Near-infrared Range Research Articles

Speckle wavemeter based on a multi-core fiber and compressive imaging.

Random speckle patterns contain valuable information about the incident light. Researchers have successfully constructed spectrometers and wavemeters by utilizing the speckles generated by inter-mode interferences of a multimode fiber (MMF). However, cameras were often employed to record the speckle data in previous reports. The camera's high cost (especially in the near-infrared range), large size, and low response speed limit the applications in optical communications, metrology, and optical sensing. A seven-core fiber (SCF) was fused with an MMF to capture the speckle pattern, where each core coupled part of the speckle field. Furthermore, we take advantage of the space division multiplexing capability of the SCF by incorporating an optical switch. This allows the variety of speckles generated by the incidence of different cores into the MMF. A convolutional neural network (CNN) regression algorithm was designed to analyze the complicated speckle data. The experimental results show that the proposed wavemeter can resolve adjacent wavelengths of 1pm with an error of about 0.2pm. We also discussed how different lengths of MMF influence the wavelength resolution. In conclusion, our research presents a robust and cost-effective approach to a wavelength measurement device by use of a seven-core optical fiber.

Integration of 3D Fluorescence Imaging and Luminescent Thermometry with Core-Shell Engineered NaYF4:Nd3+/Yb3+/Ho3+ Nanoparticles.

The design of rare-earth-doped upconversion/downshifting nanoparticles (NPs) for theoretical use in nanomedicine has garnered considerable interest. Previous research has emphasized luminescent nanothermometry and photothermal therapy, while three-dimensional (3D) near-infrared (NIR) luminescent tracers have received less attention. Our study introduces Nd3+-, Yb3+-, and Ho3+-doped NaYF4 core-shell luminescent NPs as potential multiparametric nanothermometers and NIR imaging tracers. Nd3+ sensitizes at 804 nm, while Yb3+ bridges to activators Ho3+. We evaluated the photoluminescence properties of Nd3+-, Yb3+-, and Ho3+-doped core and core-shell NPs synthesized via polyol-mediated and thermal decomposition methods. The NaYF4:NdYbHo(7/15/3%)@NaYF4:Nd(15%) core-shell NPs demonstrate competitive nanothermometry capabilities. Specifically, the polyol-synthesized sample exhibits a sensitivity of 0.27% K-1 at 313 K (40 °C), whereas the thermally decomposed synthesized sample shows a significantly higher sensitivity of 0.55% K-1 at 313 K (40 °C) in the near-infrared range. Control samples indicate back energy transfer processes from both Yb and Ho to Nd, while Yb to Ho energy transfer enhances Ho3+-driven upconversion transitions in green and red wavelengths, suggesting promise for photodynamic therapy. Fluorescence molecular tomography confirms 3D NIR fluorescence nanoparticle localization in a biological media after injection, highlighting the potential of core-shell NPs as NIR luminescent tracers. The strategy's clinical impact lies in photothermal treatment planning, leveraging core-shell NPs for (pre)clinical applications, and enabling the easy addition of new functionalities through distinct ion doping.

A Highly Efficient and Energy Saving Electrochromic Platform for Adaptive Visible and Near-Infrared Light Modulation

Dual-band electrochromic devices (DBEDs) with reversible optical properties in visible (VIS) and near-infrared (NIR) spectral ranges are highly desirable for intelligent technologies (e.g. electrochromic smart windows, adaptive and military camouflages). However, most available DBEDs only have two optical states - namely the bleached and colored states, and efforts are committed to increasing the optical modulation between them, while durability of cycling is rarely reported. Herein, we report a novel multicolored rocking-chair DBED based on Prussian blue (PB) thin films as electrochromic layers and a conductive carbon cloth (CC) frame as the counter electrode. During the electrochromic process, cations from the electrolyte migrate back and forth between PB and CC, and electrolysis of aqueous electrolyte can be effectively avoided to extend device longevity. The PB-CC DBED exhibits superior dual-band electrochromic performance with a wide range of switchable colors, including transparent, blue, green and yellow, large optical modulation in VIS-NIR ranges, fast response speed, high coloration efficiency and long-term durability. Based on the diverse color change in the VIS range and thermal control in the NIR range, the camouflage ability of the device is also described. Finally, an adaptive optical modulation platform is demonstrated, obtained by connecting the PB-CC device to a voltage-controlled circuit module to realize intelligent and autonomous color switching of the device.

