Intensity Of Characteristic Peaks Research Articles

A simple SERS sensor based on antibody-modified Fe3O4@Au MNPs for the detection of CA19-9 in CRC patients.

This paper presents functionalized magnetic nanoparticles (Fe3O4@Au MNPs) combined with the surface-enhanced Raman spectroscopy (SERS) technique for sensitive detection of colorectal cancer (CRC) protein biomarker carbohydrate antigen 19-9 (CA19-9). Fe3O4@Au MNPs were constructed by the PEI-mediated seed growth method. Then, the signal molecule 5-5'-dithiobis (succinimidyl-2-nitrobenzoic acid) was used as a bridging agent to link CA19-9 antibody, and the SERS sensor was prepared. Using this sensor, detection of CA19-9 can be realized with only a one step sampling reaction. Fe3O4@Au MNPs combine the advantages of magnetic materials and noble metal nanoparticles, effectively amplifying the signal by creating numerous "hot spots" within the Au particle gaps and enhancing magnetic enrichment. Consequently, this approach lowers the detection limit (LOD) and enhances detection sensitivity. The ratio of characteristic peak intensities I1392/I1069 was selected for calculation, and a linear equation was constructed with a LOD as low as 0.27 U mL-1 by quantitative detections of the standard antigen. Finally, the sensor was used to analyze the clinical serum samples from CRC patients and healthy individuals, and the detection results were consistent with the actual results. This method exhibits notable advantages, including simplicity, high sensitivity, specificity, stability and reproducibility. It is expected to provide a new promising analytical method for clinical CA19-9 immunoassay.

Quantitative analysis of β-carotene and unsaturated fatty acids in blended olive oil via Raman spectroscopy combined with model prediction.

Blended vegetable oil is considered to be a valuable product in the market owing to favourable taste and nutritional composition. The quantification of its contents has notable implications for protecting food safety and consumer interests. Thus, a rapid and non-destructive method is needed to analyse the composition of blended oil. This study established an analytical method combining Raman spectroscopy and prediction models to determine the content of olive oil in a mixture. Competitive adaptive reweighted sampling was employed to select feature bands attributed to β-carotene and unsaturated fatty acids. Various models were used to calculate the mixture proportion, and the importance of characteristic peak intensity affecting the prediction was evaluated via grey relational analysis. The random forest model exhibited superior performance in quantitative analysis, with RMSE and R2 of 0.0447 and 0.9799, respectively. Overall, this approach was proven to effectively identify blended olive oils, exemplifying its potential in food authentication.

Investigating SERS performance of controllable fabricated Ag periodic nanostructures with morphologies of nanoclaws and nanocones in detecting SARS-CoV-2 S protein

Surface-enhanced Raman scattering (SERS) spectroscopy plays an important role in enabling high-precision detection and non-invasive diagnostics. Periodic metallic nanostructures with strong electromagnetic fields and tunable localized surface plasmon resonance can achieve high SERS sensitivity, but fabricating such nanostructures remains a challenge. In this work, the anodic aluminum oxide (AAO) nanocavity template-assisted process of fabricating periodic nanostructures with modulating morphologies from Ag nanoclaws (AgNCWs) to Ag nanocones (AgNCEs) is proposed. The morphologies-related SERS performances of nanostructures are analyzed by using rhodamine 6 g (R6G) as a probe molecule and the optimized AgNCEs possess a limit of detection (LOD) of 1 × 10−9 M. A sandwich strategy is applied to detect SARS-CoV-2 S protein in phosphate-buffered saline (PBS) and pharyngeal swab solution (PSS). The ACE2-modified AgNCEs (ACE2/AgNCEs) structure is applied to bind to the SARS-CoV-2 S protein. The 4-MBA and SARS-CoV-2 S antibody functionalized Au nanoparticles (AuNPs) are used as nanotags. By forming the ACE2/AgNCEs-SARS-CoV-2 S protein-nanotags sandwich structure, characteristic peak intensities of 1580 cm−1 are used as the report signal, and the LOD for SARS-CoV-2 S protein in PBS and PSS solution are 10 fg/mL.

