Spectroscopic Characterization Research Articles

Synthesis, Characterisation, Single Crystal Structure and Evaluation of a Redox Innocent Carbazate Functionalized Phenanthroline for Antimycobacterial and Anticancer Activity

Development of bioactive candidates for cancer and bacterial infections are ever demanding challenges due to the resistance shown by these cancer and bacterial cells for already exposed drug molecules. Methyl carbazate derivatized phenanthroline compound 6-[2-(methoxycarbonyl)diazen-1-yl]-1,10-phenanthroline-5-one (MCDPO) is synthesized in a three step reaction from 1,10-phenanthroline. The spectroscopic features of MCDPO are studied by HRMS, IR, 1H NMR and 13C NMR, UV-visible spectroscopy. The three-dimensional molecular structure of the MCDPO is confirmed by single crystal XRD study. The MCDPO crystallized in a triclinic system P-1 space group with the following unit cell parameter: a=5.0347(2) Å, b=10.3509(4) Å, c=11.8816(4) Å, α=84.431(3)°, β=84.172(3)°, γ=81.380(4)°, and V=606.92(4) Å3 at T=133 K. The MCDPO is containing aromatic rings, hydrogen bonding donors as well as hydrogen bonding acceptor groups forming supramolecular molecular arrangements through C-H···O, C-H···N, C-O···C, π-π and π···C non-covalent interactions. Electrochemical redox and electrochromic features of MCDPO are studied through cyclic voltammetry and UV-vis based spectroelectrochemistry. This compound shows good anticancer activity with IC50 values 1.438, 6.576 and 2.901 µM against 4T1, MCF-7 and PC-3 cancer cell lines respectively. The flow cytometry study on 4T1 cells suggests that the MCDPO promoted cancer cell death by inducing apoptosis, and cell cycle arrest in the G0/G1 phase. It also induces nuclear fragmentation and reactive oxygen species (ROS) generation, which was studied by DAPI, AO, and DCFH-DA based cellular staining studies by fluorescence confocal imaging. The MCDPO also studied for antibacterial activity against Escherichia Coil bacteria and Mycobacterium tuberculosis (Mtb). The MCDPO shows minimum inhibitory concentration (MIC) of 0.39 µg/mL against Mtb which is slightly better than the one of the clinically used drug candidates Ethambutol.

Mechanisms of Multiple Functional Groups in Post-CMP Cleaning Solutions for Co Interconnects

Cobalt (Co) exhibits low resistivity, excellent adhesive properties, and the ability to fill gaps seamlessly, thus it is promising to change the landscape of integrated circuits in various fields, especially in the areas of interconnections and logic contacts. The cleaning of Co surfaces after chemical mechanical polishing (CMP) is an essential step due to the potential occurrence of numerous defects, such as silicon dioxide nanoparticles, organic residues, and severe corrosion. This research delves into the mechanisms of pivotal components in cleaning solutions, including complexing agents and corrosion inhibitors, and analyzes their impact on cleaning effectiveness. Based on Derjaguin-Landau-Verwey-Overbeek theory calculation and adhesion force measurements through the liquid mode of atomic force microscope, the interaction forces between silica (SiO2) particles and Co substrate were calculated and verified. Additionally, various methods were employed to unravel the nature of the particles and the mechanism of different functional groups, encompassing electrochemical experiments, static etching tests, surface energy studies, zeta potential measurements, and X-ray photoelectron spectroscopy characterization. This comprehensive investigation offers a clear understanding of the roles played by different functional groups, establishes a functional group system for cleaning solutions tailored to Co interconnect wafers, and provides valuable guidance for the subsequent design and development of cleaning solutions.

Polycaprolactone/polylactic acid nanofibers incorporated with butyl hydroxyanisole /HP-β-CD assemblies for improving fruit storage quality.

In this study, the inclusion complex was prepared with butyl hydroxyanisole (BHA) as the functional substance and 2-hydroxypropyl beta-cyclodextrin (HP-β-CD) as the main molecule by ultrasound mediation. The inclusion complex was mixed with polycaprolactone (PCL)/polylactic acid (PLA), and nanofiber films loaded with different concentrations of BHA/HP-β-CD inclusion complex were prepared by electrospinning for fruit preservation. The scanning electron microscopy and infrared spectroscopy characterization results showed that HP-β-CD successfully embedded BHA in the cavity. The encapsulation of BHA increases the fiber diameter and thermal stability and decreases the crystallinity and hydrophobicity. The oxidation resistance experiment showed that the nanofiber film had a strong free radical scavenging ability. The BHA release rate of the nanofiber membrane was determined by high-performance liquid chromatography, and the release curve results showed that the inclusion complex prepared by ultrasonic self-assembly could significantly prolong the BHA release time. In addition, nanofiber films containing inclusion complex showed an effective fresh-keeping effect within 7 days of mango storage. In conclusion, a series of characterization tests show that the nanofiber film prepared in this study has a good market prospect in food preservation.

