Au-C Bond Research Articles

Covalent Au-C Contact Formation and C-C Homocoupling Reaction from Organotin Compounds in Single-Molecule Junctions.

Formation of new chemical species has been achieved under an electric field by the use of the scanning tunneling microscope break junction technique, yet simultaneous implementation of catalytic reactions both at the organic/metal interface and in the bulk solution remains a challenging task. Herein, we show that n-butyl-substituted organotin-terminated benzene undergoes both an efficient cleavage of the terminal tributyltin group to form a covalent Au-C bond and a homocoupling reaction to yield biphenyl product when subjected to an electric field in the vicinity to Au electrodes. By using ex situ characterization of high-performance liquid chromatography with an UV-vis detector, we demonstrate that the homocoupling reaction can occur with high efficiency under an extremely low tip bias voltage of ∼5 mV. Additionally, we show that the efficiency of the homocoupling reaction varies significantly in different solvents; the choice of the solvent proves to be one of the methods for modulating this reaction. By synthesizing and testing varied molecular backbone structures, we show that an extended biphenyl backbone undergoes homocoupling to form a quarterphenylene backbone, and the C-C coupling reactions are prohibited when additional aurophilic or bulky chemical groups that exhibit a steric blockage are introduced.

Regioselective On-Surface Synthesis of [3]Triangulene Graphene Nanoribbons.

The integration of low-energy states into bottom-up engineered graphene nanoribbons (GNRs) is a robust strategy for realizing materials with tailored electronic band structure for nanoelectronics. Low-energy zero-modes (ZMs) can be introduced into nanographenes (NGs) by creating an imbalance between the two sublattices of graphene. This phenomenon is exemplified by the family of [n]triangulenes (n ∈ ). Here, we demonstrate the synthesis of [3]triangulene-GNRs, a regioregular one-dimensional (1D) chain of [3]triangulenes linked by five-membered rings. Hybridization between ZMs on adjacent [3]triangulenes leads to the emergence of a narrow band gap, Eg,exp ∼ 0.7 eV, and topological end states that are experimentally verified using scanning tunneling spectroscopy. Tight-binding and first-principles density functional theory calculations within the local density approximation corroborate our experimental observations. Our synthetic design takes advantage of a selective on-surface head-to-tail coupling of monomer building blocks enabling the regioselective synthesis of [3]triangulene-GNRs. Detailed ab initio theory provides insights into the mechanism of on-surface radical polymerization, revealing the pivotal role of Au-C bond formation/breakage in driving selectivity.

Cyclometalated (N,C) Au(III) Complexes: The Impact of Trans Effects on Their Synthesis, Structure, and Reactivity.

ConspectusThe early years of gold catalysis were dominated by Au(I) complexes and inorganic Au(III) salts. Thanks to the development of chelating ligands, more sophisticated Au(III) complexes can now be easily prepared and handled. The choice of the ancillary ligand has great consequences for the synthesis, properties, and reactivity of the Au(III) complex in question. Among the major factors controlling reactivity are the "trans effect" and the "trans influence" that a ligand imparts at the ligand trans to itself. The kinetic trans effect manifests itself with an increased labilization of the ligand trans to a given ligand and arises from an interplay between ground-state and transition-state effects. The term trans influence, on the other hand, is a ground-state effect only, describing the tendency of a given ligand to weaken the metal-ligand bond trans to itself. Herein, we will use the term "trans effect" to describe both the kinetic and the thermodynamic properties, whereas the term "trans influence" will refer only to thermodynamic properties. We will describe how these trans effects strongly impact the chemistry of the commonly encountered cyclometalated (N,C) Au(III) complexes, a class of complexes we have studied for more than a decade. We found that the outcome of reactions like alkylation, arylation, and alkynylation as well as halide metathesis are dictated by the different trans influence of the two termini of the chelating tpy ligand in (tpy)Au(OAcF)2 (tpy = 2-(p-tolyl)pyridine, OAcF = OCOCF3, tpy-C > tpy-N). There is a strong preference for high trans influence ligands to end up trans to tpy-N, whereas the lower trans influence ligands end up trans to tpy-C. Taking advantage of these preferences, tailor-made (N,C)Au(III) complexes could be prepared. For the functionalization of alkenes at (tpy)Au(OAcF)2, the higher trans effect of tpy-C would suggest that the coordination site trans to tpy-C would be kinetically more available than the one trans to tpy-N. However, due to the thermodynamic preference of having the σ-bonded ligand, resulting from the nucleophilic addition to alkenes, trans to tpy-N, functionalization of alkenes was only observed trans to tpy-N. However, for a catalytic process, the reaction should happen trans to tpy-C, as was observed for the trifluoroacetoxylation of acetylene. When functionalizing acetylene in the coordination site trans to tpy-N, protolytic cleavage of the Au-C(vinyl) bond to release the product did not occur at all, whereas trans to tpy-C protolytic cleavage of the Au-C(vinyl) bond occurred readily, in agreement with the higher trans influence of tpy-C over tpy-N. The large impact of the trans effects in Au(III) complexes is finally exemplified with the synthesis of [(tpy)Au(π-allyl)]+[NTf2]-, which resulted in a highly asymmetric π + σ bonding of the allyl moiety. Here, the bonding is such that the most thermodynamically favorable situation is achieved, with the carbon trans to tpy-N bonded in a σ-fashion and the π-allyl double bond being coordinated trans to tpy-C.

