Study the Gold Compound (AuCl4) in KCl using Cyclic Voltammetry by Nano Sensor


Ahmed A. Mohsin1, Muhammed M. Radhi1, Wisam H. Hoidy2*

1Department of Radiological Techniques, College of Health and Medical Technology/Baghdad,

Middle Technical University (MTU), Baghdad, Iraq.

2Chemistry Department, College of Education, University of Al-Qadisiyah, Al-Qadisiyah, Iraq.

*Corresponding Author E-mail:



Gold compound AuCl4 used in different medical purpose especially in different diseases such as Arthritis, the study focused on the electrochemical properties of gold compound in an electrolyte (KCl solution) using modified glassy carbon electrode with carbon nanoparticles (CNT/GCE) as a good nanosensor to determine the chemical behavior of gold compound by the oxidation – reduction current peaks as appeared in the cyclic voltammogram at 115 and 500 mV respectively. It was studied in this study the different concentrations, scan rates, pH, and the reliability (stability), also the effect of ascorbic acid on the redox current peaks of the gold compound was studied. The results were discussed to promising the gold compound as a treatment in different disease in an alkaline medium because the Au(IV) compound acts as antioxidant by disappearing current peak of the oxidation and enhanced the reduction current peak.


KEYWORDS: AuCl4, Cyclic Voltammetry, KCl, CNT/GCE, PH, Scan Rate.




Gold compounds are studied in different fields because it's important for treatment to various diseases, so some scientists have been studied the pharma compounds by Nano sensors1-6. Oxidation-reduction properties of eleven gold(III) complexes with ligands were investigated in DMSO using cyclic and differential pulse voltammetry. In general, complexes belonging to Series I (higher cytotoxicity) could be reduced slightly more easily due to less steric hindrance around the gold core. Potentials for minimizing and anticancer are not associated7-10.


The Au(III) species' redox behavior was analyzed using cyclic voltammetry and verified the reversible redox transitions at approx. 0.38 V. Results obtained during the progress of the reaction were due to Au(0) formation. Through this way, during the rapid initial stage of the reaction, one may distinguish between a potential three-electron internal-sphere redox process and/or a replacement process11-14.


The findings clearly showed that neurite outgrowth was promoted by the existence of both Au particles. The use of composite materials such as poly (3,4-ethylenedioxythiophene)-dexamethasone / Au has been shown to be an important way to boost the efficacy of in vitro neural interfaces 15-17.


Cyclic voltammetry has been investigated into the gold electrode deposition method from a glycerol and carbon paste electrode (CPE). Voltammetric analysis suggested that AuCl4 reduced to Au0. the mechanism was mixed regulated (mass transport with transmission of electrons), possibly followed by AuCl4− decomplexation. Indeed, a complete factorial design was used to verify that the deposition charge and potential affects the changed CPE output in a solution of potassium ferrocyanide, while HAuCl4 and glycerol concentrations were affected by interactions with other factors18. [Au(C6F5)(tht)] (tht= tetrahydrothiophene) reaction with 2,2′:6′,2′′-terpyridine (terpy) results in complex [Au(C6F5)(ÿ1-terpy)] (1). Form (1) chemical oxidation with 2 equiv of [N(C6H4Br-4)3](PF6) or electrosynthetic techniques allows for Au(III) form [Au(C6F5)(3-terpy)](PF6)2(2). The bulk electrolysis of a complex 1 solution has been analyzed using spectroscopic methods which confirm the electrochemical synthesis of complex 219-21

Using a cyclic voltammetry technique gold III chloride redox reaction in acid solutions has been studied electrochemically. The paper highlights present potential sites where the gold III chloride in hydrochloric acid are important for electrochemical evaluation of gold recovery. The findings showed no increase in the lack of AuCl3 in the solutions, then cathodic and anodic peaks for the oxidation and reduction in acid solutions with various concentrations with AuCl3. The potential for reduction was in depend on concentration whereas the current was strongly depend on concentration22-25.


In this study, gold compound was studied in electrochemistry method to evaluation the chemical properties of Au(IV) in KCl as supporting electrolyte using nano-sensor with different voltammetric parameters.



Reagents and Chemicals:

AuCl4 was purchased from sigma-Aldrich, England, carbon nanotubes (purity 99%) were provided by Fluka Company (Germany), and KCl from Sinopharm Chemical Reagent Co, Ltd. (SCRC), China. Deionized water was used for preparation the solutions.



NuVant Systems Inc., Pioneering electrochemical technologies, USA, was adopted in this study for the assessment of the AuCl4 electrochemical properties using EZstat series (potentiostat/glvanostat) device.


For the Cyclic Voltammogram analysis performance, electrochemical terminals of the Bioanalytical integral system through potetiostat directed by electroanalytical softwares linked to private computer. In addition, the utilize of Ag/AgCl (3M KCl) for reference signal readings while Platinum wire (1 mm diameter) used for counter electrode.


Preparation of modified GCE with CNT (CNT/GCE):

A modified mechanical attachment technical method was used to prepare the CNT/GCE working electrode which was then employed to set up the nano-sensor by doping the GCE with CNT powder about thirty times to allow the nanomaterial adhesive on the surface of GCE13,14. The alteration of GCE involved use of multiwall carbon nanotubes (MWCNT) on the uncontaminated surface of GCE. This forms an array of MWCNT was used as a modified working electrode MWCNT/GCE and placed in Ten ml of the 0.1 M KCl solution. All electrodes were then connected to potentio-state 26.



