Raman Spectroscopy Research Articles

Raman Spectroscopy Measurements Support Disorder-Driven Capacitance in Nanoporous Carbons.

Our recent study of 20 nanoporous activated carbons showed that a more disordered local carbon structure leads to enhanced capacitive performance in electrochemical double layer capacitors. Specifically, NMR spectroscopy measurements and simulations of electrolyte-soaked carbons evidenced that nanoporous carbons with smaller graphene-like domains have larger capacitances. In this study, we use Raman spectroscopy, a common probe of local structural disorder in nanoporous carbons, to test the disorder-driven capacitance theory. It is found that nanoporous carbons with broader D bands and smaller ID/IG intensity ratios exhibit higher capacitance. Most notably, the ID/IG intensity ratio probes the in-plane sizes of graphene-like domains and supports the findings from NMR that smaller graphene-like domains correlate with larger capacitances. This study supports our finding that disorder is a key metric for high capacitance in nanoporous carbons and shows that Raman spectroscopy is a powerful technique that allows rapid screening to identify nanoporous carbons with superior performance in supercapacitors.

Drug expiration study using Raman spectroscopy and super paramagnetic clustering

Currently, there is a belief that drugs used after the expiration date no longer work, or even these can cause some damage. In the present work, several types of drugs on the market with different expiration dates are analyzed to find out if these, with the expired expiration date, present spectroscopic differences from those drugs whose expiration date is still valid. This study used the Raman spectroscopy technique to determine the chemical composition of drugs. To measure the drug Raman spectra, Horiba equipment, LabRam HR800, was used with an Olympus confocal microscope focusing a laser of 830 nm and 17 mW on the drugs through a 50 X Leica long-range objective. The Super Paramagnetic Clustering (SPC) method was applied to classify the Raman spectra. In the SPC method, the clustering process is based on a phenomenon of clustering observed in nature at the atomic level and perfectly described by a statistical physics model known as the Potts model, which describes the interacting spins on a crystalline lattice. This clustering method allows for identifying hierarchical structures in the spectra data banks. Fourteen drugs were analyzed, including 2 capsules, 5 tablets, 2 liquid samples, 4 ointments, and one spray with 1 to 3 expired expiration dates. Comparing drugs with expiration dates that are still valid and expired, the SPC results applied to the Raman spectra showed that, although some drugs indicated chemical differences, others indicated no chemical differences, even among those with up to two expired expiration dates. The results showed that Raman spectroscopy and SPC are excellent tools for discriminating between expired and non-expired drugs. The Principal Components Analysis (PCA) was also applied as a cross-checking method of the SPC result, obtaining consistent results. To our knowledge, it is the first preliminary result evaluating the usefulness of Raman spectroscopy and SPC in identifying expired drugs distributed on the market.

Development of Neural Network Potentials for Studying Chemical Behaviors of La3+/Nd3+ Ions in Molten LiCl-KCl-CsCl in Combination with Raman Spectroscopy.

The chemistry of molten salts has attracted great research interest owing to their wide applications in diverse fields. In the pyrochemical reprocessing of spent nuclear fuel or molten salt nuclear reactors, lanthanide elements as the principal fission products bring about changes in the composition and properties of molten salts. Herein, we report a comprehensive study on the coordination chemistry of the representative trivalent lanthanide ions (La3+/Nd3+) in LiCl-KCl-CsCl using a multiscale strategy combining Raman spectroscopy, deep learning, and large-scale molecular dynamics (MD) simulations. The neural network potential (NNP)-based MD and Raman spectroscopy studies revealed that La3+/Nd3+ ions prefer to form persistent octahedron complexes with the six-coordinated species as the dominant species at high temperatures. Compared to LaCl63-, NdCl63- shows higher stability with obviously longer lifetimes in LiCl-KCl-CsCl, as confirmed by the observed stronger interaction of Nd3+-Cl- pairs. The total and partial structure factors further indicated the formation of a more stable network structure in LiCl-KCl-CsCl containing NdCl3. Besides, the temperature exerts a larger influence on the local structures of the La3+ species compared to the Nd3+ analogues. According to the potential mean force calculations, the bond dissociation energies follow the order Ln-Cl > Li-Cl > K-Cl > Cs-Cl in LiCl-KCl-CsCl-LnCl3. The NNP-based large-scale MD simulations have been verified to be an efficient and powerful way in molten salt chemistry research.