Reactivity of [AuF3(SIMes)] - Pathway to Unprecedented Structural Motifs.

We report on a comprehensive reactivity study starting from [AuF3(SIMes)] to synthesize different motifs of monomeric gold(III) fluorides. A plethora of different ligands has been introduced in a mono-substitution yielding trans-[AuF2X(SIMes)] including alkynido, cyanido, azido, and a set of perfluoroalkoxido complexes. The latter were better accomplished via use of perfluorinated carbonyl-bearing molecules, which is unprecedented in gold chemistry. In case of the cyanide and azide, triple substitution gave rise to the corresponding [AuX3(SIMes)] complexes. Comparison of the chemical shift of the carbene carbon atom in the 13C{1H} NMR spectrum, the calculated SIMes affinity and the Au-C bond length in the solid state with related literature-known complexes yields a classification of trans-influences for a variety of ligands attached to the gold center. Therein, the mixed fluorido perfluoroalkoxido complexes have a similar SIMes affinity to AuF3 with a very low Gibbs energy of formation when using the perfluoro carbonyl route.

Enabling Specific Benzene Oxidation by Tuning the Adsorption Behavior on Au Loaded MgAl Layered Double Hydroxides.

Direct and selective oxidation of benzene to phenol is a long-term goal in industry. Although great efforts have been made in homogenous catalysis, it still remains a huge challenge to drive this reaction via heterogeneous catalysts under mild conditions. Herein, a single-atom Au loaded MgAl-layered double hydroxide (Au1 -MgAl-LDH) with a well-defined structure, in which the Au single atoms are located on the top of Al3+ with Au-O4 coordination as revealed by extended x-ray-absorption fine-structure (EXAFS)and density-functional theory (DFT)calculation is reported. The photocatalytic results prove the Au1 -MgAl-LDH is capable of driving benzene oxidation reaction with O2 in water, and exhibits a high selectivity of 99% for phenol. While contrast experiment shows a ≈99% selectivity for aliphatic acid with Au nanoparticle loaded MgAl-LDH (Au-NP-MgAl-LDH). Detailed characterizations confirm that the origin of the selectivity difference can be attributed to the profound adsorption behavior of substrate benzene with Au single atoms and nanoparticles. For Au1 -MgAl-LDH, single Au-C bond is formed in benzene activation and result in the production of phenol. While for Au-NP-MgAl-LDH, multiple AuC bonds are generated in benzene activation, leading to the crack of CC bond.

The role of tridentate ligands on the redox stability of anticancer gold(III) complexes

