Near-infrared Region Research Articles

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.

Microwave assisted synthesis of ErxYbyCa1-x-yMoO4 nano-phosphor for efficient temperature sensing and catalytic applications

Here, Er/Yb Co-doped CaMoO4 materials (ErxYbyCa1−x−yMoO4 NPs where x = 0, 0.01 and y = 0, 0.05, 0.10, 0.15, 0.20) were prepared by microwave-assisted method and its pure-tetragonal structure were confirmed by X-ray diffraction spectra (XRD), Rietveld-refinement and Raman-vibrational spectra. The transmission-electron microscopy (TEM) study indicates the formation of nearly spherical shaped nanomaterial with average size of ~ 15 nm. Additionally, absorption and emission properties were studied by UV–Visible–NIR and photoluminescence (PL) spectrometer. The UV–Visible–NIR spectra attribute absorption of Er3+ ion in visible region (380–700 nm) and absorption of Yb3+ ion in near-infrared region (700–1400 nm). Moreover, PL up-conversion spectra of the sample recorded under excitation wavelength 980 nm. The PL peaks were observed at 530, 544–552, and 656–670 nm. Prominent PL-intensity was observed for Er0.01Yb0.15Ca0.84MoO4 phosphor. Temperature dependent PL study reveals that present phosphor is robust phosphor for temperature sensor. In addition, Er3+/Yb3+ doped CaMoO4 nanomaterials exhibited excellent activity and selectivity in the aerial oxidation of benzoin over benzyl under oxidant-free reaction conditions. The synergistic effect Er3+/Yb3+ co-doing in CaMoO4 matrix was observed, where only CaMoO4 material found to be inactive towards above oxidation reaction. Moreover, the oxidation of primary benzyl-alcohols was furnished in presence of tertiary butyl hydroperoxideas oxidant.

Ultra‐Sensitive, Self‐powered, CMOS‐Compatible Near‐Infrared Photodetectors for Wide‐Ranging Applications

AbstractSelf‐powered near‐infrared (NIR) photodetectors are essential for surveillance systems, sensing in IoT electronics, facial recognition, health monitoring, optical communication networks, night vision, and biomedical imaging. However, silicon commercial detectors need external power to operate and cooling to suppress large dark currents. This work demonstrates a new class of CMOS‐compatible self‐powered NIR photodetector based on ferroelectric 5‐nm thick ZrO2 films which do not require cooling and therefore have two key advantages over Si, and at the same time have comparable performance metrics. At room‐temperature, under 940 nm wavelength illumination (1.4 mW cm−2 power density, 10 Hz repetition rate), and without any power applied, fast rise and fall times of ≈2 and 4 µs, respectively, are achieved in Al/Si/SiOx/ZrO2/ITO devices, along with responsivity, detectivity and sensitivity values of up to ≈3.4 A W−1, 1.2 × 1010 Jones and 4.2 × 103, respectively, far exceeding all other emerging self‐powered systems. Furthermore, dual‐band NIR detection is shown for different NIR wavelengths, proof‐of‐concept feasibility being demonstrated for the smart identification of NIR targets. Therefore, it is demonstrated, for the first time, that coupling together the pyroelectric effect, the photovoltaic effect, and the ferroelectric effect is a novel method to significantly enhance the performance of CMOS‐compatible ZrO2‐based self‐powered photodetectors in the NIR region.

Albumin‐Chaperoned Deep‐NIR Triarylmethane Dyes for High‐Contrast In Vivo Imaging and Photothermal Therapy

