UV Vis Near-infrared Research Articles

Synthesis and characterization of novel yellow-green Cr, Zn-codoped Ba(Mg6Ti6)O19 pigments with high NIR reflectance

This work reports a series of yellow-green near-infrared (NIR) reflective pigments, Ba(Mg6-x-yZnyTi6-xCr2x)O19 (x = 0–1.0, y = 0–2.5), with strong NIR reflectivity for solar thermal energy regulation. Comprehensive analyses were carried out to characterize the obtained pigments including X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–Vis–NIR spectrophotometry, and CIE L*a*b* color measurement. Absorption spectra of Ba(Mg6-xTi6-xCr2x)O19 showed that the yellow-green absorption is attributed to the octahedrally coordinated Cr3+ with d-d electron transitions of 4A2(F)→4T1(F) and 4A2(F)→4T2(F). However, their broad absorption peak centered at 1200 nm severely deteriorated the insulating properties of the pigments. Through substituting Mg with Zn, the obtained pigment Ba(Mg2.5Zn2.5Ti5Cr2)O19 showed an excellent NIR solar reflectance (R* = 67 %) with color performances (L* = 61.98, a* = −18.72, b* = 22.23). EnergyPlus simulation results show that for a warm city (Haikou), the Ba(Mg2.5Zn2.5Ti5Cr2)O19 coating for the external surface of a model house (TSR = 35 %, R* = 55 %) can reduce annual cooling energy consumption by 8 % of the house.

High‐Detectivity UV–Visible–NIR Broadband Polymer Photodetector with Polymer Charge Blocking Layer Cross‐Linked by Organic Photocrosslinker

AbstractUltraviolet (UV), visible, and near‐infrared (NIR) broadband organic photodetectors are fabricated by sequential solution‐based thin film coatings of a polymer electron blocking layer (EBL) and a polymer photoactive layer. To avoid damage to a preceding polymer EBL during a subsequent solution‐based film coating of a polymer photoactive layer due to lack of solvent orthogonality, 2‐(((4‐azido‐2,3,5,6‐tetrafluorobenzoyl)oxy)methyl)−2‐ethylpropane‐1,3‐diyl bis(4‐azido‐2,3,5,6‐tetrafluorobenzoate) (FPA‐3F) is used as a novel organic cross‐linking agent activated by UV irradiation with a wavelength of 254 nm. Solution‐processed poly[N,N′‐bis(4‐butylphenyl)‐N,N′‐bis(phenyl)‐benzidine] (poly‐TPD) films, which are cross‐linked with a FPA‐3F photocrosslinker, are used for a preceding polymer EBL. A ternary blend film composed of PTB7‐Th, COi8DFIC, and PC71BM is used as a NIR‐sensitive organic photoactive layer with strong photosensitivity in multispectral (UV–visible–NIR) wavelengths of 300–1,050 nm. Poly‐TPD films are successfully cross‐linked even with a very small amount of 1 wt% FPA‐3F. Small amounts of FPA‐3F have little detrimental effect on the electrical and optoelectronic properties of the cross‐linked poly‐TPD EBL. Finally, organic NIR photodetectors with a poly‐TPD EBL cross‐linked by the small addition of FPA‐3F (1 wt%) show the detectivity values higher than 1 × 1012 Jones for the entire UV–visible–NIR wavelengths from 300 nm to 1050 nm, and the maximum detectivity values of 1.41 × 1013 Jones and 8.90 × 1012 Jones at the NIR wavelengths of 900 and 1000 nm, respectively.