The role of iron(II) excess and phosphate to synthesize hydroxychloride green rust

Green rust (GR) is a chemically reactive mineral of interest for environmental remediation. However, the lack of stability of this compound is a major drawback for practical applications. In this study, the precipitation of hydroxychloride green rust type 1 (GR1Cl) from soluble FeII and FeIII species was studied by analyzing pH titration curves and employing XRD, Raman and Mössbauer spectroscopies to find optimal conditions for synthesizing GR1Cl. Using the stoichiometric condition for FeII-FeIII corresponding to the [FeII3FeIII(OH)8]Cl compound, FeIIIO(OH)2.9Cl0.1 was formed in a first step during the addition of NaOH and then transformed into a mixture of GR1Cl and Fe3O4. The addition of phosphate anions (PO4) at a molar ratio PO4: Fe = 1: 10 in the initial solution was shown to avoid the formation of undesired magnetite. Interestingly, GR1Cl was also the only product without adding PO4 using an excess of FeII species in solution, i.e. for an initial ferric molar fraction x = FeIII: Fetot of 0.2. First experimental evidences of a hydroxyphosphate green rust type 2 GR2PO4 were also provided by XRD and Raman spectroscopy. Therefore, this work may attract interest for a better understanding of the geochemical cycle of iron and phosphate in natural environments such as hydromorphic soils or hydrothermal chimneys where fougerite, the mineral homologue of synthetic GR, is supposed to play a significant role.

Raman spectroscopy and imaging in bio and life sciences

AbstractRaman spectroscopy is a well‐known technique to study different materials and determine their chemical composition. It is based on the inelastic scattering of light and provides a unique spectrum for the sample under study. The advances in lasers and detectors, their combination with imaging systems and the discovery of new phenomena have expanded the use of this technique in several research fields. In the particular case of biology and life sciences, it has been used to provide chemical and compositional information on plant and animal tissues, cells, biofluids, etc., with the advantage that the presence of water molecules normally does not cause interference in the measured signal.

Corrosion resistance and wear behavior of CoCrFeNiMn@Gr high entropy alloy-based composite coatings prepared by laser cladding

In this study, we utilize laser cladding to apply a CoCrFeNiMn HEA with 2 wt.% few-layer graphene (Gr) coating onto the surface of Q235B mild steel. Alcohol stirring method was used for HEA and Gr preparation of composite powder. Raman spectroscopy and energy dispersion spectroscope (EDS) indicate the successful mixing of HEA and Gr powders, with Gr adhering to the surface of the HEA powder in a lamellar structure. The X-ray diffraction (XRD), scanning electron microscope (SEM), EDS, and Electron backscatter diffraction (EBSD) analyses revealed that grain refinement and the formation of fine carbide-hard phases in the HEA/Gr coating improve microhardness and wear resistance. The average Schmidt factors of the coating decreased from 0.47 to 0.45 with the addition of Gr, indicating enhanced resistance to plastic deformation and anisotropy. Nanoindentation experiments demonstrated that the HEA/Gr coatings exhibit superior resistance to plastic deformation, effectively enhancing the coating’s durability against spalling under stress and wear conditions. The microhardness of the HEA/Gr coating increased by 99.25%, and the wear rate decreased by 86.31% compared to the HEA coating alone. The open circuit potential (OCP), linear polarization curve, Tafel curves, electrochemical impedance spectroscopy (EIS), and Mott-Schottky tests all indicated that the HEA/Gr coating possesses superior corrosion resistance. X-ray Photoelectron Spectroscopy (XPS) results suggest that the passivation film of the HEA/Gr coating, which contains more oxides and less hydroxide, is more protective and denser, thereby slowing the corrosion rate.

