Structural Characterization Research Articles

Novel azo- and bisazo-5-pyrazolone dyes and their application as a colorimetric chemosensor for naked eye recognition of Cu2+

In this study, novel azo- and bisazo-5-pyrazolones (1/2a, b, and 1/2c, d, respectively) were synthesized. The structures of the new compounds were characterized using FTIR, UV–Vis., 1H NMR, 13C NMR-APT, and HRMS spectroscopic methods. 1H-NMR study revealed that the compounds are in hydrazone- form in solution. Among fourteen metal nitrate salts, the azo-5-pyrazolones showed a colorimetric response only to the Cu2+ ion, whereas the new bisazo-5-pyrazolones did not cause a specific color change to only one cation. The produced ligand changed from orangey-yellow to very light yellow, making it possible to identify Cu2+ without the need for spectroscopic equipment. Compound 1b [4-((2,4-dimethylphenyl)diazenyl)-2-(naphthalene-1-yl)-5-phenyl-2,4-dihydro-3H-pyrazole-3-one)] was taken as a representative example of the new azo-5-pyrazolones for the chemosensor research. The Cu(1b)2 complex was also synthesized and characterized. The binding ratio between the 1b sensor and Cu2+ was found to be 2:1 (ligand:metal) from the structural characterization of Cu(1b)2 and using Job's plot method. The pH study showed that even if the pH changes, the Cu2+ ion can still bind to the 1b receptor. In the reversibility experiment, when EDTA was added to the (1b+Cu2+) solution, the spectrum returned to the 1b spectrum. The interference study showed the selectivity of 1b with Cu2+ even in the presence of other cations. A study of the detection limit (LOD) revealed considerable sensitivity towards Cu2+metal cation using absorption titration method and LOD value was found to be 4.31 μM. The association constant (Ka) of (1b+Cu2+) was determined to be 0.79×105M−1 using the Benesi-Hildebrand plot.

Effect of low-frequency ultrasound-assisted acid extraction on gel properties and structural characterization of sheep's hoof gelatin

In this study, we investigated the effects of various low-frequency ultrasound-assisted extraction processes, including ultrasound-assisted acid-soaked water bath extraction (UAW), ultrasound-assisted water bath extraction after acid soaking (AUW), acid-soaked water bath extraction followed by ultrasonics (AWU), and acid-soaked water bath extraction without ultrasound (CON), on the structural properties, thermal stability, gel properties, and microstructure of sheep's hoof gelatin. The results revealed that the primary components of sheep's hoof gelatin consisted of α1-chain, α2-chain (100–135 kDa), and β-chain. In addition, it was observed that among the three sonication groups, sheep's hoof gelatin extracted in the AUW group exhibited the highest yield (27.16 ± 0.41 %), the best gel strength (378.55 ± 7.34 g), and higher viscosity at the same shear rate. The gelling temperature (25.38 ± 0.45 °C) and melting temperature (32.28 ± 0.52 °C) of sheep's hoof gelatin in the AUW group were significantly higher than those in the other groups (p > 0.05). Moreover, our experiments revealed that the sequence of low-frequency ultrasonic pretreatment processes was a crucial factor influencing the gel properties and structural characteristics of sheep's hoof gelatin. Specifically, the acid treatment followed by the ultrasound-assisted approach in the AUW group yielded high-quality and high-yield sheep's hoof gelatin.

Structural and functional characterization of retinal impairment in T1DM patients without diabetic retinopathy: a 3-year longitudinal study.

