NIR Range Research Articles

NaYF4:Yb,Er/MnIn2S4/g-C3N4 with visible near infrared light response for efficient photocatalytic degradation

In the treatment of wastewater, the use of semiconductor photocatalysis is known to be environmentally friendly. Composites of MnIn2S4 for visible and near-infrared photocatalysis are less well studied. In this article, we have fabricated a ternary composite material, NaYF4:Yb,Er/MnIn2S4/g-C3N4, through a simple synthesis method for visible and near infrared photocatalysis. MnIn2S4 and g-C3N4 form the heterogeneous junction. The spectral response can be extended to the NIR range by integrating NaYF4:Yb,Er nanocrystals (NCs) with MnIn2S4/g-C3N4. Comparing MnIn2S4/g-C3N4 to single-component samples, photocatalytic performances under visible light irradiation showed that it had higher photocatalytic activities. When NaYF4:Yb,Er NCs are coated onto the petal-like spherical structure of MnIn2S4/g-C3N4 and integrated with it, the heterostructure and upconversion effect enhance the photocatalytic activity of the composites under Vis and NIR light. The photocatalytic mechanism of the nanocomposites has been postulated and its detailed characterization has been done. Based on the results of UHPLC-MS, the degradation process and rational pathways for degradation of CIP were proposed. The environmental toxicity of CIP degradation products was evaluated using ECOSAR software, the results showed that the toxicity of the reaction solution was diminished after 60 min of photodegradation. The current study not only avoids the generation of toxic by-products in the photocatalytic degradation process but also MnIn2S4-based composites may open up new possibilities for the design and production of composite photocatalysts that may effectively use Vis/NIR light for environmental remediation.

CaLaLiTeO6: Mn4+, Tm3+ phosphors with multiband near-infrared emission towards multifunctional applications

Near-infrared phosphors have garnered considerable interest for various detection technologies. However, effective blue light excitable phosphors emitting in the NIR range are still lacking in these devices. In this work, we synthesized a monoclinic perovskite phosphor, CaLaLiTeO6: Mn4+, Tm3+, which emits NIR light at 700 nm, 800 nm and 1450 nm under 480 nm excitation. Through systematic study of the fluorescence lifetime of doped Mn4+ ions, we determined this arises from energy transfer from Mn to Tm, enhancing Tm luminescence at 800 nm and 1450 nm. The measured internal quantum efficiency (IQE) of the phosphors can reach 66.36 %. Additionally, photoluminescence properties were examined under 808 nm laser diode excitation. Finally, we utilized a 480 nm blue light chip to excite the CaLaLiTeO6: 0.6 % Mn4+, 1.5 % Tm3+ phosphor and verified its functionality as a NIR light source. Results indicate phosphor-converted LEDs based on this material can be successfully used in a variety of disciplines, including medical infrared thermal imaging, enhanced night vision, solution concentration analysis. This information serves as a crucial reference for developing multifunctional phosphors.

MASK IMPORTANCE IN BURNED AREA MAPPING BASED ON REMOTE SENSING, GIS AND OPEN-SOURCE PRODUCTS

Abstract. Forest and field fires are an increasing problem for EU countries located in the southern parts of Europe. With each passing day, the need to develop a technological scheme for monitoring the territories affected by fires and the timely provision of open data in order to recover damages is increasing.In this study, the method used to study burned areas is based on the analysis of multispectral satellite images, the differences in terrain reflectivity and the use of indices to highlight the differences between areas with healthy vegetation and burned areas, taking into account their different signatures. Open source software - SNAP, QGIS, images from Sentinel-2 with bands in the green, red, near-infrared and short-wave infrared spectral bands were used for the purposes of the research. Data from the Inspire Directive was also used to analyze the types and characteristics of affected areas.In many cases, water bodies show a similar difference as the Normalized Burn Ratio (NBR) index, for this reason the need for their preliminary masking arises. Clouds that appear in each input image are also masked. A combined water and cloud mask is applied. To detect the water bodies, NDWI was used to maximize the reflectance of the water body in the green band and minimize the reflectance of the water body in the NIR range.

In-situ monitoring for PBF-LB/M processes: Does multispectral optical tomography add value in recognizing process deviations?

