Spectroscopy System Research Articles

An atomic force microscopy and total internal reflection fluorescence microscopy correlated system (AFM-TIRF) for fluorescence imaging and spectroscopy of a single particle.

Combining atomic force microscopy (AFM) with other optical microscopic techniques is pivotal in nanoscale investigations, particularly leveraging the surface-sensitive properties of total internal reflection fluorescence microscopy (TIRF). A novel design that integrates AFM with a multi-wavelength TIRF is displayed, providing simultaneous fluorescence imaging and spectral acquisition capabilities. We elaborate on the considerations in the instrument design process and demonstrate the performance and potential applications of the instrument through fluorescence imaging and spectroscopy testing of individual nanoparticles. This AFM and TIRF correlated system (AFM-TIRF) emerges as a promising option for single-molecule fluorescence studies, enabling simultaneous manipulation and detection of fluorescence from individual molecules.

Osteoinductive and regenerative potential of premixed calcium-silicate bioceramic sealers on vascular wall mesenchymal stem cells.

The osteogenic potential of new premixed calcium-silicate-containing bioceramic sealers (Ca-Si sealers) was tested with porcine vascular wall-mesenchymal stem cells (pVW-MSCs). Two Ca-Si-containing sealers: Ceraseal (MetaBiomed, Cheong-si, South Korea) and AH Plus Bioceramic (Maruchi, Wonju-si, South Korea), and an epoxy resin sealer (AH Plus; Dentsply, Konstanz, Germany) as a control, were prepared according to the manufacturers' indications. All samples were allowed to set for 100% of their setting time in a sterile humid cabinet at 37°C and 95% relative humidity. pVW-MSC seeding efficiency and osteogenic differentiation were analysed as marker of gene/protein expression for up to 12 days. Mineralization assay and immunofluorescence staining were performed and evaluated over a period of 21 days. Statistical analyses were conducted using one-way analysis of variance (p < .05). Additional samples were prepared and stored under the same conditions and inspected using an environmental scanning electron microscope equipped with an energy dispersive X-ray spectroscopy system. Significantly higher cell seeding efficiency (p < .05) was observed for both Ca-Si sealers from day 8. pVW-MSCs showed a significant shift towards the osteogenic lineage only when seeded in contact with Ca-Si sealers. Gene expression of osteopontin was upregulated significantly. Collagen I and osteocalcin were clearly expressed by cells in contact with Ca-Si sealers. Mineralization granules were observed in Alizarin red assays and confocal laser scanning microscopy analysis of both Ca-Si sealers. No gene expression or granule mineralization were observed on the epoxy resin sealer. Premixed Ca-Si sealers displayed a higher potential for osteogenic activity on pVW-MSCs. Epoxy resin sealer was unable to induce any osteogenic activity. The properties of both Ca-Si sealers suggest their potential as osteoinductive platforms for vascular MSCs in periapical bone.

Biosynthesis of gold nanoparticles by fungi and its potential in SERS.

Surface enhanced Raman spectroscopy (SERS) by using gold nanoparticles (AuNPs) has gained relevance for the identification of biomolecules and some cancer cells. Searching for greener NPs synthesis alternatives, we evaluated the SERS properties of AuNPs produced by using different filamentous fungi. The AuNPs were synthesized utilizing the supernatant of Botrytis cinerea, Trichoderma atroviride, Trichoderma asperellum, Alternaria sp. and Ganoderma sessile. The AuNPs were characterized by ultraviolet-visible spectroscopy (UV-Vis) to identify its characteristic surface plasmon resonance, which was located at 545nm (B. cinerea), 550nm (T. atroviride), 540nm (T. asperellum), 530nm (Alternaria sp.), and 525nm (G. sessile). Morphology, size and crystal structure were characterized through transmission electron microscopy (TEM); colloidal stability was assessed by Z-potential measurements. We found that, under specific incubation conditions, it was possible to obtain AuNPs with spherical and quasi-spherical shapes, which mean size range depends on the fungal species supernatant with 92.9nm (B. cinerea), 24.7nm (T. atroviride), 16.4nm (T. asperellum), 9.5nm (Alternaria sp.), and 13.6nm (G. sessile). This, as it can be expected, has an effect on Raman amplification. A micro-Raman spectroscopy system operated at a wavelength of 532nm was used for the evaluation of the SERS features of the AuNPs. We chose methylene blue as our target molecule since it has been widely used for such a purpose in the literature. Our results show that AuNPs synthesized with the supernatant of T. atroviride, T. asperellum and Alternaria sp. produce the stronger SERS effect, with enhancement factor (EF) of 20.9, 28.8 and 35.46, respectively. These results are promising and could serve as the base line for the development of biosensors through a facile, simple, and low-cost green alternative.