Effect of UV ageing on debonding of double glass laminates based on different crosslinking and thermoplastic PV encapsulants

To evaluate the potential of novel thermoplastic polyolefin (TPO) encapsulants as alternative for peroxide crosslinking ethylene vinyl acetate (EVA) copolymer and polyolefin elastomers (POE), compressive shear glass laminates were prepared and characterized using EVA and POE benchmark grades and TPO film adhesives (TPO-3.5, TPO-F and TPO-UV). The specimens were exposed to Xenon arc light with an UV irradiation of 40 W/m2, a black panel temperature of 65 °C and relative humidity of 10 % for up to 3,000 h. Visual, optical, mechanical and chemical changes were assessed by light microscopy, UV–visible–near infrared (UVVISNIR) spectroscopy, compressive shear testing, as well as differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) on fractured surfaces. In contrast to EVA and POE laminates, enhanced birefringence was detected due to a higher degree of crystallinity of the TPO encapsulants. Nevertheless, the investigated TPO double-glass laminates revealed a significantly better ultimate mechanical shear performance at 60 °C, also after UV exposure for 3.000 h. TPO-3.5 was the best-performing grade after 3,000 h followed by TPO-UV, TPO-F, EVA and POE. While the aged and fractured EVA, POE, TPO-F and TPO-UV laminates exhibited carboxylic acid signatures differing in intensity, no carboxylic acid residues were detected on the fractured TPO-3.5 surface. TPO-3.5 is characterized by a lower melt flow index and hence, a higher average molar mass compared to TPO-F and TPO-UV. For the crosslinked EVA and POE, the test temperature was already within the melting range of the non-crosslinked, polyethylene rich phase of these peroxide crosslinked encapsulants.

Synthesis and Optical Properties of Erbium-Doped Sodium Silicate in Sol-Gel Matrix

In this study, we investigated how the concentration of erbium (0.0, 1, 2 mol% Er) affects the structural and optical properties of thin films made from sol-gel sodium silicate doped with erbium nitrate, thermally treated at 250 °C. Through systematic investigation, we explore the structural evolution and optical behavior of the thin films across varying Er3+ concentrations. The sol-gel demonstrated effective capabilities for substantial concentrations of Er3+ oxides through doping at lower calcination temperatures. The spectroscopic characteristics were studied using visible-near infrared spectroscopy (UV–vis–NIR), transmission electron microscopy, and Fourier transform infrared spectroscopy. Increasing the Er ratio decreased both the transmission and the energy band gap (3.6–3.34 eV) of the films while the absorption peak increased. The obtained results suggest that Er3+ activators demonstrate advantageous optical properties in the evaluated sodium silicate glass matrix. With the introduction of Er, optical transmittance ranges from 85 to 55% in the visible and near-infrared (NIR) regions, highlighting their advantageous characteristics. This research contributes to advancing the understanding of erbium-doped thin films for potential applications in optoelectronic devices and photonics.

Efficient wide-spectrum one-dimensional MWO4 (M = Mn, Co, and Cd) photocatalysts: Synthesis, characterization and density functional theory study

Broadening the absorption region to near-infrared (NIR) light is critical for the photocatalysis due to the larger proportion and stronger penetration of NIR light in solar energy. In the present paper, one-dimensional (1D) MWO4 (M = Mn, Co, and Cd) materials synthesized by electrospinning technique, were studied by combining the density functional theory (DFT) with experiment results, which possessed the enhanced light absorption capability within the range of 200–2000 nm. It was proved that in the ultraviolet–visible (UV–Vis) region, the absorption bands of CoWO4 and MnWO4 samples were attributed to the metal-to-metal charge transfer mechanism, while the absorption of CdWO4 sample may be referable to the ligand-to-metal charge transfer mechanism. In the near-infrared (NIR) region, the absorption of CoWO4 and MnWO4 primarily originated from the d-d orbital transitions of Mn2+ and Co2+. The photocatalytic experimental results showed that the degradation rates for bisphenol A (BPA) over CoWO4, MnWO4, and CdWO4 photocatalysts under UV–Vis/NIR light irradiation for 140 min/12 h were 78.8 %/75.9 %, 23.8 %/21.3 %, 12.8 %/8.7 %, respectively. This research offers the novel insights into the precise construction of tungstate catalytic systems and contributes to the advancement of UV–Vis–NIR full spectrum photocatalytic technology, and lays a foundation for a cleaner and more environmental-friendly future.