To analyze the progression of structural and functional retinal impairment in type 1 diabetes mellitus (T1DM) patients with no clinical signs of diabetic retinopathy (DR) during a 3-year follow-up. This was an observational longitudinal study. Post-pediatric T1DM patients without clinical signs of DR, and sex- and age-matched healthy subjects were recruited at San Raffaele Hospital (Milan, Italy). Each patient underwent a comprehensive ophthalmological evaluation, including optical coherence tomography (OCT), OCT-angiography (OCT-A), retinal static and dynamic vessel analysis (DVA), and microperimetry. 21 eyes of 21 T1DM patients (10 females; 24 ± 2years old), and 21 age and sex-matched healthy subjects were enrolled. At baseline, T1DM eyes revealed a significantly decreased vessel length density using OCT-A (p < 0.001 and p = 0.046 in 3 × 3 and 6 × 6mm images) and a significantly increased vessel density index (p = 0.013 and p = 0.087 in 3 × 3 and 6 × 6mm images) of deep capillary plexus. DVA detected a significantly decreased vessel response to flicker light (p = 0.002). A significantly increased thickness of ganglion cellular layer 6-mm-diameter subfields in inferior and superior quadrants was found in diabetic patients (p < 0.001 in both subfields). At 3-years-follow-up no significant longitudinal changes were disclosed in all analyses. Concomitant subclinical microvascular and neurodegenerative damages could be early signs of DR onset that precede functional alterations and clinical signs of DR development. These alterations demonstrated a stable trend over time.

Experimental and Computational Study Toward Identifying Active Sites of Supported SnOx Nanoparticles for Electrochemical CO2 Reduction Using Machine-Learned Interatomic Potentials.

SnOx has received great attention as an electrocatalyst for CO2 reduction reaction (CO2RR), however; it still suffers from low activity. Moreover, the atomic-level SnOx structure and the nature of the active sites are still ambiguous due to the dynamism of surface structure and difficulty in structure characterization under electrochemical conditions. Herein, CO2RR performance is enhanced by supporting SnO2 nanoparticles on two common supports, vulcan carbon and TiO2. Then, electrolysis of CO2 at various temperatures in a neutral electrolyte reveals that the application window for this catalyst is between 12 and 30°C. Furthermore, this study introduces a machine learning interatomic potential method for the atomistic simulation to investigate SnO2 reduction and establish a correlation between SnOx structures and their CO2RR performance. In addition, selectivity is analyzed computationally with density functional theory simulations to identify the key differences between the binding energies of *H and *CO2 -, where both are correlated with the presence of oxygen on the nanoparticle surface. This study offers in-depth insights into the rational design and application of SnOx-based electrocatalysts for CO2RR.

Preparation of Calcium-Binding Peptides Derived from Mackerel (Scomber japonicus) Protein and Structural Characterization and Stability Analysis of Its Calcium Complexes.

The purpose of this study was to prepare mackerel peptides (MPs) with calcium-binding capacity through an enzyme method and to investigate the potential role they play in improving the bioavailability of calcium in vitro. The calcium-binding capacity, degree of hydrolysis (DH), molecular weight (MW), and charge distribution changes with the enzymolysis time of MPs were measured. The structural characterization of mackerel peptide-calcium (MP-calcium) complexes was performed using spectroscopy and morphology analysis. The results showed that the maximum calcium-binding capacity of the obtained MPs was 120.95 mg/g when alcalase was used for 3 h, with a DH of 15.45%. Moreover, with an increase in hydrolysis time, the MW of the MPs decreased, and the negative charge increased. The carboxyl and amino groups in aspartic (Asp) and glutamate (Glu) of the MPs may act as calcium-binding sites, which are further assembled into compact nanoscale spherical complexes with calcium ions through intermolecular interactions. Furthermore, even under the influence of oxalic acid, MP-calcium complexes maintained a certain solubility. This study provides a basis for developing new calcium supplements and efficiently utilizing the mackerel protein resource.

