparticles (HRNs) by the galvanic replacement reaction. Transmission electron microscopy confirmed an average size of 32 nm and a shell thickness of about 2.5 nm. HRNs showed superior catalytic activity compared to natural enzymes due to the advantages of their hollow structure. Based on enhanced catalytic activity, HRNs were applied to cholesterol detection using 2,2′-azino-bis (3-ethylbenzo-thiazoline-6-sulfonic acid) (ABTS) and 3,3′,5,5′-tetramethylbenzidine (TMB). These common chromogenic substrates in colorimetric methods have strong absorbance in the UV–visible and near-infrared (NIR) regions in their oxidized forms. Therefore, both substrates can serve as probes in photothermal and colorimetric assays. Two oxidized substrates absorbed the NIR laser (808 nm) and released energy in the form of heat. Consequently, the temperature of the reaction solution increased in proportion to the cholesterol concentration. In the cholesterol detection assay using ABTS, linear ranges were ranged from 0.08 to 10 mM (R2 = 0.998) for the colorimetric assay and from 0.08 to 2.5 mM (R2 = 0.996) for the photothermal assay, respectively. The limits of detection were determined to be 12.3 μM in the colorimetric method and 43.5 μM in the photothermal method. These results demonstrate that HRN is an excellent substitute for natural enzymes and a promising material for analytical applications.

Persistent Luminescence for Night‐Time Individual Identification Based on Quantum Tunneling

AbstractNight‐time individual identification requires recognizing a specific object from a bunch of homogeneous entities through night‐vision devices. It will facilitate more effective coordinated actions in night‐time disaster rescue or enforcement actions. In this work, the near infrared (NIR) persistent luminescent materials are proposed as the technology solution, which can emit the non‐visible photons continuously for hours without the external excitation. In a magnetoplumbite‐type structure, Cr3+ ions are incorporated to realize NIR emissions. By co‐doping lanthanide ions and constitutional modulation, the afterglow signal can be clearly traced under the night‐vision device over 144 h. A series of spectral measurements are utilized to reveal the mechanism behind this prolonged afterglow duration, and quantum tunneling accounts for the carrier pumping from the deep traps. It avoids the quick exhaust of carriers stored in the shallow traps, and extends the afterglow duration. In a proof‐of‐concept demonstration, the synthesized powders are used to make a quick response pattern, which can be clearly visualized in a dark room by the night‐vision devices. This work is expected to promote the research and development of persistent luminescent materials within NIR region, and to accelerate the applications in night‐time monitoring and recognition.

Structural Complexity Significantly Impacts Canopy Reflectance Simulations as Revealed from Reconstructed and Sentinel-2-Monitored Scenes in a Temperate Deciduous Forest

Detailed three-dimensional (3D) radiative transfer models (RTMs) enable a clear understanding of the interactions between light, biochemistry, and canopy structure, but they are rarely explicitly evaluated due to the availability of 3D canopy structure data, leading to a lack of knowledge on how canopy structure/leaf characteristics affect radiative transfer processes within forest ecosystems. In this study, the newly released 3D RTM Eradiate was extensively evaluated based on both virtual scenes reconstructed using the quantitative structure model (QSM) by adding leaves to point clouds generated from terrestrial laser scanning (TLS) data, and real scenes monitored by Sentinel-2 in a typical temperate deciduous forest. The effects of structural parameters on reflectance were investigated through sensitivity analysis, and the performance of the 3D model was compared with the 5-Scale and PROSAIL radiative transfer models. The results showed that the Eradiate-simulated reflectance achieved good agreement with the Sentinel-2 reflectance, especially in the visible and near-infrared spectral regions. Furthermore, the simulated reflectance, particularly in the blue and shortwave infrared spectral bands, was clearly shown to be influenced by canopy structure using the Eradiate model. This study demonstrated that the Eradiate RTM, based on the 3D explicit representation, is capable of providing accurate radiative transfer simulations in the temperate deciduous forest and hence provides a basis for understanding tree interactions and their effects on ecosystem structure and functions.

