# Model of Chronoamperometric Response towards Glucose Sensing by Arrays of Gold Nanostructures Obtained by Laser, Thermal and Wet Processes

^{1}

^{2}

^{3}

^{4}

^{*}

## Abstract

**:**

## 1. Introduction

^{−}

## 2. Materials and Methods

#### 2.1. Materials and Electrode Fabrication

_{2}atmosphere, in a Carbolite Gero oven (Verder Scientific, GmbH & Co. Retsch-Allee 1-5 42781 Haan, Germany); (c) dewetting of 17 nm thin gold layer by nanosecond pulsed laser irradiation. Nd: yttrium aluminum garnet YAG laser, operating at 532 nm of wavelength was used (Quanta-ray PRO-Series pulsed Nd:YAG equipment, Spectra Physics, 1565 Barber Lane Milpitas, CA 95035, USA). The conditions of the irradiation process were 10 ns pulse duration, fluence of 0.5 Jcm

^{−2}, in air. In the used experimental conditions, the typical spot size of the laser beam was 2 mm. To fully irradiate an area of 1 cm

^{2}, several nearby spots were made, partially overlapping each other. In all systems, the electrode working area was 1 cm

^{2}. The employed experimental conditions of thermal and laser dewetting were optimized experimentally in order to obtain reproducible results.

#### 2.2. Instrumental Characterization

_{7/2}peak of untreated gold reference, which is centered at 84 eV of binding energy [32,33], was used for the binding energy scale calibration. Electrochemical measurements were performed in air at 22 °C by a potentiostat VersaSTAT 4 (Princeton, Oak Ridge, TN, USA). In each measurement, 30 mL of fresh solutions of glucose at various concentrations in NaOH 0.1 M were used. The potential of the working electrodes was referenced to the saturated calomel electrode (SCE). Platinum wire was used as a counter. The electrochemical characterization of gold nanostructures was performed by cyclic voltammetry (CV) at a scan rate of 20 mVs

^{−1}and amperometric measurements.

## 3. Results

#### 3.1. Morphology and Electronic Structure

_{7/2,5/2}spin-orbit components centered at binding energy of 84 and 87.7 eV (3.7 eV spin-orbit coupling), respectively, thus indicating the presence of Au

^{0}states [32,33]. Instead, the spectrum of laser-dewetted gold (Figure 2d) shows the Au 4f

_{7/2,5/2}spin-orbit components centered at 84.35 and 88.05 eV (3.7 eV spin-orbit coupling), respectively. The observed shift of the binding energies can be assigned to the presence of Au(I) specie [34], which are formed by laser interaction with the gold layer, characterized by a high-temperature process.

#### 3.2. Electrochemical Characterization

^{−2}of fluence, respectively. The voltammograms show four main features, whose relative intensity depends on the type of gold nanostructure. In particular, in the forward scan ongoing from the potential of −0.5 to 1 V vs. SCE, the peak 1 at about −0.15 V is assigned to glucose adsorption on the gold surface by dehydrogenation [36,37].

_{6}H

_{12}O

_{6}+ OH

^{−}+ Au → Au(C

_{6}H

_{11}O

_{6})

_{ads}+ H

_{2}O + e

^{−}

^{-}on the gold surface, and the formation of gold hydroxide intermediate complex:

^{−}⇆ [Au(OH)

_{ads}]

^{−}

_{6}H

_{11}O

_{6})

_{ads}+ [Au(OH)

_{ads}]

^{−}→ [Au--O-(C

_{6}H

_{10}O

_{6})

_{ads}]

^{−}+ Au + H

_{2}O

_{6}H

_{10}O

_{6})

_{ads}]

^{−}→ AuOH + C

_{6}H

_{10}O

_{6}+ e

^{−}

_{ads}

^{]−}⇆ Au

_{2}O + H

_{2}O + 2e

^{−}

_{2}O + C

_{6}H

_{12}O

_{6}→ C

_{6}H

_{10}O

_{6}+ 2 AuOH

_{0}is the heterogeneous rate constant, c

_{glucose}is the bulk concentration of glucose, α

_{a}is the anodic charge transfer coefficient, and E

_{f}

^{0}is the formal potential of the redox couple. Accordingly, the current density depends on the k

_{0}, α

_{a}, and E

_{f}

^{0}, fixing the analyte concentration c

_{glucose}.