A novel combining Raman-photoluminescence method to characterize the brittle and plastic states of fused silica based on nanoscale ring structures and atomic point defects

Fused silica has been widely used in many key technical domains. However, the inevitably induced micron-sized brittle fractures during manufacturing processes seriously affect its service performance. Scanning electron and atomic force microscopes are mainly employed to estimate the brittle and plastic states (BPS) of the precise fused silica components, which would put strict demands on the dimensions of detected components and damage the detected surfaces. Herein, the evolution rules of the D2 characteristic peak intensities in Raman spectra corresponding to three-fold rings with the BPS were explored. Interestingly, it is found that the D2 peak intensity first greatly increases in brittle-plastic mixing zones and then sharply decreases in brittle zones. The evolution mechanisms of the nanoscale rings with respect to the BPS were further revealed using the molecular dynamics modeling. The enveloping-space compression of rings and the ring conversion from large- to small rings are found to be the leading factors of the significant increase of the three-fold rings in brittle-plastic mixing zones. And the abrupt destruction of ring structures due to amounts of damaged Si-O bonds in brittle zones contributes to the sharp decrease of the three-fold rings. Based on the evolution rules of the nanoscale rings with the BPS, the brittle-plastic mixing zones could be distinguished from the brittle and plastic zones. It also implies that the rings, especially three-fold rings may dominate the BPS. Moreover, the change laws of the photoluminescence properties with BPS were also studied. It has been found that the photoluminescence envelope area sharply increases with the BPS. It indicates that the concentrations of the atomic point defects would sharply increase with the BPS. Based on the evolution rules of the atomic point defects with the BPS, the brittle and plastic zones could be distinguished. Therefore, a novel Raman-photoluminescence combined method was proposed to characterize the BPS. Finally, its wide applicability was also verified in various specific cases. To sum up, the investigation develops a novel spectral method to effectively characterize the BPS. It is significant for the early warning of the material brittle fractures and the nondestructive characterization of fused silica during the manufacturing processes, which could vigorously promote the further application of fused silica components in various fields.

Thermal oxidative aging behavior and lifetime prediction of fluoroether rubber

Fluoroether rubber's performance offers extensive application potential in harsh conditions. This article investigates the thermal-oxidative aging behavior and life prediction of fluoroether rubber using methods such as Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analyzer (TGA), Differential Scanning Calorimeter (DSC) and Compression Set. Results indicate that with prolonged aging, fluoroether rubber exhibits decreased heat resistance, damaged TAIC crosslink structures, and weakened characteristic peak intensities of main chains and side groups, leading to changes in rubber structure. Throughout the aging process, hardness, physical crosslink density, glass transition temperature, and compressive stress gradually increase, while mechanical properties decline. Using compression set as an indicator, service life at various temperatures was predicted, providing theoretical guidance for improving the reliability of fluoroether rubber seals and expanding their engineering applications.

Agricultural waste valorisation – Novel Areca catechu L. residue blended with PVA-Chitosan for removal of chromium (VI) from water – Characterization, kinetics, and isotherm studies

Arecanut, an industrial crop prevalent in tropical regions such as India, Sri Lanka, and parts of Southeast Asia, generates significant agricultural waste during processing. This study explores a waste-to-wealth approach by incorporating arecanut organic residue into Polyvinyl alcohol (PVA) - Chitosan blends via an eco-friendly continuous stirring method to develop an adsorbent film for removing chromium (VI) from water. Morphological analyses confirmed enhanced surface area, porosity, and roughness in the blended films. XRD and FTIR analyses indicated a semi-crystalline nature with a decrease in the characteristic peak intensity of PVA and chitosan, confirming the incorporation of arecanut residue. Optimal conditions identified OR-4 film, using 0.4 g of adsorbent, achieving 88.68 % removal of 173 mg/L chromium (VI) at pH 9.0, within 45 minutes at 40°C. SEM images demonstrated significant surface roughness reduction before and after adsorption, confirming chromium adsorption. Kinetic studies revealed a pseudo-second-order model and adsorption isotherms confirmed film surface heterogeneity. This research advances eco-friendly materials for water purification and offers a sustainable solution for managing agricultural residues.

SERS-Encoded Nanoprobes Based on Silver-Coated Gold Nanorods for Cell Sorting.