A novel approach to modified polyethylene fibres with size effect in cement mortar

A novel method for modifying polyethylene fibres (PE) that is simple, efficient, time-saving and cost-effective is proposed in this article. Analytical techniques, including Raman spectroscopy, Fourier infrared spectroscopy and microscopic characterization, are employed to demonstrate that this new method effectively attaches graphene oxide (GO) to the surface of PE fibers. Furthermore, analyses using nanoindentation tests and scanning electron microscopy reveal that the GO on the surface of the modified fibers densifies the hydration structure in the transition zone at the interface between the fibers and the cement matrix. This densification enhances the efficiency of stress transfer from the matrix to the fibers, thereby improving the mechanical strength of the cementitious materials and significantly reducing their size effect.

Synthesis of enzyme-enriched zinc oxide nanoparticles using Lantana camara L. fruit extract for detoxification of phenol and derivatives

In this study, we evaluated the potential of Lantana camara L. (L. camara L.) fruit extract as a biogenic mediator for the synthesis of enzyme-rich zinc oxide nanoparticles (EZnO) aimed at the detoxification of phenol and its derivatives. The protein extraction yielded a maximum concentration in the 80 % cut fraction, with a protein concentration of 0.96 μg/ml. The highest peroxidase enzyme activity was measured at 41 U/min at 80 % cut using a 250 μg protein concentration, while the highest polyphenol oxidase activity of 7.16 μg/ml was observed in the 40 % cut fraction. The synthesis of EZnO nanoparticles was confirmed through a visible color change and UV–visible spectroscopy with a distinctive absorbance peak at 307. 40 nm. X-ray diffraction (XRD) analysis at 2θ angle indicated the crystalline structure of the nanoparticles, with characteristic peaks corresponding to the planes of the ZnO crystal lattice. Fourier-transform infrared spectroscopy (FTIR) characterization revealed the embedding of the peroxidase enzyme within the nanoparticles, evidenced by absorbance peaks at 1708.62 cm−1 corresponding to amide I, 1604.48 cm−1 corresponding to amide II, and 1380 cm−1 corresponding to amide III. Similarly, the presence of polyphenol oxidase was indicated by absorbance peaks at 3185.83 cm−1 and 2981.41 cm−1. Transmission electron microscopy (TEM) analysis showed the nanoparticles exhibited polydispersity with a size range of 10–100 nm, with an agglomerated morphology, suggesting successful enzyme-nanoparticle hybridization. The histogram was constructed based on the counting of nanoparticles with size which showed highest number of nanoparticles were in the range of between 10 and 20 nm. The BET analysis showed a surface area of 225.1 m2/g. The EZnO nanoparticles demonstrated effective detoxification capabilities, achieving 86 % removal of synthetic phenol, 63 % removal of synthetic 2-chlorophenol, and 69 % removal of their mixture within 24 h. These findings highlights the potential of L. camara L. fruit extract and EZnO nanoparticles for application in the detoxification of hazardous pollutants, offering a sustainable and efficient approach to environmental remediation.

A New Proton Transfer Complex Between 3,4-Diaminopyridine Drug and 2,6-Dichloro-4-nitrophenol: Synthesis, Spectroscopic Characterization, DFT Studies, DNA Binding Analysis, and Antitumor Activity.