Influences of Fluorine on Corrosion Behavior of FeCrAl Alloy in Lithiated/borated Water at 360 °C/18.5 MPa

Abstract As an accident-tolerant fuel cladding material, Iron-Chromium-Aluminium (FeCrAl) alloy shows a big potential in replacing zirconium alloy as the cladding tube for pressurized water reactors. The presence of fluorine impurity in the primary coolant of pressurized water reactors will accelerate the corrosion of fuel cladding tubes. However, studies on the influences of fluorine impurity on the service performance of FeCrAl alloy are relatively limited. In this work, corrosion behavior of FeCrAl alloy in fluorine-containing lithiated/borated water at 360 °C and 18.5 MPa was characterized by Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS), X-ray diffractometer (XRD), and Raman spectroscopy. The results indicate that FeCrAl alloy exhibited relatively good resistance to fluorine attack. Fluorine ions changed the diffusion behavior of alloying element Cr, so facilitating the formation and dissolution of FeCr2O4. Deposition of Ni and B was observed on the alloy surface. The maximum content of B reached 24.20 at.% after fluorine-containing lithiated/borated water exposure while that was 12.50 at.% in the absence of fluorine ions. Despite this, no specific compounds of B were detected in the corrosion products, but Ni existed in the form of NiFe2O4.

X-Ray Photoelectron Spectroscopy of TixAl and TixAl/A-Si:H Interlayer with Different Thicknesses on Stainless Steel to Enhancing Adhesion of DLC Films

In this research, two intermediate layers were deposited on 316L stainless steel to improve the adhesion of diamond-like carbon (DLC) films, one composed of TixAl and produced using the RF sputtering technique with three thicknesses, 100 nm, 200 nm, and 300 nm; the other, interlayer composed of amorphous hydrogenated silicon (a-Si:H). The DLC films were deposited using the pulsed-DC PECVD method with an active screen to achieve the AISI 316L/TixAl //DLC and AISI 316L/TiₓAl/a-Si/DLC configurations. The binding energy between the substrate/TixAl and TixAl/a-Si:H was investigated via X-ray photoelectron spectroscopy with high-resolution spectra. The chemical composition and microstructure of the titanium–aluminum interlayers were investigated using energy-dispersive X-ray spectroscopy and X-ray diffraction, and the microstructure of the DLC coatings was studied using Raman spectroscopy. The coatings’ adherence was measured using scratch and indentation tests, and the hardness of the DLC coatings was determined with the nanoindentation test. The X-ray diffractograms did not allow the determination of any crystalline structure in the TixAl interlayers. The XPS results showed that between the AISI 316L substrate and the TixAl intermediate layer, Ti-O-Fe and FeAl2O4 were formed. On the other hand, at the TixAl/a-Si:H interface, TiSi2 and Al2SiO5 compounds were identified. The DLC coatings grew as hydrogenated amorphous carbon with a hydrogen content of around 30 at.% and a hardness of 24 GPa. The deposition methods used and the TixAl/a-Si:H interlayers allowed the obtainment of adherent DLC coatings on AISI 316L stainless steel substrates. High critical load values of about 30 N were obtained. The novelty of this work is underscored by the absence of previous studies that thoroughly examine the bonds present in interlayers used as gradients to enhance the adhesion of DLC.

Effect of surface-active substances on the macrodispersion behavior of thermal stress-modified multi-wall carbon nanotubes in cryogenic environments