Gold(III) complexes are promising compounds for cancer chemotherapy, whose action depends on their redox stability. In this context, the choice of ligands is crucial to adjust their reactivity and biological response. The present study addressed the effect of the gold coordination sphere on the reduction potential (Eo) for ten gold(III) complexes containing five or six-membered rings tridentate ligands – [AuIII(trident)Cl]3+n (trident = N^N^N, C^N^N, C^C^N, C^N^C, and N^C^N). The calculated Eo covered a broad range of 2500 mV with the most stable complexes containing two AuC bonds (Eo = −1.85 V for [AuIII(C^C^N)Cl] – f). For complexes with one AuC bond, the N^C^N ligands stabilize the gold(III) complex more efficiently than N^N^C; however, the inclusion of the non-innocent ligand bipy (2,2′-bipyridine) in N^N portion provides an extra stabilization effect. Among the derivatives with one AuC bond, [AuIII(N^N^C)Cl]+ (N^N = bipy) (a) showed Eo = −1.20 V. For the complexes with N^N^N ligands, Eo was positive and almost constant (+0.60 V). Furthermore, the kinetics for ligand exchange reactions (Cl−/H2O, H2O/Cys and Cl−/Cys) were monitored for the most stable compounds and the energy profiles compared to the reduction pathways.

Aqueous synthesis of N-heterocyclic carbene-protected gold nanoclusters with intrinsic antibacterial activity

N-Heterocyclic carbene (NHC) is regarded as a versatile ligand to stabilize gold nanoclusters (AuNCs) via forming strong Au-C bonds. However, reports on NHC-protected AuNCs are rare, especially in aqueous systems. Herein, we present a facile one-step approach to fabricate hydrophilic AuNCs in an aqueous medium using a NHC-based ligand as both a reducing agent and stabilizer. The coordination mechanism involves formation of covalent Au-C bond, as evidenced by nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. Taking advantages of their ultrasmall size and positively charged surface, these AuNCs can readily penetrate the cell wall and accumulate in bacteria, leading to an obvious increase in intracellular reactive oxygen species. Accordingly, these AuNCs have wide-spectrum antibacterial activity toward Staphylococcus aureus (gram-positive bacterium), Escherichia coli (gram-negative bacterium), and Candida albicans (fungi).

Spectroscopic Evidence for a Covalent Sigma Au-C Bond on Au Surfaces Using 13C Isotope Labeling.

The Au–C linkage has been demonstrated as a robust interface for coupling thin organic films on Au surfaces. However, the nature of the Au–C interaction remains elusive up to now. Surface-enhanced Raman spectroscopy was previously used to assign a band at 412 cm–1 as a covalent sigma Au–C bond for films generated by spontaneous reduction of the 4-nitrobenzenediazonium salt on Au nanoparticles. However, this assignment is disputed based on our isotopic shift study. We now provide direct evidence for covalent Au–C bonds on the surface of Au nanoparticles using 13C cross-polarization/magic angle spinning solid-state NMR spectroscopy combined with isotope substitution. A 13C NMR shift at 165 ppm was identified as an aromatic carbon linked to the gold surface, while the shift at 148 ppm was attributed to C–C junctions in the arylated organic film. This demonstration of the covalent sigma Au–C bond fills the gap in metal–C bonds for organic films on surfaces, and it has great practical and theoretical significance in understanding and designing a molecular junction based on the Au–C bond.

Gold-Carbon Contacts from Oxidative Addition of Aryl Iodides.

Aryl halides are ubiquitous functional groups in organic chemistry, yet despite their obvious appeal as surface-binding linkers and as precursors for controlled graphene nanoribbon synthesis, they have seldom been used as such in molecular electronics. The confusion regarding the bonding of aryl iodides to Au electrodes is a case in point, with ambiguous reports of both dative Au-I and covalent Au-C contacts. Here we form single-molecule junctions with a series of oligophenylene molecular wires terminated asymmetrically with iodine and thiomethyl to show that the dative Au-I contact has a lower conductance than the covalent Au-C interaction, which we propose occurs via an in situ oxidative addition reaction at the Au surface. Furthermore, we confirm the formation of the Au-C bond by measuring an analogous series of molecules prepared ex situ with the complex AuI(PPh3) in place of the iodide. Density functional theory-based transport calculations support our experimental observations that Au-C linkages have higher conductance than Au-I linkages. Finally, we demonstrate selective promotion of the Au-C bond formation by controlling the bias applied across the junction. In addition to establishing the different binding modes of aryl iodides, our results chart a path to actively controlling oxidative addition on an Au surface using an applied bias.

The Chemical Bond and s-d Hybridization in Coinage Metal(I) Cyanides.

