Pecan nut–derived carbon quantum dots–modified electrode for sensitive electrochemical determination of vonoprazan using a green analytical approach

Structural and physicochemical analysis of CQDs and electrochemical habits of the functionalized electrode

Nanoscale morphology and crystallinity

TEM micrographs recorded at totally different magnifications (Fig. 1) display the formation of monodisperse, quasi-spherical CQDs with particle diameters of three.75, 4.34, 2.34, and a pair of.96 nm, yielding a median dimension of three.35 nm. This slender dimension distribution confirms managed nucleation and progress throughout synthesis^46,47. HRTEM pictures additional reveal the presence of graphitic carbon domains, as confirmed by distinct lattice fringes displaying an interplanar spacing of 0.18 nm, indicating partial structural ordering throughout the carbon framework. Such uniform nanoscale morphology offers a constant electroactive interface, which is crucial for reproducible electron-transfer processes^48,49.

TEM pictures of CQDs (A–D) captured at a number of magnifications, illustrating uniform morphology and monodisperse nanoscale particles.

Floor chemistry and useful group structure

The floor chemistry of the CQDs was systematically investigated utilizing FTIR and XPS to elucidate the character of useful teams and defect-related options. The FTIR spectrum (Fig. S1) reveals attribute bands at 3442 cm⁻¹ (O–H), 2856 cm⁻¹(C–H), 1742 cm⁻¹ (C=O), 1632 cm⁻¹ (C=C) and 1152–1051 cm⁻¹ (C–O), confirming the presence of ample oxygen-containing functionalities. These teams are identified to boost floor polarity and promote analyte adsorption^50,51,52.

XPS evaluation (Fig. S2) offers additional perception into the floor chemical states. The C 1s spectrum reveals contributions from graphitic carbon (C–C/C=C, 284.9 eV), defect-associated carbon species (C–H, 285.6 eV), and oxygenated carbon (C–O, 288.4 eV), indicating partial oxidation and the presence of structural defects. The O 1s spectrum confirms C–O/OH and C=O functionalities, supporting the FTIR outcomes. The relative atomic composition obtained from XPS suggests a excessive density of oxygenated species, which may function lively websites for interfacial interactions and facilitate cost switch^53,54,55.

Optical and digital construction

The digital construction of the CQDs was additional evaluated utilizing UV–Vis and photoluminescence (PL) spectroscopy. The absorption bands at 325 and 420 nm are attributed to π–π* transitions linked to graphitic domains and n–π* digital transitions related to floor states, respectively (Fig. S3A)^56,57. The robust PL emission centered at 440 nm upon excitation at 310 nm is attributed to defect-mediated radiative recombination (Fig. S3B), confirming the presence of electronically lively floor defects. These defect states are anticipated to introduce localized vitality ranges that may improve charge-transfer effectivity^58,59.

Microstructure and elemental composition

SEM evaluation (Fig. S4A) reveals aggregated however uniformly distributed nanoparticles, according to the TEM observations. EDX outcomes (Fig. S4B) verify a carbon–oxygen composition (C: 25.29 wt%, 31.08 at%; O: 74.71 wt%, 68.92 at%) with no detectable metallic impurities, verifying the purity of the synthesized CQDs and excluding doable interference from residual catalytic species^60,61,62.

Interfacial electron-transfer dynamics

To evaluate the affect of CQDs’ structural and floor traits on interfacial electron switch, EIS measurements had been carried out on each the naked CPE and the CQDs-modified electrode (Fig. 2). The Nyquist plots exhibit a high-frequency semicircle and a low-frequency linear area, equivalent to charge-transfer and diffusion-controlled processes, respectively. A pronounced lower in semicircle diameter was noticed after CQD modification, indicating lowered interfacial resistance⁶³. The impedance spectra had been quantitatively fitted utilizing the modified Randles equal circuit [Rs(CPE Rct W)], exhibiting good settlement with experimental information as confirmed by the low χ² values (1.4 × 10⁻⁴ for naked CPE and eight.2 × 10⁻⁵ for CQDs/CPE). The fitted Rs values remained practically fixed (0.199 and 0.231 kΩ for naked CPE and CQDs/CPE, respectively), whereas Rct considerably decreased from 2.026 to 0.165 kΩ upon CQD incorporation, demonstrating accelerated electron-transfer kinetics⁶⁴.

The fixed part ingredient parameter (Q) elevated from 3.15 to 14.82 µS sⁿ, accompanied by a rise in n from 0.82 to 0.91, revealing enhanced interfacial homogeneity and extra splendid capacitive habits. Furthermore, the lower within the Warburg coefficient from 0.385 to 0.124 kΩ s^−1/2 signifies improved diffusion and mass transport⁶⁵. Collectively, these outcomes verify that CQD-induced defect websites and oxygenated functionalities improve interfacial cost switch, floor homogeneity, and diffusion, thereby bettering the electrocatalytic efficiency of the modified electrode⁶⁶.