Application of MALDI-MS for characterization of fucoidan hydrolysates and screening of endo-fucoidanase activity

Brown macroalgae synthesize large amounts of fucoidans, sulfated fucose-containing polysaccharides, in the ocean. Fucoidans are of importance for their recently discovered contribution to marine carbon dioxide sequestration and due to their potential applications in biotechnology and biomedicine. However, fucoidans have high intra- and intermolecular diversity that challenges assignment of structure to biological function and the development of applications. Fucoidan-active enzymes may be used to simplify this diversity by producing defined oligosaccharides more applicable for structural refinement, characterization, and structure to function assignment for example via bioassays. In this study, we combined MALDI mass spectrometry with biocatalysis to show that the endo-fucoidanases P5AFcnA and Wv323 can produce defined oligosaccharide structures directly from unrefined macroalgal biomass. P5AFcnA released oligosaccharides from seven commercial fucoidan extracts in addition to unrefined biomass of three macroalgae species indicating a broadly applicable approach reproducible across 10 species. Both MALDI-TOF/TOF and AP-MALDI-Orbitrap systems were used, demonstrating that the approach is not instrument-specific and exploiting their combined high-throughput and high-resolution capabilities. Overall, the combination of MALDI-MS and endo-fucoidanase assays offers high-throughput evaluation of fucoidan samples and also enables extraction of defined oligosaccharides of known structure from unrefined seaweed biomass.

Unveiling aqueous lithium-ion batteries via advanced modelling and characterisation: A review

Aqueous lithium-ion batteries (ALIBs) are promising candidates for sustainable energy storage, offering great advantages in safety, cost, and environmental impact over the conventional nonaqueous LIBs. This paper delves into the forefront of ALIB research in electrolyte formulations, electrode materials, and design strategies of ALIBs that have stemmed from the integration of advanced modelling and characterisation techniques. A detailed examination of multiscale modelling approaches, e.g., density functional theory (DFT), molecular dynamics (MD), microscopic and spectroscopic techniques, e.g., X-ray, Raman, and particularly in situ and in operando methods that provide real-time observations of battery processes, is carried out. We note that the synergy between modelling and characterisation techniques have offered unprecedented insights into the fundamental processes governing ALIB performance, however, more methods that have been demonstrated effective in commercial LIBs, can be employed and contribute to resolving the current bottlenecks of ALIBs. The models at mesoscale, continuum-scale and even larger scales can supplement DFT and MD to investigate the electrochemical processes in electrode-electrolyte interface, bulk electrolyte, porous electrodes, and prototype cells, and cooperate with essential measurements to characterise physicochemical properties of aqueous electrolytes, which are not widely discussed. Other microscopic, structural, and multi-physical characterisations, such as scanning transmission electron microscopy, computed tomography, thermography, and acoustic techniques can provide more insights into lithium intercalation, phase change and degradation, inspiring the theory and model development of ALIBs. By amalgamating the current state-of-the-art and existing challenges, this paper paves the way for future prospects in ALIBs.

Structural, optical and morphological characterization of Zinc Selenide Nanoparticles synthesized by Solvothermal method

Zinc Selenide nanoparticles were synthesized via solvothermal method using zinc chloride and selenium powder. X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Ultraviolet – Visible spectroscopy and Photoluminescence Spectroscopy were used to analyze the sample. XRD confirmed the cubic zinc blende phase and the mean size of the particle was determined using Scherrer formula was 65nm. SEM image revealed the spherical shape of the particles. Photoluminescence spectra with excitation wavelength (325nm) show a weak emission peak at 555nm. Key Words: ZnSe ,SEM, UV – Vis, XRD

A postsynthetically modified MOF-808 as a fluorescent sensor for the detection of nitrofurazone antibiotic

The excessive use of nitrofuran drugs in human healthcare as well as in animal husbandry are a major threat to both the environment and human health. As a result, there is an urgent requirement for extensive research to develop materials that can efficiently detect these residual pollutants. However, developing sensor materials with high sensitivity, selectivity, and recyclability is still a challenging task. Herein, we design and synthesize a stable photoluminescent metal–organic framework (MOFs) named MOF-808-AAA, where we have first time integrated a fluorescent organic molecule, 3-anthracen-9-yl-acrylic acid (AAA), via solvent-assisted ligand exchange (SALE) method. Comprehensive structural characterization employing various techniques including PXRD, FT-IR spectra, N2 adsorption, 1H NMR, UV–Vis, and fluorescence spectra, confirmed the successful integration of AAA into the MOF-808 framework. The synthesized MOF-808-AAA demonstrates remarkable luminescence properties and exhibits quick sensitivity towards nitrofurazone (NFZ) with quenching constant (Ksv) of 2.98 × 104 M−1 and low detection limit of 0.51 µM in acetonitrile medium, demonstrating the efficacy of MOF-808-AAA as a promising fluorescent chemical sensor for NFZ detection. In addition, we have proposed a plausible turn off sensing mechanism based on photophysical and electrochemical studies.