Calibration Graph:

The calibration curve for the redox of gold compound on the nanosensor (CNT/GCE) in KCl solution, Fig. 1 shows the current peaks of gold compound oxidation reduction by potential of 115, 500 mV separately, study the detection limit of Au(IV) at different concentrations on the CNT/GCE. Fig. 2 illustrated the relationships between the current peaks of the oxidation reduction contrary to different conc. of Au(IV) in  0.1M KCl, it was found a low detection limit of gold ions on the nano sensor (CNT/GCE) which have oxidation–reduction reaction of equations Y=302.2X + 19.801, R2= 0.9481 and Y=-133.04X – 11.768, R2= 0.8895 ,respectively.        


Fig.1: Cyclic voltammogram of 0.0M AuCl4 at diverse concentrations in 0.1M KCl using CNT/GCE as nano sensor vesus Ag/AgCl as reference electrode and scan rate at 100 mV sec-1 on Nano sensor (CNT/GCE)


Fig.2:  Association among redox current peaks against to diverse concentration of AuCl4 in  0.1M Potassium Chloride.


Studying effect different scan rates:

Other electrochemical property of gold ions was studied at variable scan rates (0.01-0.1 Vsec-1), Figure 3 illustrated the enhancement of cyclic voltammogram of oxidation – reduction current peaks vesus increasing scan rates with good relationship poltted in Fig. 4 of equations for the reaction27:


Anodic: Y= 578.06 + 11.768, R2= 0.9172


Cathodic: Y= -292.22X + 7.8147, R2=0.9516


The sensitivity (R2) values of the oxidation – reduction equations have high values nearly to one, which indicated the redox reaction of gold compound in KCl solution on nano sensor as a reversible reaction with good electrochemical properties for the conductivity15.

Randles-Seveik equation can be used to determine the diffusion coefficient value, which is described as the reversible oxidation – reductin current peaks16,17:


Diffusion coefficient values  Redox reaction of Au(IV)/Au(II) ions in KCl solution on MWCNT/GCE was determined as Dfa = 1.5 ×10-5 cm2 /sec and Dfc = 5.6 × 10-5 cm2 /sec. Equal values of the redox reaction of the gold compound is indicated a reversible reaction. The the redox reaction of gold ions in electrolyte has chemical equation below28.

Au 4+ + 2e = Au 2+


Fig. 3: Cyclic voltammogram of 0.2 mM AuCl4 in [0.1M] KCl at pH=4, Nano sensor (CNT/GCE)



Fig. 4: Association among redox current peaks of 0.2 mM AuCl4 in 0.1M KCl against to different scan rates.


Studying different pH:

The gold compound (AuCl4) was studied in different pH to finding the chemical properties of the oxidation-reduction process of Au(IV) in alkaline medium (pH=11) decreased, while enhanced in acidic medium (pH=4) Fig. 5 which illustrated the redox peaks, so the acidic pH acts as electrocatalyst for the gold ions reaction in an electrolyte by enhancement of oxidation-reduction current peaks while disappeared in alkaline medium. It was appeared the two reduction peaks at 150 mV and -250 mV in an alkaline medium and disappeared the oxidation peaks, so the gold compound act as antioxidative reagent in an alkaline medium


Fig. 5. Cyclic voltammogram of [0.2 mM] AuCl4 in 0.1M KCl at pH4, pH11 by Nano sensor (CNT/GCE)


Studying effect different concentrations AA:

The study of the effect of ascorbic acid (AA) on the electrochemical properties of the gold compounds is very important to improve the behavior of gold ions by this method. It was found that AA acts as an antioxidant compound in an electrolyte by disappearing the anodic current peak in the cyclic voltammogram of the gold ions scan as shown in Fig. 6.


Fig. 6: Cyclic voltammogram of 0.2 mM AuCl4 in [0.1M KCl] at pH=4 with diverse concentration of AA on Nano sensor


Study Stability of Nano sensor

Stability of modified CNT on the GCE was studied for ten times of oxidation-reduction of Au (IV) in KCl solution illustrated in Fig. 7. The relative standard deviation (RSD) of anodic and cathodic peaks was determined with good value of ± 2.5 and ± 2.2, respectively29,30.


Fig. 7. Cyclic voltammogram of [0.2 mM] AuCl4 in [0.1M] KCl at pH=4 at ten times



Gold compounds have importance in different areas of life, so they were studied in electrolytes from an electrochemical analysis using the cyclic voltammetric method. It can be concluded from the current work that the electrochemical behavior of gold ions in the electrolyte medium is in follows:

1.   The electrochemical conductivity of gold ions in the acidic pH was enhanced in the oxidation-reduction current peaks, but the redox process in the alkaline pH of the Au(IV) was decreased.

2.   Gold compounds are affected by ascorbic acid (AA), where the oxidation current peak of gold ions was disappeared because of the highly affected of oxidation current peak of AA in the electrolyte.

3.   The study proved that oxidation and reduction reaction of Au(IV) in the KCl electrolyte is a reversible reaction from the scan rate study.

4.   The nanosensor CNT/GCE was discovered that the electrochemical behaviors of the gold ions in the electrolyte to easy study.



The authors declare no conflict of interest.



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Received on 16.05.2020           Modified on 15.07.2020

Accepted on 22.08.2020         © RJPT All right reserved

Research J. Pharm. and Tech. 2021; 14(6):3004-3008.

DOI: 10.52711/0974-360X.2021.00526