Comparative Nyquist plots of naked CPE and CQDs/CPE, exhibiting substantial discount in interfacial resistance and improved electrochemical response.

Batch-to-batch consistency and reproducibility evaluation of synthesized CQDs

To evaluate the robustness of the synthesis and deal with potential variability from biomass precursors, three impartial CQD batches (batch 1–3) had been evaluated. TEM evaluation (Fig. S5) confirmed imply particle sizes of two.63, 3.35, and three.33 nm for batch 1–3, respectively (SD = 0.41), indicating slender dimension dispersion. PL measurements (Fig. S6A) exhibited constant emission habits throughout batch 1–3 with minimal depth variation (SD = 0.87), confirming optical uniformity. XPS evaluation (Fig. S6B) demonstrated constant reproducible floor chemistry throughout batch 1–3, with atomic percentages of C=C/C–C (71.98, 72.32, 72.09; SD = 0.17), C–H (22.45, 21.73, 22.13; SD = 0.36), and C–O (5.42, 5.59, 5.47; SD = 0.09), alongside constant oxygen functionalities: C–O/OH (73.25, 73.07, 72.76; SD = 0.25) and C=O (26.75, 26.93, 27.14; SD = 0.19). DPV measurements (Fig. S6C) at 100 nM of VON yielded present responses of 10.27, 11.19, and 10.78 µA for batch 1–3, respectively (SD = 0.46), confirming passable electrochemical reproducibility.

Total, the minimal variability throughout batch 1–3 confirms passable artificial consistency. The absence of mineral or metallic contributions additional helps pecan nut biomass as a secure precursor, contributing to dependable sensor efficiency. The consistency throughout batches demonstrates that pecan nut biomass offers a dependable supply of carbon precursors with reproducible functionalization, supporting the sensible scalability of this method. Such batch-to-batch reproducibility ensures that the electrochemical response stays constant and dependable throughout impartial syntheses, highlighting the robustness of the CQDs as a sensing materials.

Electrochemical habits of VON at CQDs-modified carbon paste electrode

The voltammetric response of VON was evaluated at a naked CPE and CQDs/CPE in 0.01 M BRB (pH 9) by way of cyclic voltammetry (0–1.5 V, step potential 5 mV, scan fee 100 mV s⁻¹) as proven in Fig. 3A. On the unmodified electrode, VON generated a faint, broad, irreversible anodic peak close to 1.1 V, indicative of sluggish electron switch. Following CQDs modification, a pronounced, sharp peak emerged on the identical potential, reflecting considerably accelerated electron-transfer dynamics and amplified electroactive floor accessibility.

This sign intensification is attributed to the conductive carbon community, ample defect-rich websites, and expanded floor space of the biomass-derived CQDs, which synergistically facilitate speedy electron movement and promote irreversible VON oxidation. Negligible present within the clean buffer confirmed that the noticed response originates solely from VON. Collectively, these findings spotlight the CQDs/CPE as an electrocatalytically enhanced platform for delicate voltammetric quantification.

The mechanistic pathway of VON electrooxidation was interrogated by way of scan-rate-dependent cyclic voltammetry throughout 10–500 mV s⁻¹ (Fig. 3B). With rising scan fee, a progressive improve within the anodic peak present was noticed, indicating an rising contribution of mass transport to the electrooxidation response. To elucidate the controlling mechanism of the oxidation course of, the connection between the logarithm of the anodic peak present (log I_p) and the logarithm of the scan fee (log ν) was evaluated (Fig. S7A). A robust linear correlation was obtained in response to the equation: log I_p (µA) = 0.5294 log ν − 1.1043 (R² = 0.9926). The calculated slope worth (0.5294) is near the theoretical worth of 0.5 anticipated for a diffusion-controlled course of, whereas values approaching unity are attribute of adsorption-controlled habits^67,68. Though near the theoretical worth of 0.5, the slope worth of 0.5294 was interpreted as a part of a multi-parameter kinetic evaluation quite than as an remoted criterion. When thought of along with the linear I_p–ν^1/2 relationship and the Cottrell response, the convergent electrochemical proof helps a predominantly diffusion-controlled oxidation of VON.