The proton transfer (PT) complexation reaction between 3,4-diaminopyridine (3,4-DAP), an important drug, and 2,6-dichloro-4-nitrphenole (DCNP) was investigated experimentally and theoretically. The experimental results indicated a chemical reaction occurred because of a hydrogen bonding, followed by proton transfer from the DCNP to the 3,4-DAP in different polar media. The Benesi-Hildebrand equation was used to estimate the formation constant (Kf), molar absorptivity (εPT), and other physical parameters. The formed PT complex was characterized using FTIR, 1H, and 13C NMR spectra. In addition, the nanocrystalline structure, particle sizes, and surface morphology of the complex were investigated by XRD and SEM-EDX. The structure of the 1:1 PT complex was calculated theoretically in the gas phase and the presence of solvent effects. Using TD-DFT calculations, the band observed at 406 nm (Calc. 379.5 nm) and 275 nm (Calc. 272.3 nm) could be assigned to the HOMO→LUMO transition (99%), and HOMO→L+3 transition (87%), respectively. The DNA binding ability of the PT complex was investigated, revealing an intercalative binding mechanism with a binding constant Kb of 4.6 × 104 M-1. Based on the results of the Ct-DNA binding study, the binding free energy of the PT complex with the receptor of human DNA (PDB ID:1BNA) is found to be -7.2 kcal/mol. The cytotoxic effects of the PT complex were evaluated on selected cancer cell lines, demonstrating significant antitumor activity against A-549 and MCF-7 cancer cell lines.

Charge Transfer Interaction Dynamics between 2-Methyl-8-hydroxyquinoline and 2,4-Dinitrophenol: Synthesis, Spectroscopic Characterization, DNA Binding and DFT Studies

A novel charge transfer (CT) complex was formed by combining the electron-acceptor 2,4-dinitrophenol (DNP) with the electron-donor 2-methyl-8-hydroxyquinoline (MHQ). The complex obtained was further characterized using both experimental and theoretical methods. The Benesi-Hildebrand equation can be utilized to determine various spectroscopic physical measurements such as the molar absorptivity (εCT) and formation constant (KCT). The CT complex has a stoichiometry of 1:1. Multiple spectroscopic methods were employed to investigate the resultant solid compound. The existence of charge and proton transfer in the resultant complex was confirmed by FT-IR, 1H NMR, SEM-EDX and powder-XRD studies. An electron absorption spectroscopy examination was done to analyze the complex DNA binding capability. The resulting complex was determined to have an intercalative binding mechanism, with an intrinsic binding constant (Kb) value of 4.2 × 106 M-1. The experimental results were corroborated by performing theoretical calculations using DFT using a CAM-B3LYP/6-31G(d,p) basis set. The geometrical parameters, electrostatic potential maps (MEPs) and Mullikan charges were computed and examined in agreement with the experimental observations. In addition to electron transmission, the stability of the complex is influenced by the presence of a hydrogen bond.

Human prolyl hydroxylase domain 2 reacts with O2 and 2-oxoglutarate to enable formation of inactive Fe(III).2OG.hypoxia-inducible-factor α complexes

Hypoxia inducible transcription factors (HIFs) mediate the hypoxic response in metazoans. When sufficient O2 is present, Fe(II)/2-oxoglutarate (2OG)-dependent oxygenases (human PHD1-3) promote HIFα degradation via prolyl-hydroxylation. We report crystallographic, spectroscopic, and biochemical characterization of stable and inactive PHD2.Fe(III).2OG complexes. Aerobic incubation of PHD2 with Fe(II) and 2OG enables formation of PHD2.Fe(III).2OG complexes which bind HIF1-2α to give inactive PHD2.Fe(III).2OG.HIF1-2α complexes. The Fe(III) oxidation state in the inactive complexes was shown by EPR spectroscopy. L-Ascorbate hinders formation of the PHD2.Fe(III).2OG.(+/-HIFα) complexes and slowly regenerates them to give the catalytically active PHD2.Fe(II).2OG complex. Crystallographic comparison of the PHD2.Fe(III).2OG.HIF2α complex with the analogous anaerobic Fe(II) complex reveals near identical structures. Exposure of the anaerobic PHD2.Fe(II).2OG.HIF2α crystals to O2 enables in crystallo hydroxylation. The resulting PHD2.product structure, manifests conformational changes compared to the substrate structures. The results have implications for the role of the PHDs in hypoxia sensing and open new opportunities for inhibition of the PHDs and other 2OG dependent oxygenases by promoting formation of stable Fe(III) complexes.

