Optimal Wavelength Research Articles

Investigating the effect of 532 nm and 1064 nm wavelengths and different liquid media on the qualities of silver nanoparticles yielded through laser ablation

The ablation environment's effect upon the very nature of silver nanoparticles produced by a pulsed Nd: YAG laser ablation procedure in a liquid medium was probed experimentally. Accordingly, at first, generation of silver nanoparticles was done in water with no stabilizers or surfactants in two wavelengths of 532 and 1064 nm. The effect of laser wavelength on the SPR properties was then thoroughly investigated by UV–Vis absorption spectroscopy. Also, size distribution was probed through Dynamic Light Scattering (DLS), Transmission Electron Microscope (TEM) and field emission scanning electron microscopy (FE-SEM) of silver nanoparticles. The optimum wavelength for synthesizing silver nanoparticles was obtained at the wavelength of 532 and the effect of this wavelength was investigated in different liquid media. Eventually, pulses of an Nd: YAG laser of 532 nm wavelength were applied for irradiating the silver target in different environments in water, acetone, cetyltrimethylammonium chloride (CTAC), sodium dodecyl sulfate (SDS) and polyvinyl pyrrolidone (PVP). Characterization of the obtained nanoparticles was done by UV–Vis, Atomic absorption spectroscopy (AAS) and DLS. The obtained results showed that the maximum ablation rate occurred in acetone, and the smallest nanoparticles were produced in PVP. The present research study then developed a technique for controlling the size distribution, production efficiency as well as aggregation of silver nanoparticles by modifying the liquid medium's nature.

Unsafe food additive sensing through octagonal-core photonic crystal fibre sensor

To detect food additives, a simple photonic crystal fibre design based on an octagonal hole and hollow circular cladding holes in two layers has been introduced. The numerical study of the design is conducted by simulation in the COMSOL Multiphysics software with the infiltrated test analytes: saccharin, sorbitol, and butyl acetate, operating in the wavelength variation from 1.6 to 4.0 μm. The performance of the proposed sensor is determined by analysing the principal optical parameters: effective refractive index, power fraction, relative sensitivity, confinement loss, chromatic dispersion, propagation constant, V-parameter, spot size, and beam divergence. At the optimal wavelength of 2.0 μm, the sensor design depicts high relative sensitivities of 98.06% for saccharin, 97.05% for sorbitol, 95.81% for butyl acetate, and 3.82 × 10−23 dBm−1 for saccharin, 3.44 × 10−22 dBm−1 for sorbitol, and 1.81 × 10−21 dBm−1 for butyl acetate for confinement loss, which is extremely low. Hence, the proposed food additive sensor is suitable for actual sensing applications based on these obtained results.

Measurement of rat and human tissue optical properties for improving the optical detection and visualization of peripheral nerves.

Peripheral nerve damage frequently occurs in challenging surgical cases resulting in high costs and morbidity. Various optical techniques have proven effective in detecting and visually enhancing nerves, demonstrating their translational potential for assisting in nerve-sparing medical procedures. However, there is limited data characterizing the optical properties of nerves in comparison to surrounding tissues, thus limiting the optimization of optical nerve detection systems. To address this gap, the absorption and scattering properties of rat and human nerve, muscle, fat, and tendon were determined from 352-2500 nm. The optical properties highlighted an ideal region in the shortwave infrared for detecting embedded nerves, which remains a significant challenge for optical approaches. A 1000-1700 nm hyperspectral diffuse reflectance imaging system was used to confirm these results and identify optimal wavelengths for nerve imaging contrast in an in vivo rat model. Optimal nerve visualization contrast was achieved using 1190/1100 nm ratiometric imaging and was sustained for nerves embedded under ≥600 µm of fat and muscle. Overall, the results provide valuable insights for optimizing the optical contrast of nerves, including those embedded in tissue, which could lead to improved surgical guidance and nerve-sparing outcomes.