Corrosion analysis and performance investigation of hybrid MXene/C-dot Nanofluid-Based direct absorption solar collector

Nanofluids having exceptional thermo-optical characteristics can enhance the performance of direct absorption solar collectors (DASC). Conventional nanofluids have either high optical properties or thermal properties. In this study, carbon quantum dot (C-dot) nanomaterial with high stability and optical absorption along the UV range, and MXene nanoparticles with high thermal conductivity and absorption along visible and near-infrared (NIR) spectral range was selected for synthesizing a hybrid nanomaterial with synergistic thermo-optical properties. Hybrid MXene/C-dot nanofluid exhibits higher stability, thermal conductivity, and complementary absorption properties of individual nanomaterials. A two-step method was used for the synthesis of nanofluids using water as the base fluid. Thermal conductivity, UV–Vis-NIR spectroscopy, and stability analysis were conducted on nanofluids, and the concentration was optimized for corrosion study and application in direct absorption parabolic trough collector (DAPTC). Optimised concentrations of C-dot, MXene, and hybrid nanofluids were 0.15 wt%, 0.1 wt% and 0.15 wt%, respectively. The corrosion study states that copper electrodes dipped in the hybrid nanofluid exhibited the least corrosion rate of 0.6 mm/year with an anticorrosion efficiency of 64.5 % over DI water. Thermal efficiency and entropy generation in the system with different HTFs were measured and compared with that of the base fluid. The study shows that C-dot and MXene/C-dot nanofluids were producing the highest efficiencies of 50.5 % and 47.5 % at a flow rate of 1.2 lpm. This study shows that hybrid MXene/C-dot nanofluid exhibited exceptional thermal stability, reduced corrosion effects, and considerable enhancement in photothermal conversion efficiency of the DASC.

Electrically tunable dual polarization states of light using lithium niobate-based nanograting.

Tuning polarization states of light electrically has unique advantages in the integration of optoelectronic devices. Here, a lithium niobate-based nanograting is proposed to dynamically tune the polarization state of both the reflected and transmitted lights simultaneously in the near-infrared range. By judiciously designing the nanograting, a quasi-bound state in the continuum (qBIC) is excited under the excitation of an obliquely incident plane wave. The excited mode with a high quality-factor and enhanced local electric field can respond to a refractive index change in nanograting structures as small as 10-4 level, which can be generated with a low external voltage via the electro-optic effect. As a result, both the polarization states of reflected and transmitted lights can be dynamically tuned from a right circular polarization to a linear polarization state. The proposed lithium niobate-based nanograting for tuning dual polarization states of light with a qBIC mode suggests a promising electrical scheme for achieving high speed optoelectronic devices.

Fast quantitative analysis and chemical visualization of amylopectin and amylose in sweet potatoes via merging 1D spectra and 2D image

The quantitative analysis and spatial chemical visualization of amylopectin and amylose in different varieties of sweet potatoes were studied by merging spectral and image information. Three-dimensional (3D) hyperspectral images carrying 1D spectra and 2D images of hundreds of the samples (amylopectin, n = 644; amylose, n = 665) in near-infrared (NIR) range of 950–1650 nm (426 wavelengths) were acquired. The NIR spectra were mined to correlate with the values of the two indexes using a linear algorithm, generating a best performance with correlation coefficients and root mean square error of prediction (rP and RMSEP) of 0.983 and 0.847 g/100 mg for amylopectin, and 0.975 and 0.500 g/100 mg for amylose, respectively. Then, 14 % of the wavelengths (60 for amylopectin, 61 for amylopectin) were selected to simplify the prediction with rP and RMSEP of 0.970 and 1.103 g/100 mg for amylopectin, and 0.952 and 0.684 g/100 mg for amylose, respectively, comparable to those of full-wavelength models. By transferring the simplified model to original images, the color chemical maps were created and the differences of the two indexes in spatial distribution were visualized. The integration of NIR spectra and 2D image could be used for the more comprehensive evaluation of amylopectin and amylose concentrations in sweet potatoes.

