Raman Experiments Research Articles

High-Performance Ir1/CeO2 Single-Atom Catalyst for the Oxidation of Toluene.

The elimination of toluene is an obligatory target with increasing VOC emission in recent years. This study successfully prepared a single-atom Ir catalyst (Ir1/CeO2) by a simple incipient wetness impregnation method, confirmed by in situ CO DRIFTS and AC-HAADF-STEM. Compared to the cluster Ir catalyst (Ir/CeO2-C), Ir1/CeO2 exhibited excellent catalytic performance, stability, and water resistance for the oxidation of toluene. By Raman, H2-TPR, O2-TPD, and XPS experiments, abundant oxygen defects and a unique Ir3+-Ov-Ce3+ structure were formed for the Ir1/CeO2 sample because it had a lower oxygen vacancy formation energy. Furthermore, the DFT results revealed that the Ir1/CeO2 sample had a lower ring-opening energy barrier and adsorption energy of the ring-opening products, which was the rate-determining step for the oxidation of toluene. This work provides instructive insights into the construction of Ir/CeO2 catalysts for the highly efficient removal of VOCs.

Phonon Pseudoangular Momentum in α-MoO3.

In recent studies, it has been discovered that phonons can carry angular momentum, leading to a series of investigations into systems with three-fold rotation symmetry. However, for systems with two-fold screw rotational symmetry, such as α-MoO3, there has been no relevant discussion. In this paper, we investigated the pseudoangular momentum of phonons in crystals with two-fold screw rotational symmetry. Taking α-MoO3 as an example, we explain the selection rules in circularly polarized Raman experiments resulting from pseudoangular momentum conservation, providing important guidance for experiments. This study of pseudoangular momentum in α-MoO3 opens up a new degree of freedom for its potential applications, expanding into new application domains.

Tailoring crystalline Mn5O8 nanostructures: Kinetic control and stabilization for enhanced electrocatalytic O2 evolution

The stabilization of manganese oxide nanostructures with tunable oxidation states and morphologies is crucial for regulating catalytic properties. In this study, we aim to stabilize the metastable monoclinic Mn5O8 phase and control the morphology of the Mn5O8 nanostructures using a hydrothermal assisted calcination process in the presence of different precipitating agents. Raman experiments confirmed that the interaction of aqueous Mn2+ salts with different precipitating agents such as NaOH, ammonia, and oleylamine, resulted in the formation of Mn5O8. On the other hand, the precipitation of Mn2+ salt using diammonium oxalate monohydrate as a precipitating agent led to complete oxidation forming Mn2O3. Detailed phase and microstructural analyses were conducted using PXRD, XPS, and FESEM. The analyses revealed the formation of the monoclinic Mn5O8 phase with various morphologies, including hexagonal nanoplates, nanorods, and random nanoplates, when using NaOH, ammonia, and oleylamine as precipitating agents. The synthesized Mn5O8 phase was deposited onto an iron sheet as a substrate. Furthermore, we demonstrated the effect of the structure, morphology, and size of the Mn5O8 material on O2 evolution activity. The catalytic performance of irregularly shaped Mn5O8 nanoplates showed significantly lower η10 (270 mV) and η50 (350 mV) compared to Mn5O8 hexagonal nanoplates, Mn5O8 nanorods, and Mn2O3 nanostructure. Additionally, an insight into the catalytic performance was investigated in detail by evaluating electrochemical active sites, impedance spectroscopy, and hydrophilicity/hydrophobicity of the Mn5O8 material.

Ir metal nanoparticles and IrO2 for acidic oxygen evolution reaction: Insight from Raman spectroscopy

Due to their high activity and stability, Ir-based materials are state-of-the-art electrocatalysts for oxygen evolution reaction (OER) under acidic conditions. However, many factors such as the influence of the activation/conditioning protocol and the resulting oxidation state or the effect of electrolyte adsorption on activity are still debated or overlooked. Herein, Raman spectroscopy was performed on commercial Ir black and IrO2 nanopowders to reveal differences in the samples after activation, as well as adsorption of perchlorates. Specifically, three different activation protocols were performed, 0.05 to 1.45 VRHE (activated), 0.05 to 1.6 VRHE (activated-long range (l.r.)), and 1.1 to 1.6 VRHE (activated-short range (s.r.)), resulting in different OER activity as well as different Raman spectra. However, only Ir(IV) bands remain visible in the ex situ Raman experiments, which was not sufficient to reveal the hydrated phases in the iridium samples. Therefore, mimicked in situ experiments were performed, which allowed the observation of the hydrated phase, particularly for Ir black, but also showed adsorption of perchlorate anions. In addition, the influence of solvation on Raman band shifts is revealed - along with DFT calculations. Overall, this work paves the way for our future in situ Raman spectroscopy experiments with iridium-based electrocatalysts during activation and OER.

