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Monitoring of Microwave-Assisted Acid-Catalyzed Transesterification for Biodiesel Production Using FT-NIR Spectroscopy with Continuous-Flow Cell
摘要： The homogeneous microwave-assisted sulfuric acid-catalyzed transesterification of soybean oil, waste Brazil nut oil, sunflower oil and chicken fat for ethylic and methylic biodiesel production is described herein. The experiments were carried out in pilot-scale multimode reactors. The effects of the alcohol to oil molar ratio, catalyst concentration and irradiation time on the conversion to biodiesel were investigated. The transesterification reactions were performed at relatively small alcohol to oil molar ratios (9:1, 8:1 and 6:1) affording near 100% of conversion in reaction times of 60 to 120 min. Partial least squares (PLS) regression analysis using FT-NIR spectroscopy was performed to monitor the progress of the acid-catalyzed methanolysis of soybean oil. The NIR spectra were collected during the transesterification reaction with a spectrophotometric continuous-flow cell. 1H NMR spectroscopy was employed to determine the conversion percentage and used as a reference to build the PLS calibration model employing NIR spectroscopy data.
关键词： vegetable oils,sulfuric acid,FT-NIR spectroscopy,Animal fat,homogeneous acid catalysis,microwave-induced transesterification
更新于2025-09-23 15:21:01
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Vis- and NIR-Based Instruments for Detection of Black-Tip Damaged Wheat Kernels: A Comparative Study
摘要： Black-tip (BT) is a non-mycotoxic fungus that attacks wheat kernels, forming a dark brown or black sooty area at the tip of the kernel. Visual inspection, which is the approved reference method for determining the amount of BT in wheat, requires substantial time and has high potential for subjective evaluation. Three spectrometers covering the spectral ranges 950-1636 nm (Spec1), 600-1045 nm (Spec2), and 380-780 nm (Spec3) were evaluated for their ability to predict the presence of BT. Kernels were quantified into four levels: (A) sound, (B) low black-tip symptoms (BTS), (C) high BTS, and (D) BT damaged (BTD). Discriminant classification models were developed to evaluate combinations of levels. The combinations were (1) levels A, B, C, and D separately; (2) A, B+C, and D; and (3) A+B and C+D. Spectral data for 2,760 kernels obtained from 23 hard red winter (HRW) wheat samples, each comprising 30 kernels that were visually selected for each of the four levels of black-tip severity (A, B, C, and D), were collected with each spectrometer. Discriminant calibration models for each spectrometer and classification category were developed based on (1) three combinations of 17 HRW wheat samples, with the six remaining samples used for independent validation, and (2) combinations of 20 randomly selected kernels from each of the 23 HRW wheat samples as calibration samples, with the remaining ten kernels used as validation samples. Discriminant analysis was based on five wavelengths for each model. Spectra pretreatment was the standard normal variate (SNV). Results showed that all three spectrometers were capable of detecting BT damage on wheat kernels. BT classification accuracy was observed to have been affected by wheat varieties for Spec1 and Spec2 (both with NIR wavelengths) but not for Spec3, which was entirely in the visible region. The two-category classification (A+B, C+D) provided higher accuracy than the three-category (A, B+C, D) and four-category (A, B, C, D) classifications. Based on the percent correct classification and Youden’s index, Spec2 performed better in detecting sound and BTD wheat kernels, with classification accuracies of the best two-category classification calibration model ranging from 85.6% to 87.5%, compared to Spec1 at 74.8% to 78.4% and Spec3 at 76.7% to 79.2%. This study also showed the potential of using a five-wavelength model, which equates to the potential for developing simple, less expensive, high-speed photoelectric detection instruments. These instruments can serve as important tools in plant breeding, grading, or grain processing facilities to enable BT detection and, with proper selection of wavelengths, may also find applications in simultaneous single-kernel detection, measurement, and segregation of other chemical characteristics, such as protein and starch content.