AbstractFluorophores absorbing/emitting in the deep near‐infrared (deep NIR) spectral region, that is, 800 nm and beyond, hold great promise for in vivo bioimaging, diagnosis, and phototherapy due to deeper tissue penetration. The bottleneck is the lack of bright, stable, and readily synthesized deep NIR fluorophores. Here, it is reported that the albumin‐chaperon strategy is a viable one‐for‐all strategy to address these difficulties. A focused library of deep‐NIR absorbing dyes (EA5) is easily synthesized via a two‐step cascade. They are neither very stable nor bright in phosphate buffer due to a propeller‐type flexible scaffold. Through screening, EA5_c3 is found to exhibit a high affinity toward bovine serum albumin (BSA). Binding‐associated structural rigidification resulted in a gigantic 26‐fold fluorescence enhancement. The albumin chaperone also greatly improved the stability of EA5_c3 by shielding the bisbenzannulated triarylmethane core from nucleophilic or oxidative species. The resulting EA5_c3@BSA exhibits high biocompatibility. It offered high‐resolution vasculature, lymph systems, tumors, and other tissue imaging with its bright deep NIR emission. At the same time, it exhibits prominent potential in photoacoustic imaging and photothermal treatment of subcutaneous and orthotopic breast tumors. These findings provide insights into robust and high‐performance fluorophores with deep NIR regions for theranostic against aggressive cancers.

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 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-1(λ∼ 900 nm) in the near-infrared region and ∼1.36 A W-1(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 technology.

Planar Chiral Charge-Transfer Cyclophanes: Convenient Synthesis, Circularly Polarized Light-Responsive Photothermal Conversion and Supramolecular Chiral Assembly.

We report herein a series of macrocycles in which the densely π-stacked charge-transfer (CT) donor/acceptor with naphthalenediimides (NDIs) or perylene diimide (PDI) as acceptor moiety pairing various donor moieties are locked by covalent bond. The X-ray crystallography of C8BDT-NDI reveals a short intramolecular π-stacking distance around 3.4 Å and the existence of intermolecular donor/acceptor π-stacking (3.7 Å). The intramolecular CT is highly dependent on the electron-donating ability of donor moiety and replacing carbazole (C8KZ) with benzo[1,2-b:4,5-b']dithiophene (C8BDT) or dihydroindolo[3,2-b]indole (C8DN) redshift CT absorption into NIR region. Notably, both C8BDT-NDI and C8DN-NDI demonstrate excellent photothermal performance, which is a result of the active non-radiative pathways. Interestingly, the different molecular symmetry between donor and acceptor moiety in cyclophanes endow C8BDT-NDI and C8DN-NDI with intrinsic planar chirality. The enantiomeric C8BDT-NDI shows chiral selectivity for incident light, i.e., when irradiated by left-circularly polarized light, (R)-C8BDT-NDI is more sensitive and a higher maximum stable temperature is achieved. While, enantiomeric C8DN-NDI pack with different orientations forming M- and P-handedness helix, respectively, demonstrating molecular planar chirality being transferred and amplified through molecular assembly. These results provide insight into the intramolecular charge transfer in enforced D/A π-stacks in which CT interactions and planar chirality would be engineered through structural control.

Advancements in Tumor Diagnostics through Carbon Dot‐Assisted Photoacoustic Imaging

AbstractSerendipitously discovered, carbon dots (CDs) have attracted significant attention as a potential contrast agent for photoacoustic imaging (PAI) in the biomedical sector. CDs play an essential role in PAI, contributing significantly to the early detection of diseases and monitoring treatment progress, particularly in tumor imaging. This review emphasizes the role of CDs in the domain of PAI, highlighting their characteristics like biocompatibility, enhanced spatial resolution, optical absorption in the NIR region, and facile surface functionalization for tumor‐ targeted imaging. The study explores the use of CDs for enhancing spatial resolution in PAI for improved detection and visualization of tumors in organs such as the breast, cervical, liver, gastrointestinal, skin, cardiovascular system, nervous system, and others. Challenges associated with PAI, such as optimizing the signal‐to‐noise ratio and ensuring stability under physiological conditions, have also been discussed.