Photonic crystal fibre for blood components sensing

A photonic crystal fibre (PCF)-based sensor has been proposed and thoroughly investigated for the identification of blood components, including red blood cells, haemoglobin, white blood cells, plasma, and water. To evaluate the sensor's sensing and propagation properties, a numerical analysis was performed using the COMSOL Multiphysics software. The proposed sensor design features an octagonal core and two layers of cladding with octagonal and circular air holes. At the optimal wavelength of 7.0 μm, the extensive simulation results confirms that the proposed sensor achieves high relative sensitivity of 99.89%, 99.13%, 97.95%, 97.77%, and 96.68% for red blood cells, haemoglobin, white blood cells, plasma, and water, respectively. Furthermore, the design demonstrates favourable confinement loss, propagation constant, V-parameter, spot size, and beam divergence. Therefore, the proposed PCF-based sensor holds great promise not only for medical sensing applications but also for optical communications. Its advanced design and highly sensitive capabilities make it a valuable tool for a wide range of potential applications in the biomedical and telecommunications fields.

HPLC-UV Analysis of Chrysophanol in Senna occidentalis Extract Obtained by Using the RSM-Optimized Ultrasonic Extraction Process

In this experiment, chrysophanol analysis in Senna occidentalis (aerial parts) extract obtained by optimizing ultrasound-assisted extraction (UAE) variables (temperature, time, and liquid-to-solid ratio) using response surface methodology (RSM) was performed by employing the HPLC-UV method. For UAE process optimization, a highly significant quadratic model (p < 0.001) was projected to attain maximum chrysophanol yield. The extraction temperature, time, and liquid-to-solid ratio for the best UAE method were determined to be 49.3 °C, 57.7 min, and 18.7 mL/g, respectively. The optimized extract was subjected to a chrysophanol analysis utilizing HPLC-UV (fitted with a Pinnacle C18 column), and a gradient mobile phase composed of 0.5% formic acid (solvent A), acetonitrile (solvent B), methanol (solvent C), at a flow rate of 1.0 mL/min, and an optimum wavelength of 279 nm, respectively. It furnished a compact and intense peak of chrysophanol at Rt = 23.809 min. The experimental value (20.47 mg/g) of chrysophanol obtained was close to the predicted value (19.32 mg/g), indicating that they agreed under the optimized extraction condition. UAE also displayed remarkable improvement in chrysophanol extraction compared with the conventional solvent extraction (CSE) method. Hence, our improved ultrasonic extraction process showed a potential use for effective chrysophanol extraction from commercial herbal supplements comprising the Senna species.

Emulsification-assisted spectroscopic analysis of black seed oil in alginate beads: method development and validation

This study aimed to develop and validate an ultrasonication-aided UV-Vis spectroscopy method for quantifying black seed oil (BSO) in alginate beads. The method utilized sonication at 10% power rate for 120 seconds to stabilize the emulsion droplet size of 10 mL of the emulsion diluents derived from breaking BSO-alginate beads in phosphate buffer. Absorbance measurements were taken at 400 nm, which was found to be the optimal wavelength for measuring the absorbance of turbid emulsion diluents. The method showed excellent linearity between 0.8 - 5 mg/mL (R2 = 0.9977), with Limit of Detection (LOD) and Limit of Quantification (LOQ) values of 0.082 and 0.249 mg/mL, respectively. The method also exhibited good accuracy and precision, with recovery percentages ranging from 98.02 - 101.9% (RSD = 0.15 - 1.24%) and intra-day/inter-day precision with RSD less than 2%. These findings suggest that the ultrasonication-aided spectroscopy method is a quick, accurate, and precise way to quantify encapsulated oils and could be useful for oils analysis during R&D, In Process Quality Control (IPQC), and Quality Control (QC) tests, as well as in other applications such as industrial manufacturing and academic research.