关键词： Black-tip damage,Wheat,VIS,NIR,Spectroscopy
更新于2025-09-23 15:21:01
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Multi-Algorithm Indices and Look-Up Table for Chlorophyll-a Retrieval in Highly Turbid Water Bodies Using Multispectral Data
摘要： Many approaches have been proposed for monitoring the eutrophication of Case 2 waters using remote sensing data. Semi-analytical algorithms and spectrum matching are two major approaches for chlorophyll-a (Chla) retrieval. Semi-analytical algorithms provide indices correlated with phytoplankton characteristics, (e.g., maximum and minimum absorption peaks). Algorithms’ indices are correlated with measured Chla through the regression process. The main drawback of the semi-analytical algorithms is that the derived relation is location and data limited. Spectrum matching and the look-up table approach rely on matching the measured re?ectance with a large library of simulated references corresponding to wide ranges of water properties. The spectral matching approach taking hyperspectral measured re?ectance as an input, leading to dif?culties in incorporating data from multispectral satellites. Consequently, multi-algorithm indices and the look-up table (MAIN-LUT) technique is proposed to combine the merits of semi-analytical algorithms and look-up table, which can be applied to multispectral data. Eight combinations of four algorithms (i.e., 2-band, 3-band, maximum chlorophyll index, and normalized difference chlorophyll index) are investigated for the MAIN-LUT technique. In situ measurements and Medium Resolution Imaging Spectrometer (MERIS) sensor data are used to validate MAIN-LUT. In general, the MAIN-LUT provide a comparable retrieval accuracy with locally tuned algorithms. The most accurate of the locally tuned algorithms varied among datasets, revealing the limitation of these algorithms to be applied universally. In contrast, the MAIN-LUT provided relatively high retrieval accuracy for Tokyo Bay (R2 = 0.692, root mean square error (RMSE) = 21.4 mg m?3), Lake Kasumigaura (R2 = 0.866, RMSE = 11.3 mg m?3), and MERIS data over Lake Kasumigaura (R2 = 0.57, RMSE = 36.5 mg m?3). The simulated reflectance library of MAIN-LUT was generated based on inherent optical properties of Tokyo Bay; however, the MAIN-LUT also provided high retrieval accuracy for Lake Kasumigaura. MAIN-LUT could capture the spatial and temporal distribution of Chla concentration for Lake Kasumigaura.
关键词： Red-NIR algorithm,spectral matching,look-up table,Case 2 waters,bio-optical model,inland lakes,MERIS
更新于2025-09-23 15:21:01
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Diffuse Reflectance Spectroscopy (Vis-Nir-Swir) as a Promising Tool for Blue Carbon Quantification in Mangrove Soils: A Case of Study in Tropical Semiarid Climatic Conditions
摘要： The assessment of the soil organic carbon (SOC) stocks in mangrove ecosystems is essential for coastal management activities seeking the mitigation of CO2 emissions. However, the wet chemical analysis conventionally used to quantify SOC may overestimate SOC content due to oxidation of reduced compounds. This work focused on the use of diffuse reflectance spectroscopy (DRS) for predicting SOC in mangrove forest areas. When used properly, DRS may be, in some cases, a more accurate and more efficient method for the determination of SOC in mangrove soils than conventional analytical approaches. Furthermore, variable selection may simplify and improve prediction accuracy, reducing collinearity in the dataset used and allowing better SOC quantification through more interpretable and robust models.