Photovoltaic Cell Prepared from Nanoparticles of CdS/CdTe on ITO Substrate and its Characterization

CdS/CdTe based photovoltaic cell has shown the markable efficiency. The CdS/CdTe nanoparticles are being synthesized and deposited on the ITO glass plate. ITO glass has a large bandgap of about approximately 3.6 eV and is suitable to use in the fabrication of photovoltaic cell. As ITO behaves as negative terminal, it is used as front layer for capturing the light intensity. During fabrication of photovoltaic cell, the deposition of Cadmium sulphide and Cadmium telluride nanoparticles layer was done by brush painting technique. The CdS layer is used as window layer and CdTe acts as absorbing layer. The window layer’s primary function is to absorb light particularly in the visible region of the spectrum to generate electricity. The CdS layer forms p-n junction with the CdTe layer. The nanoparticles of CdS and CdTe have been synthesized first and optical characterization was carried out using UV-visible spectroscopy to obtain bandgap of CdTe and CdS. Structural characterization was being obtained by XRD. The size of the nanocrystallites of CdS and CdTe have been obtained by Debye Scherrer equation and the result was 1.64 nm and 4.09 nm respectively. The CdTe layer which was used as absorbing layer consists of high optical absorption coefficient with high mobility, good carrier lifetime and an enhanced properties of crystallographic. Silver paste was used as a back contact for good conduction.

Crystal Structures, Molecular Docking and In Vitro Investigations of Two 4-Substituted 2-(5,5-dimethyl-3-styrylcyclohex-2-enylidene)malononitrile Derivatives as Potential Topoisomerase II Inhibitors

Type II topoisomerases (TOP2s) play a key role in altering the DNA topology by transiently cleaving both strands of a DNA duplex. Therefore, increased TOP2 activity is associated with many cancers. Herein, we present the synthesis, structural characterization, virtual screening, and structural exploration, as well as evaluation of the antiproliferative effects of two new 4-substituted 2-(5,5-dimethyl-3-styrylcyclohex-2-enylidene)malononitrile derivatives with potential application in the drug design of isoform-specific TOP2 inhibitors. Both compounds 1 and 2 were verified by ESI-TOF-MS, NMR, and single-crystal X-ray diffraction (SCXRD) analysis. Furthermore, we applied our recently proposed SCXRD/HYdrogen DEsolvation (HYDE) technology platform in order to perform molecular modeling, virtual screening, and structural exploration with 1 and 2. For this purpose, we used the crystal structure of human TOP2β complexed to DNA and the anticancer drug etoposide. Moreover, we further evaluated the antiproliferative activity of 1 and 2 on human hepatocarcinoma HepG2 cells and compared the observed effects with those of the reference hTOP2β inhibitor etoposide. Based on the obtained results, compounds 1 and 2 showed a virtually higher binding affinity (Ki HYDE values) over etoposide towards hTOP2β but lower antiproliferative activity compared to those of etoposide.

