Infrared Spectroscopy Research Articles

Small world properties of schizophrenia and OCD patients derived from fNIRS based functional brain network connectivity metrics

Individuals suffering from obsessive compulsive disorder (OCD) and schizophrenia (SCZ) frequently exhibit symptoms of cognitive disassociations, which are linked to poor functional integration among brain regions. The loss of functional integration can be assessed using graph metrics computed from functional connectivity matrices (FCMs) derived from neuroimaging data. A healthy brain at rest is known to exhibit small-world features with high clustering coefficients and shorter path lengths in contrast to random networks. The aim of this study was to compare the small-world properties of prefrontal cortical functional networks of healthy subjects with OCD and SCZ patient groups by use of hemodynamic data obtained with functional near infrared spectroscopy (fNIRS). 13 healthy subjects and 47 patients who were clinically diagnosed with either OCD (N = 21) or SCZ (N = 26) completed a Stroop test while their prefrontal cortex (PFC) hemodynamics were monitored with fNIRS. The Stroop test had a block design consisting of neutral, congruent and incongruent stimuli. For each subject and stimuli type, FCMs were derived separately which were then used to compute small world features that included (i) global efficiency (GE), (ii) clustering coefficient (CC), (iii) modularity (Q), and (iv) small-world parameter (σ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sigma $$\\end{document}). Small-world features of patients exhibited random networks which were indicated by higher GE and lower CC values when compared to healthy controls, implying a higher neuronal operational cost.

ZnH2P4N8: Case Study on Topochemical Imidonitridophosphate High-Pressure Synthesis.

Nitridophosphates are subject of current research, as they have a broad spectrum of properties and potential applications, such as ion conductors or luminescent materials. Yet, the subclass of imidonitridophosphates has been studied less extensively. The primary reason is that the controlled N-H functionalization of nitridophosphates is not straight forward, making targeted synthesis more challenging. Inspired by the high-pressure (HP) post-synthetic modification of nitridophosphates, we present the topochemical HP deprotonation of phosphorus nitride imides using the high-pressure polymorph β-PN(NH) as an example. Additional incorporation of Zn2+ results in the first quaternary transition metal imidonitridophosphate ZnH2P4N8. The crystal structure was elucidated by single-crystal X-ray diffraction (SCXRD), energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD) and solid-state magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). In addition, the presence of H as part of an imide group was confirmed by IR spectroscopy. The potential of this defunctionalization approach for controlling the N-H content is demonstrated by the preparation of partially deprotonated intermediates ZnxH4-2xP4N8 (x≈0.5, 0.85). This topochemical high-pressure reaction represents a promising way to prepare, control and manipulate new imide-based materials without altering their overall anionic framework.

Solvent assisted mechanochemical synthesis, antimicrobial and antioxidant studies of Ni2+, Mn2+, Cr<sup>2+</sup> , and Cu<sup>2+</sup> Metal complexes of some ligands derived from l-histidine and l-alanine

Mechanochemistry enables rapid, quantitative reactions to occur at or close to 27℃. It is a one-step process that allows for reactant homogenization, product nucleation, and particle growth. These processes use little or no solvent, making them less wasteful and more environmentally friendly than solvent-based reactions. Ni2+ , Mn2+, Cr2+and Cu2+ metal ions were synthesized by grinding in an agate mortar with pestle using ligands derived from amino acids (Histidine &Alanine) which were further synthesized to form complexes. The entire experiment was carried out by solvent solvent-assisted mechanochemical process and ethanol was used as liquid liquid-assisted solvent. The complexes were characterized by IR spectroscopy, U-V spectroscopy, X-ray analysis, melting point, solubility test, and conductivity measurement. The Solubility test showed that the complexes are soluble in DMSO, DMF, and ethanol and are insoluble in both hexane and tetrachloromethane. The molar conductivity values are in the range of (6.05-28.56) Ω-1cm2mol-1 ) indicating the complexes behave as non-electrolytes. IR analysis showed a vibrational frequency band observed at (1620-1625) cm-1 which is assigned to the ʋ(C=N) of the azomethine, also the new bands M=N, M=O indicate the coordination reaction between the metal and the ligands. The UV visible analysis shows various transitions, the metal complexes showed adsorption bands at λ of 420 and 575nm respectively because of the ligand-to-metal charge transfer (LMCT). The XRD analysis showed that there was a change in phase between the starting material and the product which indicate that a reaction occurred, also the nature of the spectra showed that the compounds are all crystalline. The Antimicrobial activity showed that both the complexes and the ligands have good activity against the bacterial isolates. Antioxidant activity was also tested and the compound appeared to have moderate scavenging activities compared to the reference used. The values indicated that the activities are more pronounced when coordinated with metal ions.