Ultraviolet Raman spectroscopy for remote detection of chlorine gas

As a primary material frequently used in industry, chlorine is relatively easy to obtain and available even in large quantities. Despite its high toxicity, molecular chlorine is readily available since it is an essential educt in the chemical industry. Over the past decades, numerous accidents involving injured and dead victims have occurred. Furthermore, it was already misused as a warfare agent at the beginning of the last century with still reported attacks. Early detection, localization, and monitoring of sources and cloud movements are essential for protecting stationary facilities, mobile operations, and the public. In contrast to most chemical hazardous materials, where it is possible to detect them by vibrational spectroscopic methods (e.g., passive hyper-spectral absorption technologies in the infrared), halogens are inactive to infrared absorption. Raman-based technologies rely on changes in the polarizability of the molecule and provide vibrational-spectroscopic access to such diatomic molecules and therefore close the gap in infrared detection capabilities. Here we present a straightforward approach for a standoff Raman detector in a backscattering configuration. This paper uses a simplified model to discuss optimum excitation wavelengths in achievable detection ranges. We validate the model by spontaneous (vibrational) Raman spectroscopic measurements between 20 and 60 m standoff distance. We also briefly discuss detection performances and technical and physical aspects as prospects of system design.

Luminescence properties of glass ceramics doped with Tb4O7 and containing Na3Gd (PO4)2

It has been determined that 374 nm is the optimal excitation wavelength for Tb4O7 doped glass ceramics. XRD, SEM, UV spectrophotometer, and photoluminescence spectroscopy were used to study glass ceramics morphology and luminescence properties. 730°C is the optimal temperature for crystallizing. At 0.4mol% Tb4O7 concentration and 2h crystallization time, this is the optimum solution. The results of this study indicate that glass-ceramics doped with Tb3+ can be applied to green lasers and other systems.

Development and Validation of RP-HPLC Method of Lafutidine (API)

The goal of this study is to develop and validate an RP HPLC technique for estimating Lafutidine in bulk form. A thorough review of the literature found that there are ways available, but none of them are as straightforward, specific, exact, or accurate as the established approach for estimating Lafutidine. The chromatographic method was found to be suitable for effective separation of Lafutidine with good resolution, peak shape. The mobile phase composed of 0.1M ammonium acetate buffer (pH 7.5): Methanol (80:20 v/v), at a flow rate of 1.4 ml/min was selected as it gave well resolved peaks of standard Lafutidine. The optimum wavelength 290nm selected for detection and quantitation. According to ICH criteria, the devised approach was validated.
 Keywords: , , ,

DIAL hygrometer based on powerful laser diodes: calibration function and modulation of laser radiation

A differential absorption lidar method utilizing the spectral and energetic properties of high-power, pulsed laser diodes for remote sensing of atmospheric humidity is reported. The laser radiation of selected complementary laser diodes is multiplexed in dual spectral channels centered at optimal wavelength of 0.86µm and 0.911µm. Humidity profiles are retrieved integrating multiple resonance lines in the tunable range within the absorption spectrum of water vapor. The integral spectrum is less affected by the variable atmospheric pressure and temperature, which is an essential advantage allowing direct and reliable DIAL measurement.

Non-destructive determination of soluble solids content in intact apples using a self-made portable NIR diffuse reflectance instrument

The soluble solids content (SSC) is an important internal quality parameter of fruits that is monitored on the fruit market to meet different consumer demands. The aim of this study was to develop a self-made portable near-infrared (NIR) diffuse reflectance instrument to evaluate and monitor the SSC of intact apples. The visible and near-infrared (Vis-NIR) spectra of 118 ‘Fuji’ apples were collected using a Vis-NIR diffuse reflectance spectroscopic measurement system in the spectral range of 450–1100 nm. Savitzky-Golay convolution smoothing and first derivative methods were subsequently applied to eliminate noise interference and baseline shift. Successive projections algorithm (SPA) was performed to extract feature wavelengths from the pretreatment spectra, and the back-propagation artificial neural network (BP-ANN) and multivariate nonlinear regression (MNLR) models were employed to evaluate the predictive ability of the extracted and selected feature wavelengths for the SSC of apples. Seven wavelengths (881, 890, 901, 926, 941, 951, 978 nm) were selected as optimal feature wavelengths from the extracted feature wavelengths (18 wavelengths). The MNLR model (R2 = 0.953, RMSE = 0.391 %) exhibited a high prediction accuracy compared to the BP-ANN model (R2 = 0.865, RMSE = 0.754 %). Based on the results, NIR combined with the MNLR model could be applied in the self-made portable instrument to innovatively monitor the SSC of apples. Finally, a self-made portable NIR diffuse reflectance instrument was designed and developed, and the spectral information of 298 ‘Fuji’ apples was collected using the instrument. According to the results, the MNLR model could well predict the SSC of apples (R2 = 0.871, RMSE = 0.687 %). The overall results also revealed that the developed portable NIR instrument is a promising device for rapid non-destructive monitoring of fruit SSC, thereby meeting the practical application requirement of postharvest commercial processing systems. This instrument could also be beneficial to customers, growers, and producers.