#### 3.3. Modeling of the Current-Time Curves

^{−10}m

^{2}s

^{−1}) [41], the convergent diffusion approaches the semi-infinite linear diffusion as depicted in the scheme of Figure 5:

_{0}, according to Equation (12).

_{0}used for the simulations are reported in Table 1. Since n, F, and c are the same for the two curves of Figure 6b,d, the different values of the parameter B

_{0}used for the 8 nm 300 °C and laser-irradiated nanostructures reflect the extension of the active area of the two samples. In particular, the parameter B

_{0}is about 4 times higher for the 8 nm 300 °C with respect to the laser-irradiated nanostructure. Thus, the two nanostructures resemble a macro-electrode. This mechanism occurs because of the gold nano-spheres and nano-islands, although the existence of a convergent diffusion mechanism can be hypothesized in the proximity of the electro-active particles separated by the inactive material, the mechanism itself is modified, and the resultant is a semi-infinite linear diffusion (see Figure 5) [10,11].

_{2}H, CAS # 1271-42-7), and proposed Equation (17) to model the chronoamperometric curve [44]:

_{1}and k

_{2}represent the heterogeneous rate constants of glucose adsorption, forming the intermediate, and intermediate decay to gluconolactone, respectively. In Table 1, the heterogeneous rate constants k

_{1}and k

_{2}are similar for 17 nm 400 °C and laser dewetted samples and are effective in the fit of the curve transient in the initial few seconds. In these two gold nanostructures, due to the highly developed surface; hence, the high concentration of adsorbed molecules of glucose, the rate of oxidation process is not limited by diffusion at the early stage of current-time curves. For the transient region, the current is determined by the kinetics of the overall oxidation reaction characterized by the constants k

_{1}and k

_{2}, and, therefore, by the exponential terms present in Equation (18). For a long time, when adsorbed glucose is consumed, the limit current is determined by the diffusion limiting factor, as in the case of systems which satisfy the Cottrellian equation. The term $\mathrm{N}\frac{4\mathrm{nFADc}}{\mathsf{\pi}\mathrm{r}}{\mathrm{B}}_{1}$ represents the steady state current.

#### 3.4. Glucose Determination in Amperometric Mode

## 4. Conclusions

_{1}and k

_{2}, of the mixed second-order formation of the intermediate of adsorbed glucose followed by its first-order decay to gluconolactone. The mechanisms were well modeled by a two-phase exponential decay function. At times beyond the transient, when adsorbed glucose is consumed, the steady state current is determined by the diffusion limiting factor, as in the case of systems that satisfy the Cottrellian equation. The work we have presented shows how by simulating the current-time response, it is possible to obtain information both on the diffusion model, whether convergent or planar and also on the mechanisms and kinetics of the electrochemical reactions taking place at the electrode–solution interface.