Preparation of Lyocell Fibers from Solutions of Miscanthus Cellulose.

Both annual (cotton, flax, hemp, etc.) and perennial (trees and grasses) plants can serve as a source of cellulose for fiber production. In recent years, the perennial herbaceous plant miscanthus has attracted particular interest as a popular industrial plant with enormous potential. This industrial crop, which contains up to 57% cellulose, serves as a raw material in the chemical and biotechnology sectors. This study proposes for the first time the utilization of miscanthus, namely Miscanthus Giganteus "KAMIS", to generate spinning solutions in N-methylmorpholine-N-oxide. Miscanthus cellulose's properties were identified using standard methods for determining the constituent composition, including also IR and atomic emission spectroscopy. The dry-jet wet method was used to make fibers from cellulose solutions with an appropriate viscosity/elasticity ratio. The structural characteristics of the fibers were studied using IR and scanning electron microscopy, as well as via X-ray structural analysis. The mechanical and thermal properties of the novel type of hydrated cellulose fibers demonstrated the possibility of producing high-quality fibers from miscanthus.

Orientation Distribution of Crystalline β-Sheet Domains in Bombyx mori Silk Fiber Studied with Vibrational Sum Frequency Generation Spectroscopy.

Silk fibers have good biocompatibility and mechanical properties, which make them attractive in biomaterial applications as well as textile industries. It is believed that the superior mechanical property is associated with the crystalline β-sheet structure in the fiber; but a deeper understanding of the structure-property relationship is still needed for full exploitation of its physical properties. Especially, accurate information on hydrogen-bonding interactions within β-sheet domains at the nanoscale and their spatial distributions at the mesoscale are critically needed. In this study, we demonstrate the selective detection of crystalline β-sheet domains in Bombyx mori silk fiber using sum frequency generation (SFG) spectroscopy and its use to determine the angular distribution of the β-sheet crystallites with respect to the fiber axis. Numerical simulations of the SFG signal of the amide-I band were carried out using tensors based on the B2 symmetry of the D2 point group and compared with experimental data. This comparison found that the crystalline β-sheet domains are aligned along the fiber axis with a standard deviation of ∼27° and parallel to the fiber surface with a standard deviation of ∼5°. It was also found that the amide bands in the SFG spectra cannot be fully explained with the assumption that the crystalline β-sheet vibrations can be described with the D2 point group. Being able to monitor the amide group vibrations sensitive to both interchain hydrogen bonding and crystallite orientations, SFG analysis has a potential to unveil the structure-mechanical property relationship that may not be readily assessable with other characterization techniques.

Machine Learning Classification of Integrin-Expression-Based Magnetic Sorted SW 620 Cells by Simultaneous O-PTIR and SERS.

Immortalized cell lines are commonly used for in vitro studies such as drug efficacy, toxicology, and life cycle due to their cost effectiveness and accessibility; however, subpopulations within a cell line can arise from random mutations or asynchronous cell cycles which may lead to results that make interpretation difficult. A method that could classify these differences and separate unique subpopulations would increase our understanding of heterogeneous cellular responses. In the present work, we explore spectroscopic signals associated with subpopulations of cells magnetically sorted on the basis of α5β1 integrin binding to cyclic-RGDfC which mimics fibronectin in the extracellular matrix. SW620 colon cancer cells were incubated with cyclic-RGDfC functionalized gold-coated, iron core nanoparticles and magnetically sorted. The subpopulations from the sort were imaged (N = 10 positive and N = 10 negative, number of cells) via simultaneous surface-enhanced Raman scattering (SERS) and optical-photothermal infrared spectroscopy (O-PTIR). Pearson correlations of the standard peptide-protein interaction in the SERS channel allowed for visualization of the cyclic RGDfC-integrin α5β1 interaction. Partial least-squares discriminant analysis of the O-PTIR spectra collected from cell maps successfully classified the positively or negatively sorted cells. These results demonstrate that biochemical changes within a single cell line can be sorted via an integrin-activity-based assay using simultaneous SERS and O-PTIR.