Sub-1-Volt Electrically Programmable Optical Modulator Based on Active Tamm Plasmon.

Reconfigurable optical devices hold great promise for advancing high-density optical interconnects, photonic switching, and memory applications. While many optical modulators based on active materials have been demonstrated, it is challenging to achieve a high modulation depth with a low operation voltage in the near-infrared (NIR) range, which is a highly sought-after wavelength window for free-space communication and imaging applications. Here, electrically switchable Tamm plasmon coupled with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is introduced. The device allows for a high modulation depth across the entire NIR range by fully absorbing incident light even under epsilon near zero conditions. Optical modulation exceeding 88% is achieved using a CMOS-compatible voltage of ±1V. This modulation is facilitated by precise electrical control of the charge carrier density through an electrochemical doping/dedoping process. Additionally, the potential applications of the device are extended for a non-volatile multi-memory state optical device, capable of rewritable optical memory storage and exhibiting long-term potentiation/depression properties with neuromorphic behavior.

Characterizing Diploid and Tetraploid Potato Cultivars with Reflectance Spectroscopy

Characterizing potato cultivars is essential for diagnosing the specific production and management requirements. Employing techniques that facilitate rapid, objective, and cost-effective identification of various aspects of plant physiology is crucial for generating this valuable information. In this study, our goal was to identify different potato cultivars across three distinct phenological phases utilizing reflectance spectroscopy within the visible and near-infrared ranges. Reflectance spectra were measured using a portable spectrometer on leaves obtained from five different potato cultivars. We constructed classification models to determine the accurate classification percentages for each cultivar within specific phenological stages. General trends in the reflectance spectra were observed, which were consistent across all five cultivars within the measured range. During the vegetative phase, there was a uniform reflectance of around 5% in the green region. This value experienced a slight decrease during the flowering phase and subsequently rose to approximately 12% during the senescence phase. In the near-infrared (NIR) range, a reduction in reflectance from 50 to 30% was noted during the flowering phase, followed by a cultivar-dependent increase towards senescence. The specific wavelengths identified in the spectra enabled the accurate classification of plants from each cultivar across the vegetative, flowering, and senescence phases. The classification rates were notably high, with a success rate of 87% for Var. Paola, 96% for Var. Paysandú, 93% for Var. Violeta, and 100% for cv. 448 and 440. The Var. Paola exhibited superior correct classification rates, ranging from 85% for Paysandú and Violeta, 90% for cv. 440, to 100% for cv. 448. The characterization of potato cultivars using spectroscopy techniques yields valuable information that serves as fundamental input for precision agriculture systems.

Ultra-broadband high-efficiency solar absorber based on Ti-GaAs-Au structure for UV to near-infrared spectral range

In this study, we propose an ultra-broadband solar absorber composed of a trapezoidal base, an outer circular ring, and four nano-cylinders. The absorber has a covered bandwidth range of 300–4000 nm and a temperature range of 373–973 K. The average absorptance within the mentioned wavelength range is over 96.52%, and the efficiency of solar energy thermal conversion is above 0.9 at 373–973 K under a solar concentration factor of 1000, with a maximum efficiency of 0.9644. Analysis of its absorption mechanism using the finite-difference time-domain method indicates that the proposed solar absorber’s outstanding absorption performance is due to the excitation of surface plasmon polaritons, localized surface plasmon resonances, and cavity resonances enhanced electromagnetic fields. This result has also been validated by the impedance matching theory. Moreover, the proposed solar absorber exhibits insensitivity to different polarization angles and maintains a high absorption effect in the range of 0°–70° incidence angle. The designed solar absorber has potential applications in areas such as seawater purification, wastewater treatment, and steam power generation systems.