Optically-encoded probes have great potential for applications in the fields of biosensing and imaging. By employing specific encoding methods, these probes enable the detection of multiple target molecules and high-resolution imaging within the same sample. Among the various encoding methods, surface-enhanced Raman scattering (SERS) spectral encoding stands out due to its extremely narrow linewidth. Compared to fluorescence spectral encoding, SERS encoding significantly reduces crosstalk between adjacent peaks, thereby achieving a larger encoding capacity and enabling multi-channel parallel analysis. This article presents the design and construction of two novel sets of SERS-encoded probes based on noble metal core-shell nanostructures. Two different encoding strategies are successfully applied to encode the SERS spectra of the probes: 1D encoding based on the wavenumber of characteristic peaks in the SERS spectrum, and 2D encoding combining both wavenumber and intensity of characteristic peaks in the SERS spectrum. In addition, this study also demonstrates the potential application of 1D encoded probes in cell sorting. These studies verify the feasibility of applying these two encoding methods to SERS core-shell probes and provide new insights into the construction of optically encoded probes.

The Identification of Six Estrogen Preparations by Combining Thin-Layer Chromatography with Micro-Raman Imaging Spectroscopy.

A method for identifying six estrogen preparations by thin-layer chromatography combined with Raman imaging microscopy (TLC-RIM) was established. An appropriate pretreatment method was adopted to extract and purify the six estrogen preparations. After that, each estrogen extraction solution was spotted on a thin-layer chromatography plate. Estriol (E3), estradiol (E2), estradiol valerate (EV), estradiol benzoate (EB), nilestriol (CEE), and ethinylestradiol (EE2) were separated by TLC, and their Rf value and localization were determined under a UV lamp at 254 nm, followed by the in situ enrichment of the drug component. Using a 532 nm laser as the light source, the Raman scattering spectrum of the component was directly collected by micro-Raman imaging. The Rf values after TLC separation of the six estrogens and their Raman spectra can, respectively, reflect differences in polarity and structure, and they are not affected by the excipients of preparation. The detection limits of the six estrogens are 0.636, 1.00, 0.687, 0.497, 0.649, and 0.626 mg/mL. Based on the intensity of the minimum characteristic peak, the stability results within 40 min showed that the RSD of each substance is 1.34, 2.06, 1.65, 3.99, 1.16, and 2.71%, respectively. This method has strong specificity, good stability, and high sensitivity, and it can provide a new reference for improving the identification standards of estrogen preparations.

Exploration ofcucurbituril-mediated SERS plasmonic nanoarrays with sub-nanometer gaps.

The uneven distribution of hotspots and the challenges associated with precise analyte localization within these hotspots present significant hurdles in the field of surface-enhanced Raman scattering (SERS). Here, at the water-oil interface, gold nanoparticles (AuNPs) interconnected by cucurbiturils[8] (CB[8]) with sub-nanometer gaps (AuNPs:CB[8]) were organized into plasmonic arrays. This arrangement was engineered to generate highly efficient hotspots. The CB[8] molecules, serving a dual role, not only facilitated the assembly of AuNPs with sub-nanometer (~ 1nm) gaps to create intense plasmonic hotspots but also acted as molecular traps, enabling the precise localization of molecules within these hotspots. By comparing the enhancement effect of probe molecule on Au nanofilm, AuNPs:CB[8] colloids, and AuNPs:CB[8] nanofilm, it was found that the SERS intensity of the E1 characteristic peak in AuNPs:CB[8] nanofilm is five times higher than that on Au nanofilm, and more than 104 times higher than that of AuNPs:CB[8] colloids. The gaps are also accessible to different electronegativite molecules, such as estrone, p-aminoazobenzene, or methylene blue, which are captured at the plasmonic hotspots by the interaction of CB[8]. Themethod was employed for the practical detection of artificial antioxidant butylated hydroxyanisole (BHA), which has a weak Raman scattering cross-section, by coupling it with a reaction to enhance its SERS effect. The detection limit of BHA in soybean oil sample is 5.89 × 10-8mol/L, with the recovery range 85.1-115%. In conclusion, this hot-spot design and molecular capture approach will offer a highly effective method for detecting weak Raman scattering cross-section molecules and holds great promise for practical applications in the future.