Uncovering the potential of industrial waste: turning discarded resources into sustainable advanced materials

To identify solutions for utilizing industrial wastes (slag, sludge, fly ash, and bottom ash) in the development of pro-environmental systems, this paper reviews existing literature and explores material characterization methods. A review analysis was conducted to uncover their potential, and it was found that many utilizations can be made to recycle them into sustainable materials. Structure characterization, optical-dielectric function, and morphology analysis were analyzed to confirm the recent review. Structural properties are represented by crystallite size and crystallinity, where nickel slag shows the smallest distribution (55 ± 10) nm with the highest crystallinity (25.42%), indicating its association with uniformity of response to external disturbances and micro-structural stability. From the analysis of optical and dielectric functions via Kramers Kronig relation, the widening of ∆(LO−TO) was shown by fly ash and slag indicating stable bonding suitable as x-ray shielding and sensor, while high electron loss functions were shown by sludge and bottom ash indicating high potential electronic transition performance. Based on their chemical and physical properties, these industrial wastes are not limited as construction materials and can even be upgraded to more advanced development materials.

17-β-Estradiol—β-Cyclodextrin complex as an aqueous solution: Structural and physicochemical characterization supported by MM and QM calculations

17-β-estradiol (EST) is an Active Pharmaceutical Ingredient characterized by a low water solubility. Complexation with β-cyclodextrin (βCD) enhances its bioavailability, hence such complex is an interesting research object from pharmaceutical point of view. However, basic facts like description of complex's structure and definition of its molar ratio, were debatable already for decades. This work for the first time justifies the EST:βCD molar ratio as 1:2 using the HRMS (high-resolution mass spectrometry) and phase solubility studies. The latter are used to define complex stability constant, as well. The structure and stability is analyzed using a variety of computational approaches: Quantum Mechanics (QM) based methods (DFT, semiempirical approaches) and MD/MMGBSA approach. In case of the QM, for the first time in the computational analysis of cyclodextrin complexes, a thorough benchmarking test is presented. Different computational parameters (solvent model, presence/absence of dispersion correction etc.) are used. Obtained results are compared with the experimental data.

Unlocking Giant Third-Order Optical Nonlinearity in (MA)2CuX4 through Introducing Jahn-Teller Distortion.

Nonlinear absorption coefficient and modulation depth stand as pivotal properties of nonlinear optical (NLO) materials, while the existing NLO materials exhibit limitations such as low nonlinear absorption coefficients and/or small modulation depths, thereby severely impeding their practical application. Here we unveil that introducing Jahn-Teller distortion in a Mott-Hubbard system, (MA)2CuX4 (MA = methylammonium; X = Cl, Br) affords the simultaneous attainment of a giant nonlinear absorption coefficient and substantial modulation depth. The optimized compound, (MA)2CuCl4, demonstrates a nonlinear absorption coefficient of (1.5 ± 0.08) × 105 cm GW-1, a modulation depth of 60%, and a relatively low optical limiting threshold of 1.22 × 10-5 J cm-2. These outstanding attributes surpass those of most reported NLO materials. Our investigation reveals that a more pronounced distortion of the [CuX6]4- octahedron emerges as a crucial factor in augmenting optical nonlinearity. Mechanism study involving structural and spectral characterization along with theoretical calculations indicates a correlation between the compelling performance and the Mott-Hubbard band structure of the materials, coupled with the Jahn-Teller distortion-induced d-d transition. This study not only introduces a promising category of high-performance NLO materials but also provides novel insights into enhancing the performance of such materials.

Synthesis and characterization of low-dimensional N-heterocyclic carbene lattices.

The covalent interaction of N-heterocyclic carbenes (NHCs) with transition metal atoms gives rise to distinctive frontier molecular orbitals (FMOs). These emergent electronic states have spurred the widespread adoption of NHC ligands in chemical catalysis and functional materials. Although formation of carbene-metal complexes in self-assembled monolayers on surfaces has been explored, design and electronic structure characterization of extended low-dimensional NHC-metal lattices remains elusive. Here we demonstrate a modular approach to engineering one-dimensional (1D) metal-organic chains and two-dimensional (2D) Kagome lattices using the FMOs of NHC-Au-NHC junctions to create low-dimensional molecular networks exhibiting intrinsic metallicity. Scanning tunneling spectroscopy and first-principles density functional theory reveal the contribution of C-Au-C π-bonding states to dispersive bands that imbue 1D- and 2D-NHC lattices with exceptionally small work functions.