Cobalt‐based Co3Mo3N/Co4N/Co Metallic Heterostructure as a Highly Active Electrocatalyst for Alkaline Overall Water Splitting

AbstractAlkaline water electrolysis holds promise for large‐scale hydrogen production, yet it encounters challenges like high voltage and limited stability at higher current densities, primarily due to inefficient electron transport kinetics. Herein, a novel cobalt‐based metallic heterostructure (Co3Mo3N/Co4N/Co) is designed for excellent water electrolysis. In operando Raman experiments reveal that the formation of the Co3Mo3N/Co4N heterointerface boosts the free water adsorption and dissociation, increasing the available protons for subsequent hydrogen production. Furthermore, the altered electronic structure of the Co3Mo3N/Co4N heterointerface optimizes ΔGH of the nitrogen atoms at the interface. This synergistic effect between interfacial nitrogen atoms and metal phase cobalt creates highly efficient active sites for the hydrogen evolution reaction (HER), thereby enhancing the overall HER performance. Additionally, the heterostructure exhibits a rapid OH− adsorption rate, coupled with great adsorption strength, leading to improved oxygen evolution reaction (OER) performance. Crucially, the metallic heterojunction accelerates electron transport, expediting the afore‐mentioned reaction steps and enhancing water splitting efficiency. The Co3Mo3N/Co4N/Co electrocatalyst in the water electrolyzer delivers excellent performance, with a low 1.58 V cell voltage at 10 mA cm−2, and maintains 100 % retention over 100 hours at 200 mA cm−2, surpassing the Pt/C||RuO2 electrolyzer.

Cobalt-based Co3Mo3N/Co4N/Co Metallic Heterostructure as a Highly Active Electrocatalyst for Alkaline Overall Water Splitting.

Alkaline water electrolysis holds promise for large-scale hydrogen production, yet it encounters challenges like high voltage and limited stability at higher current densities, primarily due to inefficient electron transport kinetics. Herein, a novel cobalt-based metallic heterostructure (Co3Mo3N/Co4N/Co) is designed for excellent water electrolysis. In operando Raman experiments reveal that the formation of the Co3Mo3N/Co4N heterointerface boosts the free water adsorption and dissociation, increasing the available protons for subsequent hydrogen production. Furthermore, the altered electronic structure of the Co3Mo3N/Co4N heterointerface optimizes ΔGH of the nitrogen atoms at the interface. This synergistic effect between interfacial nitrogen atoms and metal phase cobalt creates highly efficient active sites for the hydrogen evolution reaction (HER), thereby enhancing the overall HER performance. Additionally, the heterostructure exhibits a rapid OH- adsorption rate, coupled with great adsorption strength, leading to improved oxygen evolution reaction (OER) performance. Crucially, the metallic heterojunction accelerates electron transport, expediting the afore-mentioned reaction steps and enhancing water splitting efficiency. The Co3Mo3N/Co4N/Co electrocatalyst in the water electrolyzer delivers excellent performance, with a low 1.58 V cell voltage at 10 mA cm-2, and maintains 100 % retention over 100 hours at 200 mA cm-2, surpassing the Pt/C||RuO2 electrolyzer.

SIMULATION AND EXPERIMENTAL RESEARCH STUDIES ON TEMPERATURE FIELD FOR THE PRODUCTION OF DIAMOND-COATED MILLING TOOLS BY HFCVD DEVICE WITH SEPARATED WORKTABLES

Diamond-coated tools have extremely extraordinary physical and chemical properties and have become ideal tools for machining the emerging materials that are hard to machine. In mass production of diamond-coated milling tools, the homogeneity of diamond coatings has always been sought for and is highly influenced by the uniformity of temperature field near the tool substrate. In order to further improve the uniformity of the temperature field and deposit diamond coatings with uniform thickness, a novel hot filament chemical vapor deposition (HFCVD) device with separated worktables and plates for mass production of diamond-coated milling tools is proposed. First, the simulation models of previous device with integrated worktable versus new device with separated worktables are established using finite volume method. The simulation results shows that the temperature distribution is more uniform in the device with separated worktables. Second, temperature measurement experiments are conducted, which prove the correctness of simulation model. Subsequently, experiments involving the deposition of diamond coatings on milling tools are conducted using two kinds of worktables, utilizing the same parameters as in the simulation. Finally, high-speed milling experiments are conducted to test the diamond-coated milling tools. According to the results of SEM, Raman and high-speed milling experiments, it can be concluded that the homogeneity of coating thickness and cutting performance of the milling tools produced by HFCVD device with separated worktables and plates are better.