关键词： Tropical semiarid climatic conditions,Mangrove soils,Vis-NIR-SWIR,Blue Carbon,Diffuse reflectance spectroscopy
更新于2025-09-23 15:21:01
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Quantitative Sensitization Efficiencies in NIR-Emissive Homoleptic Ln(III) Complexes Using 2-(5-Methylpyridin-2-yl)-8-hydroxyquinoline
摘要： A series of lanthanide complexes [Ln(MPQ)3] (Ln = Nd, Gd, Er, Yb, Lu) using a monoanionic tridentate methylpyridyl-substituted 8-hydroxyquinoline ligand (MPHQ = 2-(5-methylpyridin-2-yl)-8-hydroxyquinoline) have been prepared and characterized using elemental analysis (CHN), single-crystal X-ray diffraction (XRD), and 1H NMR spectroscopy. This ligand forms homoleptic charge-neutral lanthanide complexes with three coordinated ligands arranged in an 'up?up?down' fashion around the metal center. The photophysical properties of the Nd, Er, and Yb complexes were investigated using absorption and emission spectroscopy, with the latter species displaying efficient sensitization in the Near Infra-Red (NIR) region and a photoluminescence quantum yield (PLQY) as high as 1.0% in CH2Cl2 solution. The intersystem crossing and energy-transfer processes involved in the antenna effect were further investigated using transient absorption techniques, which revealed essentially quantitative sensitization efficiencies for the NIR-emitting cations.
关键词： lanthanide complexes,8-hydroxyquinoline ligand,homoleptic,quantitative sensitization efficiencies,NIR-emissive
更新于2025-09-23 15:21:01
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Organic Upconversion Display with an over 100% Photon-to-photon Upconversion Efficiency and a Simple Pixelless Device Structure
摘要： Comparing to traditional near infrared (NIR) imaging devices, NIR-to-visible upconversion display which integrated a NIR photodetector with a visible light-emitting diode have merits of simple device structure, low cost, high resolution, and a simple pixelless structure. However, photon-to-photon upconversion efficiencies of these devices are typically much lower than unity. Here we report an all-organic NIR-to-visible upconversion display with a photon-to-photon upconversion efficiency higher than 100% by integrating a photomultiplying organic NIR photodetector with a high-efficiency thermally activated delayed fluorescent organic light-emitting-diode. To the best of our knowledge, this is the first report showing a photon-to-photon upconversion efficiency over 100% without using a built-in transistor for current amplification.
关键词： organic photodetector,NIR-to-visible upconversion,photon-to-photon efficiency,thermally activated delayed fluorescence,organic light-emitting diode
更新于2025-09-23 15:21:01
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Controlled Synthesis of Ag <sub/>2</sub> Te@Ag <sub/>2</sub> S Corea??Shell Quantum Dots with Enhanced and Tunable Fluorescence in the Second Neara??Infrared Window
摘要： Fluorescence in the second near-infrared window (NIR-II, 900–1700 nm) has drawn great interest for bioimaging, owing to its high tissue penetration depth and high spatiotemporal resolution. NIR-II fluorophores with high photoluminescence quantum yield (PLQY) and stability along with high biocompatibility are urgently pursued. In this work, a Ag-rich Ag2Te quantum dots (QDs) surface with sulfur source is successfully engineered to prepare a larger bandgap of Ag2S shell to passivate the Ag2Te core via a facile colloidal route, which greatly enhances the PLQY of Ag2Te QDs and significantly improves the stability of Ag2Te QDs. This strategy works well with different sized core Ag2Te QDs so that the NIR-II PL can be tuned in a wide range. In vivo imaging using the as-prepared Ag2Te@Ag2S QDs presents much higher spatial resolution images of organs and vascular structures as compared with the same dose of Ag2Te nanoprobes administrated, suggesting the success of the core–shell synthetic strategy and the potential biomedical applications of core–shell NIR-II nanoprobes.