In the preparation of nanocomposites, the agglomeration of multi-walled carbon nanotubes (MWCNTs) in the composite due to their low colloidal stability limits their use in industrial areas. To overcome these problems, it is important to develop simpler, economical, high-yield and non-hazardous techniques to replace existing techniques with low yields, expensive additional equipment or hazardous liquids. This study explores how surfactants affect the macrodispersion of thermal stress-modified MWCNTs in cryogenic environments, focusing on their application in polymer film preparation. Firstly, optimal conditions for modifying MWCNTs through thermal stress were identified using liquid nitrogen. Parameters assessed included the number of cycles (2, 4, and 6), duration in liquid nitrogen (10, 20, and 30 min), and subsequent waiting time at room temperature (5, 12, and 20 min). Results showed that the highest surface area was obtained with 2 cycles, 20 min in liquid nitrogen, and 5 min at room temperature. Analytical techniques such as Brunauer-Emmett-Teller (BET), X-Ray Diffraction (XRD), High Contrast Transmission Electron Microscopy (CTEM) and Raman spectroscopy were used to evaluate the functionalization process's effects on MWCNTs' internal graphitic structure and physicochemical properties. CTEM micrographs indicated that thermal stress reduced the length of MWCNTs, while Raman analysis showed improved graphite quality. The modification process, carried out with 100 % efficiency and no sample loss, increased the BET surface area from 297.551 m2/g to 397.295 m2/g. The study also investigated the impact of surfactants (polyethylene glycol sorbitan monooleate-Tween 80, sodium dodecyl sulfate-SDS, and hexadecyltrimethylammonium bromide-CTAB) on MWCNTs' macrodispersion degrees (DM%) and energy band gaps via UV–visible (UV–Vis) absorption spectroscopy. CTAB provided the highest and most stable macrodispersion, reducing the energy band gaps of MWCNTs from 5.65 to 5.75 eV to 3.53–3.60 eV. CTAB showed excellent colloidal stability with a zeta potential of 44.2 mV, while SDS had −49.9 mV. Polyvinyl alcohol (PVA) polymer films, created using MWCNT solutions with optimal macrodispersion, were confirmed by Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimeters (DSC), and BET surface area analyses to have successfully and homogeneously incorporated MWCNTs. In addition to the superior properties of MWCNTs modified with the functionalization technique developed within the scope of this study by increasing their specific surface area and porosity, the excellent colloidal stability provided may have various effects in many industrial areas. These advantages enable MWCNTs functionalized with the developed technique to have a wider range of applications in industrial applications and provide more efficient and sustainable solutions.

Graphite and multi-layer graphene from a low molecular weight carbon source

While carbonaceous structures formed by pyrolysis of macromolecular carbon sources with silicates are well described in the literature, information on the structure of carbons obtained in the similar way from low molecular weight (LMW) carbon sources is not sufficient. This study is therefore aimed at characterizing the material obtained by pyrolyzing (1300 °C; Ar atmosphere) montmorillonite containing ∼25-50 wt.% LMW cations as a carbon source. Pyrolyzed samples contained ∼5-20 wt.% carbon, and thermogravimetric and elemental analysis showed a higher yield for a higher original amount of the LMW carbon source. In addition to amorphous carbon, graphite was formed during pyrolysis, as confirmed by X-ray diffraction analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. The presence of graphene-based nanomaterial, specifically multi-layer graphene, was revealed by transmission electron microscopy (TEM). Electrical conductivity of the silicate/carbon material reached ∼35 S·m-1. Raman spectra and TEM images are similar to those from studies describing the use of macromolecular carbon sources. LMW compounds are a sufficient source of carbon for the preparation of electrically conductive materials containing graphite and multi-layer graphene.

Optimal synthetic route for obtaining Co/In layered double hydroxide

Cobalt-indium layered double hydroxides were successfully synthesized via coprecipitation and mechanochemical synthesis with subsequent soft hydrothermal treatment and additional crystallization. The latter method was shown to have advantages over coprecipitation and therefore the mechanochemical route was considered to be optimal for obtaining well-crystallized LDH samples, which do not contain extraneous crystalline phases within the detection limit of X-ray diffraction. The samples were characterized by FTIR spectroscopy, Raman spectroscopy, and transmission electron microscopy. The peroxidase-like activity of the samples was estimated, and the crystal lattice parameters were calculated. The possibility of obtaining cobalt-indium layered double hydroxides with a cationic ratio of Co2+: In3+ = 2 : 1 and 1.5 : 1 was shown. Increasing the aging temperature presumably led to the partial oxidation of cobalt in the samples into trivalent state resulted in the peroxidase-like activity of the samples.

