One Pot Hemimicellar Synthesis of Amphiphilic Janus Gold Nanoclusters for Novel Electronic Attributes

Abstract

A one-pot hemimicellar synthesis of oriented, amphiphilic, and fluorescent Janus gold clusters, establishing the Janus character in terms of ligand asymmetry and distribution, has been demonstrated. The method was based on the efficient Langmuir strategy, where the in situ two-dimensional (2D) reduction of Au(3+) in the sprayed micellar electrostatic complex, TOA(+)-AuCl(4)(-), was accomplished by subphase tryptophan that acted as the hydrophilic protecting ligand on one hemisphere of the spherical gold cluster. In contrast to the reported micelle-assisted Janus cluster formation, here the cluster growth occurred inside the surface pressure driven hemimicelles, which rapidly formed 2D cluster arrays without any interfacial reorientation. The Janus structure was validated using angle dependent polarized Fourier Transform Infrared Reflection-Absorption Spectroscopy (FT-IRRAS), where orientation dependent vibrational changes in the adsorbed ligand functionalities were detected. Electrochemical impedance measurements of the transferred Janus layers onto hydrophobized ITO revealed the heterogeneous electron transfer rate constant k(ET) to show a clear orientational odd-even parity effect with the odd layers showing much higher rates. Isobaric area relaxation investigations further evidenced toward a hemispherical instantaneous nucleation with edge growth mechanism of the nanoclusters formed at the tryptophan subphase. Surface pressure as a thermodynamic variable effectively controlled the interparticle separation; intercluster electron coupling exhibited insulator-metal transition in the Janus cluster monolayers through scanning electrochemical microscopy investigations.

Interfacial Janus gold nanoclusters as excellent phase- and orientation-specific dopamine sensors

“…The orientation specific Janus cluster monolayer fabrication followed an interfacially confined micellar media, based on the efficient Langmuir strategy, which was reported by us recently. 37 In brief, the Janus character was attributed in terms of ligand asymmetry and distribution, where the subphase tryptophan acted as the reductant as well as the capping agent at the lower hemisphere and the hydrophobic tetraoctylammonium ion (TOA + ) protected the upper hemisphere of the clusters at the airwater interface. Based on our previous report, the Janus structure was validated using angle dependent polarized Fourier Transform Infrared Reflection Absorption Spectroscopy (FT-IRRAS), where orientation dependent vibrational changes in the adsorbed ligand functionalities were detected.…”

“…[23][24][25][26][27][28][29][30][31][32][33][34][35][36] In spite of these significant advances in miniaturized electrodes, their utility is still limited by a poor lifetime and insufficient stability in high ionic strength media. Following our recent and first report 37 on the interfacial micellar synthesis of Janus gold nanoclusters, the present investigation uses them as effective DA electrochemical sensors. Modified electrodes fabricated using the Langmuir-Schaeffer method showed greater catalytic activity where improved detection limits were obtained as strong functions of Janus gold cluster monolayer orientation and phase state.…”

Bio-inspired Janus gold nanoclusters with lipid and amino acid functional capping ligands: micro-voltammetry and in situ electron transfer in a biogenic environment

“…1a comply with our previously reported experiments. 24,28 The p-A isotherms of the mixed precursor amphiphile (DPPC/TOA-AuCl 4 À complex) at pure water and at the tyrosine-modied subphase at a basic pH ¼ 10 depict enhanced interfacial tension and molecular area for the latter, evidencing cluster formation. Fig.…”

“…Recently, we have reported a one-pot 2D synthesis of Janus nanoparticles, in which in situ reduction of Au 3+ in a sprayed micellar electrostatic complex was accomplished by subphase tryptophan, which acted as a capping ligand. 24 By adaptive surface chemistry, the present investigation uses a bi-functional strategy for the synthesis of Janus Au quantum clusters with DPPC lipid and tyrosine amino acid as ligand functionalities, and aims towards a versatile biosensor platform for future nano-bioelectronic devices. In situ synthesized 2D Janus gold clusters and the preformed architectures were tapped through real-time angle-dependent polarized FT-IRRAS spectroscopy upon detecting the orientation-dependent vibrational changes in the adsorbed ligand functionalities that provided the geometrical orientation of the ligands on the Janus gold nanocluster surface.…”

Synthesis and characterization of gold glyconanoparticles functionalized with sugars of sweet sorghum syrup

“…Recently, researchers have showed that mineralization at the air/water interface is an effective method for the synthesis of asymmetrical particles or inorganic films 20, 22, 23. Janus gold clusters, for example, have been successfully synthesized using a Langmuir strategy at the air/water interface:24 TOA + AuCl 4– formed the LB films where the cluster growth occurred and the tryptophan acted as the reductant as well as the capping agent at the lower hemisphere of the clusters at the air/water interface. Fairland et al obtained single‐crystalline aragonite tablets/films at the air/water interface using poly(acrylic acid sodium salt) in combination with Mg 2+ ions as soluble agents and a Langmuir monolayer based on resorcarene 25.…”