Optimization of mid-infrared dispersive wave generation at 3 µm in LiNbO3 waveguides

We propose an effective scheme to enhance mid-infrared dispersive wave (DW) emission, which includes dispersion engineering of the waveguide and the assistance of a CW trigger. Our suggested approach can help achieve better coherence and higher signal-to-noise ratio by adding a weak CW trigger with the femtosecond pulse pump in dispersion engineered lithium niobate (LiNbO3) waveguides. First, the integrated dispersion profile of LiNbO3 waveguides is designed based on dispersion engineering regarding the sidewall angle and slab thickness. Second, with the assistance of a weak CW trigger, the mid-infrared DW is enabled or further enhanced. The optimal CW-triggered wavelength and operating conditions are ascertained. Mid-infrared emission at around 3 µm with a sufficient power level is accessible after optimization, which is feasible for multi-species greenhouse gas detection through gas absorption spectroscopy.

Quantitative Assessment of Apple Mosaic Disease Severity Based on Hyperspectral Images and Chlorophyll Content

The infection of Apple mosaic virus (ApMV) can severely damage the cellular structure of apple leaves, leading to a decrease in leaf chlorophyll content (LCC) and reduced fruit yield. In this study, we propose a novel method that utilizes hyperspectral imaging (HSI) technology to non-destructively monitor ApMV-infected apple leaves and predict LCC as a quantitative indicator of disease severity. LCC data were collected from 360 ApMV-infected leaves, and optimal wavelengths were selected using competitive adaptive reweighted sampling algorithms. A high-precision LCC inversion model was constructed based on Boosting and Stacking strategies, with a validation set Rv2 of 0.9644, outperforming traditional ensemble learning models. The model was used to invert the LCC distribution image and calculate the average and coefficient of variation (CV) of LCC for each leaf. Our findings indicate that the average and CV of LCC were highly correlated with disease severity, and their combination with sensitive wavelengths enabled the accurate identification of disease severity (validation set overall accuracy = 98.89%). Our approach considers the role of plant chemical composition and provides a comprehensive evaluation of disease severity at the leaf scale. Overall, our study presents an effective way to monitor and evaluate the health status of apple leaves, offering a quantifiable index of disease severity that can aid in disease prevention and control.

Microwave-Assisted Synthesis of Room Temperature Long Persistent Luminescent Materials and Their Imaging Applications

In this study, we utilized a simple and efficient microwave heating method with polyethyleneimine (PEI) and phosphate as raw materials to synthesize room temperature persistent luminescence (RTPL) materials that emit phosphorescent light for up to 10 s. Our investigation revealed that the optimal synthesis conditions were a microwave radiation power of 560 W and a heating time of 5 min. The synthesized RTPL materials had an average particle size of 2 nm and exhibited excellent RTPL performance, with optimal excitation and emission wavelengths of 360 nm and 544 nm, respectively. Additionally, these materials displayed good water solubility. We conducted mapping experiments and in situ phosphorescent imaging of plants to showcase the potential applications of RTPL materials in the fields of biological imaging and anti-counterfeiting. Overall, our findings demonstrate the promising potential of these RTPL materials as versatile tools for various practical applications.

A Miniaturized 3D-Printed Quartz-Enhanced Photoacoustic Spectroscopy Sensor for Methane Detection with a High-Power Diode Laser.

