In Situ Stepwise Synthesis of Functional Multijunction Molecular Wires on Gold Electrodes and Gold Nanoparticles

Ashwell, Geoffrey J.; Urasinska‐Wojcik, Barbara; Phillips, Laurie J.

doi:10.1002/anie.200906607

Cited by 28 publications

(34 citation statements)

References 36 publications

(33 reference statements)

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“…This clearly suggests the existence of oxidized thiolate staples on the cluster surface. The S 2p 3/2 peak, seen at 163.1 eV (Au 25 ) and 162.8 eV (red luminescent species), for both clusters supports the Au-S thiolate binding to the core 65 and confirms the existence of only one type of S. On the basis of the above results, the enhanced luminescence in Au 25 SBB 18 upon heating could be attributed to the charge transfer from the oxidized surface thiolate ligands to the core of QC through the Au-S bonds and direct donation of delocalized electrons from electron-rich ligands to the metal core, as described by Jin et al 9 The presence of the thiolate shell around the cluster surface was further verified by thermogravimetric analysis (TGA). The red-emitting Au 29 QCs showed higher organic content (observed metal to the organic content ratio (57.9% : 42.0%)), than the parent Au 25 (60.2% : 39.7%) (Fig.…”

Section: Resultsmentioning

confidence: 65%

Efficient red luminescence from organic-soluble Au₂₅ clusters by ligand structure modification

et al. 2015

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An efficient method to enhance visible luminescence in a visibly non-luminescent organic-soluble 4-(tert butyl)benzyl mercaptan (SBB)-stabilized Au25 cluster has been developed. This method relies mainly on enhancing the surface charge density on the cluster by creating an additional shell of thiolate on the cluster surface, which enhances visible luminescence. The viability of this method has been demonstrated by imparting red luminescence to various ligand-protected quantum clusters (QCs), observable to the naked eye. The bright red luminescent material derived from Au25SBB18 clusters was characterized using UV-vis and luminescence spectroscopy, TEM, SEM/EDS, XPS, TG, ESI and MALDI mass spectrometry, which collectively proposed an uncommon molecular formula of Au29SBB24S, suggested to be due to different stapler motifs protecting the Au25 core. The critical role of temperature on the emergence of luminescence in QCs has been studied. The restoration of the surface ligand shell on the Au25 cluster and subsequent physicochemical modification to the cluster were probed by various mass spectral and spectroscopic techniques. Our results provide fundamental insights into the ligand characteristics determining luminescence in QCs.

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Section: Resultsmentioning

confidence: 65%

Efficient red luminescence from organic-soluble Au₂₅ clusters by ligand structure modification

et al. 2015

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“…S2 †), which are the characteristic features of thiolate. 28 Thus, it is evident that the cluster core is stabilized by the thiol groups of the protein (predominantly from the cysteine residues, since they are highly reactive) in view of the large affinity of S to noble metals. The atomic Au : S and Ag : S ratios suggested one cluster per intact protein with excess thiol-thiolate groups.…”

Section: Resultsmentioning

confidence: 99%

Luminescent, bimetallic AuAg alloy quantum clusters in protein templates

et al. 2012

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We report the synthesis of luminescent AuAg alloy quantum clusters (QCs) in bovine serum albumin (BSA), for the first time, with experimentally determined atomic composition. Mixing of the as-synthesized protein-protected Au and Ag clusters resulted in the formation of alloy AuAg clusters within the BSA. Mass spectrometric analysis of the product of a 1 : 1 molar ratio reaction mixture of Au(QC)@BSA and Ag(QC)@BSA suggested that the alloy clusters could be Au(38-x)Ag(x)@BSA. Further analyses by standard techniques revealed that the alloy cluster core of ∼1.2 nm diameter is composed of nearly zero valent Au and Ag atoms that exhibit distinctly different steady state and time resolved excited state luminescence profiles compared to the parent clusters. Tuning of the alloy composition was achieved by varying the molar ratio of the parent species in the reaction mixture and compositional changes were observed by mass spectrometry. In another approach, mixing of Au(3+) ions with the as-synthesized Ag(QC)@BSA also resulted in the formation of alloy clusters through galvanic exchange reactions. We believe that alloy clusters with the combined properties of the constituents in versatile protein templates would have potential applications in the future. The work presents interesting aspects of the reactivity of the protein-protected clusters.