A black pigment that shows strong near-infrared reflectivity for solar heat control

Solar thermal energy regulation is important for sustainable development, comfortable housing, and living. Black compounds are usually considered as an absorber of solar heat. This work reports a series of black near-infrared reflective pigments, Ca2-yMgyMn(1)1-xMn(2)xO4 (x = 0–1, y = 0–0.5), which show strong near-infrared (NIR) reflectivity. Comprehensive analyses were carried out to characterize the obtained pigments including X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and UV–Vis–NIR spectrophotometry. Through the substitution of MnO2 with Mn2O3, NIR solar reflectance of the black pigment can be enhanced by 13%, which might be mainly attributed to differences in particle size and lattice parameters. Meanwhile, through Mg doping, the obtained pigment Ca1.8Mg0.2MnO4 shows excellent color performances (L* = 43, a* = 0.36, b* = −0.37) and NIR solar reflectance (R*, ∼60%). EnergyPlus simulation results show that for a warm city (Haikou), using the Ca1.8Mg0.2MnO4 coating (L* = 25, R* = 51%) can reduce annual cooling energy consumption by 21%.

Effect of micro-crystallization on near-infrared shielding performance of Li0.09K0.23WO3 doped glass for energy-saving window

Effect of micro-crystallization (based on annealing time and temperature) on near-infrared (NIR)-shielding properties of Li0.09K0.23WO3 doped glass was investigated. The tungsten bronze doped glass was prepared by a facile melt-quenching technique. Structure and optical properties of the glass and glass-ceramics were characterized by X-ray diffraction analysis (XRD), Raman, and UV–Vis–NIR spectrophotometry, respectively. Increasing the annealing temperature increases in the range from 400 °C to 500 °C, the tungsten-functional unit Li0.09K0.23WO3 structure, which is responsible for NIR-shielding, changes the structural state from amorphous state to crystalline state gradually. Thus, the NIR-shielding properties of glass are significantly enhanced. Furthermore, annealing glass samples at 450 °C, during timeframe from 2 h to 8 h, causes crystallization and grain growth of the functional units, thus NIR-shielding property of the glasses is enhancing. It worth to be mentioned, that the increase of annealing temperature and time duration causes excessive grain growth in the glass matrix, which leads to decreasing of the optical transmittance in the visible light wavelength region. We have found, that the glass sample annealing temperature is at 450 °C with treatment time of 6 h yields the best results. In such manner the optical transmittance at λ = 1500 nm wavelength is 16.5 % and the highest transmittance of visible light wavelength region reaches 65 %. We conclude, that the NIR-shielding properties are adjustable and can be tailored by annealing temperature and time duration, which is expected to enhance the design and vary visual aspects of energy-saving windows.

Effect of global damp heat ageing on debonding of crosslinked EVA- and POE-glass laminates

Polyolefin elastomers (POE) have been established as a promising alternative to commonly used peroxide crosslinked ethylene vinyl acetate copolymer (EVA) photovoltaic encapsulation materials. The main objective of this work was to assess the long-term ageing behavior of double-glass laminates based on UV-transparent EVA and POE under damp heat (85 °C, 85 %rh) conditions for up to 10,000h. Ageing induced changes were characterized by microscopy, UV–visible–near infrared (UVVISNIR) spectroscopy, compressive shear testing (CST), differential scanning calorimetry (DSC), macro- and microscopic Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Within the laminates, the formation of birefringent spheric microdomains (maltese-crosses) was confirmed after an exposure time of more than 2,000h. The compressive shear behavior of EVA laminates was not significantly affected by damp heat ageing. Interestingly, the POE laminates revealed an even improved compressive shear performance. Whereas the tested EVA laminates failed in an interfacial manner independent on damp heat ageing time, POE laminates exhibited a failure mode transition from interfacial (unaged) to combined interfacial and cohesive (10,000h). On the interfacially fractured surfaces of EVA and POE laminates, carboxylic acid groups were ascertained. Deprotonated silanol and water bands were discernible on the opposite glass sides. Damp heat exposure of POE laminates for 10,000h resulted in pronounced glass ageing close to the interface associated with a partly cohesive failure within glass. This phenomenon was quite different to EVA and was attributed to the alkaline characteristics of the hindered amine light (HALS) stabilized, less-polar, UV-transparent POE encapsulant.