A pixel-level assessment method of the aging status of silicone rubber insulators based on hyperspectral imaging technology and IPCA-SVM model

Acidic environments are a significant factor in the aging and failure of silicone rubber insulators. Addressing the effective assessment of insulators’ aging state to prevent power transmission accidents has been a critical and urgent issue for the power grid. Therefore, hyperspectral imaging (HSI) technology was employed in this paper, capturing spectral line data of silicone rubber in six aging states in both visible and near-infrared regions, respectively. To reduce data redundancy, genetic algorithm (GA) and band weighting were introduced to improve traditional principal component analysis (PCA), with performance compared using overall accuracy (OA) and Kappa, against 12 other feature extraction or dimensionality reduction methods. The improved principal component analysis − support vector machine (IPCA-SVM) model proposed effectively minimizes irrelevant information in hyperspectral original data, exceeding 93% accuracy and improving OA by 8.26% compared to all bands data. Finally, the IPCA-SVM model was used for pixel-level assessment of the surface aging state of silicone rubber insulators, demonstrating its reliability. This method effectively characterizes the aging state of composite insulators, providing a solid foundation for the safe and stable operation of power grids.

Diarenofuran[b]-fused BODIPYs: One-Pot SNAr-Suzuki Synthesis and Properties.

We present a streamlined methodology that integrates regioselective tetrahalogen-BODIPY and o-hydroxyphenylboronic acid in a one-pot process, leveraging SNAr nucleophilic substitution in conjunction with Suzuki coupling to afford diarenofuran [b]-fused BODIPYs (DBFB1-9) with commendable yields (85-95%) and short reaction times (0.5-1.0 h). X-ray structure analyses of DBFB5,7-9 elucidate that these diarenofuran[b]-fused BODIPYs adopt a "butterfly" conformation, maintaining a highly rigid planarity. A comprehensive examination of the spectroscopic and electrochemical properties of these diarenofuran[b]-fused BODIPY derivatives, incorporating various substituents, reveals intriguing characteristics, including pronounced absorption and emission in the near-infrared region (NIR), elevated fluorescence quantum yields (ΦF = 75-89% in dichloromethane), and tunable HOMO-LUMO levels. Remarkably, compared to DBFB1-8, DBFB9 possesses a large extended π-conjugated system, resulting in significant red shifts in its absorption and emission maxima, reaching 623 and 635 nm, respectively, and a reduced HOMO-LUMO gap. Despite this substantial structural expansion, DBFB9 maintains a surprisingly high fluorescence quantum yield (ΦF = 80%), underscoring its exceptional photophysical performance and strong potential for applications requiring efficient NIR emission and robust fluorescence retention.

Development of a near infrared region based non-invasive therapy device for diabetic peripheral neuropathy

Diabetic Peripheral Neuropathy (DPN) is a nerve damage that is treated with painkillers and steroids which have the drawback of interference with other medications and the dangers of side effects. Novelty of the proposed work is to develop a Near Infrared Region (NIR) based non-invasive therapy device called ‘DPNrelief-1.0V’developed with a 890 nm wavelength diodes. DPNrelief-1.0V delivers a total dosage of 6.174 J/cm2 with heat absorption by tissue of 61.74 Joules at 30 minutes. The device was tested by carrying out a pilot study with 8 patients where 4 were treatment group and control group. The DPNrelief-1.0V is validated by Nerve Conduction Study (NCS) test. The degenerated nerves pre-therapy showed less amplitude, Conduction Velocity (CV) and latency which was improved post-therapy by 100% in amplitude of nerve signal, 100% in CV and a decrease of 36.2% in latency. Independent t-test was conducted to find the difference between control and treatment, wherein a p value < 0.05 was obtained depicting significant difference between two groups. Furthermore, the performance of the device is validated by one-way test repeated measures Analysis of Variance (ANOVA), wherein a p value of < 0.05 was obtained depicting a difference in nerve condition pre-and post-therapy. The performance of DPNrelief-1.0V has outperformed Anodyne therapy device with lesser dosage, treatment time and portability and in curing the symptoms of DPN. DPNrelief-1.0V finds its potential in the field of medicine for treating DPN.