Laser powder bed fusion of metallic components (PBF-LB/M) is gaining acceptance in industry. However, the high costs and lengthy qualification processes required for printed components create the need for more effective in-situ monitoring and testing methods. This article proposes multispectral Optical Tomography (OT) as a new approach for monitoring the PBF-LB/M process. Compared to other methods, OT is a low-cost process monitoring method that uses long-time exposure imaging to observe the build process. However, it lacks time resolution compared to expensive thermographic sensor systems. Monochromatic OT (1C-OT) is already commercially available and observes the building process layer-wise using a single wavelength window in the NIR range. Multispectral OT (nC-OT) utilizes a similar setup but can measure multiple wavelength ranges per location simultaneously. By comparing the classical 1C-OT and nC-OT approaches, this article examines the advantages of nC-OT (two channel OT and RGB-OT) in reducing the false positive rate for process deviations and approximating maximum temperatures for a better comparison between different build processes and materials. This could ultimately reduce costs and time for part qualification. The main goal of this contribution is to assess the advantages of nC-OT compared to 1C-OT for in-situ process monitoring of PBF-LB/M.

Effects of high-power laser radiation on polymers for 3D printing micro-optics

3D printing has become a widely used technique for manufacturing micro-optical components for sensing, measurements, biomedical and quantum technologies. Hence, knowing the maximum usable power or damage thresholds of 3D-printed micro-optics becomes crucial. Here we present a first study of the damage threshold values of the IP-S photoresist under high-power cw-, fs-, and ns-pulsed laser radiation with wavelengths in the NIR range. We also study the differences between visual evaluation using bright-field microscopy, DIC-microscopy, and beam-profile damage detection. Finally, we present several application-inspired use cases of 3D printed fiber micro-optics, reaching 10.5 W output power of cw-radiation at 915 nm and 4.5 W and 550 fs pulsed operation at 1040 nm.

Tuning the optoelectronic properties of reduced graphene Oxide@MoS2 nanocomposite for room temperature photodetection application

Due to the precise manipulation of its optical and electrical characteristics, MoS2 has been described as the most novel two-dimensional material for photodetectors, gas sensing, and temperature sensing applications. Monolayer MoS2 is considered an emerging optoelectronic material because its direct bandgap allows a high absorption coefficient and efficient generation of electron–hole pair under photoexcitation. But it lacks sufficient carrier density and carrier mobility as well, which in turn, mars its prospect to be competitive with its peers in terms of characteristic parameters required for an efficient optical detector. Hence, reduced graphene oxide (RGO) is chosen to compensate those factors where the right stoichiometry of the RGO@MoS2 composite is employed to improve the sensing characteristics of the MoS2 mono-to-few layers-based optical detector. It resulted in a widened photodetection range (Vis-NIR) and fast detection response because of – (i) RGO’s passible role to inject free carriers to MoS2 to improve its free carrier density, and (ii) MoS2′s direct role to demonstrate its sensing performance. The experimental study reveals that the sensor shows a responsivity of ∼1.17 mA W−1 with a good detectivity of ∼1.84 × 1011 Jones and response and recovery time of 3.52 and 3.48 s, respectively. The fabricated RGO@MoS2 nanocomposite sensor shows a fast-sensing response, and enhancement of photo-sensing parameters such as photoresponsivity, and detectivity, sensor response, and recovery time. These results are encouraging due to the fast sensor response and extended range of detection from visible to NIR range.

IR-775 - Hyptis loaded bioactive nanoparticles for enhanced phyto-photothermal therapy of breast cancer cells