Enhancing the NIR shielding ability and controlling the surface wettability of RF magnetron sputter deposited WO3-x thin films by tuning the oxygen vacancies

Enhancement in the near-infrared (NIR) shielding property of tungsten oxide (WO3-x, 0 < x < 1) thin films by the induction of further oxygen vacancies via vacuum annealing is discussed in this work. The property is comprehensively analysed by UV–Vis–NIR spectroscopy and variable angle spectroscopic ellipsometry techniques. From transmittance spectra, an average visible transmittance of ∼48% along with an average NIR transmittance of ∼15% (with Tvis/Tsol ratio of 1.49) is obtained for WO3-x thin films vacuum annealed at 500 °C for 1.5 h. The pronounced NIR absorption is attributed to the enhanced polaron absorption and surface plasmon resonance effects produced by the increased oxygen vacancies in the film. In order to realize their potential as energy saving window coatings, thermal shielding test is performed in which vacuum annealed WO3-x thin films could restraint the indoor temperature of the heat box efficiently. X-ray diffractometry, field emission scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy measurements were also performed on the films for elucidating structural, morphological, and compositional characteristics. In addition, contact angle measurements revealed that vacuum annealing could reduce the surface wettability of WO3-x thin films considerably. The present work is significant in the field of development of NIR shielding materials for energy conserving smart window applications, especially for buildings and automobiles.

High-performance broadband photodetector based on plasmonic semiconductor-semiconductor p-n Cu1.8S/AZO interface

Plasmonic semiconductor nanocrystals (NCs) provide intriguing optical properties which offer opportunities to extend the photo-response corresponding to photons with energies less than the semiconductor energy band gap. However, the performance of photodetectors based on individual plasmonic semiconductors is restricted due to very short-living photo-carriers, followed by carrier recombination (∼ 100 ps). Herein, a plasmonic semiconductor-semiconductor p-n interface (Cu1.8S/AZO NCs) was constructed representing 2-fold optical characteristics containing an inter-band electronic transition from the valence to conduction band in response to ultraviolet-visible (UV–vis) excitation and plasmon-induced interfacial charge-transfer transition (PICTT) in response to near infrared (NIR) excitation. We demonstrated that AZO NCs, are appropriate candidates to generate chemical interface damping (CID) of plasmons in Cu1.8S NCs as an acceptor, which is required for PICTT pathway. The device displayed outstanding broadband UV–vis–NIR photoresponsivity (R) and response-time (Trise/Tfall) as high as R = 51.48 A/W, Trise/Tfall= 130/100 ms in 390 nm, R = 37.2 A/W, Trise/Tfall= 50/60 ms in 535 nm, R = 45.6 A/W, Trise/Tfall= 400/10 ms in 750 nm and R = 38.7 A/W and Trise/Tfall= 60/50 ms in 950 nm. This study demonstrates the promising potential of plasmonic semiconductor-semiconductor p-n hybrid systems as high-performance broadband photodetectors (PDs).

Lanthanide-doped upconversion glass–ceramic photocatalyst fabricated from fluorine-containing waste for the degradation of organic pollutants