A novel dual-function fluorescence sensor Eu/CDs@MOF-808 for the sensitive detection of adenosine triphosphate and uric acid

Designing and developing a reliable method for the detection of potential biomarker molecules are crucial for prevention and early diagnosis of diseases. In this study, we present a novel functionalized metal–organic framework material (MOF-808) that is developed to construct ratiometric fluorescence sensing platform (Eu/CDs@MOF-808) for the detection of adenosine triphosphate (ATP) and uric acid (UA). The fluorescent probe Eu/CDs@MOF-808 prepared through the in-situ encapsulation of fluorescent carbon dots (CDs) within the structure of MOF-808 exhibits excellent optical properties. Additionally, rare earth ions (Eu3+) are incorporated into the CDs@MOF-808 using a post-synthetic modification strategy. The presence of ATP significantly enhances the characteristic peak of carbon dots (CDs) at 440 nm, while the peak of Eu3+ at 614 nm remains relatively unchanged. Furthermore, the concentration of ATP exhibits a strong linear relationship with the ratiometric fluorescence intensity (F440/F614) in the concentration range of 0.5–450 μM, with a detection limit of 0.22 μM. Notably, the addition of uric acid (UA) to this fluorescence sensing platform leads to a marked reduction in the characteristic peak intensity of Eu3+, which results in a satisfactory linear relationship between the ratiometric fluorescence intensity and UA concentration in the concentration ranges of 0.04–300 μM and 300–650 μM, with a detection limit of 0.04 μM. Additionally, the fluorescent sensor has been successfully applied for the detection of ATP and UA in real serum and urine samples.

Urine-based SERS and multivariate statistical analysis for identification of non-muscle-invasive bladder cancer and muscle-invasive bladder cancer.

Bladder cancer (BC) is an epidemiological urologic malignancy that continues to increase each year. Early diagnosis and prognosis monitoring is always significant in clinical practice, especially in distinguishing non-muscle-invasive bladder cancer (NMIBC) from muscle-invasive bladder cancer (MIBC), due to the various depths of tumor invasion related to different therapeutic schedules and recurrence rates. Common diagnostic approaches are too invasive or generally inefficient in accuracy and specificity. In this work, a totally non-invasive and cost-effective method is established by investigating urine samples using surface-enhanced Raman spectroscopy (SERS) and multivariate statistical analysis. The comparison of urine SERS spectra shows the intensities of characteristic peaks for DNA/RNA, hypoxanthine, albumin, D-( +)-galactosamine, fatty acids, and some amino acids are distinguishable in BC occurrence and invasion progression. A PLS-LDA-based two-step binary classification scheme is performed on urine SERS spectra and the diagnostic accuracies were 97.7% and 96.3% for healthy individuals versus BC patients and NMIBC versus MIBC patients, respectively. Moreover, the impact of urine SERS spectral lengths in reaching high-precision recognition of BC is investigated. The results show that the Raman peaks at 803, 893, 1139, 1375, and 1466cm-1 play an essential role in correctly categorizing healthy control, NMIBC, and MIBC patients, and SERS spectra ranges from 400 to 1600cm-1 are enough for this identification task. These findings provide a sensitive, label-free, rapid, and totally non-invasive way for assessment of invasion depth of BC to its early diagnosis and prognosis monitoring, as well as valuable insights for selecting reasonable spectral range to enhance the measurement efficiency especially in large-scale sample datasets.

Ultrasensitive SERS Detection of Five β-Blockers Achieved Using Chemometrics with a Two-Dimensional Substrate Formed by Large-Sized Ag@SiO2 Nanoparticles.

We report on a surface-enhanced Raman scattering (SERS) platform for the detection of five beta-blockers (β-blockers): atenolol, esmolol, labetalol, sotalol, and propranolol. Key to this platform was a two-dimensional substrate formed by self-assembling large Ag@SiO2 nanoparticles (Ag@SiO2 NPs) on a silicon wafer. The close arrangement of these large nanoparticles on the surface generated a strong and uniform electromagnetic field, which enhanced SERS signal intensity for the detection of small amounts of the target molecules. The intensities of characteristic peaks of the five β-blocker drugs increased linearly with the increase of their concentrations in the range of 10-5 to 10-8 mol/L. The detection limits were 10-10 mol/L for propranolol, 10-9 mol/L for atenolol, labetalol, and sotalol, and 10-8 mol/L for esmolol. Determination of these five β-blocker drugs added to human urine samples, using a portable Raman spectroscopy instrument, showed quantitative recovery (93-101%). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) of SERS spectral data improved the differentiation among these five β-blockers. This study highlights the potential of the developed SERS platform for rapid, on-site detection of illicit drugs and for antidoping screening.