We present a four-component relativistic density functional theory study of the chemical bond and s-d hybridization in the group 11 cyanides M-CN (M = Cu, Ag, and Au). The analysis is carried out within the charge-displacement/natural orbital for chemical valence (CD-NOCV) scheme, which allows us to single out meaningful contributions to the total charge rearrangement that arises upon bond formation and to quantify the components of the Dewar-Chatt-Duncanson bonding model (the ligand-to-metal donation and metal-to-ligand back-donation). The M-CN bond is characterized by a large donation from the cyanide ion to the metal cation and by two small back-donation components from the metal toward the cyanide anion. The case of gold cyanide elucidates the peculiar role of the relativistic effects in determining the characteristics of the Au-C bond with respect to the copper and silver homologues. In AuCN, the donation and back-donation components are significantly enhanced, and the spin-orbit coupling, removing the degeneracy of the 5d atomic orbitals, induces a substantial split in the back-donation components. A simple spatial analysis of the NOCV-pair density, related to the ligand-to-metal donation component, allows us to quantify, with unprecedented accuracy, the charge rearrangement due to the s-d hybridization occurring at the metal site. The s-d hybridization plays a key role in determining the shape and size of the metal; it removes electron density from the bond axis and induces a significant flattening at the metal site in the position trans to the ligand. The s-d hybridization is present in all noble metal complexes, influencing the bond distances, and its effect is enhanced for Au, which is consistent with the preference of gold to form linear complexes. A comparative investigation of simple complexes [AuL]+/0 of Au+ with different ligands (L = F-, N-heterocyclic carbene, CO, and PH3) shows that the s-d hybridization mechanism is also influenced by the nature of the ligand.

Sol-gel entrapped Au0- and Ag0-nanoparticles catalyze reductive de-halogenation of halo-organic compounds by BH4−

This study investigated the reductive de-halogenations of toxic Br3CCO2−, Br2CHCO2−, BrCH2CO2−, CH3CHBrCO2−, CH2BrCH2CO2−, CH2BrCHBrCO2−, Cl3CCO2−, Cl2CHCO2- and ClCH2CO2− by sodium borohydride catalyzed by sol-gel silica entrapped Au0 and Ag0 nanoparticles. The results indicate that the mechanism of reduction of Br3CCO2− differs from that of Cl3CCO2−. Calculated by DFT, the source of this difference lies in the larger bond strength of CCl compared to that of CBr and the weaker M0C bond strength in Au0-CBr2CO2− compared to those of Au0-CCl2CO2− and Au0-CH2CO2−. Furthermore, the de-halogenation mechanisms catalyzed by Ag0-NPs differ from those catalyzed by Au0-NPs. The latter observation is attributed to the different AgC and AuC bond strengths and to the different over-potentials for H2 release of these M0-NPs. In addition, product composition depends on the rate of BH4− addition. Proton labeling experiments prove that nearly all the hydrogen atoms in the products originated from the water solvent and not from the BH4−. The detailed mechanistic conclusions that can be drawn from these results differ considerably from those commonly accepted for de-halogenation processes.

Gold(II) Trihalide Complexes from Organogold(III) Precursors.

The mononuclear gold(II) halide complexes [AuCl3 ]- and [AuBr3 ]- are formed in the gas phase by collision-induced homolytic splitting of the only Au-C bond in the monoalkylgold(III) precursors [CF3 AuX3 ]- . The geometries of the whole series of [AuX3 ]- complexes (X=F, Cl, Br, I) have been calculated by DFT methods. It has also been found that the neutral AuX2 molecules behave as unsaturated species, showing significant affinity for an additional X- ligand. Moreover, in the open-shell [AuX3 ]- anions, homolytic splitting of one of the Au-X bonds and formation of the lower-valent [AuX2 ]- anions is favored over non-reducing halide dissociation. They should therefore be prone to disproportionation.

Spectroscopic Identification of the Au-C Bond Formation upon Electroreduction of an Aryl Diazonium Salt on Gold.

Electroreduction of aryl diazonium salts on gold can produce organic films that are more robust than their analogous self-assembled monolayers formed from chemical adsorption of organic thiols on gold. However, whether the enhanced stability is due to the Au-C bond formation remains debated. In this work, we report the electroreduction of an aryl diazonium salt of 4,4'-disulfanediyldibenzenediazonium on gold forming a multilayer of Au-(Ar-S-S-Ar)n, which can be further degraded to a monolayer of Au-Ar-S- by electrochemical cleavage of the S-S moieties within the multilayer. By conducting an in situ surface-enhanced Raman spectroscopic study of both the multilayer formation/degradation and the monolayer reduction/oxidation processes, coupled to density functional theory calculations, we provide compelling evidence that an Au-C bond does form upon electroreduction of aryl diazonium salts on gold and that the enhanced stability of the electrografted organic films is due to the Au-C bond being intrinsically stronger than the Au-S bond for a given phenylthiolate compound by ca. 0.4 eV.