Fluorine-containing waste is one kind of hazardous waste characteristic by hard disposal and utilization, it is an attractive way to prepare for fluoride-based luminescent matrix. In this work, to realize the high value-added utilization of fluorine-containing waste and reduce cost of the raw materials for preparation near-infrared (NIR) glass–ceramic (GC) photocatalyst, the pure fluoride of luminescent matrix was replaced by introducing fluorine-containing waste. The waste contained NIR GC photocatalyst was synthesis by the method of facile in-situ etching of an upconversion GC with HCl, which possesses core–shell structure, where the GC micro-powder including optically active centers lanthanides doped CaF2 nanocrystals are displayed as the core, and the BiOCl is as the superficial coating. The upconversion emission performance of CaF2 based luminescent matrix in photocatalyst is not weakened with HCl etching. NIR GC photocatalyst has high methyl orange and enrofloxacin degradation rate of 86 % and 82 % over 180 min after NIR light irradiation, respectively. The UV–Vis–NIR photocatalytic activity was enhanced degradation rate (93 % in 15 min) of enrofloxacin compared with those of commercial P25 and BiOCl. In addition, the photocatalyst had stable photocatalytic activity and it also can be regenerated. The study provided references for high value-added utilization fluorine-containing waste.

In situ facile one-step solvothermal synthesizing hexagonal ammonium tungsten bronze (NH4)0.33WO3 to tap NIR light absorption ability by controlling crystallinity

Tungsten bronze (TB) has potentially high visible light transparency and excellent near-infrared (NIR) shielding ability. To fully dig out the concealed optical properties of TB with specific chemical components, in this work, hexagonal ammonium tungsten bronze (h-ATB) (NH4)0.33WO3 was fabricated by a one-step solvothermal reaction. Through X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible–near infrared (UV–vis–NIR) spectroscopy to characterize h-ATB, which unraveled that controlling crystallinity could adjust the optical property of h-ATB. In particular, when the crystallinity of the h-ATB is over 95%, it exhibits the attractive NIR light shielding capability, which is in line with the predicted optical property via the first principle calculation based on density functional theory (DFT). Given the result, this work can provide a feasible research idea to explore the hidden optical properties of TB.

Solution-processed ZnO nanoparticles (NPs)/CH3NH3PbI3/PTB7/MoO3/Ag inverted structure based UV–visible-Near Infrared (NIR) broadband photodetector

This paper reports a ZnO Nanoparticles (NPs)/CH3NH3PbI3/PTB7/MoO3/Ag inverted structure based UV–visible-Near Infrared (NIR) broadband photodetector fabricated on the fluorine-doped tin oxide (FTO) coated glass substrate. ZnO NPs layer acts as the electron transport layer (ETL), CH3NH3PbI3 acts as the active layer, PTB7 acts as the hole transport layer (HTL) and MoO3 is used to optimize the recombination current in the proposed photodetector structure. Spin coating method has been used for depositing the layers of ZnO NPs, CH3NH3PbI3 and PTB7 in the proposed structure while the MoO3 layer has been grown by the thermal evaporation method. The optical measurements over 350–850 nm wavelength range give the maximum photoresponsivity, detectivity and external quantum efficiency (EQE) of ∼0.36 A/W, ∼7.8x1012 Jones and ∼83.67% under −2 V, respectively. The proposed photodetector gives a rise time and fall time of 81 ms and 75 ms, respectively.

Synthesis of an efficient paramagnetic ZnFe2O4 agent for NIR-I/II responsive photothermal performance

Photothermal therapy (PTT) is a promising alternative strategy to traditional cancer therapy. Photothermal agents (PTAs) in the second near-infrared (NIR) window (1000–1350 nm) hold excellent potential for enhanced PTT treatment of deep tumors compared with the first NIR window (780–1000 nm). Herein, paramagnetic ZnFe2O4 nanospheres with an average of 150 nm and defective structure were synthesized by a simple solvothermal method. The samples were characterized by X-ray diffraction, scanning electron microscopy, UV–vis–NIR spectroscopy, photoluminescence spectrum, and vibrating sample magnetometer. The photothermal mechanism and performance under bio-safe NIR-Ⅰ/Ⅱ laser irradiation have been discussed in detail. The samples represented good magnetic property and photothermal conversion efficiency (PCE) of 64.64% (808 nm, 0.33 W cm−2) and 35.75% (1064 nm, 1 W cm−2), surpassing many previous nano-PTAs active in the NIR-Ⅰ/II region. This work provides a simple method to acquire clinical paramagnetic PTAs in bio-imaging mediated NIR-II photothermal therapy.