关键词： NIR-II nanoprobes,Ag2Te@Ag2S,bioimaging,core–shell quantum dots
更新于2025-09-23 15:19:57
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EXPRESS: Comparison of Individual and Integrated Inline Raman, Near-Infrared, and Mid-Infrared Spectroscopic Models to Predict the Viscosity of Micellar Liquids
摘要： In many industries, viscosity is an important quality parameter which significantly affects consumer satisfaction and process efficiency. In the personal care industry, this applies to products like shampoo and shower gels whose complex structures are built up of micellar liquids. Measuring viscosity offline is well established using benchtop rheometers and viscometers. The difficulty lies in measuring this property directly in the process via on or inline technologies. Therefore, the aim of this work is to investigate whether proxy measurements using in-line vibrational spectroscopy, e.g., near infrared (NIR), mid-infrared (MIR), and Raman, can be used to predict the viscosity of micellar liquids. As optical techniques, they are non-destructive and easily implementable process analytical tools where each type of spectroscopy detects different molecular functionalities. Inline fiber optic coupled probes were employed; a transmission probe for NIR measurements, an attenuated total reflectance (ATR) probe for MIR and a backscattering probe for Raman. Models were developed using forward interval partial least squares (iPLS) variable selection and log viscosity was used. For each technique combinations of pre-processing techniques were trialed including detrending, Whittaker filters, standard normal variate (SNV) and multiple scatter correction (MSC). The results indicate that all three techniques could be applied individually to predict the viscosity of micellar liquids all showing comparable errors of prediction: NIR: 1.75 Pa s; MIR: 1.73 Pa s; and Raman: 1.57 Pa s. The Raman model showed the highest relative prediction deviation (RPD) value of 5.07, with the NIR and MIR models showing slightly lower values of 4.57 and 4.61, respectively. Data fusion was also explored to determine whether employing information from more than one dataset improved the model quality. Trials involved weighting datasets based on their signal to noise ratio and weighting based on transmission curves (IR datasets only). The signal to noise weighted NIR-MIR-Raman model showed the best performance compared with both combined and individual models with a RMSECV of 0.75 Pa s and an RPD of 10.62. This comparative study provides a good initial assessment of the three prospective process analytical technologies for the measurement of micellar liquid viscosity but also provides a good basis for general measurements of inline viscosity using commercially available process analytical technology. With these techniques typically being employed for compositional analysis, this work presents their capability in the measurement of viscosity–an important physical parameter, extending the applicability of these spectroscopic techniques.
关键词： MIR,viscosity,near-infrared,micellar liquids,spectroscopy,partial least squares,Raman,mid-infrared,NIR,PLS,Inline
更新于2025-09-23 15:19:57
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Efficiency and spectral performance of narrowband organic and perovskite photodetectors: a cross-sectional review
摘要： The capability of detecting visible and near infrared light within a narrow wavelength range is in high demand for numerous emerging application areas, including wearable electronics, the Internet of Things, computer vision, artificial vision and biosensing. Organic and perovskite semiconductors possess a set of properties that make them particularly suitable for narrowband photodetection. This has led to rising interest in their use towards such functionality, and has driven remarkable progress in recent years. Through a comparative analysis across an extensive body of literature, this review provides an up-to-date assessment of this rapidly growing research area. The transversal approach adopted here focuses on the identification of: (a) the unifying aspects underlying organic and perovskite narrowband photodetection in the visible and in the near infrared range; and (b) the trends relevant to photoconversion efficiency and spectral width in relation to material, device and processing strategies. A cross-sectional view of organic and perovskite narrowband photodetection is thus delineated, giving fresh insight into the status and prospects of this research area.
关键词： narrowband organic photodetectors,narrowband perovskite photodetectors,NIR photodetectors,colour sensors,spectral selectivity
更新于2025-09-23 15:19:57
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Integrated Perovskite/Organic Photovoltaics with Ultrahigh Photocurrent and Photoresponse Approaching 1000a??nm
摘要： To enhance photoresponse of common-used perovskite materials in the near-infrared (NIR) region, a fused-ring electron acceptor (F8IC) with strong NIR absorption and high electron mobility was used to blend with a narrow-bandgap polymer donor (PTB7-Th) to construct organic bulk heterojunction (OBHJ), and this OBHJ was then integrated with the perovskite solar cells. The integrated perovskite/OBHJ solar cells exhibit strong photoresponse approaching 1000 nm and an ultrahigh short-circuit current density of 28.2 mA cm-2, which is much higher than the traditional perovskite solar cells and organic solar cells.
关键词： integrated solar cell,perovskite solar cell,ultrahigh photocurrent,NIR photoresponse,organic solar cell
更新于2025-09-23 15:19:57