Dyeing ability of C. longa L. and T. stans (L.) Juss. Ex Kunth on unmordanted and mordanted silk and cotton fabrics

The work was on the extraction of both the C. longa rhizomes and the petals of T. stans using four different solvents (ethanol, ethyl acetate, water, and n-hexane). The dyeing potential of the C. longa and T. stans extracts was evaluated on cotton and silk fabrics without or with mordants using potash alum, phosphomolybdic acid, iron (II) sulphate, and tartaric acid at varied temperatures and tested for colour fastness properties (wash and light fastness). The pH and absorbance of the dye bath before and after dyeing were studied. However, cotton, which is cellulosic, was better dyed than silk, which is proteinous, which showed a better choice for fabrics dyeing at 80 °C; hence, it had a good colour efficiency. Iron (II) sulphate exhibited complexes in the octahedral configuration of the coordination six with CH2O- of cotton and NH3+ and COO- of silk fabric. In addition, it was also observed that the higher the dyeing temperature, the greater the dyeing intensity. The spectroscopic characterization of the extracts was determined with the help of UV-Vis and FTIR. The UV-Vis and FTIR spectral analyses revealed the chromophore, auxochrome groups, and functional groups, respectively, within the extracts. Curcumin and rutin were identified as being responsible for the dyeing of the fabric.

Rapid detection and spectroscopic feature analysis of mineral content in camel milk using fourier-transform mid-infrared spectroscopy and traditional machine learning algorithms

Camel milk is rich in nutrients and bioactive factors, with mineral content generally higher than that of cow milk, but there is currently no internationally established, rapid, batch-testing method for the mineral content. This study collected samples of camel milk from 113 locations in Xinjiang, China. For the first time internationally, based on the true mineral values determined by ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy) and the extracted mid-infrared spectra data, a quantitative prediction model for 10 key minerals (Ca, Fe, K, Mg, Mn, Na, P, Sr, Zn, and Se) was established using Fourier-Transform Mid-Infrared Spectroscopy (FT-MIRS) and the traditional machine learning algorithm Partial Least Squares Regression. The Rt2 of the test set ranged from 0.61 to 0.91, RMSEt ranged from 2.21ug/kg(Se) to 197.08 mg/kg(K) and the RPDt from 1.59 to 3.28. In addition, the distribution, patterns, and correlations of mineral-related characteristic wavenumbers in camel milk were summarized. This study opens a new avenue for the rapid detection of minerals in camel milk and fills the research gap in in using FT-MIRS to detect mineral content in camel milk.

Synthesis, spectroscopic characterization, and evaluation of the antibacterial activity of 3d transition metal complexes derived from bis(pyrazolyl)methane ligand

Synthesis, spectroscopic characterization, and evaluation of the antibacterial activity of 3d transition metal complexes derived from bis(pyrazolyl)methane ligand

Enhancing Organic Pollutant Degradation Efficiency through a Photocatalysis-Electro-Fenton System via MoS2 Crystal Morphology Regulation.

A photocatalysis-electro-Fenton (PEF) system was constructed via molybdenum disulfide (MoS2) to remove tetracycline (TC) without an external oxidant supply and solution pH adjustment. In the system, original graphite felt (GF) was used as a cathode, from which H2O2 was in situ generated continuously under power. MoS2 was motivated by visible light to facilitate the cycle of Fe2+/Fe3+, enhancing the Fenton process to produce •OH. The experimental results showed that the system can increase the degradation rate of pollutants by more than 5 times. Moreover, the quenching and electron paramagnetic resonance (EPR) tests demonstrated that •OH was the dominant active species. X-ray photoelectron spectroscopy (XPS) characterization, Mo concentration, and cycle experiments proved the excellent catalytic activity and chemical stability of MoS2. It is worth mentioning that the photocatalytic performances of different morphologies of MoS2 (flower, flake, and radar) were compared. As a result, flower-like MoS2 exhibited a much superior photoresponse than flake and radar, which could accelerate the Fe2+/Fe3+ cycle further effectively. These findings highlight the morphology-performance relationship of MoS2 under a PEF system and the mechanisms of contaminant degradation, which is of great significance for developing photoelectric Fenton technology.

N, S-Codoped Carbon Quantum Dots with High Inhibition Efficiency: Implications for Corrosion Mitigation of Carbon Steel in Acidic Environments.

The environmental friendliness, economic feasibility, and high efficiency of carbon quantum dots (CQDs) render them as highly promising candidates for corrosion inhibitors. The present study proposed the fabrication of nitrogen- and sulfur-codoped CQDs via an one-step hydrothermal method using l-cysteine and 4-aminosalicylic acid as precursors. The structure, particle size, and surface ligands of the prepared CQDs were determined through spectroscopy and transmission electron microscopy characterization. Subsequently, the inhibition performance of the CQDs on carbon steel in a 0.5 M sulfuric acid solution was evaluated through weight loss measurement, electrochemical methods, and surface analysis. The CQDs exhibited remarkable inhibition efficiencies of 97.9% at 293 K and 98.9% at 313 K, with a concentration of 150 ppm. In addition, the obtained CQDs demonstrated a combined physisorption and chemisorption adsorption behavior, which complied with the Langmuir adsorption isotherm. These findings provide insight into the inhibition mechanism and highlight the potential of codoped CQDs for corrosion mitigation applications in acidic environments.