Additional affirmation of the mass-transfer-controlled nature of the oxidation course of was obtained by analyzing the dependence of the anodic peak present on the sq. root of scan fee (({nu}^{1/2})) (Fig. S7B). The linear relationship described by ({I}_{p}) (µA) = (0.1247,nu^{1/2}-0.2372) (R² = 0.9943) demonstrates that the oxidation present follows the attribute habits predicted for diffusion-controlled electrochemical reactions⁶⁹. The linearity of the I_p–ν^1/2 relationship (R² = 0.9943) offers proof that the faradaic response is primarily ruled by semi-infinite linear diffusion of VON from the majority resolution towards the CQDs/CPE interface, quite than by floor accumulation.

Moreover, chronoamperometric measurements carried out on the oxidation potential exhibited a steady lower in present with time, according to the depletion of electroactive VON species close to the electrode floor. The linear correlation between present response and ({t}^{(-1/2)})(Fig. S7C) expressed as I (µA) = 10.473 ({t}^{(-1/2)}-0.1173) (R² = 0.9987), agrees effectively with the Cottrell relationship: I = nFAD^1/2C/(π^1/2 t^1/2)⁷⁰. The linearity of the Cottrell plot offers additional proof for the diffusion-dependent depletion of electroactive VON species throughout the interfacial diffusion layer.

Collectively, these findings present mutually supportive proof for the proposed mass-transfer habits. The mixed proof from the near-theoretical log I_p–log ν slope (0.5294), the linear I_p–ν^1/2 relationship supporting diffusion from the majority resolution towards the electrode interface (R² = 0.9943), and the Cottrell plot supporting diffusion-dependent depletion (R² = 0.9987) signifies that VON electrooxidation on the CQDs/CPE interface is predominantly a diffusion-controlled course of, quite than floor adsorption.

The Randles–Sevcik equation was utilized for estimating the electroactive floor space of the electrodes: Ip = (2.99 × 10⁵) n (αn₀)^1/2 A D^1/2 C ν^1/271. The naked CPE exhibited 0.004 cm², whereas CQDs/CPE confirmed 0.008 cm², confirming a two-fold improve upon CQDs modification. This enhancement corroborates the pronounced anodic peak of VON and displays the improved electron-transfer kinetics and accessibility supplied by the defect-rich CQDs community.

(A) Comparative cyclic voltammograms of fifty nM VON recorded at CQDs/CPE, naked CPE, and clean BRB (0.01 M, pH 9), demonstrating the improved anodic response of the CQDs-modified interface. (B) Scan-rate-dependent cyclic voltammograms of fifty nM VON recorded in 0.01 M Britton–Robinson buffer (pH 9), revealing the kinetic options of the oxidation course of.

Proposed mechanism of electrochemical oxidation of VON

The oxidation pathway of VON was inferred from the voltammetric traits and scan-rate evaluation, which collectively point out an irreversible electrode course of. The anodic transformation is attributed to electron abstraction from the terminal amine performance, producing a reactive intermediate that undergoes proton dissociation to achieve structural stabilization⁷².

It’s well-established within the literature⁷³ that the impact of pH on the height potential for proton-coupled electron switch could be rationalized utilizing a generalized relationship:

the place (y) corresponds to the variety of protons concerned within the electrochemical step and (n) signifies the variety of electrons exchanged.

To scrupulously consider this relationship, the anodic peak potential was plotted towards pH within the vary of pH 7.0–12.0, and the corresponding linear regression evaluation is introduced in Fig. S8A. A linear relationship was obtained, as expressed by the regression equation:

The excessive dedication coefficient (R² = 0.9951) confirms the robust linearity and statistical reliability of the information. The experimental slope of − 0.030 V/pH (− 30 mV/pH) intently matches the theoretical Nernstian slope of − 0.0295 V/pH anticipated for a system with a proton-to-electron ratio (y/n) of 1/2 (i.e., 1 H⁺/2e⁻ switch). This commentary offers quantitative assist for the proposed two-electron/one-proton mechanism, substantiating the involvement of protons within the total oxidation pathway.

To additional substantiate the electron-transfer kinetics and validate the proposed mechanism, Laviron’s mannequin for irreversible methods was utilized by correlating the height potential (({E}_{p})) with the logarithm of the scan fee (log ν)⁷⁴. A well-defined linear relationship was obtained (Fig. S8B), described by ({E}_{p})= 0.0596 log ν + 0.9806 (R² = 0.9975). Based mostly on the slope and assuming a cost switch coefficient (α) of 0.5, the variety of electrons concerned within the rate-determining step was calculated to be 1.99, which is successfully equal to a two-electron switch course of.

