Observation of Isomerization of an Azobenzene Derivative in Gold Nanoparticle Aggregates Using SERS

Yoon, Jun Hee; Yoon, Sangwoon

doi:10.5012/bkcs.2009.30.12.2877

Cited by 9 publications

(3 citation statements)

References 16 publications

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“…Within 15 min of the initial surface-catalyzed reaction in air, gradual increase in the Raman bands at 1515 and 592 cm –1 is observed. As observed in the case of surface-catalyzed isomerization of azobenzene, − these Raman bands at 1515 and 592 cm –1 can be attributed to the NN str and CNNC torsion of the cis isomer of DHDCAB. The formation of the trans isomer of DHDCAB and its decay to form the cis isomer as a function of time is shown in Figure b.…”

Section: Resultsmentioning

confidence: 57%

Catalytic Reactions on the Surface of Ag Nanoparticles: A Photochemical Effect and/or Molecule Property?

2014

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Using time-dependent surface-enhanced Raman scattering (TDSERS), we demonstrate the surface-catalyzed oxidation of 3-hydroxy anthranilic acid (HAA) to its azo derivatives. No external source either in the form of laser excitation or heat was required for the surface-catalyzed reaction, which clearly established that thermal energy alone was sufficient. But the possibility of enhanced reaction rate due to the surface plasmon resonance could not be ignored. To mimic in vivo conditions that prevail in healthy and unhealthy cells, SERS measurements were recorded under different environmental conditions. It is shown that the surface-catalyzed azo formation and its isomerization were strongly dependent on the external conditions, namely, temperature, pH, and environment. A plausible mechanism based on electron transfer to the adsorbed O 2 is proposed for the trans−cis isomerization. This study can lead toward a new strategy of surface-catalyzed reactions not only for the synthesis of azo dyes but also to distinguish between the normal and abnormal cells.

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Section: Resultsmentioning

confidence: 57%

Catalytic Reactions on the Surface of Ag Nanoparticles: A Photochemical Effect and/or Molecule Property?

2014

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“…We have recently reported planetsatellite nanoparticle assemblies based in part on the finding of the current work. 21 A number of reports have significantly contributed to this issue by studying nanoparticle aggregation, 22 the linear nature of the assembly of gold nanospheres, 18,19,23,24 the adsorption of molecular cross-linkers and ligands on metal substrates, 25,26 the optical behavior of cross-linker mediated nanoparticle aggregates, 27 and the thermodynamic aspects. 19,28 A few studies have highlighted the importance of pH on the self-assembly dynamics, 3,29 electrostatic interactions, 18 ligand concentration, 23 or salt concentration, 30 but no direct correlation was made with the other parameters involved in the process, such as the ionization degree of the linker, its pK a and concentration, the concentration of the nanoparticles and their pH and the effect on the final zeta (ζ) potential.…”

Section: Introductionmentioning

confidence: 99%

Molecular Linker-Mediated Self-Assembly of Gold Nanoparticles: Understanding and Controlling the Dynamics

et al. 2012

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This study sheds light on the mechanism and dynamics of self-assembly of gold nanoparticles (AuNPs) using molecular linkers such as aminothiols. An experimental model is established that enables a fine control and prediction of both assembly rate and degree. Furthermore, we have found that under certain conditions, the increase in the molar ratio of linker/AuNPs beyond a certain threshold unexpectedly and dramatically slows down the assembly rate by charge reversal of the surface of nanoparticles. As a result, the assembly rate can be easily tuned to reach a maximum growth within seconds to several days. The decrease of the same molar ratio (linker/AuNPs) below a certain value leads to self-termination of the reaction at different phases of the assembly process, thus providing nanoparticles chains of different length. This work introduces new handles for a rational design of novel self-assembled architectures in a very time-effective manner and contributes to the understanding of the effect of the assembly morphology on the optical properties of gold nanoparticles.

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“…One study showed isomerization of the trans form to the cis form at a wavelength of 450 nm with a quantum yield of 0.25 [128]. A recent article has shown the observation of isomerization of an azobenzene derivative in a SERS experiment [131], although it should be emphasized that these experiments were conducted in the near-UV (at 365 nm). In our case, while the possibility of photoisomerization can not be excluded for the particular BTZ molecule under study, there were no signs in the experiments that it was a problem, and it is expected given the results for azobenzene that excitation at 633 nm is too low to allow photoconversion, particularly as it is thought that the isomerization is mediated via electronic transition.…”

Section: Biasers Experimentsmentioning

confidence: 99%

Quantification of the Enhancement Factor in Surface-Enhanced Raman Scattering

Blackie¹

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<p>This thesis presents a rigorous stepwise methodology towards the accurate measurement and quantification of the SERS enhancement factor (EF), the key parameter in describing the SERS effect. The work represents, we believe, a successful attempt to resolve some of the inconsistencies in the literature and to refocus the field by emphasizing the importance of consistent definitions and rigorous quantification to elucidate matters of fundamental importance in SERS. The success in our approach is that it combines careful experimental measurements upon a sound theoretical framework, and utilizes a 'toolbox' of techniques developed in recent years, such as bi-analyte SERS (BiASERS) techniques for single-molecule (SM) detection, and isotopic editing. In experimental work, we measure the bare Raman cross-sections of five common probes used in SERS as a first step in measuring the analytical enhancement factor (AEF) and single-molecule enhancement factor (SMEF). The methodology in measuring these EFs involved the use of a reference standard of known cross-section along with a careful characterization of the scattering volume through beam profiling experiments. As a guide to validating the reference cross-section we make extensive use of density functional theory (DFT) calculations to obtain estimates for the intrinsic Raman cross-sections of small, non-resonant probes. The results of this work showed that previous upper limits for the EF reported in the literature of 1014 were based on a faulty normalization of the EF. In fact, EFs of 108 were sufficient to see single molecules, which is much lower than previously expected; under optimum conditions, even lower EFs, possibly down to 105 could be sufficient for the SM detection of resonant probes. As a valuable extension of BiASERS, we elaborate on the synthesis of isotopic analogues of a rhodamine dye as ideal partners for SM experiments. The synthesis and definitive characterization of these probes enable their use in an experiment to determine the SM regime in a liquid colloidal sample. Isotopically edited dyes such as these, in combination with the methodologies of EF quantification outlined herein, set the standard for those interested in accurate quantification of the SERS effect. This approach is useful in terms of both basic theoretical questions and applications such as the effective comparison of SERS substrates. Finally, we extend the techniques developed over the thesis to a long-standing and largely unresolved question in SERS: What is the minimum intrinsic Raman cross-section that can be measured as a single molecule in standard SERS conditions. In this work, we explore the SM detection non-resonant probes, which are the molecules of interest for many practical applications such as forensics and biological assays. Specifically, we demonstrate the successful SM detection of isotopically edited adenine probes.</p>

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Observation of Isomerization of an Azobenzene Derivative in Gold Nanoparticle Aggregates Using SERS

Cited by 9 publications

References 16 publications

Catalytic Reactions on the Surface of Ag Nanoparticles: A Photochemical Effect and/or Molecule Property?

Catalytic Reactions on the Surface of Ag Nanoparticles: A Photochemical Effect and/or Molecule Property?

Molecular Linker-Mediated Self-Assembly of Gold Nanoparticles: Understanding and Controlling the Dynamics

Quantification of the Enhancement Factor in Surface-Enhanced Raman Scattering

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