Direct growth Bi2O2Se nanosheets on SiO2/Si substrate for high-performance and broadband photodetector

Bi2O2Se, a newly emerging two-dimensional (2D) material, has attracted significant attention as a promising candidate for optoelectronics applications due to its exceptional air stability and high mobility. Generally, mica and SrTiO3 substrates with lattice matching are commonly used for the growth of high-quality 2D Bi2O2Se. Although 2D Bi2O2Se grown on these insulating substrates can be transferred onto Si substrate to ensure compatibility with silicon-based semiconductor processes, this inevitably introduces defects and surface states that significantly compromise the performance of optoelectronic devices. Herein we employ Bi2Se3 as the evaporation source and oxygen reaction to directly grow Bi2O2Se nanosheets on Si substrate through a conventional chemical vapor deposition method. The photodetector based on the Bi2O2Se nanosheets on Si substrate demonstrates outstanding optoelectronics performance with a responsivity of 379 A W−1, detectivity of 2.9 × 1010 Jones, and rapid response time of 0.28 ms, respectively, with 532 nm illumination. Moreover, it also exhibits a broadband photodetection capability across the visible to near-infrared range (532–1300 nm). These results suggest that the promising potential of Bi2O2Se nanosheets for high-performance and broadband photodetector applications.

Tailoring of Visible to Near-Infrared Active 2D MXene with Defect-Enriched Titania-Based Heterojunction Photocatalyst for Green H2 Generation.

A wide solar light absorption window and its utilization, long-term stability, and improved interfacial charge transfer are the keys to scalable and superior solar photocatalytic performance. Based on this objective, a noble metal-free composite photocatalyst is developed with conducting MXene (Ti3C2) and semiconducting cauliflower-shaped CdS and porous Cu2O. XPS, HRTEM, and ESR analyses of TiOy@Ti3C2 confirm the formation of enough defect-enriched TiOy (where y is < 2) on the surface of Ti3C2 during hydrothermal treatment, thus creating a third semiconducting site with enough oxygen vacancy. The final material, TiOy@Ti3C2/CdS/Cu2O, shows a broad absorption window from 300 to 2000 nm, covering the visible to near-infrared (NIR) range of the solar spectrum. Photocatalytic H2 generation activity is found to be 12.23 and 16.26 mmol g-1 h-1 in the binary (TiOy@Ti3C2/CdS) and tertiary composite (TiOy@Ti3C2/CdS/Cu2O), respectively, with good repeatability under visible-NIR light using lactic acid as the hole scavenger. A clear increase of efficiency by 1.53 mmol g-1 h-1 in the tertiary composite due to NIR light absorption supports the intrinsic upconversion of electrons, which will open a new prospective of solar light utilization. Decreased charge-transfer resistance from the EIS plot and a decrease in PL intensity established the improved interfacial charge separation in the tertiary composite. Compared to pure CdS, H2 generation efficiency is 29.6 times higher on the noble metal-free tertiary composite with an apparent quantum efficiency of 12.34%. Synergistic effect of defect-enriched TiOy formation, creation of proper dual p-n junction on a Ti3C2 sheet as supported by the Mott-Schottky plot, significant NIR light absorption, increased electron mobility, and charge transfer on the conductive Ti3C2 layer facilitate the drastically increased hydrogen evolution rate even after several cycles of repetition. Expectantly, the 2D MXene-based heterostructure with defect-enriched dual p-n junctions of desired interface engineering will facilitate scalable photocatalytic water splitting over a broad range of the solar spectrum.

A near-infrared superoxide generator based on a biocompatible indene-bearing heptamethine cyanine dye.