Photo-responsive therapy is an emerging treatment modality due to its bioimaging and therapeutic properties. Phototherapy induces localized hyperthermia and selectively eradicates cancer cells. The current study showed that multifunctional biodegradable liposome nanosystem (HIL NPs) containing Hyptis suaveolens bioactive molecules and IR-775, a NIR dye showed efficient bioavailability to cancer ells and allowed tumor ablation upon NIR laser irradiation. The resulting entities present in the nanosystem, i.e., bioactive molecules of Hyptis, serve as an anticancer agent, and IR-775 helps in the photothermal ablation of highly metastatic breast cancer cells. Hyptis suaveolens is a weed that grows rampantly, impeding the growth of neighboring plants; nonetheless, its bioactive compounds have demonstrated therapeutic benefits. The obtained HIL NPs, photothermally active liposome nanosystem showed a high fluorescence absorption peak in the NIR range and delivered a photothermal conversion efficiency of 55.20 % upon NIR laser irradiation. TEM and particle size analyzer revealed that HIL NPs have a size of 141 ± 30 nm with a spherical shape. The results of in-ovo (zebrafish) experiments have shown efficient bioimaging capabilities with minimal concentrations of HIL NPs compared to respective controls. Furthermore, in-vitro studies of HIL NPs against triple-negative breast cancer (4T1) indicated effective anticancer activity by a combined cytotoxic effect and hyperthermia. Tumor ablation was facilitated by reactive oxygen species production and hyperthermia, leading to DNA damage and apoptosis due to overexpression of ɣ-H2AX, Cathepsin B, and p53, which halted cancer cell proliferation. Therefore, HIL NPs demonstrated effective anticancer effects induced by combined phyto-photothermal therapy when evaluated against an in-vitro breast cancer model.

Enhanced Photothermal Property of NDI-Based Conjugated Polymers by Copolymerization with a Thiadiazolobenzotriazole Unit.

Solar steam generation (SSG) is a promising photothermal technology to solve the global water storage issue. The potential of π-conjugated polymers as photothermal materials is significant, because their absorption range can be customized through molecular design. In this study, naphthalenediimide (NDI) and thiadiazolobenzotriazole (TBZ) were employed as bifunctional monomers to produce conjugated polymers. There are two types of polymers, P1 and P2. P1 is based on NDI, while P2 is a copolymer of NDI and TBZ in a ratio of 9:1. Both polymers had high molecular weights and sufficient thermal stability. UV-vis-near-infrared (NIR) absorption spectra revealed that both polymers have large extinction coefficients ascribed to the NDI and TBZ chromophores. Notably, the absorption spectrum of P2 exhibited a significant red shift compared to P1, resulting in a narrow optical bandgap and absorption in the NIR range. This result suggested that P2 has a higher light absorption than P1. Photoluminescence (PL) spectra were measured to elucidate the conversion of the absorbed light into thermal energy. It was found that P2 has a reduced fluorescence quantum yield as a result of the TBZ unit, signifying a proficient conversion of the photothermal energy. Based on the results, it appears that the P2 film has a greater photothermal property compared to that of the P1 film. The surface temperature of the P2 film reached approximately 50 °C under the investigated conditions. In addition, copolymer P2 exhibited an impressive SSG efficiency of 72.4% under 1 sun (1000 W/m2) irradiation. All the results suggested that narrow bandgap conjugated polymers containing the TBZ unit are highly effective materials for achieving optimal performance in SSGs.

Thermally stable illuminating characteristics of Tb3+/Sm3+ ions activated BaO–SrO–Al2O3–B2O3–SiO2 glasses for photonic applications

A set of Tb3+ and Tb3+/Sm3+ co-doped barium strontium aluminium borosilicate (BaSrAlBSi) glasses were produced to examine optical properties carefully. The transparent BaSrAlBSi glass amorphous nature was established by the XRD pattern. The absorption profile demonstrates the various peaks from n-UV to NIR range caused by the Tb3+ as well Sm3+ ions in BaSrAlBSi glass. BSi:Tb1.0 glasses give intense green emission under λex = 368 nm, BSi:Sm1.0 glasses exhibit the emission spectrum caused by the transitions of the Sm3+ ions. The Tb3+/Sm3+ co-doped BaSrAlBS glasses exhibit a mixture of emission exhibited by individual ions when excited at 368 nm, whereas it exhibits only red-orange light emission when excited under 402 nm. The PL lifetimes demonstrated a reduction in decay time as Sm3+ ions concentration increased in Tb3+ doped BaSrAlBSi glasses. CIE coordinates show the green emission was tuned towards the warm white region via co-doping of Sm3+ in Tb3+ doped BaSrAlBSi glasses. The strong thermal stability of BSi:TbSm1.0 glass is confirmed via a temperature-dependent emission profile. The observed results indicate that the transparent BSi:TbSm1.0 glasses as made will be directly useful for photonic device applications as n-UV pumping results in green warm white and orange emissions.

Feasibility study of detecting some milk adulterations using a LED-based Vis-SWNIR photoacoustic spectroscopy system.