Germanium-incorporated Si-Ge-Si heterojunction phototransistors for a high-limit of detection and wide linear dynamic range near-infrared light detection

This paper investigates overcoming the limitations of conventional silicon (Si) bipolar junction transistors (BJTs) for near-infrared (NIR) light detection. Silicon BJTs have inherent limitations in the NIR region due to silicon’s bandgap. To address this, the paper proposes high-performance silicon-germanium-silicon (Si-Ge-Si) heterojunction bipolar phototransistors (HPTs). The key innovation is introducing a thin germanium (Ge) layer at the base-collector junction and engineering its doping concentration. This Ge layer extends the BJT phototransistor’s optical response into the NIR region by enhancing optical absorption. The paper analyses the performance of the HPTs, demonstrating linear photoresponsivity of 432 mA/W over a wide optical power range, leading to an exceptional linear dynamic range of 159 dB and a very low dark current, which produces a limit of detection of -99.64 dBm. Additionally, the device exhibits a large photo-to-dark current ratio of 2.16 ×107 (at optical power of 5 µW) and a fast response time of 11.35 ps to modulated NIR optical signals within the linear dynamic range. This research paves the way for high-performance CMOS-compatible NIR phototransistors using Si-Ge-Si heterostructures.

Numerical study of a tapered fiber magnetic field sensor based on the ENZ mode

This study introduces what we believe to be a novel magnetic field sensor that utilizes a tapered optical fiber coated with indium tin oxide (ITO) and titanium dioxide (TiO2), operating on an epsilon-near-zero (ENZ) mode. The evanescent field around the tapered optical fiber can excite the ENZ mode of the ITO film, and the TiO2 layer can ensure the phase matching between the fiber core mode and the ENZ mode. The sensor, immersed in magnetic fluid, leverages the unique properties of ENZ materials to achieve a high sensitivity and resolution in the near-infrared (NIR) region. Through a simulation, the sensor demonstrated a maximum sensitivity of 6900 nm/RIU and a magnetic field sensitivity of 370 pm/Oe. The findings suggest that ENZ mode-based optic sensing presents a promising alternative to traditional plasmonic sensing methods, offering potential applications in various fields requiring precise magnetic field measurements.

Comparison between consumer-oriented and laboratory benchtop near-infrared spectrometers for total soluble solids measurement in grape

Portable near-infrared (NIR) spectrometers are gaining interest as a non-destructive tool for fruit quality determination in the decade. In this study, the performance of the portable NIR spectrometer for TSS prediction of grapes was evaluated and compared to the benchtop spectrometer. A total of 105 table grapes were individually measured NIR spectra at short-wavelength (740 – 1070 nm) and long-wavelength NIR region (1000 – 2500 nm) using SCiO and NIRFlex N-500 spectrometers, respectively. Partial least square (PLS) regression analysis was performed on berry spectra from both devices afterward significant wavelengths were identified and used to develop multiple linear regression (MLR) models. The best PLS prediction model was obtained from SNV pretreating spectra for both devices and spectral data acquired from SCiO showed better prediction performance (= 0.854, SEP = 0.452°Brix) than NIRFlex N-500 spectra (= 0.667, SEP = 0.675°Brix). Low predicting ability was gained for the MLR calibration model for both device with an RPD of about 1.70. From the results, a pocket-size spectrometer has the potential to be a non-destructive sorting and screening tool in fruit industries.