Multi-excitation photoluminescence spectroscopy system for gemstone analysis.

Luminescence spectra can reveal important chemical and structural information that can be used for gemstone characterization and identification. Traditionally, gemstone UV-excited luminescence is evaluated visually under mercury vapor lamp illumination. This approach is limited by several factors, including the mixture of mercury's emission peaks, possible filter degradation, an inability to separate overlapping emission features, and the sensitivity and subjectivity of human vision and color interpretation. A multi-excitation photoluminescence (PL) spectroscopy system has been built for gemstone analysis, incorporating 261 and 405nm laser excitations to study gemstone emission features between 270 to 1000nm. This system presents significant improvements, extending the detection spectral range, increasing the sensitivity, accuracy and reproducibility of gemstone luminescence analysis. Luminescence analysis of commercially valuable gemstones are presented to demonstrate the system's suitability for gemstone identification. Examples include distinguishing natural from laboratory-grown diamonds, thermal and color treatment detection for corundum and pearls, respectively, and mineral type separation of emeralds and other green gemstones.

The Multi-Detectors System of the PANDORA Facility: Focus on the Full-Field Pin-Hole CCD System for X-ray Imaging and Spectroscopy

The Multi-Detectors System of the PANDORA Facility: Focus on the Full-Field Pin-Hole CCD System for X-ray Imaging and Spectroscopy

Wavelength-swept spontaneous Raman spectroscopy system improves fiber-based collection efficiency for whole brain tissue classification.

Raman spectroscopy is a valuable technique for tissue identification, but its conventional implementation is hindered by low efficiency due to scattering. Addressing this limitation, we are further developing the wavelength-swept Raman spectroscopy approach. We aim to enhance Raman signal detection by employing a laser capable of sweeping over a wide wavelength range to sequentially excite tissue with different wavelengths, paired with a photodetector featuring a fixed narrow-bandpass filter for collecting the Raman signal at a specific wavelength. We experimentally validate our technique using a fiber-based swept-source Raman spectroscopy setup. In addition, simulations are conducted to assess the efficacy of our approach in comparison with conventional spectrometer-based Raman spectroscopy. Our simulations reveal that the wavelength-swept configuration leads to a significantly stronger signal compared with conventional spectrometer-based Raman spectroscopy. Experimentally, our setup demonstrates an improvement of at least 200× in photon detection compared with the spectrometer-based setup. Furthermore, data acquired from different regions of a fixed monkey brain using our technique achieves 99% accuracy in classification via -nearest neighbor analysis. Our study showcases the potential of wavelength-swept Raman spectroscopy for tissue identification, particularly in highly scattering media, such as the brain. The developed technique offers enhanced signal detection capabilities, paving the way for future in vivo applications in tissue characterization.

Broadband Quasielastic Scattering Spectroscopy Using a Multiline Frequency Comblike Spectrum in the Hard X-Ray Region.

We developed a novel quasielastic scattering spectroscopy system that uses a multiline frequency comblike resolution function to overcome the limit on the accessible timescale imposed by the inherent single-energy resolution of conventional spectroscopy systems. The new multiline system possesses multiple resolutions and can efficiently cover a wide time range, from 100ps to 100ns, where x-ray-based dynamic measurement techniques are being actively developed. It enables visualization of the relaxation shape and wave-number-dependent dynamic behavior using a two-dimensional detector, as demonstrated for the natural polymer polybutadine without deuteration.