The general response is due to this fact ruled by a two-electron/one-proton switch sequence, selling the conversion of the amine moiety right into a extra conjugated iminium-like construction accompanied by double-bond growth (Scheme 2). This interpretation is additional supported by Laviron evaluation, which yielded an electron variety of (n ≈ 2), confirming the involvement of a two-electron switch step. Combining this with the experimental E_p versus pH slope of − 0.030 V/pH helps the involvement of a single proton (y = 1) within the rate-determining step. The noticed response displays the established anodic habits of amine-substituted heterocycles, wherein proton-coupled electron switch triggers subsequent chemical evolution that renders the oxidation electrochemically irreversible.

Proposed proton-coupled electron-transfer pathway for the irreversible oxidation of VON.

Voltammetric methodology optimization and parameter analysis

Optimization of the electrochemical setting encompassed pH management, CQDs-mediated floor engineering, and adjustment of DPV variables. This built-in tuning markedly improved sign depth and peak sharpness.

Impact of pH and supporting electrolyte

The anodic oxidation of VON was evaluated throughout pH 2–12 in 0.04 M BRB. Within the acidic area (pH 2–6), no oxidation peaks had been noticed, yielding featureless DPV curves much like the clean baseline (Fig. S9). This lack of electrochemical exercise underneath acidic situations could also be related to the protonation of the essential nitrogen moieties of VON. The ensuing cationic species could exhibit lowered electron density on the electroactive website, which can contribute to the absence of an observable oxidation sign throughout the monitored potential window.

Oxidation peaks emerged solely within the pH vary 7–12. A scientific shift within the peak potential with rising pH was recorded, indicating that proton availability modulates the rate-determining step, according to the proton-coupled electron switch (PCET) mechanism. Beneath alkaline situations, partial deprotonation of the terminal amine enhances its electron-donating capability, facilitating electron abstraction and stabilizing the intermediate species fashioned throughout oxidation.

The height present reached a most at pH 9 (Fig. 4), reflecting an optimum steadiness between proton participation and molecular deprotonation. At this pH, the partially deprotonated amine permits environment friendly cost switch whereas retaining enough proton involvement for chemical stabilization of the oxidized species. This habits aligns with scan-rate evaluation, which revealed a predominantly diffusion-controlled course of. Moreover, favorable interactions between the analyte and oxygen-rich useful teams on the CQDs floor could additional improve electron-transfer kinetics. These mechanistic insights assist the two-electron/one-proton oxidation pathway and justify the choice of pH 9 because the optimum medium for delicate, reproducible voltammetric dedication of VON.

As well as, the affect of the supporting electrolyte was examined by evaluating 0.05 M borate buffer with 0.04 M BRB at pH 9 (Fig. S10) Though borate buffer offers efficient buffering capability underneath alkaline situations, a relatively decrease anodic peak present was obtained relative to BRB. This distinction could also be attributed to the distinct ionic composition and buffering traits of the 2 methods, which may affect proton-transfer processes and the interfacial charge-transfer habits on the CQDs-modified electrode floor. In distinction, BRB, as a multicomponent buffer system, offers an acceptable ionic setting that facilitates proton change and promotes environment friendly electron-transfer processes. Consequently, 0.04 M BRB was chosen because the optimum supporting electrolyte for all subsequent measurements.

pH-dependent differential pulse voltammetric response of fifty nM VON at CQDs/CPE in 0.04 M BRB, illustrating anodic peak variation (0.8–1.4 V, 5 mV step, 50 mV modulation, 100 mV/s).

Impact of electrode floor modification on electrochemical response

The impression of floor modification on the electrochemical habits of the electrode was systematically evaluated utilizing MWCNTs (1–2%), CdO (1–2%), ZnO (1%), and CQDs as compared with naked CPE and the clean, as proven in Fig. 5. The unmodified electrode produced a comparatively weak anodic sign, indicating hindered electron-transfer kinetics. Though MWCNTs improved the present response by way of enhanced conductivity and floor space, CdO and ZnO yielded solely modest amplification, possible resulting from much less favorable interfacial cost transport.

Strikingly, the CQDs/CPE exhibited the best peak depth, reflecting markedly accelerated charge-transfer kinetics and enhanced analyte accumulation, attributable to the defect-rich carbon matrix and ample floor functionalities. To evaluate the potential contribution of PEG-400, clean experiments had been carried out utilizing CQDs/CPE within the absence of VON. No faradaic response was noticed in both CV (Fig. S11A) or DPV (Fig. S11B), confirming that PEG-400 doesn’t contribute to the electrocatalytic enhancement, however quite acts as a stabilizing agent throughout CQD synthesis; the noticed sign arises solely from the interplay of VON with the engineered CQD-modified electrode interface. Accordingly, CQDs had been chosen because the optimum modifier for establishing a delicate electrochemical sensing platform.