Using portable visible and near-infrared spectroscopy to authenticate beef from grass, barley, and corn-fed cattle

Meat product labels including information on livestock production systems are increasingly demanded, as consumers request total traceability of the products. The aim of this study was to explore the potential of visible and near-infrared spectroscopy (Vis-NIRS) to authenticate meat and fat from steers raised under different feeding systems (barley, corn, grass-fed). In total, spectra from 45 steers were collected (380–2,500 nm) on the subcutaneous fat and intact longissimus thoracis (LT) at 72 h postmortem and, after fabrication, on the frozen-thawed ground longissimus lumborum (LL). In subcutaneous fat samples, excellent results were obtained using partial least squares-discriminant analysis (PLS-DA) with the 100 % of the samples in external Test correctly classified (Vis, NIR or Vis-NIR regions); whereas linear-support vector machine (L-SVM) discriminated 75–100 % in Test (Vis-NIR range). In intact meat samples, PLS-DA segregated 100 % of the samples in Test (Vis-NIR region). A slightly lower percentage of meat samples were correctly classified by L-SVM using the NIR region (75–100 % in Train and Test). For ground meat, 100 % of correctly classified samples in Test was achieved using Vis, NIR or Vis-NIR spectral regions with PLS-DA and the Vis with L-SVM. Variable importance in projection (VIP) reported the influence of fat and meat pigments as well as fat, fatty acids, protein, and moisture absorption for the discriminant analyses. From the results obtained with the animals and diets used in this study, NIRS technology stands out as a reliable and green analytical tool to authenticate fat and meat from different livestock production systems.

Enhancing Near-Infrared Photothermal Performance by Molecular Aggregation Optimization in Semiconductive Coordination Polymers.

Near-infrared (NIR) photothermal conversion materials have recently received widespread attention due to their potential in diverse applications. However, highly efficient organic-based NIR photothermal agents remain limited. Developing strategies to enhance the efficiency of NIR photothermal materials and elucidating the relationship between the NIR photothermal performance and molecular aggregation are highly desired. Herein, we report two coordination polymers {[Cd2(ONDI)(ox)]·2/3(H2O)}n (1) and [Ba(ONDI)(H2O)2]n (2), in which the ONDI2- ligands assemble into different π-π stacking arrangements. Compound 1 exhibits H-aggregation, while compound 2 displays X-aggregation. The X-aggregation in compound 2 extends the optical absorption into the NIR region and enhances the absorption intensity. Consequently, compound 2 demonstrates a 1.8-fold increase in NIR photothermal efficiency (68.6%) compared to compound 1 (38.8%), attributed to more effective π-π interactions in X-aggregation. In addition, both compounds show semiconductive properties, with conductivities of 2.1 × 10-7 S/cm for compound 1 and 3.0 × 10-7 S/cm for compound 2 at 30 °C in a nitrogen atmosphere. These properties arise from the synergistic effects of "band-like" charge transport within crystals and "hopping" charge transport across grain boundaries. By integration of their NIR photothermal effects and semiconductive properties, compounds 1 and 2 show interesting NIR photoelectrical responses.

Utilization of Tin(IV) Complex of N-Confused Porphyrin for Antiproliferative Activity and Antimicrobial Photodynamic Chemotherapy.

Sn(IV) complex of N-Confused Porphyrin (Sn(IV)-NCP) has been prepared and characterized by several spectroscopic techniques to verify its structure and purity. Sn(IV)-NCP shows a red shift in both the Soret and Q bands compared to the free base NCTPP. The last Q band appears in the NIR region. Based on these characteristics, we investigated the antiproliferative properties and antimicrobial photodynamic therapy (a-PDT) efficiency of Sn(IV)-NCP against the bacteria Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Further, we investigated the photodynamic activity of Sn (IV)-NCP against Michigan cancer foundation-7 (MCF-7) cancer cells, to assess its potential as an effective therapeutic agent. Treated MCF-7 cells with the compound show cytotoxic effects as compared to the untreated ones. At a higher concentration (128 μg/ml), Sn(IV)-NCP exhibited 90 % inhibition, while at a lower concentration (32 μg/ml), it showed 70 % inhibition in MCF-7 cells. The IC50 value for this compound against MCF-7 cells was found 16.67 μg/ml. At 32 μg/ml, Sn(IV)-NCP showed only around 4 % cell inhibition, indicating minimal cytotoxic effects on human embryonic kidney cells (HEK293).