Microcavity-assisted multi-resonant metasurfaces enabling versatile wavefront engineering

Metasurfaces have exhibited exceptional proficiency in precisely modulating light properties within narrow wavelength spectra. However, there is a growing demand for multi-resonant metasurfaces capable of wavefront engineering across broad spectral ranges. In this study, we introduce a microcavity-assisted multi-resonant metasurface platform that integrates subwavelength meta-atoms with a specially designed distributed Bragg reflector (DBR) substrate. This platform enables the simultaneous excitation of various resonant modes within the metasurface, resulting in multiple high-Q resonances spanning from the visible to the near-infrared (NIR) regions. The developed metasurface generates up to 15 high-Q resonant peaks across the visible-NIR spectrum, achieving a maximum efficiency of 81% (70.7%) in simulation (experiment) with an average efficiency of 76.6% (54.5%) and a standard deviation of 4.1% (11.1%). Additionally, we demonstrate the versatility of the multi-resonant metasurface in amplitude, phase, and wavefront modulations at peak wavelengths. By integrating structural color printing and vectorial holographic imaging, our proposed metasurface platform shows potential for applications in optical displays and encryption. This work paves the way for the development of next-generation multi-resonant metasurfaces with broad-ranging applications in photonics and beyond.

Solution Processed Bilayer Metal Halide White Light Emitting Diodes.

Metal halide perovskites and perovskite-related organic metal halide hybrids (OMHHs) have recently emerged as a new class of luminescent materials for light emitting diodes (LEDs), owing to their unique and remarkable properties, including near-unity photoluminescence quantum efficiencies, highly tunable emission colors, and low temperature solution processing. While substantial progress has been made in developing monochromatic LEDs with electroluminescence across blue, green, red, and near-infrared regions, achieving highly efficient and stable white electroluminescence from a single LED remains a challenging and under-explored area. Here, a facile approach to generating white electroluminescence is reported by combining narrow sky-blue emission from metal halide perovskites and broadband orange/red emission from zero-dimensional (0D) OMHHs. For the proof of concept, utilizing TPPcarz+ passivated two-dimensional (2D) CsPbBr3 nanoplatelets (NPLs) as sky blue emitter and 0D TPPcarzSbBr4 as orange/red emitter (TPPcarz+ = triphenyl (9-phenyl-9H-carbazol-3-yl) phosphonium), white LEDs (WLEDs) with a solution processed bilayer structure have been fabricated to exhibit a peak external quantum efficiency (EQE) of 4.8% and luminance of 1507 cd m-2 at the Commission Internationale de L'Eclairage (CIE) coordinate of (0.32, 0.35). This work opens a new pathway for creating highly efficient and stable WLEDs using metal halide perovskites and related materials.

Recent Advances in NIR-Switchable Multi-Redox Systems Based on Organic Molecules.

In recent years, near-infrared (NIR) dyes, exhibiting absorption in the NIR region (750-2500 nm), have been applied to various optical applications such as security marking, photovoltaic cells and chemotherapy of deep tissues in vivo. Electrochromic systems capable of switching NIR absorption are attractive from the viewpoint of applications for material and life science, and thus several examples have been reported to date. The development of organic-based materials is needed to reduce the environmental impact and improve biocompatibility, however, the switching of NIR absorption based on redox interconversion is still a challenging issue regarding reversibility and durability during interconversion. To overcome this potential instability, several studies on organic electrochromic systems that allow ON/OFF switching of NIR absorption have been developed in recent years. In this review, we focus on redox-active well-defined small molecules that enable ON/OFF switching of NIR absorption, and present recent studies on their intrinsic electrochemical and spectroscopic properties and/or structural characterization of their charged states. We also address more sophisticated electrochromic systems that can modulate their properties in response to external stimuli such as light, heat, and electric potential.

Recent advances of photoresponsive nanomaterials for diagnosis and treatment of acute kidney injury.

Non-invasive imaging in the near-infrared region (NIR) offers enhanced tissue penetration, reduced spontaneous fluorescence of biological tissues, and improved signal-to-noise ratio (SNR), rendering it more suitable for in vivo deep tissue imaging. In recent years, a plethora of NIR photoresponsive materials have been employed for disease diagnosis, particularly acute kidney injury (AKI). These encompass inorganic nonmetallic materials such as carbon (C), silicon (Si), phosphorus (P), and upconversion nanoparticles (UCNPs); precious metal nanoparticles like gold and silver; as well as small molecule and organic semiconductor polymer nanoparticles with near infrared responsiveness. These materials enable effective therapy triggered by NIR light and serve as valuable tools for monitoring AKI in living systems. The review provides a concise overview of the current state and pathological characteristics of AKI, followed by an exploration of the application of nanomaterials and photoresponsive nanomaterials in AKI. Finally, it presents the design challenges and prospects associated with NIR photoresponsive materials in AKI.