The aim of this study is to evaluate a previousely developed photoacoustic spectroscopy system with light sources of visible to short-wave near infrared (Vis-SWNIR, 395-940nm) for detection of adulterations in cow's milk including formalin, urea, hydrogen peroxide, starch, sodium hypochlorite, and detergent powder. The results of principal component analysis (PCA) showed a very good visual differentiation of different adulterations. The artificial neural networks (ANN) showed the highest classification accuracy (97.6%) in detection of adulteration type and adulteration level (nearly 100%). It can be generally concluded that the Vis-SWNIR photoacoustic spectroscopy system is a reliable and potent instrument for detecting various types of milk adulterations. Further studies are suggested with including cow's milk of different sources with probable variations in composition to generalize the findings of the present study. With the extension of the light sources to the range of long-wave NIR, the system can be applied as a diagnostic tool for quality evaluation of other liquid foods.

Nanomechanical Photothermal Near Infrared Spectromicroscopy of Individual Nanorods.

Understanding light-matter interaction at the nanoscale requires probing the optical properties of matter at the individual nanoabsorber level. To this end, we developed a nanomechanical photothermal sensing platform that can be used as a full spectromicroscopy tool for single molecule and single particle analysis. As a demonstration, the absorption cross-section of individual gold nanorods is resolved from a spectroscopic and polarization standpoint. By exploiting the capabilities of nanomechanical photothermal spectromicroscopy, the longitudinal localized surface plasmon resonance in the NIR range is unraveled and quantitatively characterized. The polarization features of the transversal surface plasmon resonance in the VIS range are also analyzed. The measurements are compared with the finite element method, elucidating the role played by electron surface and bulk scattering in these plasmonic nanostructures, as well as the interaction between the nanoabsorber and the nanoresonator, ultimately resulting in absorption strength modulation. Finally, a comprehensive comparison is conducted, evaluating the signal-to-noise ratio of nanomechanical photothermal spectroscopy against other cutting-edge single molecule and particle spectroscopy techniques. This analysis highlights the remarkable potential of nanomechanical photothermal spectroscopy due to its exceptional sensitivity.

Self-driven high-performance broadband photodetector based on WSe2 nano-speckles

Long-term exposure to visible or infrared light may have harmful biological consequences, such as erythema, that can damage the cornea and retina. Additionally, trapped infrared light contributes to climate change on a global scale. Self-driven broadband photodetectors, which do not need an auxiliary battery and function in a multiband region of the electromagnetic spectrum, can be the solution to monitor such radiation. Though two-dimensional (2D) materials offer excellent optoelectronic characteristics, these materials still need to be fully explored to fabricate high-performance self-driven broadband photodetector. The study proposes nano-speckles like WSe2-based self-driven photodetection that operate in a broad spectral range from vis to NIR. The developed device exhibits 2.1 mAW−1 high responsivity at 860 nm illumination at zero bias (self-driven mode). Also, at zero bias a responsivity of 1.09 mAW−1 for 532 nm light illumination and 1.05 mAW−1 for 625 nm light illumination was obtained. Further, the device shows ultra-high responsivity of 1.2 × 104 mAW−1 and a very high external quantum efficiency of 2.84 × 103% with low noise equivalent power 3.27 × 10−13 WHz−1/2 at 860 nm light illumination under photoconductive mode. This report provides a promising simple synthesis method for fabricating a self-driven photodetection device that covers vis to NIR range with high sensitivity for future optoelectronic applications.

Photoresponse in the ultraviolet–visible–NIR range of octahedral MnCo2O4 microparticles synthesized by the solution method

Photoresponse in the ultraviolet–visible–NIR range of octahedral MnCo2O4 microparticles synthesized by the solution method

A Series of Novel 3D Coordination Polymers Based on the Quinoline-2,4-dicarboxylate Building Block and Lanthanide(III) Ions-Temperature Dependence Investigations.