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

- Baig, N.; Kammakakam, I.; Falath, W. Nanomaterials: A review of synthesis methods, properties, recent progress, and challenges. Mater. Adv.
**2021**, 2, 1821. [Google Scholar] [CrossRef] - Khan, I.; Saeed, K.; Idrees, K. Nanoparticles: Properties, applications and toxicities. Arab. J. Chem.
**2019**, 12, 908–931. [Google Scholar] [CrossRef] - Tsuji, T. Preparation of NPs using laser ablation in liquids: Fundamental aspects and efficient utilization. In Laser Ablation in Liquid: Principles and Applications in the Preparation of Nanomaterials; Yang, G., Ed.; Jenny Stanford Publishing: Singapore, 2012; pp. 2027–2257. ISBN 9789814310956. [Google Scholar]
- Marzun, G.; Streich, C.; Jendrzej, S.; Barcikowski, S.; Wagener, P. Adsorption of colloidal platinum nanoparticles to supports: Charge transfer and effects of electrostatic and steric interactions. Langmuir
**2014**, 30, 11928–11936. [Google Scholar] [CrossRef] [PubMed] - Zhang, J.; Oko, D.N.; Garbarino, S.; Imbeault, R.; Chaker, M.; Tavares, A.C.; Guay, D.; Ma, D. Preparation of PtAu alloy colloids by laser ablation in solution and their characterization. J. Phys. Chem. C
**2012**, 116, 13413–13420. [Google Scholar] [CrossRef] - Reichenberger, S.; Marzun, G.; Muhler, M.; Barcikowski, S. Perspective of Surfactant-Free Colloidal Nanoparticles in Heterogeneous Catalysis. ChemCatChem
**2019**, 11, 4489–4518. [Google Scholar] [CrossRef] - Wei, H.; Wang, E. Nanomaterials with enzyme-like characteristics (nanozymes): Next-generation artificial enzymes. Chem. Soc. Rev.
**2013**, 42, 6060–6093. [Google Scholar] - Huang, Y.; Ren, J.; Qu, X. Nanozymes: Classification, Catalytic Mechanisms, Activity Regulation, and Applications. Chem. Rev.
**2019**, 119, 4357–4412. [Google Scholar] - Wu, J.; Wang, X.; Wang, Q.; Lou, Z.; Li, S.; Zhu, Y.; Qin, L.; Wei, H. Nanomaterials with enzyme-like characteristics (nanozymes): Next-generation artificial enzymes (II). Chem. Soc. Rev.
**2019**, 48, 1004–1076. [Google Scholar] - Welch, C.M.; Compton, R.G. The use of nanoparticles in electroanalysis: A review. Anal. Bioanal. Chem.
**2006**, 384, 601–619. [Google Scholar] [CrossRef] - Simm, A.O.; Ward-Jones, S.; Banks, C.E.; Compton, R.G. Novel Methods for the Production of Silver Microelectrode-Array: Their Characterisation by Atomic Force Microscopy and Application to the Electro-reduction of Halothane. Anal. Sci.
**2005**, 21, 667–671. [Google Scholar] - Kang, M.; Park, S.; Jeong, K. Repeated Solid-state Dewetting of Thin Gold Films for Nanogap-rich Plasmonic Nanoislands. Sci. Rep.
**2015**, 5, 14790. [Google Scholar] [CrossRef] [Green Version] - Oh, Y.J.; Jeong, K.H. Glass Nanopillar Arrays with Nanogap-Rich Silver Nanoislands for Highly Intense Surface Enhanced Raman Scattering. Adv. Mater.
**2012**, 24, 2234–2237. [Google Scholar] - Zhang, D.; Gökce, B.; Barcikowski, S. Laser Synthesis and Processing of Colloids: Fundamentals and Applications. Chem. Rev.
**2017**, 117, 3990–4103. [Google Scholar] [CrossRef] - Liang, S.; Zhang, L.; Reichenberger, S.; Barcikowski, S. Design and perspective of amorphous metal nanoparticles from laser synthesis and processing. Phys. Chem. Chem. Phys.
**2021**, 23, 11121–11154. [Google Scholar] - Semaltianos, N.G. Nanoparticles by laser ablation of bulk target materials in liquids. In Handbook of Nanoparticles; Aliofkhazraei, M., Ed.; Springer: Cham, Switzerland, 2016; pp. 67–92. [Google Scholar] [CrossRef]
- Khorasani, M.; Gibson, I.; Ghasemi, A.H.; Hadavi, E.; Rolfe, B. Laser subtractive and laser powder bed fusion of metals: Review of process and production features. Rapid Prototyp. J.
**2023**. [Google Scholar] [CrossRef] - Scandurra, A.; Censabella, M.; Gulino, A.; Grimaldi, M.G.; Ruffino, F. Gold nanoelectrode arrays dewetted onto graphene paper for selective and direct electrochemical determination of glyphosate in drinking water. Sens. Bio-Sens. Res.
**2022**, 36, 100496. [Google Scholar] [CrossRef] - Scandurra, A.; Ruffino, F.; Censabella, M.; Terrasi, A.; Grimaldi, M.G. Dewetted Gold Nanostructures onto Exfoliated Graphene Paper as High Efficient Glucose Sensor. Nanomaterials
**2019**, 9, 1794. [Google Scholar] [CrossRef] [Green Version] - Lin, Y.; Ren, J.; Qu, X. Nano-Gold as Artificial Enzymes: Hidden Talents. Adv. Mater.
**2014**, 26, 4200–4217. [Google Scholar] - Scandurra, A.; Ruffino, F.; Sanzaro, S.; Grimaldi, M.G. Laser and Thermal Dewetting of Gold Layer onto Graphene Paper for non-Enzymatic Electrochemical Detection of Glucose and Fructose. Sens. Actuators B Chem.