Functionalized cements incorporated with nanocomposite photocatalysts for self-cleaning applications

The constantly escalating pollution on the surface of cement-based materials affects architectural aesthetics and residents′ health, necessitating frequent cleaning and maintenance, which contradicts the concept of sustainable development. This study aimed to develop a novel photocatalytic cement material to enhance the self-cleaning capabilities of cement-based materials, thereby extending their service life and reducing maintenance costs. To achieve this, carbon quantum dots (CDs) and g-C3N4 (CN) nanocomposite photocatalysts (CDs@CN) were synthesized and integrated into white cement to prepare photocatalytic cements. The materials were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible–near infrared (UV–Vis–NIR) spectroscopy. Photocatalytic performance was evaluated by the degradation of Rhodamine B (RhB) under xenon (Xe) lamp, Vis light and UV light. The CDs@CN nanocomposite displayed superior photocatalytic activity, particularly under Xe lamp irradiation, achieving over 95 % degradation of RhB within 1 h. Even under Vis and UV light, the photocatalytic cement retains robust self-cleaning capabilities, achieving pollutant degradation rates of 81 % and 63 %, respectively, within 1 h. This performance exceeded that of pristine CN and control samples, demonstrating effective light absorption and charge separation. The optimal photocatalyst concentration in cement was identified as 0.1∼5.0 wt%, balancing performance and dispersion. The developed CDs@CN-based photocatalytic cement material offers a sustainable solution for self-cleaning and environmental purification. This study provides insights into the design of functional cementitious materials and contributes to the sustainable development of the construction industry.

The Study on Synthesis and Characterization of Insensitive Energetic Materials Based on 5‐(5‐Nitro‐1H‐1,2,4‐Triazol‐3‐yl)‐1H‐Tetrazole

ABSTRACTThe design and synthesis of insensitive energetic materials are a necessary and challenging work. The synthesis of novel nitrogen‐rich salts based on 5‐(5‐Nitro‐1H‐1,2,4‐triazol‐3‐yl)‐1H‐tetrazole (H2NTT) has been presented. Structural characterization of these two salts was accomplished by utilizing NMR, MS, IR spectroscopy, and X‐ray diffraction. The standard heats of formation were calculated, and the differential scanning calorimetry (DSC) and sensitivity test were carried out. Their detonation performances were estimated by EXPLO 5 program. These newly synthesized salts showed highly positive heat of formation and low sensitivity. It is noteworthy that the diaminoguanidine salt b exhibited good detonation performance superior to traditional explosive TNT (Trinitrotoluene), making it a prospective candidate for insensitive energetic material.

Metal-organic frameworks with a sulfur-rich heterocycle: synthesis, gas adsorption properties, and metal exchange.

Three new three-dimensional (3D) metal-organic frameworks [M2(ttdc)2(dabco)] (M = Zn(II), 1-Zn; Cu(II), 1-Cu; and Zn/Cu, 1-ZnCu) based on thieno[3,2-b]thiophene-2,5-dicarboxylate (ttdc2-) were synthesized and characterized by a combination of physicochemical methods (single crystal X-ray diffraction, powder X-ray diffraction, chemical and thermogravimetric analyses and IR spectroscopy). 1-Cu demonstrated permanent porosity (Vpore = 0.790 cm3 g-1 and SBET = 1725 m2 g-1) and significant CO2, CH4, C2H2, C2H4 and C2H6 gas uptakes under ambient conditions. The adsorption selectivities for gas mixtures, calculated by IAST, were 10.8 (10.7), 14.6 (9.4), 1.7 (1.6) and 1.5 (1.6) for the equimolar gas mixture compositions CO2/N2, C2H6/CH4, C2H6/C2H4 and C2H6/C2H2 at 1 bar and 273 K (298 K), respectively. The mixed-metal compound 1-ZnCu was prepared by a crystal-to-crystal ion exchange metathesis reaction from 1-Zn with a 52% degree of ion substitution, confirmed by energy-dispersive X-ray spectroscopy, optical microscopy and single crystal X-ray diffraction analysis.