One of the most significant limitations of photodynamic therapy is its reduced efficacy in hypoxic microenvironments, which are typical of the majority of tumors. This work demonstrates that indolenine heptamethine cyanines with different substituents in the polymethine chain and at the terminal heterocycles are effective superoxide generators that can be activated in the near-infrared range. The introduction of an indene moiety into the polymethine chain results in a significant enhancement in photostability compared to dyes with a cyclohexene moiety or an unsubstituted polymethine chain. A hydrophilic indene-bearing heptamethine cyanine dye is shown to be efficiently internalized by Vero E6 cells and to give bright intracellular fluorescence in the 700-850 nm range. Furthermore, the dye generates superoxide anion radicals and induces severe oxidative stress in cells upon activation in the near-infrared range (∼750 nm), ultimately resulting in cell death. The capacity of heptamethine cyanines to generate a superoxide anion radical may prove advantageous for enhancing the efficacy of photodynamic therapy under hypoxic conditions.

Water content estimation of recycled building materials based on near-infrared spectroscopy

Recycling of construction and demolition waste (CDW) is one key component of the circular economy. Reusing construction materials opens the opportunity to preserve finite natural resources and their corresponding landscapes, and also reduces the emission of greenhouse gases.Unfortunately, recycling of CDW is challenging when the new product ought to be used on the same quality level as the demolished one and down-cycling should be avoided. Therefore, the CDW needs to be classified and impurities must be removed. The water content quantification of the recycled aggregates is important because the amount of existing water needs to be known, e.g., when calculating a mixture for recycling concrete. New developments in the classification and the sorting of CDW make use of the information from the spectral range in the visual and infrared region. Therefore, the approach of this study is to examine whether this information can be used to estimate the water content of various CDW materials. Based on reflection measurements in the near-infrared range between 1000nm and 2300nm a mathematical relationship between the spectral measurements and the water content is established. Three estimates for the water content are set up. The mean absorption, the water index, and the absorption difference are later tested on CDW material samples covering concrete, autoclaved aerated concrete, lightweight concrete, brick, roof tile, calcium silicate brick and gypsum.

Sensitive monitoring of NAD(P)H levels within cancer cells using mitochondria-targeted near-infrared cyanine dyes with optimized electron-withdrawing acceptors.

A series of near-infrared fluorescent probes, labeled A to E, were developed by combining electron-rich thiophene and 3,4-ethylenedioxythiophene bridges with 3-quinolinium and various electron deficient groups, enabling the sensing of NAD(P)H. Probes A and B exhibit absorptions and emissions in the near-infrared range, offering advantages such as minimal interference from autofluorescence, negligible photo impairment in cells and tissues, and exceptional tissue penetration. These probes show negligible fluorescence when NADH is not present, and their absorption maxima are at 438 nm and 470 nm, respectively. In contrast, probes C-E feature absorption maxima at 450, 334 and 581 nm, respectively. Added NADH triggers the transformation of the electron-deficient 3-quinolinium units into electron-rich 1,4-dihydroquinoline units resulting in fluorescence responses which were established at 748, 730, 575, 625 and 661 for probes AH-EH, respectively, at detection limits of 0.15 μM and 0.07 μM for probes A and B, respectively. Optimized geometries based on theoretical calculations reveal non-planar geometries for probes A-E due to twisting of the 3-quinolinium and benzothiazolium units bonded to the central thiophene group, which all attain planarity upon addition of hydride resulting in absorption and fluorescence in the near-IR region for probes AH and BH in contrast to probes CH-EH which depict fluorescence in the visible range. Probe A has been successfully employed to monitor NAD(P)H levels in glycolysis and specific mitochondrial targeting. Furthermore, it has been used to assess the influence of lactate and pyruvate on the levels of NAD(P)H, to explore how hypoxia in cancer cells can elevate levels of NAD(P)H, and to visualize changes in levels of NAD(P)H under hypoxic conditions with CoCl2 treatment. Additionally, probe A has facilitated the examination of the potential impact of chemotherapy drugs, namely gemcitabine, camptothecin, and cisplatin, on metabolic processes and energy generation within cancer cells by affecting NAD(P)H levels. Treatment of A549 cancer cells with these drugs has been shown to increase NAD(P)H levels, which may contribute to their anticancer effects ultimately leading to programmed cell death or apoptosis. Moreover, probe A has been successfully employed in monitoring NAD(P)H level changes in D. melanogaster larvae treated with cisplatin.