Comparative DPV of fifty nM VON at nanomodified CPEs in 0.04 M BRB (pH 9), demonstrating the essential contribution of electrode interface design to the enhancement of the oxidation sign.

Optimization of CQDs interface loading quantity

To maximise electrocatalytic effectivity, the loading quantity of the biomass-derived CQDs suspension throughout the carbon paste matrix was systematically diversified from 5 to 40 µL. The amount of this nanostructured modifier crucially dictates the electrochemically lively floor space and subsequent charge-transfer resistance. As illustrated in Fig. S12, incremental immobilization of the CQDs resolution as much as 20 µL induced a progressive amplification within the anodic peak present of VON, attributed to an elevated density of graphitic domains and oxygenated floor functionalities that develop accessible digital floor states and speed up interfacial electron-transfer kinetics. Conversely, rising the modifier loading past 20 µL resulted in a lower within the voltammetric response and a rise within the capacitive background present. This efficiency deterioration is ascribed to extreme accumulation of the carbon nanomaterial, which induces mass-transport limitations, impedes analyte diffusion, and generates a thick, poorly conductive interfacial layer that partially passivates the underlying conductive graphite networks. Consequently, a 20 µL loading quantity was established because the optimum operational normal, guaranteeing a great compromise between speedy interfacial kinetics, structural stability, and peak sensitivity.

Optimization of differential pulse voltammetric parameters

The electroanalytical effectivity of the fabricated sensing interface is intrinsically ruled by instrumental parameters; due to this fact, key DPV variables had been rigorously optimized to boost present response with out compromising peak decision.

Scan fee

The DPV scan fee was investigated throughout 5–120 mV s⁻¹ to elucidate its affect on the voltammetric habits (Fig. S13A). The anodic present elevated constantly with scan fee, suggesting facilitated charge-transfer processes and improved electrochemical responsiveness. The sign attained its highest depth at 100 mV s⁻¹; additional increments provided negligible enhancement and should promote non-faradaic contributions that adversely have an effect on peak readability. Consequently, 100 mV s⁻¹ was adopted for subsequent analyses because it offers an optimum compromise between sign amplification and voltammetric decision.

Potential amplitude

The impression of pulse amplitude was evaluated over the vary of 10–100 mV (Fig. S13B). Elevating the amplitude progressively intensified the oxidation sign as much as 50 mV, indicative of strengthened faradaic processes. Nevertheless, amplitudes past this threshold led to noticeable peak widening and not using a commensurate rise in present, implying diminished analytical precision. Due to this fact, 50 mV was chosen because the optimum pulse amplitude, because it ensures enhanced sensitivity whereas preserving distinct and well-defined peak morphology.

Analytical efficiency of the proposed methodology

The sensing effectivity of the CQDs/CPE nanosensor for the voltammetric dedication of VON was comprehensively evaluated underneath the optimized experimental situations. The engineered sensing interface produced sharp, well-resolved oxidation peaks that elevated systematically with rising analyte focus, signifying the robust electrocatalytic affect of the CQDs and the facilitated charge-transfer kinetics on the electrode floor.

A transparent linear correlation between the anodic peak present (I_p) and VON focus was established over the ultralow vary of 1.0 × 10⁻⁸–1.0 × 10⁻⁷ mol L⁻¹, as illustrated in Fig. 6. Every focus was measured in triplicate, and the usual deviation (SD) of the ensuing currents was calculated. Error bars representing ± SD had been included into the calibration plot to mirror experimental reproducibility. The calibration plot obeyed the regression equation: ({I}_{p}=0.0977,conc,left(ntext{mol},{L}^{-1}proper)+0.55), with a powerful correlation coefficient (R² = 0.9992). The slope and intercept of the calibration curve had been additional validated by their 95% confidence intervals, calculated as 0.0977 ± 0.00227 (0.0954–0.0999) and 0.55 ± 0.1407 (0.409–0.691), respectively, indicating minimal statistical dispersion and reliability of the regression parameters. Residuals, calculated because the distinction between noticed and predicted anodic peak currents, exhibited a imply of − 0.0015 µA and SD of 0.07993 µA, with random distribution round zero (Fig. S14), confirming linearity and homoscedasticity of the calibration mannequin.

The detection sensitivity was additional quantified by way of dedication of the detection and quantification limits (LOD and LOQ), as decided from the clean sign normal deviation (σ) and the calibration curve slope (s), in response to accepted validation pointers (LOD = 3.3 σ/s and LOQ = 10 σ/s). The CQDs/CPE sensor delivered an exceptionally low LOD of three.9 × 10⁻¹⁰ mol L⁻¹ and an LOQ of 1.19 × 10⁻⁹ mol L⁻¹, underscoring its efficient efficiency in sub-nanomolar detection. Such enhanced sensitivity could be primarily ascribed to the enlarged electroactive floor space, excessive density of edge-plane-like websites, and defect-rich carbon construction of the CQDs.