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“…12 iii) The reproducibility, yield, and operational lifetime of many of these systems have been low, or have not been reported. 13 iv) Other asymmetries in the junction unrelated to the molecular component -for example, electrodes of different materials, or junctions with two different types of contacts of the SAM with electrodes -may have contributed to rectification (without a molecular origin). 11,19 Cahen et al 20,21,22 showed that their Si-alkyl//Hg based junctions can give detailed information about the mechanisms of charge transport across these The junction at one bias is the reference for the junction at the opposite bias, because the value of R is determined by dividing the current in on direction of bias by the current measured at the opposite direction (eq.…”

Section: Introductionmentioning

confidence: 99%

A Molecular Half-Wave Rectifier

et al. 2011

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The field of molecular electronics applies the techniques and principles derived from studying inorganic electronic devices to investigating charge transport in organic molecules. While electrical engineers routinely use both alternating current (AC) and direct current (DC) to characterize traditional semiconductor devices, researchers in molecular electronics have, so far, relied mainly on DC measurements. Here, we show that using AC signals to investigate charge transport in self-assembled monolayers (SAMs) yields new information, including information that could not be obtained using DC signals alone, and provides a straightforward means of comparing the performance of molecular diodes against that of diodes based on traditional semiconductor technology.This paper describes half-wave rectification of AC (50 Hz) signals by junctions based on SAMs. These junctions comprised SAMs of 11-(ferrocenyl)-1-undecanethiol (SC 11 Fc) or 11-(biferrocenyl)-1-undecanethiol (SC 11 Fc 2 ), supported on template-stripped Ag (Ag TS ) bottom electrodes, and contacted by top electrodes of eutectic indiumÀgallium (EGaIn, 75.5% Ga and 24.5% In by weight, 15.7 °C melting point, with a superficial layer of Ga 2 O 3 ; Figure 1). 1,2 Similar junctions based on SAMs of 1-undecanethiol (SC 10 CH 3 )-SAMs lacking the ferrocenyl terminal group-did not rectify AC signals.Previous experiments conducted using a DC bias of (1.0 V, and junctions based on SAMs of SC 11 Fc 1 and SC 11 Fc 2 , 3 yielded rectification ratios, R (defined by eq 1, where J is the current density (A/cm 2 ) and V is the voltage (V)), of >10 2 . These high values of R make it possible to conduct physical-organic studies to determine the mechanism(s) of charge transport across these SAMs. We show that these systems-which are, in fact, "molecular diodes"-can substitute for conventional diodes in a simple circuit-a half-wave rectifier (Figure 1)-that converts an input AC signal into an output DC signal. 4These molecular diodes, indeed, provide the basis for halfwave rectifiers. The circuits were stable for 30À40 min of operation, at a frequency of 50 Hz; this interval corresponds to more than 10 5 cycles. At low frequencies (∼1 Hz) and at large input voltages (∼5 V for SC 11 Fc and ∼10 V for SC 11 Fc 2 , see the Results and Discussion section), the junctions broke down more

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In Situ Stepwise Synthesis of Functional Multijunction Molecular Wires on Gold Electrodes and Gold Nanoparticles

Abstract: Tunneling through: The sequencing of electron‐donating and electron‐accepting components that are separated by a σ‐electron bridge has resulted in the highest rectification ratio to date from a molecular diode.

Cited by 28 publications

References 36 publications

Efficient red luminescence from organic-soluble Au₂₅ clusters by ligand structure modification

Efficient red luminescence from organic-soluble Au₂₅ clusters by ligand structure modification

Luminescent, bimetallic AuAg alloy quantum clusters in protein templates

A Molecular Half-Wave Rectifier

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In Situ Stepwise Synthesis of Functional Multijunction Molecular Wires on Gold Electrodes and Gold Nanoparticles

Abstract: Tunneling through: The sequencing of electron‐donating and electron‐accepting components that are separated by a σ‐electron bridge has resulted in the highest rectification ratio to date from a molecular diode.

Cited by 28 publications

References 36 publications

Efficient red luminescence from organic-soluble Au25 clusters by ligand structure modification

Efficient red luminescence from organic-soluble Au25 clusters by ligand structure modification

Luminescent, bimetallic AuAg alloy quantum clusters in protein templates

A Molecular Half-Wave Rectifier

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Product

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Efficient red luminescence from organic-soluble Au₂₅ clusters by ligand structure modification

Efficient red luminescence from organic-soluble Au₂₅ clusters by ligand structure modification