Facile SERS screening of melamine in bovine milk with 2D printed AgNPs/glass fabric filter paper as the flexible substrate

Melamine is one of the most frequently detected adulterants in dairy products. The current study proposes a surface-enhanced Raman spectroscopy (SERS)-based analytical tool for fast and reliable screening of melamine in bovine milk. A hand-held Raman spectrometer was used in conjunction with a substrate composed of silver nanoparticles (AgNPs) that was 2D printed onto glass fiber (GF) filter paper. Under optimized conditions, a sensitive and fingerprint-like signal at 674 cm−1 was obtained. The AgNPs/GF substrate exhibited high sensitivity to melamine in milk down to 1.9498 × 10−5 mg/mL, which is well below the USA and EU safety limits (2.5 × 10−3 mg/mL). Remarkably, the proposed technology was also highly reproducible, showing spot-to-spot and block-to-block variations below 3.3 % and 4.9 % at 674 cm−1 in Raman intensity, respectively. The characteristic peak intensity and concentration of melamine showed an acceptable linear relationship (R2 = 0.9909) within the range of 0.0001–1 mg/mL. Overall, the method established in this study can provide an efficient and effective method for the quantitative target screening and detection of melamine in dairy products.

Physiological response of Bidens pilosa to cadmium stress monitored by Fourier Transform Infrared Spectroscopy

The cadmium (Cd) pollution of soil causes serious environmental problems. The present paper deals with the physiological response of the changes in chemical components in the root, stem and leaf of Bidens pilosa seedlings stressed by excess cadmium ions (Cd2+) using Fourier transform infrared spectroscopy technique (FTIR). Cadmium accumulation in plant and distribution in subcellular by atomic absorption spectroscopy were tested under different concentrations cadmium stress. Results indicated that at a Cd concentration of 7 mg·L-1, B. pilosa maintained normal growth without visible Cd toxicity symptoms, though biomass was reduced compared to controls. FTIR analysis revealed that the overall peak shapes of roots, stems, and leaves remained largely unchanged before and after heavy metal treatment, suggesting that the structural integrity of plant organs was not compromised. However, shifts in specific functional group absorption peaks, including hydroxy (3387-3417 cm-1), carboxyl (1411-1419 cm-1), and amide groups (1635 cm-1), were observed, indicating their involvement in the heavy metal absorption process. The characteristic peak intensity of leaves was higher at high Cd concentration than at medium-low Cd concentration, while peaks in stems and roots remained consistent with or exceeded those of the control group. Cd predominantly accumulated in cell walls (46.21%-55.32%) and was minimally distributed in chloroplasts and mitochondria (4.11%-8.43%). These findings suggest that B. pilosa exhibits strong tolerance to Cd-contaminated soil and has significant potential for phytoremediation. The FTIR method offers strong evidence supporting the development of phytoremediation technology.

Study of the relationship among biomarkers, cell and tissue of glioma through Raman spectroscopy

Glioma is the most common brain tumors with high mortality and recurrence rates. Currently, the diagnosis methods for glioma are mainly based on tissue level, cellular level and biomarker level. In this paper, the characteristics of biomarkers (γ-aminobutyric acid and matrix mtalloproteinses-2), U87MG glioma cell and tissue were studied based on Raman spectroscopy, respectively. The results showed that the γ-aminobutyric acid concentration exhibited a linear relation with the intensity of characteristic peaks in 800–1600 cm−1 region, whereas the spectral baseline increased with the increasing of sample concentration in 200–700 cm−1 region. The Raman characteristics of matrix mtalloproteinses-2 in 20–1800 cm−1 region was investigated. Especially, it is demonstrated that the matrix mtalloproteinses-2 showed sixteen low-wavenumber Raman peaks in the range of 20–300 cm−1. Moreover, the U87MG glioma cell showed seven different Raman characteristic peaks in 600–1800 cm−1 region. Compared with the normal tissue, the Raman intensity of tumor tissue showed apparent intensity differences in 300–1800 cm−1, where the intensity changes of these Raman peaks were related to the reducing of the lipid metabolic pathways, and increase of the RNA in tumor tissue region. Furthermore, it is found that the Raman spectra of U87MG glioma cell and tumor tissue had corresponding peaks in the Raman spectra of the liquid γ-aminobutyric acid and matrix mtalloproteinses-2. It is suggested that the γ-aminobutyric acid and matrix mtalloproteinses-2 contributed to the formation and growth of glioma cell and tissue. Thus, Raman spectroscopy not only can diagnose glioma at the biomarkers, cellular and tissue level, but also analyze the relationship among the three. Furthermore, the results provided a physical marker for the detection of glioma in clinically.