Optimum Combination of Spectral Variables for Crop Mapping in Heterogeneous Landscapes based on Sentinel-2 Time Series and Machine Learning

Abstract. This article aimed to determine a workflow for more efficient large-scale crop mapping using a time series of images from the Sentinel-2 Satellite, statistical methods of attribute selection, and machine learning. The proposed methodology explores the best possible combination of spectral variables related to vegetation (16 vegetation indices in the RGB, NIR, SWIR, and Red Edge regions) to characterize different spectro-temporal profiles of Land Use and Land Cover (LULC) in spatially heterogeneous landscapes. First, we applied a data dimensionality reduction analysis using the PCA (Principal Component Analysis) method. Subsequently, the variables that showed the highest statistical correlation between each other were used in the spectro-temporal classification process, using the Random Forest, TempCNN, and LightTAE algorithms, following three different strategies: C1 (ALL), C2 (BE + IV (Red Edge)) and C3 (BE + IV (without Red Edge)), where ALL – All variables; BE – Spectral Bands; IV – Vegetation Indices. Given the results found, the C2 classification scenario (with bands B3, B4, B5, B6, B7, B8, and B8A and the NDRE1, RESI, and MSR indexes) demonstrated the best LULC classification accuracy at the crop pattern level, compared to the other scenarios, with average values of 0.91, 0.88, 0.91, 0.89, and 0.89 (Global Accuracy, Producer Accuracy, User Accuracy, Kappa index, and F1-Score, respectively, for the TempCNN model), the which emphasized the importance of both qualitative and quantitative variability of sampling data and variables based on the Red Edge region for improving LULC classification processes in large-scale heterogeneous landscapes.

Enhancement in Photodetector Sensitivity Using All‐Inorganic Perovskite Absorber RbGeI3 and Copper Bismuth Thiocyanate for Superior Charge Transport

This study investigates a photodetector design using the nontoxic, all‐inorganic perovskite material RbGeI3, which is distinguished by its efficient light absorption and excellent photoelectric conversion properties. Incorporating copper bismuth thiocyanate (CBTS) and indium gallium zinc oxide layers, this design enhances charge transport, leading to a photodetector that exhibits exceptional sensitivity across the visible spectrum, along with a peak responsivity of 0.63 A W−1 and a detectivity of 1.37 × 1013 Jones in the near‐infrared (NIR) at 900 nm. The proposed photodetector exhibits wide‐spectrum detection, encompassing both the visible range and the NIR region. These results position RbGeI3 and CBTS as compelling alternatives to traditional photodetector materials such as Si‐Ge, InGaAs, ZnO, and GaN. Validation is achieved through simulations using the SCAPS‐1D simulator, underscoring the potential of perovskite materials for advanced photodetector applications.

Advanced plasmonic few-layered InSe nanosheet heterojunctions for enhanced photoelectrochemical water splitting

The selenide-based Van der Waals heterojunctions show great potential for the next generation of photoelectronic nanodevices. Herein, we construct a 2D photoanode nanocatalyst that consists of ZnSe nanocrystals with exposed active surfaces coupled with few-layered InSe nanosheets decorated by Au nanoparticles. The resultant ZnSe/AuNPs@InSe multi-heterojunction photoanode demonstrates an outstanding photocurrent density of 4.86 mAcm−2 under AM 1.5 G simulated sunlight (100 mWcm−2), which is 8 times greater than that of the pristine InSe photoanode (0.61 mAcm−2). Moreover, the lifetime of photogenerated charge carriers is extended by a factor of 3. This significant enhancement in photoelectrochemical water splitting in the near-infrared region is attributed to the surface plasmonic effect produced by the modification of Au NPs when bulk InSe is exfoliated into multi-layered flakes. The interfacial coupling effects on carrier transfer dynamics, as revealed by impedance spectroscopy assisted with the First-Principal calculations, show that this photoanode significantly minimizes the internal resistance, boosts the charge carrier separation efficiency, and promotes water oxidation.