Biaxial strain tuning of exciton energy and polarization in monolayer WS2

We perform micro-photoluminescence and Raman experiments to examine the impact of biaxial tensile strain on the optical properties of WS2 monolayers. A strong shift on the order of −130 meV per % of strain is observed in the neutral exciton emission at room temperature. Under near-resonant excitation, we measure a monotonic decrease in the circular polarization degree under the applied strain. We experimentally separate the effect of the strain-induced energy detuning and evaluate the pure effect coming from the biaxial strain. The analysis shows that the suppression of the circular polarization degree under the biaxial strain is related to an interplay of energy and polarization relaxation channels as well as to variations in the exciton oscillator strength affecting the long-range exchange interaction.

Raman Spectroscopic Study of Ruddlesden—Popper Tetragonal Sr2VO4

The lattice dynamics of tetragonal Sr2VO4 with a Ruddlesden—Popper-layered crystal structure was studied via Raman spectroscopy. We observed three of the four expected Raman-active modes under ambient conditions. Mode Grüneisen parameters and the implicit fractions of two A1g Raman-active modes were determined from high-pressure and high-temperature Raman spectroscopy experiments. The low-energy A1g Raman-active mode involving Sr motions along the c direction has a large isothermal Grüneisen parameter about seven times larger than that of the high-energy A1g Raman-active mode involving apical O motions along the c direction and is, therefore, more anharmonic. The thermodynamic Grüneisen parameter is significantly smaller in Sr2VO4 than in Sr2TiO4 due to the smaller Grüneisen parameter of the high-energy A1g Raman-active mode and other vibrational modes that still need to be identified. The explicit contribution of the low-energy A1g Raman-active mode is negative, and the implicit contribution due to volume change is much larger. Both volume implicit and anharmonic explicit contributions of the high-energy A1g Raman-active mode have similar positive values. The Raman experiment in the air shows that Sr2VO4 begins to decompose above 200 °C.

The initial stages of Li2O2 formation during oxygen reduction reaction in Li-O2 batteries: The significance of Li2O2 in charge-transfer reactions within devices

Lithium-oxygen batteries are a promising technology because they can greatly surpass the energy density of lithium-ion batteries. However, this theoretical characteristic has not yet been converted into a real device with high cyclability. Problems with air contamination, metallic lithium reactivity, and complex discharge and charge reactions are the main issues for this technology. A fast and reversible oxygen reduction reaction (ORR) is crucial for good performance of secondary batteries’, but the partial knowledge of its mechanisms, especially when devices are concerned, hinders further development. From this perspective, the present work uses operando Raman experiments and electrochemical impedance spectroscopy (EIS) to assess the first stages of the discharge processes in porous carbon electrodes, following their changes cycle by cycle at initial operation. A growth kinetic formation of the discharge product signal (Li2O2) was observed with operando Raman, indicating a first-order reaction and enabling an analysis by a microkinetic model. The solution mechanism in the evaluated system was ascribed for an equivalent circuit with three time constants. While the time constant for the anode interface reveals to remain relatively constant after the first discharge, its surface seemed to be more non-uniform. The model indicated that the reaction occurs at the Li2O2 surface, decreasing the associated resistance during the initial discharge phase. Furthermore, the growth of Li2O2 forms a hetero-phase between Li2O2/electrolyte, while creating a more compact and homogeneous on the Li2O2/cathode surface. The methodology here described thus offers a way of directly probing changes in surface chemistry evolution during cycling from a device through EIS analysis.