Hydrogen resistance of reduced graphene oxide coatings prepared by electrophoretic deposition on duplex stainless steel

In this study, reduced graphene oxide (rGO) coatings were fabricated on duplex stainless steel (DSS) substrates using the electrophoretic deposition (EPD) method to evaluate their hydrogen resistance performance. The successful fabrication of rGO coatings was confirmed using Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). The structural characteristics were characterized using Raman spectroscopy and X-ray Diffraction (XRD). The results indicate that the EPD voltage is a crucial factor affecting the surface quality of and hydrogen resistance performance of rGO. Lower voltages resulted in lower degrees of rGO reduction and higher surface wrinkle density, while higher voltages caused bubble formation, significantly degrading the coating quality and hydrogen resistance performance. The optimal hydrogen resistance was achieved at an EPD voltage of 7.5V and a deposition time of 6 minutes. Electrochemical hydrogen charging tests and thermal desorption analysis (TDA) demonstrated that rGO coatings prepared under optimal conditions exhibited excellent hydrogen resistance efficiency, significantly reducing hydrogen atom penetration in hydrogen environments. The study further revealed that bubble formation significantly reduces the hydrogen resistance of rGO, which is attributed to increased interlayer spacing and the loss of the “labyrinth effect”.

Influence of the substitution of CaO by SrO on the structure, degradation and in vitro apatite formation of sol–gel derived SiO2–CaO–SrO–P2O5system bioactive glasses

The present study investigates the influence of the substitution of CaO by SrO on the structure, degradation and in vitro apatite formation of sol–gel-derived bioactive glasses with composition of 58SiO2–(38-x)CaO–xSrO–4P2O5, where x varies between 0 and 10 mol.%. The IV-type nitrogen adsorption/desorption isotherms and pore size values (ranging from 5.41 to 12.56 nm) confirmed the mesoporous structure of the synthesized glasses. The detailed structural analysis was carried out by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). As network modifiers, the addition of Ca and Sr oxides disrupted the bonds of bridging oxygens (BOs) and resulted in the formation of non-bridging oxygens (NBOs), where the substitution of Ca with Sr led to an increase in Q1 units and a decrease in Q3 units. The effects of the addition of Sr on sample degradation and apatite formation were assessed using an assay in tris-(hydroxymethyl)-aminomethane and hydrochloric acid (Tris–HCl) and simulated body fluid (SBF). The results demonstrated that the substitution of CaO by SrO in the CaO–SiO2–P2O5 bioglass system altered the glass structure, resulting in reduced sample degradation and delayed apatite formation. This suggests that the incorporation of Sr into bioactive glasses may serve as a promising strategy to regulate the structure, dissolution behavior and apatite formation of silicate-based glasses, particularly concerning their long-term applications within the human body.

Electrochemical Carboxylation: Green Synthesis of Atrolactic Acid Using Boron-Doped Diamond Electrodes

Electrochemical CO2 fixation is vital for sustainability in the chemical industry, yet the selective synthesis of multi-carbon products remains challenging. Organic electrosynthesis offers promise by enabling precise control over reaction conditions and facilitating novel reactivity patterns. One such technique, electrochemical carboxylation, involves coupling CO2 with organic molecules to produce carboxylic acids. Specifically, electro-carboxylation of acetophenone yields atrolactic acid, a valuable precursor for nonsteroidal anti-inflammatory drugs, providing a greener alternative to traditional production methods. This study focuses on the synthesis and characterization of boron-doped diamond (BDD) films using the microwave plasma-assisted chemical vapor deposition (MP-CVD) method and synthesized BDD electrodes were then used for the electrolytic carboxylation of acetophenone. Various analytical techniques, including X-ray diffraction (XRD), Raman spectroscopy, and laser microscopy, etc. were employed to characterize the BDD films. Various BDD films synthesized for different durations were utilized in the electrolytic carboxylation of acetophenone, with the highest yield of atrolactic acid (25%) achieved using a BDD film synthesized over 6 hours. Also, the effect of BDD surface modification i.e. oxygen and hydrogen terminated BDD on the synthesis of atrolactic acid. Additionally, different electrolytes were employed in the synthesis process of atrolactic acid. A comparative study between Pt and BDD electrodes for the electrolytic carboxylation of acetophenone was conducted, and a mechanism for the formation of atrolactic acid was proposed.

Investigation of the chemiluminescence behavior of Ti3C2 MXene quantum dots as a sensing platform for uric acid

The current study explores the application of Ti3C2 MXene quantum dots (MQDs) as a chemiluminescent (CL) probe to determine uric acid (UA) in biological samples. The MQDs sensor was synthesized using ultrasonic-assisted hydrothermal method and characterized through Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, high-resolution transmission electron microscopy, and X-ray diffraction. The presence of MQDs significantly enhances the ultra-weak Fe(II)–S2O82− CL system. Subsequently, quenching of the probe’s CL signal was observed in the presence of UA. Thus, the designed CL sensor offers an excellent analytical capability for determining UA in the 0.15–2.5 µM range, with a limit of detection of 0.093 µM. The method was effectively used to analyze UA in human serum and urine, yielding recovery rates between 94.4 % and 108.3 % with relative standard deviations (RSD) ranging from 1.9 % to 5.9 %.