Electronic-grade epitaxial (111) KTaO3 heterostructures.

KTaO3 heterostructures have recently attracted attention as model systems to study the interplay of quantum paraelectricity, spin-orbit coupling, and superconductivity. However, the high and low vapor pressures of potassium and tantalum present processing challenges to creating heterostructure interfaces clean enough to reveal the intrinsic quantum properties. Here, we report superconducting heterostructures based on high-quality epitaxial (111) KTaO3 thin films using an adsorption-controlled hybrid PLD to overcome the vapor pressure mismatch. Electrical and structural characterizations reveal that the higher-quality heterostructure interface between amorphous LaAlO3 and KTaO3 thin films supports a two-dimensional electron gas with substantially higher electron mobility, superconducting transition temperature, and critical current density than that in bulk single-crystal KTaO3-based heterostructures. Our hybrid approach may enable epitaxial growth of other alkali metal-based oxides that lie beyond the capabilities of conventional methods.

Bisgermylene-Stabilized Stannylone: Catalytic Reduction of Nitrous Oxide and Nitro Compounds via Element-Ligand Cooperativity.

This study describes the synthesis, structural characterization, and catalytic application of a bis(germylene)-stabilized stannylone (2). The reduction of digermylated stannylene (1) with 2.2 equiv of potassium graphite (KC8) leads to the formation of stannylone 2 as a green solid in 78% yield. Computational studies showed that stannylone 2 possesses a formal Sn(0) center and a delocalized 3-c-2-e π-bond in the Ge2Sn core, which arises from back-donation of the p-type lone pair electrons on the Sn atom to the vacant orbitals of the Ge atoms. Stannylone 2 can serve as an efficient precatalyst for the selective reduction of nitrous oxide (N2O) and nitroarenes (ArNO2) with the formation of dinitrogen (N2) and hydrazines (ArNH-NHAr), respectively. Exposure of 2 with N2O (1 atm) resulted in the insertion of two oxygen atoms into the Ge-Ge and Ge-Sn bonds, yielding the germyl(oxyl)stannylene (3). Moreover, the stoichiometric reaction of 2 with 1-chloro-4-nitrobenzene afforded an amido(oxyl)stannylene (4) through the complete scission of the N-O bonds of the nitroarene. Stannylenes 3 and 4 serve as catalytically active species for the catalytic reduction of nitrous oxide and nitroarenes, respectively. Mechanistic studies reveal that the cooperation of the low-valent Ge and Sn centers allows for multiple electron transfers to cleave the N-O bonds of N2O and ArNO2. This approach presents a new strategy for catalyzing the deoxygenation of N2O and ArNO2 using a zerovalent tin compound.

Synthesis, structural characterization and biological applications of mono- and binuclear Cu(II) and Ni(II) complexes with N2O2 Schiff bases

The present work aims to synthesize and characterize new Schiff base metal complexes (Cu(II) and Ni(II)) derived from 4,5-Dichloro-o-phenylenediamine and 3,5-Dichloro-2-hydroxyacetophenone. The synthesized Schiff base and their complexes have been characterized with the support of more than a few standard physicochemical techniques such as elemental analysis, spectroscopic, thermal, and cyclic voltammetry studies. Further the molecular structures are ascertained by computational methods like density functional theory (DFT) methods. The newly synthesized Schiff base ligand acts as ONNO donor tetradentate chelate and coordinated through an azomethine nitrogen and phenoxo oxygen atom to the Cu(II) and Ni(II). Moreover, all the newly prepared compounds exhibit moderate biological activity such as antibacterial. The synthesized compounds were screened for their antibacterial by the disc agar diffusion method. Spectral analysis exhibits square planar geometry for Cu(II) & Ni(II) mono and binuclear complexes. The antimicrobial results indicate that the homo binuclear copper (II) complex was more active than the other mono and binuclear complexes. The theoretical DFT calculations were applied to verify the molecular geometry of chelators and their complexes. The DFT optimized geometries of the complexes are in agreement with experimental observations.

