Biphenyl-4,4′-dithiol Research Articles

Adhesion of thin Au layers on glass treated with Ar plasma and biphenyl-4,4′-dithiol

Glass is an often used substrate for preparation of thin metal films for use in electronics or optics, but due to its surface morphology and chemical properties its adhesion to sputtered Au layers is usually poor. A method utilizing Ar+ plasma treatment and grafting of biphenyl-4,4′-dithiol (BPD) was employed to improve adhesion between sputtered thin Au layers and glass surface. The proposed method leads to changes of surface chemistry of the glass, introducing chemical groups (namely SH) with good affinity to Au. The plasma treatment was used to activate the glass surface to react with the BPD and create a strong bond. Nanoindentation and scratch tests were performed on the thin Au layers deposited on pristine and treated glass. The results show the plasma treatment leads to improvements of the adhesion by itself with the BPD grafting not having a positive effect in this matter. Scanning electron microscopy showed the substrate modification has influence on the microstructure of the subsequently grown Au layers which leads to change of their optical properties as well.

Thiol-based electrolyte additives for high-performance lithium-sulfur batteries

The discharge and charge mechanisms of the Li-S battery involve the formation of soluble lithium polysulfide species that can diffuse through the battery and cause issues related to capacity fade and poor Coulombic efficiency. In order to control the behavior of the lithium polysulfides, thiol-based electrolyte additives such as biphenyl-4,4′-dithiol (BPD) were used to enhance capacity retention in lithium-sulfur batteries by controlling polysulfide dissolution. In situ Raman spectroscopy, in situ UV–vis spectroscopy, and electrospray ionization mass spectrometry show that an additional sulfur reduction process observed at ~2.1 V vs. Li/Li+ as a result of BPD addition is associated with the formation of BPD-short chain polysulfide complexes such as BPD-Sn anion (1≤n≤4). The interaction between BPD and short chain polysulfide postpones formation of soluble short chain polysulfides and alters the kinetics of the dissolution process. A smooth SEI/Li entangled phase is found on the Li anode with BPD addition. The BPD additive increases the capacity retention of lithium-sulfur batteries, mainly due to the formation of various BPD-polysulfide complexes which prevents polysulfide dissolution. Comparison with other thiol-based additives shows that the optimal additive balances solubility and polysulfide-additive stabilization.

Improved DET communication between cellobiose dehydrogenase and a gold electrode modified with a rigid self-assembled monolayer and green metal nanoparticles: The role of an ordered nanostructuration

Efficient direct electron transfer (DET) between cellobiose dehydrogenase from Corynascus thermophilus (CtCDH) and a novel gold electrode platform, obtained by covalent linking of green AuNPs and AgNPs modified with a dithiol self-assembled monolayer, consisting of biphenyl-4,4′-dithiol (BPDT), was presented. The green AuNPs and AgNPs were synthesized using quercetin as reducing agent at room temperature. TEM experiments showed that the AuNPs and AgNPs were circular in shape with an average diameter of 5 and 8nm, respectively. Cyclic voltammetry of CtCDH immobilized onto the AuNPs/BPDT/AuE and the AgNPs/BPDT/AuE electrode platforms were carried out and compared with naked AuE, BPDT/AuE, AuNPs/AuE, and AgNPs/AuE. A pair of well-defined redox waves in neutral pH solution due to efficient DET of CtCDH was present with both MNPs/BPDT/AuE platforms. No DET communication was found with platforms without MNPs linked to BPDT. The apparent heterogeneous electron transfer rate constants (kS) of CtCDH were calculated to be 21.5±0.8s−1 and 10.3±0.7s−1, for the AuNPs/BPDT/AuE and the AgNPs/BPDT/AuE platforms, respectively.The modified electrodes were successively used to develop an eco-friendly biosensor for lactose detection. The CtCDH/AuNPs/BPDT/AuE based biosensor showed the best analytical performances with an excellent stability, a detection limit of 3µM, a linear range between 5 and 400µM and a sensitivity of 27.5±2.5µAcm−2mM−1. Such performances were favorably compared with other lactose biosensors reported in literature.The biosensor was successively tested to quantify lactose content in real milk and cream samples. No significant interference present in the sample matrices was observed.