Performance enhancement of solar-blind UV photodetector by doping silicon in β-Ga2O3 thin films prepared using radio frequency magnetron sputtering

Si-doped β-Ga2O3 thin films were prepared on c-plane (001) sapphire substrates by radio frequency magnetron sputtering, and then annealed at 800 °C under Ar atmosphere for 1 h. Finally, Metal-Semiconductor-Metal type solar-blind UV photodetectors were prepared using the annealed β-Ga2O3 films. The structure, composition, optical properties and photoelectric detection performance of the films were studied using XRD, EDS, UV–Vis, PL spectroscopy and Keithley-4200 system. Results show that after silicon doping, the preferred orientation of the β-Ga2O3 film varies from (−201) to (200) and (201) crystal planes. EDX and XPS results show that 2.34 at% silicon was doped into Ga2O3 films by substituting Ga atoms. Both XPS and PL results show a decline of defect concentration within the Si-doped films, including oxygen vacancy. Si-doped β-Ga2O3 films exhibit enhanced solar-blind detection performance, with lower dark current (32.2 × 10−12 A) under 15 V bias, higher light-to-dark current ratio (3.2 × 104), higher light power density of 2.4 μW/cm2, and shorter response time. The resultant responsivity, detectivity, and external quantum efficiency are 1.146A/W, 7.14 × 1011Jones, and 5.605 %, respectively, more than one order of magnitude higher than the undoped device. This work indicates that Si is an effective n-type dopant for improving the detection performance of β-Ga2O3 film based solar-blind UV photodetectors.

Terahertz Sensing of L-Valine and L-Phenylalanine Solutions.

To detect and differentiate two essential amino acids (L-Valine and L-Phenylalanine) in the human body, a novel asymmetrically folded dual-aperture metal ring terahertz metasurface sensor was designed. A solvent mixture of water and glycerol with a volume ratio of 2:8 was proposed to reduce the absorption of terahertz waves by reducing the water content. A sample chamber with a controlled liquid thickness of 15 μm was fabricated. And a terahertz time-domain spectroscopy (THz-TDS) system, which is capable of horizontally positioning the samples, was assembled. The results of the sensing test revealed that as the concentration of valine solution varied from 0 to 20 mmol/L, the sensing resonance peak shifted from 1.39 THz to 1.58 THz with a concentration sensitivity of 9.98 GHz/mmol∗L-1. The resonance peak shift phenomenon in phenylalanine solution was less apparent. It is assumed that the coupling enhancement between the absorption peak position of solutes in the solution and the sensing peak position amplified the terahertz localized electric field resonance, which resulted in the increase in frequency shift. Therefore, it could be shown that the sensor has capabilities in performing the marker sensing detection of L-Valine.

Diffuse reflectance spectroscopy for optical characterizations of orthotopic head and neck cancer models in vivo.

We demonstrated an easy-to-build, portable diffuse reflectance spectroscopy device along with a Monte Carlo inverse model to quantify tissue absorption and scattering-based parameters of orthotopic head and neck cancer models in vivo. Both tissue-mimicking phantom studies and animal studies were conducted to verify the optical spectroscopy system and Monte Carlo inverse model for the accurate extraction of tissue optical properties. For the first time, we reported the tissue absorption and scattering coefficients of mouse normal tongue tissues and tongue tumor tissues. Our in vivo animal studies showed reduced total hemoglobin concentration, lower tissue vascular oxygen saturation, and increased tissue scattering in the orthotopic tongue tumors compared to the normal tongue tissues. Our data also showed that mice tongue tumors with different sizes may have significantly different tissue absorption and scattering-based parameters. Small tongue tumors (volume was ∼60 mm3) had increased absorption coefficients, decreased reduced-scattering coefficients, and increased total hemoglobin concentrations compared to tiny tongue tumors (volume was ∼18 mm3). These results demonstrated the potential of diffuse reflectance spectroscopy to noninvasively evaluate tumor biology using orthotopic tongue cancer models for future head and neck cancer research.

Edible Bite Force Sensor: A Novel Approach to Measuring Bite Force in Biomedical and Dental Applications.