**2019**, 301, 127113. [Google Scholar] [CrossRef] - Müsse, A.; La Malfa, F.; Brunetti, V.; Rizzi, F.; De Vittorio, M. Flexible Enzymatic Glucose Electrochemical Sensor Based on Polystyrene-Gold Electrodes. Micromachines
**2021**, 12, 805. [Google Scholar] [CrossRef] - Funtanilla, V.D.; Candidate, P.; Caliendo, T.; Hilas, O. Continuous Glucose Monitoring: A Review of Available Systems. Pharm. Ther.
**2019**, 44, 550–553. [Google Scholar] - Brett, C.; Brett, A.M.O. Electrochemistry: Principles, Methods, and Applications; Oxford University Press: Oxford, UK, 1993. [Google Scholar]
- Hood, S.J.; Kampouris, D.K.; Kadara, R.O.; Jenkinson, N.; Javier del Campo, F.; Muñoz, F.X.; Banks, C.E. Why ‘the bigger the better’ is not always the case when utilizing microelectrode arrays: High density vs. low density arrays for the electroanalytical sensing of chromium(VI). Analyst
**2009**, 134, 2301–2305. [Google Scholar] [CrossRef] [PubMed] - Cottrell, F.G. Der Reststrom bei galvanischer Polarisation, betrachtet als ein Diffusionsproblem. Z. Für Phys. Chem.
**1903**, 42U, 385. [Google Scholar] [CrossRef] - Aoki, K.; Osteryoung, J. Diffusion-controlled current at the stationary finite disk electrode: Theory. J. Electroanal. Chem.
**1981**, 122, 19–35. [Google Scholar] [CrossRef] - Shoup, D.; Szabo, A. Chronoamperometric Current at Finite Disk Electrodes. J. Electroanal. Chem. Interfacial Electrochem.
**1982**, 140, 237–245. [Google Scholar] [CrossRef] - Coen, S.; Cope, D.K.; Tallman, D.E. Diffusion current at a band electrode by an integral equation method. J. Electroanal. Chem. Interfacial Electrochem.
**1986**, 215, 29–48. [Google Scholar] [CrossRef] - Elliott, J.R.; Le, H.; Yang, M.; Compton, R.G. Using Simulations to Guide the Design of Amperometric Electrochemical Sensors Based on Mediated Electron Transfer. ChemElectroChem
**2020**, 7, 2797–2815. [Google Scholar] [CrossRef] - Thompson, M. Xrump. Available online: www.genplot.com (accessed on 7 November 2022).
- Xiong, Z.; Zhang, L.L.; Ma, J.; Zhao, X.S. Photocatalytic degradation of dyes over graphene–gold nanocomposites under visible light irradiation. Chem. Commun.
**2010**, 46, 6099–6101. [Google Scholar] [CrossRef] - Briggs, D.; Seah, M.P. (Eds.) . Practical Surface Analysis, 2nd ed.; John Wiley & Sons: Chichester, UK, 1990; Volume 1. [Google Scholar]
- Yong, V.; Hahn, H.T. Synergistic, effect of fullerene-capped gold nanoparticles on graphene electrochemical supercapacitors. Adv. Nanopart.
**2013**, 2, 1–5. [Google Scholar] [CrossRef] [Green Version] - Tang, L.; Chang, S.J.; Chen, C.-J.; Liu, J.-T. Non-Invasive Blood Glucose Monitoring Technology: A Review. Sensors
**2020**, 20, 6925. [Google Scholar] [CrossRef] - Viet, N.X.; Takamura, Y. Electrodeposited Gold Nanoparticles Modified Screen Printed Carbon Electrode for Enzyme-Free Glucose Sensor Application, VNU J. Sci. Nat. Sci. Technol.
**2016**, 32, 83–89. [Google Scholar] - Juſík, T.; Podešva, P.; Farka, Z.; Kováſ, D.; Skládal, P.; Foret, F. Nanostructured gold deposited in gelatin template applied for electrochemical assay of glucose in serum. Electrochim. Acta
**2016**, 188, 277–285. [Google Scholar] [CrossRef] - Leontiev, A.P.; Napolskii, K.S. Numerical Simulation of Chronoamperograms and Voltammograms for Electrode Modified with Nanoporous Film. Russ. J. Electrochem.
**2022**, 58, 741–750. [Google Scholar] [CrossRef] - Kakihana, M.; Ikeuchi, H.; Satô, G.P.; Tokuda, K. Diffusion current at microdisk electrodes—Application to accurate measurement of diffusion coefficients. J. Electroanal. Chem.
**1981**, 117, 201–211. [Google Scholar] [CrossRef] - Heinze. J. Diffusion processes at finite (micro) disk electrodes solved by digital simulation. J. Electroanal. Chem.
**1981**, 124, 73–86. [Google Scholar] [CrossRef] - Lide, D.R. (Ed.) . Handbook of Chemistry and Physics; CRC Press: Boca Raton, FL, USA, 2005. [Google Scholar]
- Bard, A.J.; Faulkner, L.R. Electrochemical Methods: Fundamentals and Applications; Wiley: New York, NY, USA, 1982. [Google Scholar]
- Xiong, L. Leigh Aldous, Martin, C. Henstridge and Richard, G. Compton, Investigation of the optimal transient times for chronoamperometric analysis of diffusion coefficients and concentrations in non-aqueous solvents and ionic liquids. Anal. Methods
**2012**, 4, 371–376. [Google Scholar] [CrossRef] - Hernández, W.T. Electrochemical Characterization of Mass Transport at Microelectrode Arrays. Rev. Cienc.
**2014**, 18, 101–110. [Google Scholar] [CrossRef] [Green Version] - Kiss, V.; Ősz, K. Double Exponential Evaluation under Non-Pseudo–First-Order Conditions: A Mixed Second-Order Process Followed by a First-Order Reaction. Int. J. Chem. Kinet.
**2017**, 49, 602–610. [Google Scholar] [CrossRef]