Spectroscopic Signature of Metal-hydroxo and Peroxo Species in K-edge X-ray Absorption Spectra.

Metal-dioxygen species are important intermediates formed during dioxygen activations by metalloenzymes in various biological processes, by catalysts in fuel cells, and prior to O2 evolution by photosystem II. In this work, we focus on manganese-porphyrin complexes using tetramesitylporphyrin ligand (TMP) to explore changes in Mn K-edge X-ray absorption spectroscopy (XAS) associated with the formation of Mn-hydroxide and Mn-O2 peroxide species. With limited spectroscopic characterization of these compounds, Mn Kβ X-ray emission spectroscopy (XES), XAS, density functional theory (DFT), and time-dependent DFT (TD-DFT) analysis will enhance our understanding of their complex electronic structure. We show that the shape of the pre-edge in the K-edge Mn X-ray absorption near-edge structure (XANES) can serve as a spectroscopic signature of the MnIII-peroxo formation and thus can be used to track the presence of the side-on peroxide as an intermediate in time-resolved or in situ experiments. Our results will help to further summarize the spectroscopic fingerprints for peroxo and hydroxo species, addressing the challenge of identifying the reactive metal species in catalytic reactions.

Hierarchically Structured Conductive Lanthanide Metal Organic Framework Nanorods for Ultrastable Flexible Magnesium Ion Capacitors

AbstractAqueous multivalent metal ion capacitors are very attractive owing to their high capacitance, low cost, environmental benignity, and safety. Herein, hierarchically structured, conductive lanthanide metal‐organic frameworks (MOFs) assembled by nanorods for ultrastable flexible magnesium ion capacitors (MICs) is designed. Three MOFs, consisting of lanthanide metals (La, Ho, and Yb) and 2,3,6,7,10,11‐hexahydroxytriphenylene (HHTP), are structurally stabilized through the covalent bonds and electronically conductive due to π‐d conjugation. Among 3 MOFs, Ho‐HHTP electrodes in a full‐cell system achieved long‐term cyclic stability with a high capacitance retention of 65.0% after 12 000 cycles and a high Coulombic efficiency of 96.9%. Furthermore, flexible pouch cells are fabricated using Ho‐HHTP as anode, reduced graphene oxide as cathode, and poly(vinyl alcohol) (PVA)/Mg(ClO4)2 as gel electrolyte, demonstrating a low capacitance decay rate of 0.00444% per cycle during 10 000 cycles owing to the hierarchical structure and intrinsic electronic conductivity. As indicated by density functional theory and spectroscopic characterizations, Mg2+ ions are faradaically stored in the catechol part of the ligand, and Mg2+ inserted into the vacant Ho sites contributes to structural stability. Furthermore, operando 2D correlation Raman spectroscopy identified how Mg2+ ions interact with the ligand of Ho‐HHTP and demonstrated the sequential change of peak change.

Synthesis, structural and spectroscopic characterization of defect-rich forsterite as a representative phase of Martian regolith.

Regolith draws intensive research attention because of its importance as the basis for fabricating materials for future human space exploration. Martian regolith is predicted to consist of defect-rich crystal structures due to long-term space weathering. The present report focuses on the structural differences between defect-rich and defect-poor forsterite (Mg2SiO4) - one of the major phases in Martian regolith. In this work, forsterites were synthesized using reverse strike co-precipitation and high-energy ball milling (BM). Subsequent post-processing was also carried out using BM to enhance the defects. The crystal structures of the samples were characterized by X-ray powder diffraction and total scattering using Cu and synchrotron radiation followed by Rietveld refinement and pair distribution function (PDF) analysis, respectively. The structural models were deduced by density functional theory assisted PDF refinements, describing both long-range and short-range order caused by defects. The Raman spectral features of the synthetic forsterites complement the ab initio simulation for an in-depth understanding of the associated structural defects.