Gold Complexes for Therapeutic Purposes: an Updated Patent Review (2010-2015).

Gold has always aroused great interest in the history of mankind. It has been used for thousands of years for jewelry, religious cult valuables, durable goods and in the art world. However, few know that such a precious and noble metal was exploited in the past by the ancients also for its therapeutic properties. More recently, in the twentieth century some complexes containing gold centers in the oxidation state +1 were studied for the treatment of the rheumatoid arthritis and the orally-administered drug Auranofin was approved by the FDA in 1985. From the chemical point of view, gold derivatives deserve special attention due to the unique position of this metal within the periodic table, which results in unconventional relativistic effects and, ultimately, in the highest electronegativity, electron affinity and redox potential among all metals. In this review, after an introduction concerning the use of gold complexes in medicine, we have examined all the patents internationally or nationally published in the years 2010-2015 (until December 31, 2015) and describing new inorganic compounds containing gold(I) and gold(III) with proved therapeutic properties. These patents were filed to mainly protect compounds with promising anticancer and anti-inflammatory activities (total 18 and 4, respectively). In particular, this work explores both coordination compounds containing ligands with various donor atoms (e.g., N-, O-, S- and -P) and organo-gold derivatives with at least one Au-C bond. The toxicological profile and the intracellular targets reported for some among the patented gold derivatives are discussed.

π Activation of Alkynes in Homogeneous and Heterogeneous Gold Catalysis.

The activation of alkynes toward nucleophilic attack upon coordination to gold-based catalysts (neutral and positively charged gold clusters and gold complexes commonly used in homogeneous catalysis) is investigated to elucidate the role of the σ donation and π back-donation components of the Au-C bond (where we consider ethyne as prototype substrate). Charge displacement (CD) analysis is used to obtain a well-defined measure of σ donation and π back-donation and to find out how the corresponding charge flows affect the electron density at the electrophilic carbon undergoing the nucleophilic attack. This information is used to rationalize the activity of a series of catalysts in the nucleophilic attack step of a model hydroamination reaction. For the first time, the components of the Dewar-Chatt-Duncanson model, donation and back-donation, are put in quantitative correlation with the kinetic parameters of a chemical reaction.

The Addition of Gold and Tin to Bismuth-Triiridium Carbonyl Complexes.

The reaction of Ir3(CO)9(μ3-Bi) with PhAu(NHC) (1), where NHC = 1,3-bis(2,6-diisopropylphenylimidazol-2-ylidene), has yielded the compound Ir3(CO)8(Ph)(μ3-Bi)[μ-Au(NHC)] (2) by the loss of one CO ligand and the oxidative addition of the Au-C (phenyl) bond of 1 to one of the iridium atoms. The Au(NHC) group bridges one of the Ir-Bi bonds of the cluster. On the basis of X-ray crystal structural analysis and molecular orbital and quantum theory of atoms in molecules calculations, the Au-Bi interaction was determined to be substantial and is comparable in character to the Ir-Bi and Ir-Ir bonds in this cluster. Compound 2 reacts with 2 equiv of HSnPh3 to yield the compound Ir3(CO)7(SnPh3)2(μ3-Bi)[μ-Au(NHC)](μ-H) (3), which contains two terminally coordinated SnPh3 ligands. Compound 3 reacts with H2O to yield the compound Ir3(μ3-Bi)(CO)7[μ-Ph2Sn(OH)SnPh2][μ-Au(NHC)] (4) by cleavage of a phenyl ring from each of the SnPh3 ligands and formation of a bridging OH group between the two tin atoms to form a chelating Ph2Sn(OH)SnPh2 ligand.

Mechanism of the Aerobic Homocoupling of Phenylboronic Acid on Au₂₀⁻: A DFT Study.