Hybrid Ag-mesh/Ta-doped TiO2 thin film configuration as a visible and near-infrared transparent electrode

This study focuses on the fabrication of a hybrid Ag-mesh/Ta-doped TiO2 (TTO) electrode that has a low sheet resistance and high transparency in the visible and near-infrared region, thereby holding significant commercialization potential. Here, ∼82 nm thick TTO film is deposited on the glass substrate using radio frequency magnetron sputtering technique, over which Ag mesh is carved using the metal aerosol jet printing method. As compared to TTO, sheet resistance of the entire hybrid configuration is found to show a 2-3 order improvement, with the loss of a mere ∼12 % in the visible and ∼8 % in NIR transmittance. The electronic structure of the Ag/TTO interface demonstrates the formation of an ohmic junction, thereby making it suitable for the fabrication of a network-based transparent electrode. Moreover, the overall functionality and preparation route of this electrode makes it more promising as compared to those of the conventional metal mesh and metal-oxide electrodes.

Multifunctional Near-Infrared Luminescence Performance of Nd3+ Doped SrSnO3 Phosphor

The phosphors with persistent luminescence in the NIR (near-infrared) region and the NIR-to-NIR Stokes luminescence properties have received considerable attention owing to their inclusive application prospects in the in vivo imaging field. In this paper, Nd3+ doped SrSnO3 phosphors with remarkable NIR emission performance were prepared using a high temperature solid state reaction method; the phase structure, morphology, and luminescence properties were discussed systematically. The SrSnO3 host exhibits broadband NIR emission (800–1300 nm) with absorptions in the near ultraviolet region. Nd3+ ions emerge excellent NIR-to-NIR Stokes luminescence under 808 nm laser excitation, with maximum emission at around ~1068 nm. The concentration-dependent luminescence properties, temperature dependent emission, and the luminescence decay curves of Nd3+ in the SrSnO3 host were also studied. The Nd3+ doped SrSnO3 phosphors exhibit exceptional thermal stability; the integrated emission intensity can retain approximately 66% at 423 K compared to room temperature. Most importantly, NIR persistent luminescence also can be observed for the SrSnO3:Nd3+ samples, which is in the first and second biological windows. A possible mechanism was proposed for the persistent NIR luminescence of Nd3+ based on the thermo-luminescence spectra. Consequently, the exciting results indicate that multifunctional NIR luminescence has been successfully realized in the SrSnO3:Nd3+ phosphors.

Plasmon-enhanced NIR-II photoluminescence of rare-earth oxide nanoprobes for high-sensitivity optical temperature sensing.

With ongoing advancements in photothermal therapy, achieving efficient tumor cell eradication while minimizing damage to healthy tissues necessitates a highly effective and non-invasive real-time temperature monitoring technique for human tissues. Herein, we report a near-infrared (NIR)-II optical temperature sensing nanoprobe featuring rare-earth-doped gadolinium oxide nanocrystals (RENCs) attached to the dumbbell mesoporous silica-coated gold nanorods (AuNRs). The composite nanoprobe presents an intense absorption in the NIR region, and NIR-II photoluminescence (PL) increases by 97.2 to 102-fold compared to pure RENCs upon 980 nm irradiation. The localized electric field generated through surface plasmon resonance effects of AuNRs demonstrated a dumbbell-shaped distribution that aligns with the structure of nanoprobes, maximizing the PL enhancement of RENCs. Moreover, the NIR-II emissions are changed with the rising temperature, with an exceptional relative sensitivity of 7.25% K-1 at 338 K based on PL lifetime, indicating the nanoprobe is highly potential for optical temperature sensing.