Synthesis, structural characterization, in vitro biological activity, and DFT calculations of Cu(II) complex

Using a diazonium combination of aniline and 1,3‐diphenylpropane‐1,3‐dione, the Japp‐Klingemann reaction yielded the 1,3‐diphenyl‐2‐(2‐phenylhydrazono)propane‐1,3‐dione ligand (HL). The copper (II) complex has been made using copper (II) acetate salt. The geometry of HL and its Cu (II) chelate were described through CHN analyses, FTIR, UV–Visible, XRD, TGA, and magnetic susceptibility tests. According to the spectral data, the ligand exhibits monobasic bidentate behavior by connecting through the N atom of hydrazone moiety (=N − NH−) by deprotonating beside the oxygen atom of the carbonyl (C=O) group forming octahedral geometry. Density functional theory (DFT) calculations were done by molecular studio software to examine the optimal geometry of HL and its complexity. MCF‐7 and HepG‐2 cell lines demonstrated anticancer action in response to the HL and its copper (II) complex. Additionally, inhibition zone diameter was used to assess the in vitro antibacterial action of HL and particular complex toward Gram +ve bacteria Staphylococcus aureus and Gram‐ve bacteria Escherichia coli (E. coli). Both viscosity and absorption spectra of Calf‐thymus DNA binding experimentations were used to examine the compounds.

Raman Spectroscopy for the characterization of the macromolecular structure of Highveld coals (South Africa)

Industrial applications of coal rely on understanding its macromolecular structure, which is primarily controlled by coal type and rank. The present study assessed five (5) samples from different collieries extracting coal from the No. 4 Seam of the Highveld Coalfield and their float products, produced at relative densities (RD) of 1.7 and 1.9 g/cm3. The aim was to assess changes in maceral composition and coal quality following the density fractionation, and to use Raman Spectroscopy to compare differences in macromolecular structures between the parent samples and the float products. Raman parameters were also determined for specific macerals, i.e., semifusinite and collotelinite. Mean random vitrinite reflectance (%RoV) values for the studied coals range between 0.57 and 0.60% (medium rank D/C bituminous) and the parent coals are inertinite-rich (70.3 to 88.7 vol% mmf), enriched in semifusinite and inertodetrinite. Following density fractionation, reactive macerals (a combination of liptinite, vitrinite, and reactive semifusinite) are enriched in the float products (designated by “F”), specifically in the products obtained at the 1.7 RD. In comparison, the proportion of inert macerals is higher in the F1.9 samples. These differences in maceral composition are reflected in the Raman spectra and parameters. Although the G and D1 bands for the parent coals and F1.9 samples are similar, these bands are narrower than for the F1.7 samples, indicative of greater aromaticity. The G FWHM values for the F1.9 samples are comparable to those for the parent coal samples, and lower than for the F1.7 samples. This reflects larger differences in maceral composition between the parent coals and the F1.7 samples. In contrast, the D1 FWHM values for the float products, particularly the F1.7 samples, are slightly higher than the parent coals, reflecting a disordered aromatic character mainly related to the presence of aliphatic chains. The Raman spectra for the F1.7 samples are more like that for collotelinite. In contrast, the Raman spectra and parameters (G and D1 FWHM) for the F1.9 samples are more comparable to semifusinite. Thus, the increased aliphaticity for the F1.7 samples is attributed to the relative enrichment of reactive macerals, whereas higher aromaticity for the F1.9 samples reflects a larger proportion of inert macerals. Raman spectroscopy expanded on the petrographic data by interrogating the macromolecular structure of the isorank Highveld coals and their float products. This may assist in predicting the behaviour of the coals during industrial applications (i.e., liquefaction, gasification, combustion, and carbon fibre production).