A quick method for fraud detection in egg labels based on egg centrifugation plasma

The aim of this work was to develop a quick and cheap method for fraud detection in egg labels according to the four legal farming method of the EU. The plasma obtained from egg centrifugation was investigated for this purpose. Initial protein content in egg, plasma protein content, plasma colour parameters (L*, a* and b*) and plasma UV–VIS-NIR (Ultraviolet–Visible-Near-infrared) spectra were evaluated. The classification algorithms applied were SVM (Support-Vector-Machine), LDA (Linear-Discriminant-Analysis) and QDA (Quadratic-Discriminant-Analysis). The analysis of the protein content did not detect differences. Colour parameters and spectral measurements showed significant differences between eggs. Spectra analysis with QDA gave sensitivity of 100% in the calibration set. The validation set scored 87.5% sensitivity and 94.07% specificity using the visible spectra. This work established plasma spectral measurements combined with classification algorithms as a powerful tool to discriminate the four farming systems. This work presents a fast tool for the egg label control.

Near-infrared spectra and molar absorption coefficients of trivalent lanthanides dissolved in molten LiCl–KCl eutectic

Determining the concentration of the dissolved lanthanide species in LiCl–KCl eutectic salt is important to the development of pyrochemical reprocessing of used nuclear fuel. In this process, lanthanide fission products are found dissolved in the electrorefiner electrolyte in their trivalent oxidation state. The presence of dissolved trivalent lanthanides increases the liquidus temperature of the electrolyte mixture and can lead to the formation of insoluble oxide or oxychloride phases and must therefore be continuously monitored and controlled during the operation.Absorbance spectroscopy is a promising method for continuous measurement of the concentration of lanthanides and other elements dissolved in the electrolyte. The absorption of light by elements is linearly proportional to the concentration of the element for relatively dilute solutions according to the Beer-Lambert law. Although measurement of the absorption of ultraviolet and visible range light by lanthanides in LiCl–KCl eutectic molten salt have been explored previously, near infrared (NIR) absorption spectroscopy has received far less attention. It may, however, provide a better analytical signal when insoluble phases are present due to less Raleigh scattering compared to shorter wavelength radiation. Additionally, it may allow for concentration determination for certain elements using NIR absorption features where UV and visible range features are overlapping with features from other species.In this study, we report the UV–Vis–NIR spectra of the trivalent lanthanide chlorides of neodymium, samarium, and dysprosium in LiCl–KCl eutectic. Molar absorption coefficients are reported for analytically useful absorption maxima, with a focus on the molar absorption coefficients for NIR absorption maxima which have not been reported previously. Additionally, we observe a NIR-range absorption band of Nd3+ which was previously predicted but never experimentally observed. We compare the calculated crystal field levels to the newly observed absorbance band and find them to be in good agreement with previous predictions.

S-Shaped Fused Azacorannulene Dimer: Structural and Redox Properties

S-Shaped Fused Azacorannulene Dimer: Structural and Redox Properties

Functionalization of polyfluorene‐wrapped carbon nanotubes using thermally cleavable side‐chains

AbstractThe length and nature of side‐chains in conjugated polymer‐wrapped carbon nanotubes can impact their conductivity. We investigate functionalization of polyfluorene‐single‐walled carbon nanotubes (SWNT's) using cleavable side‐chains that are removable post‐processing. The triethylene glycol side‐chains contain a thermally cleavable carbonate linker. Upon heating the films to 170 °C, the conductivity increased, reaching a plateau of (2.0 ± 0.1) × 10−2 S/m after 16 h, compared to (1.0 ± 0.2) × 10−3 S/m for the control sample. UV–Vis–near‐infrared (NIR) and Raman spectroscopy show well‐dispersed SWNT samples and confirm that the heating treatment did not damage the nanotubes. Functionalization using longer polyethylene glycol side‐chains was also investigated. After heating, cleavage of the longer chains resulted in conductivity of (8.2 ± 1.6) × 10−4 S/m compared to (8.1 ± 1.4) × 10−5 S/m for the control. UV–Vis–NIR and Raman spectroscopy showed well‐dispersed SWNT samples and confirmed that the nanotubes were not damaged. Finally, we investigate dispersions in triethylene glycol monomethyl ether and tetraethylene glycol dimethyl ether, generally deemed “green” solvents. Polymer‐SWNT complexes functionalized with shorter side‐chains did not form stable dispersions, resulting in precipitation of the nanotubes upon standing for a few minutes after the removal of tetrahydrofuran, while complexes functionalized with longer side‐chains formed stable dispersions.