Extrinsic chirality tailors Stokes parameters in simple asymmetric metasurfaces.

Metasurfaces tailor electromagnetic confinement at the nanoscale and can be appropriately designed for polarization-dependent light-matter interactions. Adding the asymmetry degree to the desing allows for circular polarizations of opposite handedness to be differently absorbed or emitted, which is of interest in fields spanning from chiral sensing to flat optics. Here, we show that simple, low-cost asymmetric metasurfaces can control Stokes parameters in the transmitted far-field. With only 50 nm of asymmetric plasmonic shells on self-assembled polystyrene nanospheres, our metasurfaces allow for great spectral and incident angle tunability. We first investigated broadband extrinsic chirality in metasurfaces with asymmetric plasmonic semishells; we found high extinction circular dichroism (CD) in the near-infrared range. We then excited it with linear polarization and performed hyperspectral Stokes polarimetry on the transmitted field. We showed that the S3 parameter follows the behavior of CD in extinction, and that the output field position on the Poincaré sphere can be widely controlled by using the incidence angle and wavelength. Furthermore, simulations agreed well with the experiments and showed how the near-field chiro-optical response influences the extrinsic chiral behavior in absorption and the polarization state of the transmitted field.

Bright near-infrared emission from the Au39(SR)29 nanocluster.

The synthesis of atomically precise gold nanoclusters with high photoluminescence quantum yield (PLQY) in the near-infrared (NIR) region and understanding their photoluminescence mechanism are crucial for both fundamental science and practical applications. Herein, we report a highly luminescent, molecularly pure Au39(PET)29 (PET = 2-phenylethanethiolate) nanocluster with PLQY of 19% in the NIR range (915 nm). Steady state and time-resolved PL analyses, as well as temperature-dependent PL measurements reveal the emission nature of Au39(PET)29, which consists of prompt fluorescence (weak), thermally activated delayed fluorescence (TADF), and phosphorescence (predominant). Furthermore, strong dipole-dipole interaction in the solid-state (e.g., Au39(PET)29 nanoclusters embedded in a polystyrene thin-film) is found to narrow the energy gap between the S1 and T1 states, which results in faster intersystem crossing and reverse intersystem crossing; thus, the ratio of TADF to phosphorescence varies and the total PLQY is increased to 32%. This highly luminescent nanocluster holds promise in imaging, sensing and optoelectronic applications.

Enhancing the performance of PbS:CsPbBr3 bulk-heterojunction photodetectors by treating with imidazolium-based ionic liquids.

All-inorganic lead halide perovskites and quantum dots (QDs) have gained significant attention since their emergence, owing to their immense potential for applications in optoelectronic devices. Here, enhanced-performance broadband photodetectors based on the bulk-heterostructure of a CsPbBr3 perovskite and PbS colloidal quantum dots (CQDs) are presented, and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4) ionic liquids as a dual-purpose additive were introduced in the blended film to regulate the surface of QDs by facilitating surface passivation, adjusting energy levels, and coupling with longer alkyl chains as compared to iodide ions (I-). As a result, a superior-quality bulk-heterostructure based photodetector with long-term stability was obtained, showing outstanding performance in photodetection across the visible to near-infrared wavelength range, demonstrating a high photoresponsivity of 22.4 A W-1 with a response time of 16.2 ms and a specific detectivity of 1.58 × 1014 Jones under 405 nm illumination. Thus, this work provides a novel modification strategy for PbS:CsPbBr3 as a promising material for novel optoelectronics.

Synergistic charge-transfer dynamics of novel pyridoquinazolindone-containing triphenylamine-based push-pull chromophores: from structural optimization to performance metrics in photovoltaic solar cells and static, dynamic, solvent-dependent nonlinear optical response applications.