Rapid determination of fat content: Advanced spectroscopic methods across diverse fish species

The rapid estimation of fat content using spectroscopic-based sensors, irrespective of fish species (salmon, trout, sea bass, sea bream, tuna, cod, and mackerel), was primarily investigated in the present study. The fat content and fatty acid (FA) composition was quantified with reference methods. Fourier-Transform Infrared (FTIR) and Fourier-Transform Near-Infrared (FT-NIR) spectroscopy, along with multispectral imaging (MSI) instruments (both benchtop and portable), were evaluated for their ability to rapidly predict fat content in ground samples using data analysis. The performance of the PLS-R models was evaluated according to root mean square error (RMSE), coefficient of determination (R2) and residual prediction deviation (RPD). Also fish were classified as fat/low-fat and low/medium/high-fat using partial least squares discriminant analysis (PLS-DA). All fish species exhibited a consistent pattern of unsaturated fatty acids (UNFA) > monounsaturated fatty acids (MUFA) > polyunsaturated fatty acids (PUFA) > saturated fatty acids (SFA) and the range of fat content was from 22.8 (salmon) to 0.02 (cod), expressed in g/100 g of sample based on the reference methods. In terms of fat content prediction using rapid sensors the best performance indices of the test set were obtained from the benchtop-MSI (RMSE = 1.475, R2 = 0.847, RPD = 2.581) and FT-NIR (RMSE = 1.638, R2 = 0.855, RPD = 2.651) instruments, while FTIR and portable-MSI had scores of RMSE = 1.874, R2 = 0.815, RPD = 2.309 and RMSE = 1.737, R2 = 0.786, RPD = 2.191, respectively. All sensors discriminated fat from low-fat samples (accuracy = 100%). For low/medium/high fat the best results were achieved by benchtop-MSI (accuracy = 94.12%), followed by portable-MSI (accuracy = 88.24%) and FTIR (accuracy = 84.21%). Results were less satisfactory for the FT-NIR method (accuracy = 68.75%). This study demonstrates that vibrational and multispectral imaging spectroscopies, when coupled with data analysis, have potential to provide information about the nutritional quality (e.g., fat content) independent of the fish species. Such insights could contribute to the automation and potential digitalization of processes within the fields of food nutrition and the seafood industry.

Mitigation effect of a biodegradable surfactant N,N,N-trimethyl-2-(((hexadecyloxy)carbonyl)oxy)ethan-1-aminiumiodide for mild steel corrosion in 5% HCl: Experimental and theoretical insights

A cleavable cationic surfactant having carbonate linkage, N,N,N-trimethyl-2-(((hexadecyloxy)carbonyl)oxy)ethan-1-aminiumiodide referred to as THC was synthesised and characterized employing elemental analysis, FT-IR (Fourier Transform Infrared Spectroscopy), 1H NMR (Nuclear Magnetic Resonance) and 13C NMR. The extent of corrosion inhibition of THC was for the first time studied experimentally and theoretically on mild steel (MS) substrate in 5 % HCl solution at temperatures 303, 313, 323, 333, 343, 353 K. Experimental investigations include gravimetric analysis, potentiodynamic polarization (PDP) and electrochemical impedance analysis (EIS). THC provided maximum inhibition efficiency of 93.2 % at concentration of 1×10−4 M at 303 K which was further raised to 98.1 % at 353 K. PDP studies reveal that given surfactant is mixed type inhibitor. Surface studies such as contact angle measurement, AFM (Atomic Force Microscopy), SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray Analysis), and XPS (X-ray Photoelectron Spectroscopy) were employed to justify the adsorption of inhibitor molecules on MS surface. Furthermore, biodegradability test on THC was done to support the environment friendly nature of the surfactant.