Optimization of GC-IMS parameters and determination of volatile fingerprint of flavors and fragrances using GC-IMS

ABSTRACT To investigate the optimum parameters of gas chromatography ion mobility spectrometry (GC-IMS) in determination of flavors and fragrances in tobacco. The effects of reaction parameters such as chromatographic column temperature, incubation temperature, incubation time and injection volume are evaluated with the number of identified characteristic peaks, peak intensity and peak pacing as indexes by an orthogonal L9 (34) test. Furthermore, prediction of test results is conducted based on the PLS method. Particle Swarm Optimization (PSO) is used to optimize the parameters. The collection of 30 different flavors and fragrances are tested by GC – IMS which operation parameters are set according to optimal results. The results show that a total of 60 kinds of the volatile organic compounds (VOCs) are identified across all samples, including aldehydes, ketones, alcohols, esters, ethers and so on. Therefore, by means of fingerprints can infer the general composition of fragrance-base or distinguish flavors and fragrances.

Abatement of algal extracellular organic matter by vacuum ultraviolet: Effect of dissolved oxygen and role of in-situ formed reactive oxygen species

Algal extracellular organic matter (EOM) in water produced during the outbreak of algal blooms is difficult to be effectively removed by conventional water treatment processes. Compared with ultraviolet (UV), vacuum ultraviolet (VUV) can additionally radiate 185 nm photons, and VUV can split water to produce reactive oxygen species (ROS) in-situ. Herein, abatement and characteristic variation of EOM under VUV irradiation and the mechanism were investigated. Results indicated that EOM abatement by VUV irradiation were significantly higher than that by UV irradiation. The mineralization rate constant of EOM under VUV was 2.25 times of that under UV. Besides, under VUV irradiation, the abatement efficiency of EOM was promoted with the increased dissolved oxygen (DO), and EOM with a lower initial concentration had a higher abatement efficiency. Intensities of characteristic fluorescence peaks of EOM decreased obviously after VUV irradiation, and removal rates of specific fluorescent organic components were ≥ 74.4%. Under VUV irradiation, organic matter in EOM with higher molecular weight was transformed into that with lower molecular weight. Moreover, hydroxyl radical (•OH) generated in-situ by VUV dissociating water with different DO was directly identified by fluorescence molecular probe technology, and the higher DO caused the higher production of •OH. Furthermore, the mechanism of EOM abatement by VUV was proposed. DO and the produced ROS enhanced the abatement efficiency of EOM, and they played important roles in EOM abatement. This study disclosed abatement characteristics of EOM under VUV irradiation and provided great value for expanding the utilization of VUV in water treatment.

Exploring the analytical potential of total reflection X-ray fluorescence (TXRF) combined with partial least square (PLS) for simple determination of ash content in various coal types

Ash content, as a crucial indicator of coal quality, its rapid and accurate determination is pivotal to improve the energy utilization of coal and reduce environmental pollution. Traditional spectroscopic methods face significant challenges in acquiring accurate information from coal samples due to the notorious matrix effects arising from their complex composition, vast molecular structure, and diverse coal types. In this study, the feasibility of total reflection X-ray fluorescence (TXRF) combined with partial least squares (PLS) for the determination of coal ash was firstly investigated based on the TXRF being unaffected by matrix effects. Firstly, coal samples were prepared as suspensions, and the effects of sample particle size and different dispersants on the results of TXRF analyses were evaluated. The accuracy and applicability of the chosen sample preparation strategies were further validated using inductively coupled plasma mass spectrometry (ICP-MS) and two certified reference materials (CRMs). Subsequently, based on the analysis of 19 coal samples, the impact of three different predictive variables on the performance of the PLS model was investigated: (a) TXRF full spectrum normalized by the net intensity of the internal standard; (b) net intensity of characteristic peaks for 12 elements (Al, Si, K, Ca, Ti, Fe, Cr, Mn, Cu, Ni, and Sr) normalized by the net intensity of the internal standard; (c) concentrations of the aforementioned 12 elements. The results demonstrate that the PLS model constructed usingthe TXRF full spectrum normalized by the net intensity of the internal standard exhibits the best predictive capabilities, with the determination coefficient of calibration set (R2) and mean square error (MSE) of the prediction set reaching 0.9736 and 0.99 %, respectively. Moreover, the measurement accuracy of this model was six times greater than that obtained with traditional X-ray fluorescence (XRF). Presented analytical results display the possibilities of combining TXRF with PLS for coal quality evaluation.