Modern technological breakthroughs depend on nonlinear optical (NLO) and photovoltaic (PV) materials, essential for creating advanced photonic devices and efficient solar cells. Herein, the NLO, PV, electrical, and photophysical characteristics of proposed chromophores (WLK-1-WLK-6) designed from pyridoquinazolindone-containing triphenylamine have been systematically altered by the addition of different spacers categorized as K1, K2, K3, K4, K5, and K6 (named as i-series). This fine-tuning was accomplished using TD-DFT, DFT computations, and the Scharber model. The impact of spectrum of medium polarity, ranging from the least polar to the most polar, including water (ε = 78.36), methanol (ε = 32.61), DMSO (ε = 46.83), tetrahydrofuran (ε = 7.43), benzene (ε = 2.27) and chloroform (ε = 4.71), is explored in detail utilizing the IEFPCM model on NLO and PV properties. Moreover, the response of different analyses like DOS, NCI, NBO, FMO, dipole moments (µ), and hyperpolarizability (β) in both gas, polar and non-polar solvents was analyzed. Our structure-property relationship studies revealed that adding extra spacer groups, particularly those containing thiophene spacers, considerably impacted the lowering of the energy gap (3.853-4.190 eV). The simulated UV-Vis spectra illustrate significant π → π* transitions and lower n → π* transitions, primarily in the near-infrared (IR) range of 558.613 to 429.844 nm. Push-pull chromophores showed extraordinary frequency-dependent NLO properties, SHG β(-2ω, ω, ω), and EOPE β(-ω, ω, 0) effect computed at laser frequencies of 1064 and 532 nm. Among the proposed compounds, WLK-6 with the K6 spacer demonstrated a smaller energy gap (3.853 eV), resulting in a maximum optical absorption peak at λ max = 558.613 nm and the maximum hyperpolarizability in benzene (9.00 × 104 a.u.), methanol (1.22 × 105 a.u.), THF (1.12 × 105 a.u.), DMSO (1.23 × 105 a.u.), and water (1.23 × 105 a.u.). Our study found that WLK-6, WLK-5, and WLK-1 compounds also had good photovoltaic (PV) capabilities, reaching a power conversion efficiency (PCE) of around 5% and an injection efficiency (ΔG inject) of 0.191. In addition to these analyses, we performed topologic studies, such as TDM, ELF, NCI, MEP, LOL, and electron-hole overlap plots to better understand both intra and intermolecular interactions. Based on these results, it is clear that modifying longer π-linker groups in A-D-π-A conjugated systems benefits the optoelectronic characteristics and NLO responses for organic PV devices.

Research on Broadband Antireflection Coat-ings in the Visible and Near-Infrared Spectral Ranges

Research on Broadband Antireflection Coat-ings in the Visible and Near-Infrared Spectral Ranges

Accuracy Evaluation of Visible-Near Infrared Spectroscopy for Detecting Insect Damage in Acorns of Quercus acuta

Abstract This study aimed to test near-infrared spectroscopy to assess insect damage to oak acorns collected from a seed orchard of Quercus acuta in Jeju Island, Korea. A total of 550 acorns were sorted into 362 sound and 178 unsound (insect-damaged) acorns, followed by near-infrared spectroscopy. To minimize spectral data errors, preprocessing techniques such as first derivative, multiplicative scatter correction, standard normal variate, and Savitzky-Golay filter were applied, along with multivariate analysis methods like partial least squares. Then the model performance, including accuracy and precision, was evaluated using the Variable Importance in Projection. The near-infrared wavelength of the acorns showed strong absorption peaks at 660~720nm and a slight downward trend at 900~1000nm. The most effective model for distinguishing unsound acorns was Savitzky-Golay filtering treatment applied in the 400~1000nm range and used partial least squares, showing prediction accuracy of 86 % (p&lt;0.05). The performance was significantly influenced by absorption points at 660~720nm and 960~1000nm, with the latter range believed to be affected by changes in moisture and carbohydrates due to insect damage. The former range showed lower classification capability due to chlorophyll and color variation but affected the model performance when used with near-infrared wavelength range. These findings can narrow down the scope of investigation for future research using wider wavelength ranges or multispectral analysis.