Binary Biosorption of Cu(II) and Cr(VI) by Naturally Formed Biofilm Matrices

Water pollution poses a significant ecological threat, contributing to the widespread degradation of aquatic ecosystems. Among the pollutants, heavy metals pose severe risks to both organisms and human health, emphasizing the urgent need for effective pollution control technologies. Biosorption presents a promising, cost-effective, and environmentally friendly solution to mitigate heavy metal contamination. Biofilms, consisting of microbial communities, have emerged as potential biosorbents for heavy metals. Since heavy metals can exist as cations and anions concurrently in aquatic environments, understanding their behavior in binary systems is essential for biosorption strategies. This study focuses on the binary biosorption of Cu(II) and Cr(VI), representing cationic and anionic heavy metals. Specific adsorption sites are identified by analyzing adsorption kinetics, isotherms, and IR spectra of biofilms. The results indicate that biofilms, in a binary scenario, demonstrate nearly identical adsorption capacities for Cu(II) and Cr(VI). Moreover, the adsorption process follows the Langmuir adsorption model, emphasizing the potential of biofilms as effective biosorbents for the simultaneous removal of cationic and anionic heavy metals. This study advocates for a sustainable approach to heavy metal remediation through the utilization of biofilms.

CODI: Enhancing machine learning-based molecular profiling through contextual out-of-distribution integration

Abstract Molecular analytics increasingly utilize machine learning (ML) for predictive modeling based on data acquired through molecular profiling technologies. However, developing robust models that accurately capture physiological phenotypes is challenged by the dynamics inherent to biological systems, variability stemming from analytical procedures, and the resource-intensive nature of obtaining sufficiently representative datasets. Here, we propose and evaluate a new method: Contextual Out-of-Distribution Integration (CODI). Based on experimental observations, CODI generates synthetic data that integrate unrepresented sources of variation encountered in real-world applications into a given molecular fingerprint dataset. By augmenting a dataset with out-of-distribution variance, CODI enables an ML model to better generalize to samples beyond the seed training data, reducing the need for extensive experimental data collection. Using three independent longitudinal clinical studies and a case-control study, we demonstrate CODI's application to several classification tasks involving vibrational spectroscopy of human blood. We showcase our approach's ability to enable personalized fingerprinting for multi-year longitudinal molecular monitoring and enhance the robustness of trained ML models for improved disease detection. Our comparative analyses reveal that incorporating CODI into the classification workflow consistently leads to increased robustness against data variability and improved predictive accuracy.

Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analysis of human nails: Implications for age determination in forensics.

A person's age estimation from biological evidence is a crucial aspect of forensic investigations, aiding in victim identification and criminal profiling. In this study, we present a novel approach of utilizing Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) spectroscopy to predict the age of donors based on nail samples. A diverse dataset comprising nails from donors spanning different age groups was analyzed using ATR FT-IR, with subsequent multivariate analysis techniques used for age prediction. The developed partial least squares regression (PLS-R) model demonstrated promising accuracy in age estimation, with a root mean square error of prediction (RMSEP) equal to 11.1 during external validation. Additionally, a partial least squares discriminant analysis (PLS-DA) classification model achieved high accuracy of 88% in classifying donors into younger and older age groups during external validation. This proof-of-concept study highlights the potential of ATR FT-IR spectroscopy as a non-destructive and efficient tool for age estimation in forensic investigations, offering a new approach to forensic analysis with practical implications.

Photoexcitation Dynamics of 4-Aminopthalimide in Solution Investigated Using Femtosecond Time-Resolved Infrared Spectroscopy

Excited-state intramolecular proton transfer (ESIPT) reactions are crucial in photoresponsive materials and fluorescent markers. The fluorescent compound 4-aminophthalimide (4-AP) has been reported to exhibit solvent-assisted ESIPT in protic solvents, such as methanol, wherein the solvent interacts with 4-AP to form a six-membered hydrogen-bonded ring that is strengthened upon excitation. Although the controversial observation of ESIPT in 4-AP has been extensively studied, the molecular mechanism has yet to be fully explored. In this study, femtosecond infrared spectroscopy was used to investigate the dynamics of 4-AP in methanol and acetonitrile after excitation at 350 and 300 nm, which promoted 4-AP to the S1 and S2 states, respectively. The excited 4-AP in the S1 state relaxed to the ground state, while 4-AP in the S2 state relaxed via the S1 state without the occurrence of ESIPT. The enol form of 4-AP (Enol 4-AP) in the S1 state was calculated to be ~10 kcal/mol higher in energy than the keto form in the S1 state, indicating that keto-to-enol tautomerization was endergonic, ultimately resulting in no observable ESIPT for 4-AP in the S1 state. Upon the excitation of 4-AP to the S2 state, the transition to Enol-4-AP in the S1 state was found to be exergonic; however, ESIPT must compete with an internal conversion from the S2 to the S1 state. The internal S2 → S1 conversion was significantly faster than the solvent-assisted ESIPT, resulting in a negligible ESIPT for the 4-AP excited to the S2 state. The detailed excitation dynamics of 4-AP clearly reveal the molecular mechanism underlying its negligible ESIPT, despite the fact that it forms a favorable structure for solvent-assisted ESIPT.