An effective and specific cancer theranostic nanoplatform with NIR-II fluorescence imaging-guided photothermal/chemodynamic therapy

Nanomaterial-based second near-infrared region (NIR-II) fluorescent probes have deep tissue penetration. However, it is limited by low catalytic efficiency and specific recognition in the tumor microenvironment (TME). Herein, Ag2S-Cu(II)-Cu2-xSe diagnostic nanoparticles have been established by Cu2-xSe and Ag2S QDs, which can serve as diagnostic agents. They can improve the precise diagnosis of cancer via a NIR-II imaging-guided multimodal photothermal/chemodynamic therapy strategy under near-infrared (808 nm) light irradiation. Under neutral conditions, the fluorescence of Ag2S-Cu(II)-Cu2-xSe nanoplatforms is in the “off” mode, which is selectively turned on only in the tumor microenvironment. Ag2S-Cu(II)-Cu2-xSe NPs not only emit fluorescence specifically in the TME but also have efficient photothermal conversion properties. Significantly, Ag2S-Cu(II)-Cu2-xSe has experimentally demonstrated a strong combined therapeutic effect and can consume excess intracellular glutathione (GSH) through redox reactions. This work presents an effective strategy for achieving precise and safe multifunctional nanodiagnostic platforms.

Facile synthesis of Fe3O4 photothermal nanoparticles coated with poly-3,4-dihydroxybenzaldehyde for improved photothermal therapy of cancer cells

Given the significant rise in the number of individuals diagnosed with cancer, the management of cancer therapy has become a prominent concern in society and a formidable task in human health care. Photothermal therapy has garnered significant interest in cancer treatment because of its exceptional efficacy and minimal invasiveness. Thus, current research mainly focuses on developing biocompatible materials with excellent photothermal properties. Therefore, we synthesized Fe3O4 nanoparticles coated with poly-3,4-dihydroxybenzaldehyde (Fe3O4@PDBA) where 3,4-dihydroxybenzaldehyde was covalently polymerized onto the surface of Fe3O4. The induction of PDBA leads to a dramatical improvement in the photothermal properties of Fe3O4. Besides, the thickness of the PDBA shell layer is also a key factor in the photothermal performance and various physicochemical properties of Fe3O4@PDBA and the photothermal performance of Fe3O4@PDBA increases with increasing thickness of the PDBA shell. Additional structural characterization of the products, DFT calculations of the UV-Vis absorption spectra and the HOMO-LUMO gap under the simple model of the polymer, and product identification by the use of H1NMR, MS, and other techniques were performed. Through multiple characterizations, the reaction solution color and UV-Vis absorption spectra were essentially consistent with the computed findings. The calculations confirm that the polymerization process of PDBA is progressively red-shifted and the absorption is gradually enhanced in the NIR region. Fe3O4@PDBA exhibited strong cytotoxicity against cancer cells (Hela, 98.0%) in vitro photothermal treatment. Hence, Fe3O4@PDBA exhibits superior photothermal characteristics, targeting, biocompatibility (99.0%), and degradability, which brings about significant potential for photothermal cancer therapy.

Magneto-optic properties of highly Dy3+-doped GeO2-B2O3 glasses for NIR optical applications

Recent progress in the development of optical communication and high power laser systems in the near-infrared (NIR) region (1.5 to 2.0 μm) increased the demand for magneto-optic (MO) devices employing MO materials. These MO materials are required with lower optical absorption coefficients and higher Verdet constants at spectral range of interest. In this study, two series of highly Dy3+-doped GeO2–B2O3 glasses with and without P2O5 were fabricated using a simple melt-quenching technique. The glasses were characterized through various techniques (Raman, UV–VIS-NIR, and DTA) for the evaluation of characteristic properties with respect to the Dy2O3 concentration and glass composition. Faraday rotation measurement was carried out at 1550 nm to quantify the Verdet constant of the glasses. The Verdet constant values were found to increase linearly with increasing Dy3+ concentration for both the glass systems. The increase in Dy3+ concentration and, consequently, the number of unpaired electrons, leads to an increase in the Verdet constant. The GeO2-B2O3 glass doped with 30 mol% of Dy2O3 exhibited the highest Verdet constant of −5.36 rad/(T⋅m) at 1550 nm. The glasses exhibited a good optical transparency (>70 %) in the region covering from 400 to 2400 nm. The thermo-physical, optical, and polarizability properties of both glass systems were also investigated. The results indicate that the highly Dy3+-doped glasses are attractive for magneto-optics at 1550 nm.