Metastable phase formation in europium hexaboride on compression to 187 GPa

Transition-metal and rare-earth borides are of considerable interest due to their electronic, mechanical, and magnetic properties as well as their structural stability under extreme conditions. Here, we report on a series of high-pressure Raman and x-ray diffraction experiments on the cubic rare-earth hexaboride EuB6 to an ultrahigh pressure of 187 GPa in a diamond anvil cell. In EuB6, divalent europium ions occupy the corners of the cubic structure, which encloses a rigid boron-bonded cage. So far, no structural phase transitions have been reported, while the nanoindentation studies indicate amorphization in nanoscale shear bands during plastic deformation. Our x-ray diffraction studies have revealed that the ambient cubic phase of EuB6 shows broadening and splitting of diffraction peaks starting at 72 GPa and the broadening continuing to 187 GPa. The high-pressure phase is recovered on decompression, and the Raman spectroscopy of the recovered sample from 187 GPa shows a downward frequency shift and broadening of T2g, Eg, and A1g modes of boron octahedron. The density functional theory simulations of EuB6 at 100 GPa have identified five possible lowest energy crystal structures. The experimental x-ray diffraction data at high pressures is compared with the theoretical predictions and the role of structural distortions induced by shear stresses is also discussed.

Raman study of layered breathing kagome lattice semiconductor Nb3Cl8

Niobium chloride (Nb3Cl8) is a layered two-dimensional semiconducting material with many exotic properties including a breathing kagome lattice, a topological flat band in its band structure, and a crystal structure that undergoes a structural and magnetic phase transition at temperatures below 90 K. Despite being a remarkable material with fascinating new physics, the understanding of its phonon properties is at its infancy. In this study, we investigate the phonon dynamics of Nb3Cl8 in bulk and few layer flakes using polarized Raman spectroscopy and density-functional theory (DFT) analysis to determine the material’s vibrational modes, as well as their symmetrical representations and atomic displacements. We experimentally resolved 12 phonon modes, five of which are A 1g modes while the remaining seven are Eg modes, which is in strong agreement with our DFT calculation. Layer-dependent results suggest that the Raman peak positions are mostly insensitive to changes in layer thickness, while peak intensity and full width at half maximum are affected. Raman measurements as a function of excitation wavelength (473–785 nm) show a significant increase of the peak intensities when using a 473 nm excitation source, suggesting a near resonant condition. Temperature-dependent Raman experiments carried out above and below the transition temperature did not show any change in the symmetries of the phonon modes, suggesting that the structural phase transition is likely from the high temperature P 1 phase to the low-temperature R phase. Magneto-Raman measurements carried out at 140 and 2 K between −2 and 2 T show that the Raman modes are not magnetically coupled. Overall, our study presented here significantly advances the fundamental understanding of layered Nb3Cl8 material which can be further exploited for future applications.

Carbon-slurry optimization for lithium-ion batteries customization

The technological application of lithium-ion batteries (LIB) grows constantly, making customization of the batteries a current necessity and sometimes a challenge. In this paper we described carbon-slurry optimization process for anodes of lithium-ion batteries customization by using a surface response statistical experiment with four response variables such specific discharge capacity, coulombic efficiency, anodes mass deviation, and capacity retention. We studied two commercial graphite active materials by characterizing the materials via Raman spectroscopy, SEM, and electrochemical techniques. We corroborate the graphite structure for both materials but with morphological differences such as shape and particle size. The binder composition seems to interfere with the active carbon materials capabilities while it generates better performance for one of them. Although the chemical structure of both materials was confirmed to be the same via Raman experiments, SEM images shows critical morphological differences that interferes with the final slurry thus, affecting the electrochemical performance of the anodes. Further studies are required to understand ECSA and its possible effect on the charge/discharge capacities of the anodes.

Ti3C2Tx MXene@STPP novel waterborne long-term anti-corrosion coating with "3 + 1" multiple high-performance active-passive protection barrier mechanisms

Although environmentally friendly waterborne epoxy (WEP) coatings have the advantage of low volatile organic compounds (VOCs), their barrier performance is rather inferior to achieve long-term corrosion protection. Herein, we grafted the coupling agents KH560 and KH550 onto the etched Ti3C2Tx and sodium tripolyphosphate (STPP), respectively. On the one hand, Ti-O-Si covalent bonds can be formed to improve the water dispersion stability, and on the other hand, as a bridging agent, the functionalized modification yielded the interface-enhanced Ti3C2Tx@STPP filler. The Ti3C2Tx@STPP/WEP composite coating exhibits a high impedance value of 7.981 × 1010 Ω·cm2 after 120 days of saltwater immersion, which is at least two orders of magnitude higher than that of the pure WEP coating. Likewise, the chelating-passivation advantage of STPP with metal cations is fully exploited. The precipitation-oxidation self-healing corrosion inhibition mechanism was proposed and demonstrated by Tafel, EIS, XPS, and Raman experiments. The remarkable long-term corrosion protection performance can be concluded as (1) interface-enhanced two-dimensional Ti3C2Tx with extraordinary physical barrier to prolong the corrosion path; (2) due to high barrier properties, the further electrochemical reactions of steel surfaces can be effectively inhibited under low utilization of water and oxygen, and the Fe(OH)3 and Fe(OH)2 are converted into non-conductive Fe3O4 and/or Fe2O3 films after water loss, (3) and active protection by the chelation of STPP with iron ions to form iron tripolyphosphate passivation films, and (4) passive defense by the coating and resin itself. Therefore, a novel "3 + 1" high-performance protective coating, which integrates interface enhancement, physical barrier, and active-passive protection, is successfully prepared to achieve long-term corrosion protection of the coating.