Ultramarine blue containing paint layers: Further study of the photo-catalytic degradation of binding media

Photo-catalytic degradation of a linseed oil binder by natural ultramarine (Lapis Lazuli or Lazurite) and Sodalite in paint layers was studied. Both pigments degrade the binder under xenon arc exposure, leading to erosion of the binder at the surface, increased roughness, light scattering and desaturation of the color. Both pigments behave similarly to synthetic ultramarine blue studied earlier. The results for Sodalite provide further proof that the zeolitic nature of the aluminosilicate cage causes the catalytic degradation and that the enclathrated polysulfur radical anions S2-. and S3-. trapped inside the cage are not responsible for the catalytic action. Relatively stable synthetic binders are less affected by the presence of synthetic ultramarine blue. The paints were aged in a xenon arc apparatus using a simulated indoor environment (radiation > ca. 320 nm). The samples were analyzed using diffuse reflectance spectroscopy in the UV–vis and short wavelength infrared (SWIR) ranges, Raman spectroscopy, field-emission gun scanning electron microscopy (FEG-SEM) and FTIR.

Nano-priming of Vigna radiata seeds with opuntia stricta-derived γFe2O3Nanoparticles

The experimental investigation aimed to enhance sustainable and biocompatible nano-agriculture by examining the possible effects of biosynthesized nanoparticles (γFe2O3 NPs) on seed growth and growth parameters of Vigna radiata. The outcomes of various characterization procedures such as FTIR, XRD, UV, and Fe-SEM were used to determine the successful generation of γFe2O3 NPs (nanoparticles), which were capped with multiple phytoconstituents contained in the Opuntia stricta extract. γFe2O3 NPs were synthesized, as evidenced by the peak's presence, having a mean crystallite size of 13.9 nm, and were successfully detected using X-ray diffraction (XRD). Crucial Energy Dispersive X-ray Spectroscopy (EDS) testing also yielded unambiguous proof of the element iron's presence. Raman spectroscopy was used to confirm the synthesis of pure maghemite nanoparticles. Wide areas around 350, 500, 670, and 1330 cm-1 values verify the creation of pure maghemite. TGA analysis was performed to check the stability of nanoparticles in which the residual weight was found to be 87.62%. TEM images confirm the spherical shape, and the mean size of the nanoparticles was found to be 12.28 nm. Through a number of tests, the analysis showed that the nanoparticles have a strong antioxidant capacity. This experiment aimed to determine how biogenic γFe2O3 Nanoparticles affected Vigna radiata seed germination. Measurements of shoot and root lengths, seed vigour index, germination rates, mean daily germination, and peak value (PV) were all included of the assessment. There was a total of four distinct γFe2O3 NPs concentrations examined (25, 50, 75, and 100 μg/mL). The penetration of the γFe2O3 NPs affects the germination and growth of the Vigna radiata seeds. When compared to untreated seeds, the germination index values for Vigna radiata seeds that underwent effective treatment with γFe2O3 NPs significantly improved.