Total, the linear dynamic vary, favorable regression traits, and low detection limits assist the analytical efficiency of the proposed sensor for VON quantification in pharmaceutical evaluation.

DPV recorded on the CQDs/CPE for successive additions of VON (1.0 × 10⁻⁸–1.0 × 10⁻⁷ mol L⁻¹) in 0.04 M BRB (pH 9).

Methodology validation

The voltammetric method was rigorously validated to confirm its reliability for VON quantification. Important efficiency attributes—accuracy, precision, robustness, stability, selectivity, and interference resistance—had been evaluated following acknowledged validation rules, guaranteeing constant analytical efficiency and methodological integrity.

Accuracy

The trueness of the proposed electrochemical methodology was critically examined to ascertain its functionality for unbiased VON dedication. Accuracy was assessed by way of the evaluation of normal options at three focus ranges (15, 45, 85 nM) underneath the optimized experimental situations (Fig. S15A). Overlaid DPV curves recorded in triplicate for every focus demonstrated constant peak present responses and minimal peak potential shift. The calculated restoration values exhibited shut concordance with the corresponding theoretical quantities, reflecting minimal systematic deviation and a excessive diploma of analytical exactness. As introduced in Desk 1, the favorable restoration outcomes substantiate the methodological reliability of the CQDs/CPE sensing platform and make sure its competence for exact quantitative evaluation throughout the investigated vary.

Precision

The repeatability and intermediate precision of the CQDs/CPE voltammetric platform had been assessed by way of intraday and interday analyses of normal VON options at three focus ranges (20, 50, 80 nM). Intraday precision was evaluated by performing triplicate measurements inside a single day (Fig. S15B), whereas interday precision was evaluated throughout three consecutive days (Fig. S15C). The recorded DPV curves confirmed good sign reproducibility and constant peak potentials throughout all replicate trials. Peak present responses had been employed to compute relative normal deviations (RSD%), which remained low (starting from 0.54 to 0.64% intraday and 0.48–0.77% for interday), as summarized in Desk 2. These outcomes point out acceptable reproducibility and operational stability for routine measurements.

Robustness

The reliability of the CQDs/CPE voltammetric process was systematically examined by way of the introduction of intentional, minor modifications in operational parameters, together with step potential, pulse amplitude, scan fee, and supporting electrolyte pH. The anodic peak currents of VON remained largely unaffected (Desk S1), exhibiting solely minor fluctuations, which signifies the tactic’s resilience to typical experimental perturbations. These outcomes spotlight the sensor’s operational stability and reliability, confirming that its analytical efficiency is maintained underneath refined deviations in each instrumental settings and resolution situations.

Stability and reusability

The efficiency of the CQDs/CPE electrode and VON options was systematically evaluated for each short- and long-term stability. Quick-term stability was demonstrated by 10 consecutive DPV scans, retaining > 98% of the preliminary peak present (RSD = 1.5%, Fig. S16A), accompanied by the corresponding overlaid voltammograms exhibiting constant peak form, potential, and present response (Fig. S16B), indicating negligible floor fouling and good sign reproducibility.

Lengthy-term stability over 14 days underneath refrigerated situations preserved > 95% of the preliminary response (Fig. S16C), whereas ambient storage confirmed a average decline (~ 88%, Fig. S16C), supported by consultant DPV curves confirming sign habits over time underneath each situations (Fig. S16D), indicating higher sign retention underneath low-temperature storage.

Reusability was assessed over 20 successive measurement cycles, and the relative peak present retention was calculated for every cycle, with < 5% total sign loss (Fig. S16E), alongside the corresponding overlaid DPV profiles (Fig. S16F), whereas impartial electrode preparations exhibited an RSD of two% (Fig. S16G), with overlaid voltammograms straight demonstrating constant peak depth and potential throughout independently fabricated electrodes (Fig. S16H), supporting reproducibility of electrode fabrication. Collectively, these outcomes display a constant electrochemical response underneath the investigated situations.

Selectivity and interference analysis

The selectivity of the CQDs/CPE voltammetric platform towards VON was systematically evaluated each individually and underneath simultaneous situations in a combined resolution containing co-administered or substituted medicine, structurally associated acid-suppressing brokers, antibiotics used for H. pylori eradication, widespread electroactive species, and pharmaceutical excipients. The research included proton pump inhibitors resembling esomeprazole, antibiotics together with amoxicillin and levofloxacin, consultant electroactive biomolecules resembling ascorbic acid and uric acid, and excipients comprising croscarmellose sodium, corn starch, magnesium stearate, and lactose monohydrate.