Identification of Healthy Tissue from Malignant Tissue in Surgical Margin Using Raman Spectroscopy in Oral Cancer Surgeries.

Accurate identification of tissue types in surgical margins is essential for ensuring the complete removal of cancerous cells and minimizing the risk of recurrence. The objective of this study was to explore the clinical utility of Raman spectroscopy for the detection of oral squamous cell carcinoma (OSCC) in both tumor and healthy tissues obtained from surgical resection specimens during surgery. This study enrolled a total of 64 patients diagnosed with OSCC. Among the participants, approximately 50% of the cases were classified as the most advanced stage, referred to as T4. Raman experiments were conducted on cryopreserved tissue samples collected from patients diagnosed with OSCC. Prominent spectral regions containing key oral biomarkers were analyzed using the partial least squares-support vector machine (PLS-SVM) method, which is a powerful multivariate analysis technique for discriminant analysis. This approach effectively differentiated OSCC tissue from non-OSCC tissue, achieving a sensitivity of 95.7% and a specificity of 93.3% with 94.7% accuracy. In the current study, Raman analysis of fresh tissue samples showed that OSCC tissues contained significantly higher levels of nucleic acids, proteins, and several amino acids compared to the adjacent healthy tissues. In addition to differentiating between OSCC and non-OSCC tissues, we have also explored the potential of Raman spectroscopy in classifying different stages of OSCC. Specifically, we have investigated the classification of T1, T2, T3, and T4 stages based on their Raman spectra. These findings emphasize the importance of considering both stage and subsite factors in the application of Raman spectroscopy for OSCC analysis. Future work will focus on expanding our tissue sample collection to better comprehend how different subsites influence the Raman spectra of OSCC at various stages, aiming to improve diagnostic accuracy and aid in identifying tumor-free margins during surgical interventions.

Using pressure to unravel the structure–dynamic-disorder relationship in metal halide perovskites

The exceptional optoelectronic properties of metal halide perovskites (MHPs) are presumed to arise, at least in part, from the peculiar interplay between the inorganic metal-halide sublattice and the atomic or molecular cations enclosed in the cage voids. The latter can exhibit a roto-translative dynamics, which is shown here to be at the origin of the structural behavior of MHPs as a function of temperature, pressure and composition. The application of high hydrostatic pressure allows for unraveling the nature of the interaction between both sublattices, characterized by the simultaneous action of hydrogen bonding and steric hindrance. In particular, we find that under the conditions of unleashed cation dynamics, the key factor that determines the structural stability of MHPs is the repulsive steric interaction rather than hydrogen bonding. Taking as example the results from pressure and temperature-dependent photoluminescence and Raman experiments on MAPbBr_3 but also considering the pertinent MHP literature, we provide a general picture about the relationship between the crystal structure and the presence or absence of cationic dynamic disorder. The reason for the structural sequences observed in MHPs with increasing temperature, pressure, A-site cation size or decreasing halide ionic radius is found principally in the strengthening of the dynamic steric interaction with the increase of the dynamic disorder. In this way, we have deepened our fundamental understanding of MHPs; knowledge that could be coined to improve performance in future optoelectronic devices based on this promising class of semiconductors.

Identifying the Local Atomic Environment of the "Cu3+" State in Alkaline Electrochemical Systems.