In this invited paper, a highly sensitive methane (CH4) trace gas sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) technique using a high-power diode laser and a miniaturized 3D-printed acoustic detection unit (ADU) is demonstrated for the first time. A high-power diode laser emitting at 6057.10 cm-1 (1650.96 nm), with the optical power up to 38 mW, was selected as the excitation source to provide a strong excitation. A 3D-printed ADU, including the optical and photoacoustic detection elements, had a dimension of 42 mm, 27 mm, and 8 mm in length, width, and height, respectively. The total weight of this 3D-printed ADU, including all elements, was 6 g. A quartz tuning fork (QTF) with a resonant frequency and Q factor of 32.749 kHz and 10,598, respectively, was used as an acoustic transducer. The performance of the high-power diode laser-based CH4-QEPAS sensor, with 3D-printed ADU, was investigated in detail. The optimum laser wavelength modulation depth was found to be 0.302 cm-1. The concentration response of this CH4-QEPAS sensor was researched when the CH4 gas sample, with different concentration samples, was adopted. The obtained results showed that this CH4-QEPAS sensor had an outstanding linear concentration response. The minimum detection limit (MDL) was found to be 14.93 ppm. The normalized noise equivalent absorption (NNEA) coefficient was obtained as 2.20 × 10-7 cm-1W/Hz-1/2. A highly sensitive CH4-QEPAS sensor, with a small volume and light weight of ADU, is advantageous for the real applications. It can be portable and carried on some platforms, such as an unmanned aerial vehicle (UAV) and a balloon.

Using energy transfer to obtain warm white-emitting and thermally stable Ca3Y(AlO)3(BO3)4:Dy3+, Eu3+ phosphors

A series of color-tunable warm white-emitting phosphors Ca3Y(AlO)3(BO3)4:Dy3+,Eu3+ were synthesized and characterized for their crystal structure, luminescence properties, thermal stability, fluorescence decay and energy transfer mechanism. The results show that the optimal excitation wavelength and doping concentration of Ca3Y(AlO)3(BO3)4:Dy3+ phosphor are 350 nm and 0.05 mol%, respectively, and its concentration quenching is mainly caused by the interaction between nearest neighbor ions. Under the excitation at 350 nm, the Ca3Y(AlO)3(BO3)4:Dy3+,Eu3+ phosphor showed prominent emission peaks at 471 nm, 576 nm and 622 nm. The photoluminescence spectrum and lifetime decay curves confirmed the presence of Dy3+→Eu3+ energy transfer in Ca3Y(AlO)3(BO3)4. The phosphor of Ca3Y0·85(AlO)3(BO3)4:0.05Dy3+,0.1Eu3+ exhibited remarkable thermal stability and could maintain 87.68% of the emission intensity at 150 °C. By adjusting the doping ratio of Dy3+ and Eu3+ ions, the CIE coordinates and the related color temperature of Ca3Y(AlO)3(BO3)4:Dy3+,Eu3+ phosphors can be adjusted. The w-LED device packaged with Ca3Y0·85(AlO)3(BO3)4:0.05Dy3+,0.1Eu3+ phosphor can emit warm-white light (Tc = 3284 K, Ra = 72.7). These results suggest that Ca3Y(AlO)3(BO3)4:Dy3+,Eu3+ phosphor can provide a potential alternative for the warm w-LED market.

Hyperspectral imaging combined with fluorescence for the prediction of microbial growth in chicken breasts under different packaging conditions

The crucial feature of chicken is real-time microbial growth detection along the supply chain. Hyperspectral imaging (HSI) is an online and nondestructive technique that is well suited to microorganism analysis applications. In this study, visible and near-infrared (Vis/NIR, 400–1000 nm) HSI were utilized to establish prediction models of the total viable count (TVC) of chicken breasts stored in vacuum, pallet, and combined packaging using partial least squares regression (PLSR) and support vector machine (SVM) after spectral pretreatments and optimal wavelength selection. The SVM algorithm was used to develop the best TVC prediction models for storage, with the following outcome: vacuum (R2p = 0.91, RMSEp = 0.47, RPD = 2.44), pallet (R2p = 0.90, RMSEp = 0.54, RPD = 2.32), and combined (R2p = 0.89, RMSEp = 0.58, RPD = 2.21) packs. Successively, HSI combined with fluorescence (F–HSI) was used to predict the TVC and coliforms of chicken breasts in combined packaging. Compared to HSI, F–HSI achieved the best-predicted results for TVC (R2p = 0.93, RMSEp = 0.44, RPD = 2.74) and coliforms (R2p = 0.92, RMSEp = 0.46, RPD = 2.57). These results indicated that fluorescence, as a complementary technique for HSI, will be widely used in the chicken supply chain to predict microbial growth.