A series of novel 3D coordination polymers [Ln2(Qdca)3(H2O)x]·yH2O (x = 3 or 4, y = 0-4) assembled from selected lanthanide ions (Ln(III) = Nd, Eu, Tb, and Er) and a non-explored quinoline-2,4-dicarboxylate building block (Qdca2- = C11H5NO42-) were prepared under hydrothermal conditions at temperatures of 100, 120, and 150 °C. Generally, an increase in synthesis temperature resulted in structural transformations and the formation of more hydrated compounds. The metal complexes were characterized by elemental analysis, single-crystal and powder X-ray diffraction methods, thermal analysis (TG-DSC), ATR/FTIR, UV/Vis, and luminescence spectroscopy. The structural variety of three-dimensional coordination polymers can be ascribed to the temperature effect, which enforces the diversity of quinoline-2,4-dicarboxylate ligand denticity and conformation. The Qdca2- ligand only behaves as a bridging or bridging-chelating building block binding two to five metal centers with seven different coordination modes arising mainly from different carboxylate group coordination types. The presence of water molecules in the structures of complexes is crucial for their stability. The removal of both coordinated and non-coordinated water molecules leads to the disintegration and combustion of metal-organic frameworks to the appropriate lanthanide oxides. The luminescence features of complexes, quantum yield, and luminescent lifetimes were measured and analyzed. Only the Eu complexes show emission in the VIS region, whereas Nd and Er complexes emit in the NIR range. The luminescence properties of complexes were correlated with the crystal structures of the investigated complexes.

Direct density modulation of photo-assisted field emission from an RF cold cathode

This paper explores direct density modulation of high-current electron beam emission from an RF cold cathode using optical excitation. We theoretically study the photo-assisted field emission of periodically bunched electron beams of various pulse shapes under the combined excitation of an RF field and an optical field, using an exact quantum model. Both continuous-wave (CW) and pulsed optical fields are considered. The emission current pulse amplitude, pulse width, electron number density per pulse, as well as pulse shape and its harmonic contents are investigated in detail. For CW photon sources in the UV to NIR range (i.e., 200–1200 nm), increasing the optical intensity under an RF bias tends to change the current pulse from a Gaussian to sinusoidal-like shape, thus offering strong flexibility to control the frequency components in beam current emission. Pulsed photon sources combined with an RF field can produce sharp, high-current electron bunches with pulse duration comparable with or even less than that of the optical pulse. A contour map of the density modulation depth is constructed for different combinations of RF and laser fields. The results provide insight into unlocking new opportunities to achieve direct density modulation during electron current emission by optical means.

Morphology and luminescent properties of nanocrystalline NaGdF4 phosphors doped with neodymium(III) ions

Nanocrystalline phosphors NaGd1- x Nd x F4 ( x = 0-1) were synthesized by hydrothermal synthesis for the first time. All the synthesized compounds have hexagonal β-NaYF4 crystalline phase. Neodymium(III) ions isomorphically replace gadolinium ions. NaGd0.96Nd0.04F4 compound has the largest photoemission intensity in NIR range upon 808 nm excitation; further doping with Nd3+ results in concentration quenching.

Prediction of Soil Water Content Based on Hyperspectral Reflectance Combined with Competitive Adaptive Reweighted Sampling and Random Frog Feature Extraction and the Back-Propagation Artificial Neural Network Method

The soil water content (SWC) is a critical factor in agricultural production. To achieve real-time and nondestructive monitoring of the SWC, an experiment was conducted to measure the hyperspectral reflectance of soil samples with varying levels of water content. The soil samples were divided into two parts, SWC higher than field capacity (super-θf) and SWC lower than field capacity (sub-θf), and the outliers were detected by Monte Carlo cross-validation (MCCV). The raw spectra were processed using Savitzky–Golay (SG) smoothing and then the spectral feature variable of SWC was extracted by using a combination of competitive adaptive reweighted sampling (CARS) and random frog (Rfrog). Based on the extracted feature variables, an extreme learning machine (ELM), a back-propagation artificial neural network (BPANN), and a support vector machine (SVM) were used to establish the prediction model. The results showed that the accuracy of retrieving the SWC using the same model was poor, under two conditions, i.e., SWC above and below θf, mainly due to the influence of the lower accuracy of the super-θf part. The number of feature variables extracted by the sub-θf and super-θf datasets were 25 and 18, respectively, accounting for 1.85% and 1.33% of the raw spectra, and the variables were widely distributed in the NIR range. Among the models, the best results were achieved by the BPANN model for both the sub-θf and the super-θf datasets; the R2p, RMSEp, and RRMSE of the sub-θf samples were 0.941, 1.570%, and 6.685%, respectively. The R2p, RMSEp, and RRMSE of the super-θf samples were 0.764, 1.479%, and 4.205%, respectively. This study demonstrates that the CARS–Rfrog–BPANN method was reliable for the prediction of SWC.