BACKGROUND Measurement of bite force plays a crucial role in assessment of the masticatory system. With a growing interest in detecting occlusal irregularities, bite force sensors have garnered attention in the biomedical field. This study aimed to introduce a hydrogel bite force sensor, based on hydroxyethyl-cellulose-fructose-water (HEC-F-water), for premolar and molar teeth, and to evaluate it using optical profilometry, infrared spectroscopy (FTIR), and Instron Tension testing system, with 2.5 cm (1 inch) margins at top, bottom, right, and left. MATERIAL AND METHODS We fabricated 20 HEC-F-water hydrogel samples sized with surface of 1×1 cm, with 2 different widths - 1 mm and 5 mm. The samples were characterized using optical profilometry and FTIR and their electrical characteristics were determined using an impedance analyzer. Aluminum (Al) electrodes, fabricated using Cutting Plotter, were used to form a HEC-F-water-based transducer, which was used for bite force sensing. The Instron tensile testing system was employed, utilizing 3D printed models of the upper and lower jaw, to simulate biting. Forces in the range between 40 N and 540 N were exerted upon the transducer, and the output change in the electrical signal was measured. RESULTS The study determined the transfer function between bite force and capacitance. The fabricated sensor exhibited a sensitivity of 3.98 pF/N, an input range of 500 N, output range of 2 nF, and accuracy of 95.9%. CONCLUSIONS This study introduces an edible bite force sensor employing an edible hydrogel as a dielectric, presenting a novel avenue in the development of edible sensorics in dentistry.

Investigating the Secrets of Stonehenge with Raman Spectroscopy: Provenance of the Ancient Altar Stone

Abstract In-field compositional analysis of large prehistoric relics, such as the Altar Stone at Stonehenge (England), is limited due to the size of the relics and difficulty in obtaining samples that can be analyzed in a laboratory. In this study, a portable Raman spectroscopy system was used to analyze the Altar Stone to help determine its origin and classification, which appears to differ from other bluestones at Stonehenge. While the study is ongoing and the definitive origin of the Altar Stone is not yet known, this study demonstrates the applicability of a portable Raman spectroscopy system in the compositional analysis of large samples in the field.

In situ single-cell spontaneous Raman spectroscopy differentiates tumor-associated macrophages

The analysis of in situ single cells in tissue is crucial for the study of tumors. However, simultaneous analysis of multiple biomolecules for single cells by fluorescence immunohistochemistry is challenging. Spontaneous Raman spectroscopy provides biochemical fingerprints of individual cells in a label-free and nondestructive manner, yet it is not well applied to single cells in tissue. Here, we develop an in situ single-cell spontaneous Raman spectroscopy (SRS) system that can localize a single cell in tissue with fluorescence imaging, while obtaining the single-cell Raman spectra for molecular analysis. Our system is verified by measuring the standard polystyrene beads of different sizes. Measurements of in situ single macrophages in clinical cancerous and para-cancerous tissues are then performed. By using discriminant analysis, it is shown that CD68+ macrophages in cancerous and para-cancerous tissues are classified with an accuracy of 98.3 %. The molecular content of single macrophages in tissue is analyzed by using multivariate curve resolution-alternating least squares method. We find that the lipid content of tumor-associated macrophages in cancerous tissues is higher while both the contents of protein and nucleic acid are lower than those in para-cancerous tissues, which is challenging to achieve by conventional immunohistochemistry. Our in situ single-cell SRS system has the capability for the obtaining of molecular information of a localized single cell in tissue, which may find potential applications for clinical cancer diagnosis.

Wound Dressings from Electrospun Gelatin Fibres Coated with Zinc Oxide nano Particles

Traditional wound dressings require frequent replacement, are prone to bacterial growth and cause a lot of environmental pollution. Therefore, biodegradable and antibacterial dressings are eagerly desired. In this paper, gelatin/ZnO fibers were first prepared by side-by-side electrospinning for potential wound dressing materials. The morphology, composition, cytotoxicity and antibacterial activity were characterized by using Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), particle size analyzer (DLS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetry (TGA) and Incucyte™ Zoom system. The results show that ZnO particles are uniformly dispersed on the surface of gelatin fibers and have no cytotoxicity. In addition, the gelatin/ZnO fibers exhibit excellent antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) with a significant reduction of bacteria to more than 90%. Therefore, such a biodegradable, nontoxic and antibacterial fiber has excellent application prospects in wound dressing.