Thiol-Based Electrolyte Additives for High-Performance Lithium-Sulfur Batteries

Here, we propose thiol-based electrolyte additives (biphenyl-4,4’-dithiol (BPD)) to enhance the capacity retention of lithium-sulfur batteries. In-situ Raman and UV-Vis spectroscopy are used to investigate the effect of the additive on the sulfur reduction mechanism. Raman spectroscopy shows that long chain polysulfides (S8 2-) are formed via S8 ring opening in the first reduction process at ~2.4 V vs Li/Li+ and short chain polysulfides such as S4 2-, S4 -, S3 ․ - and S2O4 2- are observed with continued discharge at ~2.0 V vs Li/Li+ in the second reduction process. In the Kinetic study, rate constants obtained for the appearance and disappearance polysulfide species show that short chain polysulfides are directly formed from S8 decomposition. The polysulfide oxidation and reduction is quasi-reversible. With the BPD additive, an additional reduction process is observed at ~2.1 V vs Li/Li+. This reduction is associated with the formation of BPD-polysulfide complexes. The BPD-polysulfide complexes form at ~2.1 V followed by the formation of short chain polysulfides upon further discharge. The reduction of these complexes is reversible during the charge process. The BPD additive inhibits the formation rate of short chain polysulfides, suggesting that there is a strong interaction between BPD and short chain polysulfides. In-situ UV-Vis spectroscopy shows that the polysulfide solubility decreases in the presence of the BPD additive and forms thiol-polysulfide complexes during the cycling. The (-)ESI-MS shows the formation of BPD-S and BPD-S2 and BPD-S3, suggesting that BPD interacts with short chain polysulfides. The decomposition of the thiol-based additive was found during the battery cycling and resulted in a dense and smooth SEI film on the Li anode.

Role of the dithiolate backbone on the passivation of p-GaAs(111)B surface

Effects of the self-assembled layers of biphenyl 4,4′ –dithiol (BPDT) and 1,8 –octanedithiol (ODT) on the chemical and electronic properties of p-doped GaAs(111)-As terminated substrate, (p-GaAs(111)B), were investigated in order to evidence whether the hydrocarbon moiety plays a role in tailoring the semiconductor surface properties. The electrochemical properties of the BPDT and ODT coated p-GaAs(111)B substrates were studied by Electrochemical Impedance Spectroscopy (EIS). The structural and chemical changes caused by the dithiolate layers formed on p-GaAs(111)B substrates were monitored by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) investigations, respectively. The XPS data showed that BPDT and ODT bind to p-GaAs(111)B via the thiol group. The ODT layer provides better protection against the further oxidation in air of p-GaAs(111)B substrate compared to the BPDT layer. The EIS investigations are in good agreement with XPS results, pointing to better insulating properties of the ODT layer compared to the BPDT layer in the electron transfer at the electrode/solution interface. The results evidenced that backbone plays an important role in tailoring the properties of p-GaAs(111)B substrate.

Covalently linked multimers of gold nanoclusters Au102(p-MBA)44and Au∼250(p-MBA)n

We present the synthesis, separation, and characterization of covalently-bound multimers of para-mercaptobenzoic acid (p-MBA) protected gold nanoclusters. The multimers were synthesized by performing a ligand-exchange reaction of a pre-characterized Au102(p-MBA)44 nanocluster with biphenyl-4,4'-dithiol (BPDT). The reaction products were separated using gel electrophoresis yielding several distinct bands. The bands were analyzed by transmission electron microscopy (TEM) revealing monomer, dimer, and trimer fractions of the nanocluster. TEM analysis of dimers in combination with molecular dynamics simulations suggest that the nanoclusters are covalently bound via a disulfide bridge between BPDT molecules. The linking chemistry is not specific to Au102(p-MBA)44. The same approach yields multimers also for a larger monodisperse p-MBA-protected cluster of approximately 250 gold atoms, Au∼250(p-MBA)n. While the Au102(p-MBA)44 is not plasmonic, the Au∼250(p-MBA)n nanocluster supports localized surface plasmon resonance (LSPR) at 530 nm. Multimers of the Au∼250(p-MBA)n exhibit additional transitions in their UV-vis spectrum at 630 nm and 810 nm, indicating the presence of hybridized LSPR modes. Well-defined structures and relatively small sizes make these systems excellent candidates for connecting ab initio theoretical studies and experimental quantum plasmonics. Moreover, our work opens new possibilities in the controlled synthesis of advanced monodisperse nanocluster superstructures.

Raman Spectroscopy of Biphenyl‐4,4'‐dithiol and p‐Terphenyl‐4,4″‐dithiol on Gold Surfaces#

We compared the adsorption behaviors of 1,4‐benzenedithiol (BDT), biphenyl‐4,4′‐dithiol (BPDT), and p‐terphenyl‐4,4″‐dithiol (TPDT) on gold (Au) surfaces. To check the surface orientations and possibility of multilayer formation, surface‐enhanced Raman scattering was employed for the three aromatic dithiols on gold nanoparticles (AuNPs). The Raman spectra of BDT and BPDT on AuNPs were examined, whereas those of TPDT could be obtained on an Au‐coated nanostructured silicon plate. Unlike BDT, BPDT and TPDT did not exhibit a ν(S–H) band at 2560 cm−1. Because of the additional benzene rings, multilayer formation is improbable for BPDT and TPDT under colloidal conditions.

Electric field enhancement in a self-assembled 2D array of silver nanospheres.