Synergetic effect of Hexaferrite and reduced Graphene oxide (rGO) in Photothermal therapy and Hyperthermia applications

This research article describes the synthesis of composite materials by combining T-type hexagonal ferrite and reduced Graphene Oxide using the standard ceramic process. The Calcium-based T-type hexagonal ferrite was synthesized by using the sol-gel auto-combustion method whiles the reduced graphene oxide by adopting the Hummer method. The crystallite size varied in the range of 34.11 to 42.07nm as calculated from the X-ray diffraction (XRD) data. Consequently, the lattice parameters 'a' and 'c' decreased from 5.9 to 5.1Å and from 29.92 to 28.32Å, respectively. The use of atomic force microscopy (AFM) revealed a range of particle sizes at the surface, varying from 1.70nm to 3.85nm. Moreover, the saturation and remanence magnetization values demonstrated an increasing trend with T-type hexaferrites concentration whereas the coercivity decreased. The UV-vis near-infrared spectra exhibited substantial light absorption, characterized by a wide absorption range in the visible and near-infrared (NIR) region (700 to 1100nm) which indicates its use in Photothermal therapy (PTT). The Calcium T- type hexaferrite exhibited clear peaks in the blue, green, violet, and yellow spectra in its photoluminescence (PL) properties. These peaks are believed to be caused by oxygen vacancies and defects. The synthesized samples displayed a lossy behavior in the polarization-electric field (P-E) loop, with saturation polarization levels exceeding remnant polarization, which is an amenable condition for lossy behavior. Most importantly, the synthesized materials had significant thermal responses when exposed to an alternation (AC) magnetic field, indicating their potential use in magnetic hyperthermia applications.

Dynamic Rare-Earth Metal-Organic Frameworks Based on Molecular Rotor Linkers with Efficient Emissions and Ultrasensitive Optical Sensing Performance.

4,4',4″-Triphenylamine tricarboxylate (TPA-COOH) with a distinct molecular rotor structure was reacted with rare-earth (RE) metal ions to obtain seven dynamic RE-based luminescent MOFs (RE-LMOFs) (i.e., emission colors in the blue, yellow-green, red, and near-infrared regions and emission peak wavelengths between 400 and 1600 nm) via the effective transfer of absorbed energy from TPA-COOH to the RE metal ions through the antenna effect. Due to the large energy level difference between RE ions, it was rare in the early days to use the same ligand to construct energy-level matching RE-LMOF homologues with multiple RE metal centers. The uncoordinated oxygen atoms on the molecular rotor linkers in RE-LMOFs provide active sites that can specifically capture highly toxic metal ions and strong oxidative pollutants. The limit of detection (LOD) of RE-LMOF for Al(III) ions is far below the maximum concentration of Al(III) ions in drinking water stipulated by the U.S. Environmental Protection Agency (USEPA) and that for H2O2 is much lower than the H2O2 content in cancer cells, showing excellent application potential for diagnosing early cell cancelation.

CONTINUOUS MONITORING OF DISSOLVED OXYGEN CONCENTRATION USING LOW-COST MULTISPECTRAL SENSORS

This study proposed an approach for continuously monitoring dissolved oxygen concentration using absorption spectroscopy with a low-cost multispectral sensor. An experimental system was built to investigate the correlation between dissolved oxygen concentration and absorbance of several wavebands in the visible and near-infrared regions. An optimized linear regression model with four wavebands at 460, 485, 585, and 900 nm gave the best prediction results with coefficient of determination and root mean square error of 0.85 and 0.68 mg/L, respectively. The experimental results demonstrated that the proposed absorption spectroscopy with a low-cost multispectral sensor has great potential for continuously monitoring dissolved oxygen concentration in water in a non-contact manner.