Practical guidelines and challenges in the isolation and characterization of microplastics/microfibers by Raman microscopy

We address some challenges usually encountered in the analysis of microplastics (MPs) and microfibers (MFs) using Raman microscopy. Those issues are examined considering that the researchers that carry out the collection and analysis of MP contamination may not have necessarily specialized expertise in Raman microscopy or polymer chemistry. Topics such as effective particle isolation or the use of adequate substrates are approached on the base of the impact they have on the spectroscopic characterization. Issues as the control of background signal, the influence of sample digestion, and the presence of internal interferences such as pigments, dyes, and fillers, are discussed. Spectral features of the polymer families found as MP/MF contaminants are presented based upon polymer structure, properties, and applications. The use of open-source libraries to complement chemical identification is also discussed. Overall, this work aims to enhance the practice and understanding of Raman microscopy for researchers engaged in characterizing MP/MF contaminants.

Synthesis, and spectroscopic characterizations of gold(III) complexes containing nitrogen-heterocycle based pyridine derivatives as a biomolecular chelates

Three gold(III) nanostructured complexes of nicotinamide (nta), picolinic acid (pica), and isonicotinic acid (inta) were synthesized by the reacted of AuCl3 salt with nta, pica, and inta with 1:2 stoichiometry in the alcoholic medium. The solid products obtained were formulated by comparing experimental and calculated data for microanalytical (C, H, N) and metal. Both produce 1:2 compounds with metal ions. The prepared complexes were characterized by different physico-spectroscopic techniques. The FTIR, and 1H NMR spectral analysis, morphological analysis (scanning electron microscopy SEM, transmittance TEM, and X-ray powder diffraction XRD) of these complexes have been discussed. The conductive behavior of the complexes indicates that all of them behave as electrolytic behavior. The mononuclear gold(III) complexes have formulated as [Au(nta)2(Cl)2].Cl, [Au(pica)2].Cl and [Au(inta)2].Cl. The shifts of the ν(N–H) amino, ν(C=N) pyridine, and ν(C=O) carboxylic stretches have been monitored to find out the donor sites of the ligands. According to the experimental data, the three complexes can be characterized in the solid state as mononuclear, with a four-coordinate stereochemistry. KEY WORDS: Gold complex, Nicotinamide, Picolinic acid, Isonicotinic acid, Nanostructure, Spectroscopic Bull. Chem. Soc. Ethiop. 2025, 39(1), 111-121. DOI: https://dx.doi.org/10.4314/bcse.v39i1.9

Direct Spectroscopic Confirmation of the Oxygen‐Centered Diradical Character of the Tetraoxidorhenium(VII) Cation [Re(O)4]+

AbstractMononuclear inorganic diradical species are scarce. Here, we confirm, via X‐ray absorption spectroscopy in the gas phase combined with computational studies, the oxygen‐centered diradical character of the tetraoxidorhenium(VII) cation. A dioxido‐superoxido isomer, close in energy to the diradical, is also found, where rhenium appears in its rare oxidation state of +6. Addition of one or two hydrogen atoms to [Re,O4]+ forms hydroxido ligands, and strongly disfavors isomers with any oxygen‐oxygen bond. This adds spectroscopic characterization of the rhenium oxidation state and the nature of ligands to the known ability of [Re,O4]+ to perform two consecutive hydrogen‐atom abstraction reactions from methane, and demonstrates that pentaatomic [Re,O4]+ combines a metal center in its highest oxidation state with two oxygen‐centered radical ligands in a highly reactive species.

A single dielectric nanoparticle for refractive index sensing

Abstract Refractive index sensing has great application potential in a wide range of chemical and biomedical fields, however, these sensors usually require large-area and fabrication-intense arrays of unit cells. Here, we propose an ultracompact sensor based on a single dielectric nanoparticle for refractive index sensing with a footprint smaller than 2 µm^2 and numerically investigate its sensing performance. A single-mode resonance rather than multimodes interaction is adopted for the spectroscopic feature of refractometric sensing. The elaborate resonator geometry facilitates the excitation of the gapped-vortex mode and enables the exposure of electric hotspots outside the dielectric. Such design enhances the coupling to the sensing medium, thus exhibiting high sensitivity at the level of 345 nm/RIU with a figure of merit of 12.78 per RIU. The single-particle nanostructure together with the single-mode resonance exhibits robust sensing performance to dimension deviations. Importantly, a thin annular beam is employed as the illumination to increase the excitation efficiency of the single-mode resonance, which significantly improves the modulation depth without relying on the near-field coupling of array nanostructures. This work provides a miniaturization platform for the dielectric sensors and other application fields based on enhanced light-matter interaction.