Laser frequency stabilization for continuous-wave laser enhanced direct frequency comb spectroscopy system

We present the observation of high-precision direct frequency comb spectroscopy excited by an optical frequency comb and a diode laser when each of them drives one step of the two-photon transition in a rubidium vapor system. We demonstrate a stable and low noise system by directly locking the frequency of the continuous-wave laser to the rubidium two-photon transition. The frequency stability of a diode laser via the two-photon transition locking technique is 8 × 10−11 for a 1 s gate time and 3 × 10−12 for 1000 s. It proves to be a potential technique for locking the diode laser with high stability. We chose a suitable optical frequency comb pulse and the frequency of the diode laser to fulfill the double-resonance condition. These techniques eliminate spectrum line overlap and would benefit spectroscopy measurements.

Development and optimisation of a near-infrared spectroscopic system for glucose quantification in aqueous and intralipid-based samples

A non-invasive glucose sensing device could revolutionise diabetes treatment. Near Infrared (NIR) spectroscopy is a promising technology for glucose sensing; however, the design and choice of components for NIR spectroscopy can greatly affect the sensing accuracy. We aimed to develop a NIR absorption spectroscopy system to determine liquid glucose concentrations in the physiological range, by evaluating a range of NIR photodetector components and light sources. Three detection assemblies were tested: (i) a dispersive spectrometer with photodiode array, (ii) a Czerny–Turner monochromator with InGaAs photodiode and (iii) a miniature Fourier Transform Infrared (FTIR) spectrometer. A halogen lamp and NIR globar were trialled as potential light sources. The components were systematically tested by comparing the coefficient of determination and standard error of prediction (SEP) for the same set of aqueous glucose samples through 10 mmol l−1 concentration steps. The Czerny–Turner monochromator with InGaAs photodiode, along with the globar, were identified as the optimal components for the system. A range of concentration steps (1–10 mmol l−1) were scanned to identify the physiologically relevant limit of detection, which was identified as 5 mmol/l for glucose in solution. Spectra were then collected from glucose samples in 10% intralipid suspension in the 10–20 mmol l−1 range and the equivalent concentrations in solution. The SEP was greater for the intralipid samples due to strong scattering. Scattering was dominant above 1300 nm, whilst absorption was dominant below 1300 nm. Although alternative approaches achieve better resolution, our system uses simple and readily-available components and presents a platform for a non-invasive NIR glucose sensing device.

Time division multiplexing based multi-spectral semantic camera for LiDAR applications

The recent progress in the development of measurement systems for autonomous recognition had a substantial impact on emerging technology in numerous fields, especially robotics and automotive applications. In particular, time-of-flight (TOF) based light detection and ranging (LiDAR) systems enable to map the surrounding environmental information over long distances and with high accuracy. The combination of advanced LiDAR with an artificial intelligence platform allows enhanced object recognition and classification, which however still suffers from limitations of inaccuracy and misidentification. Recently, multi-spectral LiDAR systems have been employed to increase the object recognition performance by additionally providing material information in the short-wave infrared (SWIR) range where the reflection spectrum characteristics are typically very sensitive to material properties. However, previous multi-spectral LiDAR systems utilized band-pass filters or complex dispersive optical systems and even required multiple photodetectors, adding complexity and cost. In this work, we propose a time-division-multiplexing (TDM) based multi-spectral LiDAR system for semantic object inference by the simultaneous acquisition of spatial and spectral information. By utilizing the TDM method, we enable the simultaneous acquisition of spatial and spectral information as well as a TOF based distance map with minimized optical loss using only a single photodetector. Our LiDAR system utilizes nanosecond pulses of five different wavelengths in the SWIR range to acquire sufficient material information in addition to 3D spatial information. To demonstrate the recognition performance, we map the multi-spectral image from a human hand, a mannequin hand, a fabric gloved hand, a nitrile gloved hand, and a printed human hand onto an RGB-color encoded image, which clearly visualizes spectral differences as RGB color depending on the material while having a similar shape. Additionally, the classification performance of the multi-spectral image is demonstrated with a convolution neural network (CNN) model using the full multi-spectral data set. Our work presents a compact novel spectroscopic LiDAR system, which provides increased recognition performance and thus a great potential to improve safety and reliability in autonomous driving.