Dy3+ ions in fluorophosphate glasses for luminescent white light applications

Abstract In this study, a series of fluorophosphate (FP) glasses, activated with Dy3+ ions and displaying concentration dependence, have been prepared and analysed for their suitability in luminescent white light applications. The melt quenching method was utilized to fabricate a set of FP glasses, doped with Dy3+ ions and possessing the composition of (60 − x) P2O5 + 10MgO + 10ZnO + 10BiF3 + 10KF + xDy2O3, where x ranges from 0.1 to 2.0 mol%. The structural properties of the samples were analysed using x-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FTIR), and Raman spectroscopy while the optical properties of the samples were studied using absorption and emission spectra. The amorphous nature of the FP glasses was confirmed through SEM analysis and XRD profiles. Moreover, the presence of elements in their composition was verified using EDX. The FTIR spectra of the FP glasses exhibited vibration bands consistent with the characteristic phosphate groups, which was further supported by Raman analysis. The absorption spectra were used to calculate oscillator strengths (f exp & f cal) and Judd–Ofelt (JO) parameters Ω λ (λ = 2, 4, 6). The values of Ω λ (λ = 2, 4, 6) followed this order: Ω6 > Ω2 > Ω4. The emission spectra displayed three prominent transitions in the UV–visible region: (4F9/2 → 6H15/2) blue, (4F9/2 → 6H13/2) yellow, and (4F9/2 → 6H11/2) red. The peak at 553 nm (4F9/2 → 6H13/2) was the most intense and dominant. Radiative characteristics were evaluated from the emission spectra through the employment of JO intensity parameters and refractive indices. The Y/B intensity ratio values were greater than 1, indicating the high covalency of Dy3+ ions. The colour coordinates (x, y) and correlated colour temperature values of CIE 1931 were situated in the cool white region. The comprehensive analysis suggests that these glasses have the potential to become highly favourable candidates as luminescent components for solid-state white light emitting instruments.

A concise strategy for enhancing the performance of bio-based polyurethane aerogels using melamine-modified sodium alginate via Aza-Michael addition reaction

Bio-based waterborne polyurethane (PU) has garnered significant attention as a sustainable alternative petroleum-derived counterpart, offering environmentally friendly alternatives. In this work, a new approach is proposed to fabricate two kinds of composite aerogels of lowly/highly melamine-modified sodium alginate (SAML/SAMH) with methacrylate-terminated PU (SAML-PU and SAMH-PU) through dynamic covalent cross-linking via Aza-Michael addition reactions. We aim to improve the poor compatibility of polysaccharide and PU associated with traditional blending methods and impart the resulting aerogels with good biodegradability, compressive strength, thermal insulation, flame-retardant, and self-healing. Comprehensive characterizations, including Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy collectively demonstrate the successful derivatization of alginate and the effective synthesis of the Aza-Michael addition copolymer involving derivate alginate and PU. Substantial improvements in compressive strength and thermal properties are realized at comparable densities. Higher compressive strength, higher decomposition temperature and lower thermal conductivity are significantly achieved for SAML-PU (0.35 MPa, 410 °C and 0.024 W/m/K at 0.13 g/cm3) and SAMH-PU (0.58 MPa, 427 °C and 0.022 W/m/K at 0.12 g/cm3) compared to pristine PU foams (0.15 MPa, 330 °C and 0.031 W/m/K at 0.15 g/cm3). Additionally, molecular simulations of the Aza-Michael addition reaction and finite element simulations of aerogel thermal-insulation properties are conducted to corroborate experimental results. Notably, the dynamic polymers of SAML-PU and SAMH-PU exhibited excellent self-healing, recycling, biodegradability, and flame-retardant attributes. The elucidated preparation methodology and the exceptional performance and versatile applications of sodium alginate-based PU aerogels suggest a promising trajectory for future research endeavors and industrial implementation.

Improving LIBS-based mineral identification with raman imaging and spectral knowledge distillation

Combining data from different sensing modalities has been a promising research topic for building better and more reliable data-driven models. In particular, it is known that multimodal spectral imaging can improve the analytical capabilities of standalone spectroscopy techniques through fusion, hyphenation, or knowledge distillation techniques. In this manuscript, we focus on the latter, exploring how one can increase the performance of a Laser-induced Breakdown Spectroscopy system for mineral classification problems using additional spectral imaging techniques. Specifically, focusing on a scenario where Raman spectroscopy delivers accurate mineral classification performance, we show how to deploy a knowledge distillation pipeline where Raman spectroscopy may act as an autonomous supervisor for LIBS. For a case study concerning a challenging Li-bearing mineral identification of spodumene and petalite, our results demonstrate the advantages of this method in improving the performance of a single-technique system. LIBS trained with labels obtained by Raman presents an enhanced classification performance. Furthermore, leveraging the interpretability of the model deployed, the workflow opens opportunities for the deployment of assisted feature discovery pipelines, which may impact future academic and industrial applications.