Multi-dimensional signals coupling of simultaneous acquisition stripping current with laser-induced breakdown spectroscopy for accurate analysis of Cd(II) in coexisting Cu(II)

BackgroundDespite significant advancements in detecting Cd(II) using nanomaterials-modified sensitive interfaces, most detection methods rely solely on a single electrochemical stripping current to indicate concentration. This approach often overlooks potential inaccuracies caused by interference from coexisting ions. Therefore, establishing multi-dimensional signals that accurately reflect Cd(II) concentration in solution is crucial. ResultsIn this study, we developed a system integrating concentration, electrochemical stripping current, and laser-induced breakdown spectroscopy (LIBS) characteristic peak intensity through in-situ laser-induced breakdown spectroscopy and electrochemical integrated devices. By simultaneously acquiring multi-dimensional signals to dynamically track the electrochemical deposition and stripping processes, we observed that replacement reactions occur between Cu(II) and Cd(II) on the surface of Ru-doped MoS2 modified carbon paper electrodes (Ru-MoS2/CP). These reactions facilitate the oxidation of Cd(0) to Cd(II) during the stripping process, significantly increasing the currents of Cd(II). Remarkably, the ingenious design of the Ru-MoS2 sensitive interface allowed for the undisturbed deposition of Cu(II) and Cd(II) during the electrochemical deposition process. Consequently, our in-situ integrated device achieved accurate detection of Cd(II) in complex environments, boasting a detection sensitivity of 8606.5 counts μM⁻1. SignificanceBy coupling multi-dimensional signals from stripping current and LIBS spectra, we revealed the interference process between Cu(II) and Cd(II), providing valuable insights for accurate electrochemical analysis of heavy metal ions in complex water environments.

Development and characterization of PVA-based nanocomposites with graphene and natural quartz nanoparticles for energy storage applications

This study presents the development and characterization of polymer nanocomposites (PNCs) using polyvinyl alcohol (PVA) as a matrix, incorporating graphene (Gr) and natural quartz nanoparticles (NQNs) as nanofillers. The graphene content was fixed at 1 wt%, while the quartz content was varied at 3 wt%, 7 wt%, and 11 wt%. The NQNs were derived from natural quartz rocks, which were ground and milled to nanosize, emphasizing the utilization of natural materials. Comprehensive characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), UV–visible spectroscopy (UV–Vis), and extensive electrical and dielectric measurements. SEM and EDS analyses revealed the nearly spherical shape of the NQNs, with sizes ranging from 25 to 88 nm and an average size of 61.2 ± 13.1 nm. XRD patterns indicated a decrease in crystallinity of the polymer matrix with increasing NQNs content, with the PVA/Gr-11 wt% NQNs showing nearly amorphous characteristics. FTIR spectra demonstrated the incorporation of NQNs within the PVA matrix, affecting the chemical bonding and reducing the intensity of characteristic peaks. UV–Vis spectra indicated a significant decrease in the optical bandgap with the addition of NQNs, suggesting enhanced electronic properties. The electrical conductivity measurements, at a frequency range of 50 Hz to 8 MHz and temperature range from 20 °C to 80 °C, showed that the incorporation of Gr, a two-dimensional (2D) material, and NQNs significantly enhanced the conductivity of the nanocomposites, with the optimal performance observed at 7 wt% NQNs. Dielectric measurements revealed that the PVA/Gr-7 wt% NQNs nanocomposite exhibited superior dielectric properties, with higher dielectric constant and lower dielectric loss compared to pure PVA. Nyquist plots indicated reduced bulk resistance and enhanced thermal stability for the PVA/Gr-7 wt% NQNs composite. Capacitance-frequency and conductance-frequency analyses of the fabricated capacitor confirmed this composite's superior performance for dielectric capacitors. The optimized PVA/Gr-7 wt% NQNs nanocomposite, leveraging the unique properties of natural quartz and 2D graphene, demonstrated significant improvements in electrical and dielectric properties, making it a promising candidate for advanced dielectric capacitors in energy storage applications. The study confirms the innovative use of natural and 2D materials to develop energy storage devices.