Mechanistic study of the effects of ultrafine grinding on the surface properties of anthracite coal particles and interface regulation on froth flotation under multifactorial influences

Anthracite, a valuable and scarce coal, typically requires systematic liberation for deep deashing, wherein the particle size reduces to the micron level upon ultrafine grinding. Changes in the physicochemical properties of anthracite particles induced by ultrafine grinding significantly impact subsequent flotation. Accordingly, in this study, a scanning electron microscopy (SEM)-energy-dispersive X-ray spectroscopy (EDS) system, an Opton IPCAS maceral analyzer, a high-sensitivity microelectromechanical balancer, and an X-ray photoelectron spectrometer (XPS) were employed to investigate the changes in the physicochemical properties of the anthracite particle surface during ultrafine grinding. The flotation efficiency of ultrafine anthracite coal is determined by various factors such as the extent of sample liberation, surface wettability, and the state of inorganic mineral coatings. During the initial phase of ultrafine grinding, the comminution efficiency of the sample is high, leading to a progressive increase in the hydrophobicity. However, suboptimal flotation performance results from inadequate liberation. When the sample is liberated to an ultrafine scale, a higher degree of liberation is achieved. The particle surfaces become increasingly covered with inorganic minerals, accompanied by intensified oxidation, leading to a gradually reduced particle hydrophobicity that impaired the flotation performance. This study advances our knowledge on the mechanism by which ultrafine grinding alters the physicochemical properties of anthracite coal particles and affects the flotation processes. The theoretical framework of this study provides crucial insights for interface regulation in the preparation of ultra-low ash anthracite coal and ultrafine coal flotation.

A multiparameter sensing spectroscopic system for remote plastic sorting with a single laser shot: a first information report

The spectroscopic methods have been widely applied for plastic characterization and sorting to assist the recycling process. However, most of the reported works have been carried out in conventional laboratory conditions. In this study, we discuss development and application of a single-shot standoff multimodal LIBS-Raman spectroscopy system for plastic identification by modifying existing optical models for such analyses. By utilizing a unique co-axial back-collection optical geometry in standoff signal collection and a direct signal coupling scheme, the system was able to sense LIBS-Raman signals from plastics in single laser shot mode within 20 ms, with a non-gated CCD detector remotely. We examine the application of the system in characterizing four commodity plastic types of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), and polystyrene (PS)) based on atomic emissions (LIBS) and molecular structure (Raman Spectroscopy) by analyzing the respective standoff spectral data recorded from a distance of 4 m. The capability of the system to classify plastics based on standoff data is evaluated by using principal component analysis (PCA), which shows good segregation of the plastic classes depending on the intrinsic spectral features.

A Flexible Terahertz Metamaterial Sensor for Pesticide Sensing and Detection.

Terahertz (THz) waves have garnered significant interest across various fields, particularly in high-sensitivity sensing applications. Metamaterials can be employed in THz sensors, specifically for refractive index sensing and pesticide detection due to their high-sensitivity characteristics. In this Article, a dual-band flexible THz metamaterial sensor based on polyimide is proposed for refractive index and pesticide sensing, which is fabricated using ultraviolet (UV) lithography technology and measured by a THz time-domain spectroscope (TDS) system. The resonant frequencies of the sensor are at 0.37 and 1.13 THz, with transmission rates of 2.9% and 0.3%, respectively. With an analyte layer attached to the sensor's surface, the sensitivity of refractive index sensing can be calculated as 0.09 and 0.28 THz/RIU (refractive index unit) at the two resonant frequencies. In order to validate the exceptional pesticide sensing performance of the sensor, chlorpyrifos-methyl acetone solutions with various concentrations are added on it. Furthermore, a monolayer of graphene is coated on the sensor's surface, which is proved capable of improving pesticide sensing sensitivity at low concentrations due to strong π-π stacking interactions with π-electrons in chlorpyrifos-methyl solutions. Therefore, the graphene-coated sensor can be utilized in detecting pesticide solutions with low concentrations, and the sensor without graphene is preferred for high concentration detection. This work provides a novel option for the THz metamaterial sensor with high sensitivity covering a wide pesticide concentration range.