High-absorption optical stack for aluminum kinetic inductance detectors.

We present a high-absorption optical stack design for aluminum (Al) kinetic inductance detectors (KIDs). Aluminum can be easily processed in micro-fabrication and is the most conventional superconducting material for KIDs. However, it is challenging to achieve high absorption in the Al absorber because of its high reflection at optical wavelengths. By embedding the thin Al film between an anti-reflection (AR) coating layer and a dielectric-based distributed Bragg reflector, we show that close-to-unity absorption can be achieved around a single wavelength (e.g.,≈98.9% at 1518nm). The reflection and transmission measurements agree well with the calculation based on the transmission matrix model. We also show our preliminary results of absorption ≥70% in a broader wavelength range (≈230n m) with multilayer AR coatings. The absorber design in a lumped-element KID is discussed. Our work paves the way to high-efficiency photon-counting and energy-resolving Al-based KIDs in the optical to NIR range.

Spectral characterization and energy transfer study of Nd3+/Yb3+ in borosilicate glasses

Very sharp emission in near infrared region is observed for Nd3+/Yb3+ codoped 60B2O3-10SiO2-5PbO-10Al2O3-10Li2O-5ZnO (BSPbLAZ) glasses which were prepared by melt-quenching method along with Nd3+ doped BSPbLAZ glass. Photoluminescence excitation (PLE) spectra of 1 mol% of Nd2O3 doped BSPbLAZ glass shows intense band at 584 nm at an emission wavelength of 1062 nm. Photoluminescence emission (PL) spectra for 1 mol% of Nd2O3 doped BSPbLAZ glass at an excitation wavelength of 584 nm shows three characteristics emission bands in NIR range, 4F3/2→4I9/2, 4I11/2 and 4I13/2, most intense among these being the one at 1062 nm corresponding to 4F3/2→4I11/2. In the codoped system (Nd2O3/Yb2O3), prominent emission bands for Nd3+ are observed at 887, 1062 and 1336 nm corresponding to 4F3/2→4I9/2, 4I11/2 and 4I13/2 respectively, while for Yb3+ ions transition is observed at 980 nm corresponding to 2F5/2→2F7/2. Detailed investigation of characteristics like NIR emission, lifetime and energy transfer efficiency on increment of Yb2O3 doping concentration helps in understanding the utility of these glasses in the fields like photonic and optical devices. In BSPbLAZ glass Yb3+ can be easily sensitized by Nd3+ ions on account of its 4f-4f transitions. These factors provide healthy possibility for usage of Nd3+/Yb3+codoped BSPbLAZ glasses as multiple pump channel sources for laser fiber system based on Yb3+ ions.

Transition metal anchored on red phosphorus to enable efficient photocatalytic H2 generation.

Transition metal (TM) single atom catalysts (SACs) are of great potential for photocatalytic H2 production because of their abundant catalytic active sites and cost-effectiveness. As a promising support material, red phosphorus (RP) based SACs are still rarely investigated. In this work, we have carried out systematic theoretical investigations by anchoring TM atoms (Fe, Co, Ni, Cu) on RP for efficient photocatalytic H2 generation. Our density functional theory (DFT) calculations have revealed that 3d orbitals of TM locate close to the Fermi level to guarantee efficient electron transfer for photocatalytic performances. Compared with pristine RP, the introduction of single atom TM on the surface exhibit narrowed bandgaps, resulting in easier spatial separation for photon-generated charge carriers and an extended photocatalytic absorption window to the NIR range. Meanwhile, the H2O adsorptions are also highly preferred on the TM single atoms with strong electron exchange, which benefits the subsequent water-dissociation process. Due to the optimized electronic structure, the activation energy barrier of water-splitting has been remarkably reduced in RP-based SACs, revealing their promising potential for high-efficiency H2 production. Our comprehensive explorations and screening of novel RP-based SACs will offer a good reference for further designing novel photocatalysts for high-efficiency H2 generation.