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Fotochemiczna synteza nanocząstek srebra i złota

Krajczewski J., Kudelski A.

Wiadomości Chemiczne

2015

[Z] 69, 3-4

171--195

The activity in nanotechnology has recently increased enormously. This is due to numerous possible applications of nanomaterials in catalysis, optics, electronics, and even health protection. Many applications of silver and gold nanoparticles are possible because of their plasmonic properties. As an example of the plasmonic application of Au and Ag metal nanoparticles one can mention construction of devices for light concentration at the nanometer scale. Such deep-subwavelength optical energy concentrators are used, for example, in surface-enhanced Raman scattering (SERS) to increase the Raman signal by even 10 orders of magnitude, thus facilitating the optical identification of single molecules. Large increase in local field intensity also strongly enhances nonlinear scattering, which can be potentially useful for optical signal processing. In this article we review photochemical synthesis of silver and gold nanoparticles, especially those methods of synthesis which are driven by surface plasmon resonance (SPR) excited in Ag and Au nanoparticles. The most important step of the SPR-driven synthesis of nanoparticles is photocatalytical reduction of metal ions which occurs preferentially at such places of the nanoparticles, at which strong surface plasmons are excited (for example corners, etches). Therefore, during the grown of the nanoparticle, its anisotropy may increase. If the SPR of the seed particles is not excited – due to either the absence of photostimulation or a mismatch between the excitation wavelength and the SPR of the seeds – the deposition of metal does not occur. Therefore, SPR of nanoparticles may be also responsible for wavelength controlled size effects in the synthesis: as the nanoparticles grow and their SPRs shift from the excitation wavelength, the nanoparticles absorb less light and their growth slows. This allows for synthesis of very homogeneous samples of nanoparticles, which may be applied, for example, in various plasmonic sensors.

New trends in the Surface-Enhanced Raman Spectroscopy. A Short Review

Kudelski A.

Polish Journal of Chemistry

2005

Vol. 79 / nr 10

1551-1563

The first surface-enhanced Raman scattering (SERS) spectra were reported in 1974. A few years after discovery SERS became a well established surface analytical technique, which is widely used to study electrochemical and catalytic processes under in situ conditions. Recently one can observe a large increase in the interest in SERS. It is due to two very important developments in the field of SERS spectroscopy, which have been made in the last decade. The first very important achievement is the observation of SERS spectra of single molecules. The second development, having an enormous potential for surface Raman spectroscopy, is the tip-enhanced Raman scattering (TERS): an AFM or STM tip made of the SERS active metal is used to increase the Raman scattering from molecules adsorbed at a surface located underneath the tip. In this approach, a very significant increase in the spatial resolution of SERS measurements is possible. This review is an attempt to provide an overview of the state of the art and further possibilities of these two recently developed SERS techniques.