**Figure 1.**Field emission scanning electron microscopy pictures of (

**a**,

**b**) gold nanoporous obtained by five cycles of scanning potential between −0.5 and 1 V in NaOH 0.1 M; (

**c**,

**d**) gold layer 8 nm thin dewetted at 300 °C; (

**e**,

**f**) gold layer 17 nm dewetted at 400 °C; (

**g**,

**h**) gold layer 17 nm dewetted by laser at 0.5 J cm

^{−2}fluence.

**Figure 2.**Au 4f XPS spectra of: (

**a**) gold nano-porous; (

**b**) 8 nm 300 °C; (

**c**) 17 nm 400 °C; (

**d**) laser dewetted at fluence of 0.5 J cm

^{−2}.

**Figure 3.**Cyclic voltammograms of glucose 2.5, 5, 7.5, and 10 mM obtained by: (

**a**) gold nanoporous; (

**b**) 8 nm 300 °C; (

**c**) 17 nm 400 °C; (

**d**) laser dewetted at fluence of 0.5 J cm

^{−2}. The 1–4 numbers refer to the main electrochemical processes. Condition: scan rate 20 mV s

^{−1}; supporting electrolyte: NaOH 0.1 M.

**Figure 4.**Current density as function of potential of the two electrons oxidation peak of the voltammograms of Figure 3a–d for 2.5; 5; 7.5; and 10 mM glucose in 0.1 M NaOH.

**Figure 5.**Scheme of modification of convergent diffusion into semi-infinite linear diffusion, when the nanostructure size and interspacing are much smaller than the root mean square of the diffusion length (Equation (11)).