Dial Sounder of Methane Insusceptible to Variable Humidity Based on Broadband Laser Diodes

A novel differential absorption lidar method utilizing the spectral and energetic properties of pulsed, high-power, broadband laser diodes for remote sensing of methane is reported. The atmospheric gas content is retrieved using the derived calibration function, integrating multiple resonance lines of the selected CH4/Qyν3 second overtone absorption spectrum matched to a laser mode centred at optimal wavelength. The sensitivity of the lidar is effectively improved by multiplexation of the detected laser radiation in dual spectral channels eliminating the interference of the atmospheric water vapour.

Nitrogen and bromine co-doped carbon dots with red fluorescence for sensing of Ag+ and visual monitoring of glutathione in cells

Carbon dots (CDs) with red fluorescence emission have excellent advantages in cell imaging. Herein, novel nitrogen and bromine doped CDs (N,Br-CDs) were prepared with 4-bromo-1,2-phenylenediamine as precursor. The N, Br-CDs present the optimal emission wavelength at 582 nm (λex = 510 nm) at pH 7.0 and 648 nm (λex = 580 nm) at pH 3.0 ∼ 5.0, respectively. The fluorescence intensity of N,Br-CDs at 648 nm versus Ag+ concentration shows a good relationship from 0 to 60 μM with the limit of detection (LOD) of 0.14 μM. Furthermore, the fluorescence of N,Br-CDs/Ag+ is efficiently restored via the combination of glutathione (GSH) and Ag+ and linearly changes with GSH concentration from 0 ∼ 6.0 μM with LOD of 49 nM. This method has been successfully employed to monitor intracellular Ag+ and GSH with fluorescence imaging. The results suggest that the N,Br-CDs has application potential in the sensing of Ag+ and visual monitoring of GSH in cells.

Malignant versus normal breast tissue: Optical differentiation exploiting hyperspectral imaging system

Breast malignancy is a critical problem that severely affects women’s health globally with a high-frequency rate, necessitating fast, effective, and early diagnostic methods. The present study aims to measure the breast tissue’s optical properties by capturing the spectral signatures from malignant and normal breast tissue for therapeutic and diagnostic applications. The optical imaging system incorporates a hyperspectral (HS) camera to capture the spectral signatures for both the malignant and normal breast tissues within 400 ~ 1000 nm. The system was subdivided into two exploratory (reflection/transmission) to measure the tissue’s diffuse reflectance (Rd) and light transmission (Tr), respectively. The study involved 30 breast tissue (normal/tumor) samples from 30 females in the age range of 46 ~ 72 years, who were optically inspected in the visible and near-infrared (VIS-NIR) spectra. Then, the inverse adding doubling (IAD) method for breast tissue characterization and descriptive analysis (T-test) was exploited to verify the significant difference between the various types of breast tissues and select the optimum wavelength. Finally, comparing the study outcome with the histopathological examination to evaluate the system’s effectiveness by calculation (sensitivity, specificity, and accuracy). The average outcome values demonstrated that the optimal spectral bands distinguishing between the normal and the tumor tissues regarding the reflectance approach were 600 ~ 680 nm and 750 ~ 960 nm at the VIS and NIR spectrum, respectively. Then, for the transmission technique, the optimal spectral bands were 560 ~ 590 nm and 760 ~ 810 nm at the VIS and NIR spectra, respectively. Later, the T-test and the IAD verified that the highest Rd values for discrimination were 600 ~ 640 nm and 800 ~ 840 nm at the VIS and NIR spectra, respectively. On the other side, the highest Tr values were 600 ~ 640 nm and 760 ~ 800 nm at the VIS and NIR spectra, respectively. The investigation’s average reading accuracy, sensitivity, and specificity were 85%, 81.88%, and 88.8%, respectively. The experimental trials revealed that the system could identify the optimal wavelength for therapeutic and diagnostic applications through the light interaction behavior of the breast tissue’s optical properties.