Dual Wavelength based Approach with Partial Least Square Regression for the Prediction of Glucose Concentration

Diabetes mellitus is a group of metabolic disorder characterized by high blood sugar levels. Monitoring of blood glucose levels at regular intervals plays a crucial role in the management of diabetes. The non-invasive real-time monitoring of glucose using near-infrared (NIR), Raman, acoustic and bio-impedance techniques have an edge over available invasive techniques but suffers from low Signal to Noise ratio (S/N) and other interferences. In the present work, we have attempted to improve S/N for the efficient detection of feeble signals corresponding to the physiological glucose concentrations. Investigations were carried out in the NIR region particularly from 800-1400 nm for the identification of the unique absorption features of glucose using UV-Vis NIR spectrophotometer with different ranges of glucose concentrations including 5 g/dl- 45 g/dl, 1400 mg/dl -2500 mg/dl, 35 mg/dl-650 mg/dl . Savitzky Golay (SG) pre-processing filter was applied on the raw data for enhancing the S/N for better prediction of glucose concentrations. The absorption spectra of glucose revealed the presence of a peak at 960 nm. Therefore, considering the absorbance at 960 nm, provided an enhancement in the S/N ratio from 17 dB to 27 dB. Further, partial least square regression (PLSR), has been applied on SG filtered data for a better prediction of glucose concentration with a correlation coefficient ( R 2 ) value of 0.99 and root mean square error of prediction (RMSE) of 2.29 mg/dl. Further, based on the NIR spectral data, we have developed a measurement technique using two LED sources of 950 nm and 860 nm, and a wide detector (700 - 1100 nm) which converts obtained optical signal into voltage. It has been observed that by considering dual wavelength detection points the prediction of glucose concentration is improved. Furthermore, with increase in the test glucose concentrations, the voltage signal decreased corresponding to the 950 nm LED. This is attributed to reduced signal intensities reaching the photodiode as a result of the increase in glucose absorption. Incorporating dual wavelengths for PLSR reduced the RMSE from 8.98 mg/dl to 6.49 mg/dl and also improved the R 2 value from 0.97 to 0.99.

Plasmon Induced Near‐Infrared Active Photocatalysts: A Review

AbstractIn the recent past, near‐infrared (NIR) active photocatalysts have received tremendous research attention to harvest solar NIR energy as the solar spectrum carries abundant NIR light. Again, plasmonic materials with their intense surface plasmon resonance (SPR) activity in the visible and NIR range can be a suitable candidate for NIR active photocatalysis. However, the ultrafast energy relaxation of the plasmon‐generated hot electrons restricts their application in photocatalysis. In this review, the recent progress in the plasmon‐induced NIR active photocatalysis has been summarized. Particular emphasis has been given to divulging the mechanism to NIR modulation of localized surface plasmon resonance (LSPR), LSPR intensification, LSPR induction mechanism in non‐noble metals, and suitable technologies to separate the photogenerated hot electrons efficiently and their exploration in photocatalytic reactions. The drawbacks, possible solutions, and potential of non‐noble metal plasmonic photocatalysis have been discussed in detail. Finally, the review ends with concluding remarks and possible prospects of plasmonic photocatalysts. It is believed that this review will inspire researchers to rationally design broad‐spectrum (UV–vis–NIR) active photocatalysts to harvest solar light efficiently.