We investigate the plasmonic properties of a self-assembled 2D array of Ag nanospheres (average particle diameter/inter-particle separation distance of 9/3.7 nm). The structures of the individual particles and their assemblies are characterized using high-resolution transmission electron microscopy (HR-TEM). The plasmonic response of the nanoparticle network is probed using two-photon photoemission electron microscopy (TP-PEEM). HR-TEM and TP-PEEM statistics reveal the structure and plasmonic response of the network to be homogeneous on average. This translates into a relatively uniform surface-enhanced Raman scattering (SERS) response from biphenyl,4-4(')-dithiol (BPDT) molecules adsorbed onto different sites of the network. Reproducible, bright, and low-background SERS spectra are recorded and assigned on the basis of density functional theory calculations in which BPDT is chemisorbed onto the vertex of a finite tetrahedral Ag cluster consisting of 20 Ag atoms. A notable agreement between experiment and theory allows us to rigorously account for the observable vibrational states of BPDT in the ∼200-2200 cm(-1) region of the spectrum. Finite difference time domain simulations further reveal that physical enhancement factors on the order of 10(6) are attainable at the nanogaps formed between the silver nanospheres in the 2D array. Combined with modest chemical enhancement factors, this study paves the way for reproducible single molecule signals from an easily self-assembled SERS substrate.

Intrinsically Conductive Organo–Silver Linear Chain Polymers [−S–Ag–S–Biphenyl−]n Assembled on Roughened Elemental Silver

A combined experimental and theoretical study of the facile polymerization of biphenyl-4,4′-dithiol (BPDT) to form intrinsically conductive linear chain [−Ag–S–BP–S−]n polymers is described. BPDT readily polymerizes and extrudes on roughened surfaces of elemental silver under ambient conditions. The self-assembled polymers can be sharply imaged through scanning electron microscopy because of their silver content and conductivity. Cyclic current versus voltage measurements (I/V curves) using a scanning tunneling microscope establish that the conductivity is intrinsic, consistent with the metallic conductivity of the linear polymer predicted through density functional theory. Systematic calculations identify that the roughness-catalyzed polymerization is driven by mobile Ag adatoms and adatom-mobilized monomers.

Cells adhesion and growth on gold nanoparticle grafted glass

• Surface of glass treated by plasma, coated by gold and then grafted with AuNPs. • Adhesion and proliferation of vascular smooth muscle cells studied in vitro . • Adhesion and proliferation of VSMC strongly affected by Au/SiO 2 structures. • These structures could find applications in the electronics (biosensors) etc. The surface of glass substrate was plasma treated, coated by gold nano-structures and subsequently grafted with nanoparticles. The samples were plasma treated, sputtered with Au nanostructures which was followed by grafting with biphenyl-4,4′-dithiol (BPD) and then gold nanoparticles. The wettability, optical and chemical properties and surface morphology were studied. The adhesion and proliferation of vascular smooth muscle cells (VSMCs) on the samples were investigated in-vitro as well. Grafting of gold nanoparticles with the dithiol increases the UV–vis absorbance, the surface becomes more hydrophobic, rougher and more rugged compared to pristine, sputtered and only dithiol treated surface. Gold nano-particles bound over dithiol and Au nanostructures cause better cell proliferation than purely BPD treated or pristine glass.

Nanostructuring, Imaging and Molecular Manipulation of Dithiol Monolayers on Au(111) Surfaces by Atomic Force Microscopy

In this paper, we use atomic force microscopy (AFM) to nanostructure and image 1,10-decanedithiol (DDT) and biphenyl 4,4‘-dithiol (BPDT) layers on Au(111) surfaces comparing them to those prepared by self-assembly. First, layers of dithiols are self-assembled from solution onto gold surfaces and are imaged in situ with an AFM to examine the roughness of the layers. Second, 100 nm × 100 nm monolayer patches made of dithiol molecules are nanografted into a self-assembled monolayer (SAM) inert matrix made of 1-decanethiol (DT). Although nanografting of thiols routinely generates very compact layers with good height uniformity, nanostructuring of dithiols using this method always yields multilayers that form through intermolecular S−S bonds. We demonstrate in this paper two possible ways of tailoring, layer by layer, the structure of dithiols. First, we form multilayers by nanografting, using then the AFM tip to gradually shave away the top layers. In the second way, we add antioxidant to the solution while d...

Synthesis and thermal analysis of aromatic polysulfide having phosphine oxide groups.

An aromatic polysulfide was synthesized by the reaction of bis(4-fluorophenyl)phenylphosphine oxide (BFPO) with potassium salt of biphenyl-4, 4′-dithiol (BPDT) in the presence of 18-crown-6. In order to establish the characteristics of polymerization, reaction conditions such as the temperature and the time were changed. The polymerization in N-methyl-2-pyrrolidone (NMP) at 155°C gave the polysulfide having inherent viscosity of 0.71 dl/g(_??_w=6.8×104). An X-ray diffractogram of the polysulfide indicated a typical halo pattern, suggesting that it was amorphous. The thermal properties of the polysulfide were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG). The glass transition was observed in DSC at 232°C. TG measurements showed the onset of thermal decomposition in nitrogen at 480°C, and its activation energy was 158kJ/mol.