Reaction of aroylpyruvic acids methyl esters with 4-aminobenzoic acid. Antioxidant activity of the obtained compounds

4-{[(2Z)-4-Aryl-2-hydroxy-4-oxobut-2-enoyl]amino}benzoic acids were synthesized by reacting methyl esters of aroylpyruvic acids with 4-aminobenzoic (p-aminobenzoic) acid in glacial acetic acid in the presence of anhydrous sodium acetate. 4-{[(2Z)-4-Aryl-1-methoxy-1,4-dioxobut-2-en-2-yl)]amino}benzoic acids were synthesized by reacting the above reagents in a mixture of glacial acetic acid–ethanol (1:1) without adding anhydrous sodium acetate. Structure of the obtained compounds was confirmed by 1H and 13C{1H} NMR and IR spectroscopy. The antioxidant activity of the synthesized compounds was studied.

Copper(II) succinate: electrochemical synthesis, characterization and application as a precursor for micron-sized copper(II) oxide fibers

A coordination compound of copper(II) with succinic acid was obtained by electrochemical synthesis in media of various compositions. The samples were characterized by methods of quantitative analysis, ESR and IR spectroscopy, synchronous thermal analysis. The vibrational frequencies of copper(II) succinate were calculated by using DFT and the experimental IR spectra were interpreted on the basis of the results. Micro-sized copper(II) oxide fibers were obtained by thermal decomposition of synthesized samples. It was shown that the use of the water–dimethyl sulfoxide system with a volume ratio 1:1 is optimal to achieve the formation of moderately aggregated particles with a distinct filamentous morphology.

Synthesis and biological activity of substituted 5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxamides

A four-component solvent-free reaction of acetoacetic acid amide with dimedone, aromatic aldehydes and ammonium acetate leads to new substituted 5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxamides. The structures of the products were proved using IR, 1H and 13C NMR spectroscopy, mass spectrometry and X-ray diffraction analysis. The synthesized compounds were tested for antimicrobial and antinociceptive activities.

Synthesis of 1-aminoalkyl-5,6-diaryl-2-oxopyrrolo[3,4-<i>c</i>]pyrazoles

The reaction of substituted 1-aminoalkyl-3-hydroxy-3-pyrrolin-2-ones with hydrazine hydrate in boiling glacial acetic acid leads to the formation of 1-aminoalkyl-5,6-diaryl-2-oxopyrrolo[3,4-c]pyrazoles. The structure of the obtained compounds was confirmed by IR, 13C NMR and 1H NMR spectroscopy methods.

Unconventional structural evolution of an oxide surface in water unveiled by in situ sum-frequency spectroscopy.

Oxide-water interfaces host a wide range of important reactions in nature and modern industrial applications; however, accurate knowledge about these interfaces is still lacking at the molecular level owing to difficulties in accessing buried oxide surfaces. Here we report an experimental scheme enabling in situ sum-frequency vibrational spectroscopy of oxide surfaces in liquid water. Application to the silica-water interface revealed the emergence of unexpected surface reaction pathways with water. With ab initio molecular dynamics and metadynamics simulations, we uncovered a surface reconstruction, triggered by deprotonation of surface hydroxylated groups, that led to unconventional five-coordinated silicon species. The results help demystify the multimodal chemistry of aqueous silica discovered decades ago, bringing in fresh information that modifies the current understanding. Our study will provide new opportunities for future in-depth physical and chemical characterizations of other oxide-water interfaces.