DPV measurements obtained for the multicomponent combination (Fig. S17A) in addition to particular person binary options containing VON with every particular interferent (Fig. S17B–F) confirmed that these species induced negligible modifications within the anodic peak present of VON, with no observable overlapping alerts throughout the studied potential window. The anodic peak of VON appeared at roughly 1.10 V, distinctly separated from the oxidation potentials of potential interferents—amoxicillin (~ 0.30 V)⁷⁵, uric acid (~ 0.20 V)⁷⁶, ascorbic acid (~ 0.50 V)⁷⁷, esomeprazole (~ 0.70 V)⁷⁸, and levofloxacin (~ 0.80 V)⁷⁹—indicating clear peak separation underneath the investigated situations.

Moreover, quantitative evaluation of the relative peak present response (%) of VON within the presence of particular person interferents, excipients, and the mixed combination confirmed minimal sign variation (< 5% relative error, n = 3), as depicted within the corresponding bar chart with error bars (Fig. S17G). These outcomes point out that the examined co-existing species had a restricted impact on the VON response underneath the investigated situations. Accordingly, the proposed sensor could be utilized for the quantification of VON within the investigated pharmaceutical and organic matrices.

Investigation of methodology efficiency in pharmaceutical formulations, organic fluids, and environmental samples

The efficiency of the CQDs/CPE voltammetric methodology was evaluated throughout pharmaceutical formulations, organic matrices, and environmental samples. For business dosage kinds, the tactic precisely quantified VON (Desk S2), confirming its suitability for routine high quality management. In human plasma samples spiked with VON, recoveries and precision metrics (Desk S3) validated its bioanalytical applicability. Lastly, artificial industrial wastewater was analyzed (Desk S4), demonstrating dependable efficiency in complicated aqueous matrices. Collectively, these research spotlight the tactic’s broad scope, accuracy, and reproducibility, establishing it as a dependable device for pharmaceutical, medical, and environmental analyses.

Comparative analysis of the developed analytical methodology

Chromatographic methodologies^{14,15,16,17,18,19} are basically ruled by reversed-phase interactions on C18 stationary phases coupled with natural cell phases, enabling exact multi-analyte quantification and impurity profiling by way of hydrophobic partitioning equilibria. UHPLC²⁰ extends this paradigm by integrating high-pressure operation, gradient elution schemes, and structurally selective stationary phases (e.g., phenyl-hexyl), thereby bettering separation effectivity and backbone. Regardless of these benefits, such strategies stay depending on instrumentally intensive platforms and solvent-demanding protocols.

UV spectrophotometric approaches^21,22 depend on aqueous media or oxidative derivatization pathways (e.g., NBS-mediated reactions), the place detection relies on digital absorption or chromophore formation. Though operationally easy, their reliance on optical sign transduction inherently restricts selectivity, notably in complicated matrices. In distinction, spectrofluorometric strategies^23,24,25,26 supply enhanced sensitivity by way of fluorescence-based mechanisms, together with quenching interactions, dye-assisted complexation, and CQDs-enabled emission methods. Nevertheless, these approaches incessantly necessitate derivatization steps or rigorously engineered probe environments, which can restrict sensible applicability.

Electrochemical strategies present a extra direct and delicate analytical interface. Potentiometric sensors²⁷ generate responses by way of phase-boundary potentials according to Nernstian habits. Beforehand reported voltammetric methods²⁸ make the most of nanostructured composites resembling Ce-doped ZnO/rGO synthesized by way of hydrothermal routes, the place sign era arises from surface-confined electrocatalytic oxidation processes, facilitated by enhanced conductivity, enlarged lively floor space, and ample redox-active websites. However, these methods typically contain multi-step fabrication procedures and reliance on inorganic nanomaterials.

In distinction, the CQDs/CPE sensor developed herein is fabricated by way of a facile one-pot synthesis of biomass-derived carbon quantum dots, providing a sustainable and reproducible platform. The sensing mechanism is related to defect-mediated electron-transfer kinetics, whereby oxygen-containing useful teams and intrinsic structural defects introduce localized digital states that improve cost transport and promote interactions with VON, thereby amplifying the electrocatalytic response. In comparison with present electrochemical methods, the CQDs/CPE sensor combines sustainable synthesis, defect-rich electron-transfer enhancement, and broad applicability, representing a transparent authentic contribution.

As evidenced in Desk 3, these mixed attributes not solely advance mechanistic understanding but additionally translate into dependable analytical efficiency for VON dedication in pharmaceutical, organic, and environmental matrices.