**Figure 6.**Current-time curves recorded for: (

**a**) gold nano-porous; (

**b**) 8 nm dewetted at 300 °C; (

**c**) 17 nm dewetted at 400 °C; (

**d**) laser dewetted. Conditions: glucose 10 mM in NaOH 0.1 M.

**Figure 7.**Calibration curves for the glucose determination in amperometric mode. Condition: NaOH 0.1 M.

**Table 1.**Parameters used for the simulation of current-time curves by Cottrel and two-phase exponential decay function.

Cottrel | Two-Phase Exponential Decay | Adj. R^{2} | |||||
---|---|---|---|---|---|---|---|

B_{0} (A) | $\mathbf{N}\frac{4\mathbf{n}\mathbf{F}\mathbf{A}\mathbf{D}\mathbf{c}}{\mathsf{\pi}\mathbf{r}}{\mathbf{B}}_{1}\left(\mathbf{A}\right)$ | $\mathbf{N}\frac{4\mathbf{n}\mathbf{F}\mathbf{A}\mathbf{D}\mathbf{c}}{\mathsf{\pi}\mathbf{r}}{\mathbf{B}}_{2}\left(\mathbf{A}\right)$ | $\mathbf{N}\frac{4\mathbf{n}\mathbf{F}\mathbf{A}\mathbf{D}\mathbf{c}}{\mathsf{\pi}\mathbf{r}}{\mathbf{B}}_{3}\left(\mathbf{A}\right)$ | k_{1} (s^{−1}) | k_{2} (s^{−1}) | ||

Nanostructure type | - | - | - | - | - | - | - |

Nano- porous | - | 6.74 × 10^{−4} ± 3.02 × 10 ^{−6} | 0.00339 | 0.00333 | 0.363 | 0.0625 | 0.99924 |

8 nm 300 °C | 0.00633 ± 3.5 × 10 ^{−5} | - | - | - | - | - | 0.98530 |

17 nm 400 °C | - | 3.58 × 10^{−4} ± 2.83 × 10 ^{−6} | 0.00265 | 0.00119 | 0.425 | 0.0586 | 0.99715 |

Laser | 0.00152 ± 9.3 × 10 ^{−6} | - | - | - | - | - | 0.98172 |

**Table 2.**parameters used for the linear fit of the calibration curves reported in Figure 7.

Sample | $\mathbf{y}=\mathbf{a}+\mathbf{b}\mathbf{x}$ | Adj R^{2} | |
---|---|---|---|

a (μAcm^{−2}) | b (μAcm^{−2}mM^{−1}) | ||

Nano-porous | 95.49 ± 4.25 | 55.69 ± 0.89 | 0.9992 |

8 nm 300 °C | 9.48 ± 1.65 | 32.74 ± 0.36 | 0.9996 |

17 nm 400 °C | 17.54 ± 2.58 | 27.29 ± 0.58 | 0.9986 |

Laser | 30.60 ± 6.45 | 15.38 ± 1.24 | 0.9807 |

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Scandurra, A.; Iacono, V.; Boscarino, S.; Scalese, S.; Grimaldi, M.G.; Ruffino, F.
Model of Chronoamperometric Response towards Glucose Sensing by Arrays of Gold Nanostructures Obtained by Laser, Thermal and Wet Processes. *Nanomaterials* **2023**, *13*, 1163.
https://doi.org/10.3390/nano13071163

**AMA Style**

Scandurra A, Iacono V, Boscarino S, Scalese S, Grimaldi MG, Ruffino F.
Model of Chronoamperometric Response towards Glucose Sensing by Arrays of Gold Nanostructures Obtained by Laser, Thermal and Wet Processes. *Nanomaterials*. 2023; 13(7):1163.
https://doi.org/10.3390/nano13071163

**Chicago/Turabian Style**

Scandurra, Antonino, Valentina Iacono, Stefano Boscarino, Silvia Scalese, Maria Grazia Grimaldi, and Francesco Ruffino.
2023. "Model of Chronoamperometric Response towards Glucose Sensing by Arrays of Gold Nanostructures Obtained by Laser, Thermal and Wet Processes" *Nanomaterials* 13, no. 7: 1163.
https://doi.org/10.3390/nano13071163