CuO-based catalysts are active for the oxygen evolution reaction (OER), although the active form of copper for the OER is still unknown. We combine operando Raman experiments and density functional theory (DFT) electronic structure calculations to determine the form of Cu(O)xOHy present under OER conditions. Raman spectra show a distinct feature related to the active "Cu3+" species, which is only present under highly oxidizing conditions. DFT is used to produce theoretical Raman standards and match the unique Raman feature of copper under OER potentials. This method identifies a range of Cu3+-containing compounds which match the distinct Raman feature. We then integrate experimental electrochemistry to progressively eliminate possible structures and determine the stoichiometry of the active form as CuOOH, which likely takes the form of a surface-adsorbed hydroxide on a CuO surface. Bader charge analysis, site-projected wavefunctions, and density of states analysis show that electron density is removed from O 2p orbitals upon hydroxide adsorption, suggesting that the electronic structure exhibits d9L Cu2+ behavior rather than the local electronic structure of a formal Cu3+.

The conformational behavior and structure of monosubstituted 1,3,5‐trisilacyclohexanes—Part III: 1‐Methyl‐1,3,5‐trisilacyclohexane

Abstract1‐Methyl‐1,3,5‐trisilacyclohexane was synthesized and its structure and conformational properties have been determined by gas‐phase electron diffraction (GED) and quantum chemical (QC) calculations. The molecule may exist in two forms differing from each other by the substituent's position. QC results show that the equatorial conformer is predicted to be slightly more stable than the axial conformer; note that one method (M06‐2X) with basis set 6‐311G** shows an equal amount of Ax and Eq conformers: ratio (Ax/Eq) = (30–50):(70–50)% (depending on the method and basis set). From the GED data, the molar fractions of the conformers were found to be Ax:Eq = 54(10):46(10) at 280(5) K. A temperature‐dependent Raman experiment resulted in an Ax:Eq ratio of 58(4):42(4). Conformational properties are compared in series of analogous 1‐X‐1‐(hetero)cyclohexanes.

Validation of Raman spectroscopy as a tool for mapping transport parameters in inhomogeneous N‐doped 4H‐SiC

AbstractWe assess Raman spectroscopy as a tool for fast and non‐invasive mapping of charge carrier density and carrier mobility in inhomogeneously doped 4H‐SiC. For this purpose, we compare values of these transport parameters obtained by magneto‐transport and Raman measurements of N‐doped 4H‐SiC. The comparison is not straightforward. The effective charge density and mobility, which are obtained from resistivity and Hall measurements by employing the commonly used effective one‐band model, deviate from the values extracted by applying the established line‐shape models for describing the longitudinal optical phonon coupled (LOPC) modes in the Raman spectra. Differentiating between free and localized carriers in the framework of a three‐band transport model confirms that only the free charge carriers in the conduction band of N‐doped 4H‐SiC contribute to the LOPC Raman signal and their density agrees well with that obtained by the line shape analysis. The agreement of the mobility values is good keeping in mind that different frequencies of the applied electric fields are used in the two approaches, i.e., dc‐transport measurements at 0 Hz and ac‐fields of the exciting laser at about 500 THz. Moreover, the excitation of electrons into the conduction band by the laser, which is inherent to the Raman experiment, causes differences in the temperature dependence of the carrier density compared with the electrical transport data.

Investigations on the Novel Antimalarial Ferroquine in Biomimetic Solutions Using Deep UV Resonance Raman Spectroscopy and Density Functional Theory

Deep ultraviolet (DUV) resonance Raman experiments are performed, investigating the novel, promising antimalarial ferroquine (FQ). Two buffered aqueous solutions with pH values of 5.13 and 7.00 are used, simulating the acidic and neutral conditions inside a parasite's digestive vacuole and cytosol, respectively. To imitate the different polarities of the membranes and interior, the buffer's 1,4-dioxane content was increased. These experimental conditions should mimic the transport of the drug inside malaria-infected erythrocytes through parasitophorous membranes. Supporting density functional theory (DFT) calculations on the drug's micro-speciation were performed, which could be nicely assigned to shifts in the peak positions of resonantly enhanced high-wavenumber Raman signals at λexc = 257 nm. FQ is fully protonated in polar mixtures like the host interior and the parasite's cytoplasm or digestive vacuole (DV) and is only present as a free base in nonpolar ones, such as the host's and parasitophorous membranes. Additionally, the limit of detection (LoD) of FQ at vacuolic pH values was determined using DUV excitation wavelengths at 244 and 257 nm. By applying the resonant laser line at λexc = 257 nm, a minimal FQ concentration of 3.1 μM was detected, whereas the pre-resonant excitation wavelength 244 nm provides an LoD of 6.9 μM. These values were all up to one order of magnitude lower than the concentration found for the food vacuole of a parasitized erythrocyte.