Analysis of methodology greenness and environmental compatibility

Amid the shift towards sustainable laboratory practices, the ecological attributes of the proposed methodology had been evaluated. The evaluation emphasised lowering hazardous reagents, minimizing solvent consumption and waste, and streamlining procedures whereas preserving analytical effectivity. The proposed methodology offers a sustainable various with out sacrificing sensitivity, precision, or robustness.

To make sure thorough and multidimensional appraisal, the sustainability efficiency of the proposed process was evaluated utilizing 5 established analytical metrics. For comparative evaluation, a reported RP-HPLC methodology¹⁸ was chosen because the reference benchmark. RP-HPLC represents a broadly established and routinely utilized analytical method for pharmaceutical high quality management and the dedication of VON. Nevertheless, chromatographic strategies sometimes contain using appreciable volumes of natural solvents and generate chemical waste. Due to this fact, comparability with this consultant chromatographic method offers a related foundation for evaluating the environmental and sensible benefits of the proposed voltammetric methodology.

Analytical eco-scale

The environmental friendliness of the designed voltammetric methodology was evaluated utilizing the Analytical Eco-Scale, a semi-quantitative metric assigning penalty factors for reagent toxicity, solvent consumption, vitality use, and waste era to yield an total sustainability rating. Strategies scoring above 75 are thought of inexperienced⁸⁰. The proposed technique achieved a positive rating of 90, reflecting its minimal chemical hazards, conservative solvent utilization, and low waste era. By comparability, the reported chromatographic methodology¹⁸ scored 83, indicating affordable greenness however a comparatively higher ecological burden (Desk 4). These findings emphasize the decrease environmental footprint of the voltammetric method and assist its adoption as a extra sustainable analytical various.

AGREE (analytical greenness metric) method

A complete and visually informative analysis of analytical procedures is achieved by way of the AGREE (Analytical GREEnness) metric, which integrates all 12 pointers of inexperienced analytical chemistry right into a single rating spanning 0 (least inexperienced) to 1 (most inexperienced)⁸¹. The proposed voltammetric methodology attained a excessive rating of 0.83, reflecting its lowered chemical hazards, minimal solvent consumption, and streamlined operational workflow. In distinction, the reported chromatographic methodology¹⁸ scored 0.56, indicating average greenness and a relatively increased environmental burden. These findings, summarized in Desk 4, underscore the improved sustainability of the voltammetric method and its suitability as a greener analytical various.

Complicated GAPI (complementary inexperienced analytical process index)

The Complicated GAPI framework gives a multidimensional, color-coded visualization of an analytical methodology’s environmental efficiency, capturing the ecological impression throughout numerous procedural and chemical parameters⁸². The proposed voltammetric methodology demonstrated a positive profile, with 1 pink, 3 yellow, and 11 inexperienced zones, highlighting its minimal ecological footprint and powerful alignment with the rules of inexperienced analytical chemistry. In distinction, the reported chromatographic methodology¹⁸ introduced 3 pink, 8 yellow, and 4 inexperienced zones, indicating a relatively higher environmental burden (Desk 4). These findings underscore the improved sustainability of the voltammetric technique and additional substantiate its position as a extra environmentally accountable analytical various.

BAGI (blue applicability grade index) method

The BAGI offers an built-in analysis of analytical strategies by combining ecological efficiency with operational practicality, yielding a unified metric that captures each sustainability and useful effectivity⁸³. The proposed voltammetric methodology attained a powerful rating of 75, reflecting an optimum steadiness between environmental friendliness and analytical effectiveness. In distinction, the reported chromatographic methodology¹⁸ scored 65, indicating average greenness accompanied by higher procedural and useful resource calls for (Desk 4). These outcomes additional spotlight the favorable environmental and sensible profile of the voltammetric technique, reinforcing its suitability as a greener and extra environment friendly analytical various.

White analytical chemistry (RGB12) evaluation

This method gives a complete analysis by integrating three core dimensions: environmental (inexperienced), analytical efficiency (pink), and sensible feasibility (blue). It generates a single composite rating reflecting the general sustainability, effectivity, and applicability of the tactic⁸⁴. Making use of this metric, the proposed voltammetric methodology achieved a rating of 95.9, demonstrating alignment with inexperienced chemistry rules alongside good analytical efficiency and sensible applicability. In distinction, the reported chromatographic methodology¹⁸ scored 80.9, reflecting good total efficiency however a relatively increased environmental and procedural burden (Desk 4). These outcomes spotlight the improved eco-analytical steadiness of the voltammetric technique, reinforcing its suitability as a sustainable and environment friendly analytical platform.