The mechanism of the gold nanocluster-catalyzed aerobic homocoupling of arylboronic acids has been elucidated by means of DFT calculations with Au20(-) as a model cluster for the Au:[poly(N-vinylpyrrolidin-2-one)] catalyst. We found that oxygen affects the adsorption of phenylboronic acid and, by lowering the energy barrier, a water molecule enhances dissociation of the C-B bond, which is probably the rate-determining step. The key role of oxygen is in activating the surface of the gold cluster by generating Lewis acidic sites for adsorption and activation of the phenylboronic acid, leading to the formation of biphenyl through a superoxo-like species. Moreover, the oxygen adsorbed on the Au nanocluster can act as an oxidant for phenylboronic acid, giving phenol as a byproduct. As shown by NBO analysis, the basic aqueous reaction medium facilitates the reductive elimination process by weakening the Au-C bond, thereby enhancing the formation of biphenyl. The coupling of phenyl and reductive elimination of biphenyl occur at the top or facet site with low-energy-barrier through spillover of phenyl group on Au NC. The present findings are useful for the interpretation or design of other coupling reactions with Au NC.

Cationic gold(III) alkyl complexes: generation, trapping, and insertion of norbornene.

Migratory insertion of alkenes into gold-carbon bonds, a fundamental yet unprecedented organometallic transformation, has been investigated from a discrete (P,C) cyclometalated gold(III) dimethyl complex. Methide abstraction by B(C6F5)3 is shown to generate a highly reactive cationic Au(III) complex that evolves spontaneously by C6F5 transfer from boron. In the presence of norbornene, migratory insertion into the Au-C bond proceeds readily. The resulting norbornyl complex is efficiently trapped with pyridines or chloride to give stable four-coordinate adducts.

Trimethyltin-mediated covalent gold-carbon bond formation.

We study the formation of covalent gold-carbon bonds in benzyltrimethylstannane (C10H16Sn) deposited on Au in ultra-high-vacuum conditions. Through X-ray photoemission spectroscopy and X-ray absorption measurements, we find that the molecule fragments at the Sn-benzyl bond when exposed to Au surfaces at temperatures as low as -110 °C. The resulting benzyl species is stabilized by the presence of Au(111) but only forms covalent Au-C bonds on more reactive Au surfaces like Au(110). We also present spectroscopic proof for the existence of an electronic "gateway" state localized on the Au-C bond that is responsible for its unique electronic properties. Finally, we use DFT-based nudged elastic band calculations to elucidate the crucial role played by the under-coordinated Au surface in the formation of Au-C bonds.

Spontaneous grafting: A novel approach to graft diazonium cations on gold nanoparticles in aqueous medium and their self-assembly on electrodes

The spontaneous grafting of aminophenyl groups on gold nanoparticles (AuNPs) by reaction with in situ generated 4-aminophenyl diazonium cations (APD) in an aqueous medium was described. The spontaneous grafting was likely to proceed by transfer of electrons from AuNPs to the APD cations to form an aminophenyl radical and subsequent attachment with AuNPs. The aminophenyl (AP) functionalized gold nanoparticles (AP-AuNPs) were characterized by UV–visible spectroscopy, high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction, FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS) and surface-enhanced Raman spectroscopy (SERS). The absence of characteristic vibrational bands corresponding to diazonium group in the FT-IR spectrum confirmed the reduction of the aminophenyl diazonium cations at the surface of AuNPs. The spontaneous attachment of AP on AuNPs was confirmed by XPS from the observed binding energy values for NH2 at 399.4eV and NN at 400.2eV. The SERS spectrum reveals the presence AuC (437cm−1) bond on AP-AuNPs. Further, the AP-AuNPs were self-assembled on GC/ITO electrode (AP-AuNPs modified electrode) with the aid of free amine groups present on the surface of AP-AuNPs via Michael’s nucleophilic addition reaction. The AP-AuNPs modified electrode was characterized by cyclic voltammetry, impedance spectroscopy, UV–visible spectroscopy and scanning electron microscopy. Impedance studies show that the electron transfer reaction of [Fe(CN)6]3−/4− was higher at the AP-AuNPs modified electrode (1.81×10−4cms−1) than at bare (3.77×10−5cms−1) GC electrode. Finally, the electrocatalytic activity of the AP-AuNPs modified electrode was demonstrated by studying the oxidation of dopamine (DA).