142
G. Compagnini et al.
the size of the formed spheres also increases. This result agrees with our experimental
results regarding titania.
4.3 Case Studies
We want now to discuss two typical applications of nanomaterials produced by using
laser processing in liquids. In this respect, we want to stress both advantages and
problems in the use of such a kind of synthetic method relatively to each of the
applications proposed. The first example concerns with the use of laser-generated
silver nanoparticles for protein biosensing through the use of the so-called Surface
Enhanced Raman (SER) effect. The second is related to the possible modification of
TiO 2 NPs and graphene oxide by laser irradiation of a colloidal solution. In this case,
the modified nanoparticles are employed for several purpouses, such as the pollutant
removal from water and photocatalytic water splitting applications.
We want to stress that the processing of nanomaterials through lasers in liquid
environments can be considered as an added value with respect to other materials
manipulation by conventional methods.
4.3.1 SERS Biosensing of Proteins
Surface-enhanced Raman spectroscopy (SERS) was originally discovered in the
1970s [32–35]. Almost 30 years after the discovery of SERS, interest in SERS has
exploded. Thanks to exciting advances in techniques for preparing nanoparticles and
to the laser and optics technology associated with measuring the Raman spectra, a
number of important applications have been reported.
Under favorable circumstances, Raman enhancements as large as 14 orders of
magnitude can be achieved [36]. This is a very high degree of enhancement, capable of
single-molecule detection [37] and raises a great interest in creating an ultrasensitive
sensing platform with molecular identification capabilities, especially as a sensor for
biological molecules.
The large enhancement of the Raman scattering intensity has been explained
by two mechanisms: the electromagnetic and chemical mechanisms. The former is
attributed to the increase of the local electromagnetic field of the adsorbate because
of the excitation of the surface plasmon on the metal surface. On the other hand,
the chemical adsorption mechanism is attributed to short distance effects due to the
charge transfer between the metal and the adsorbed molecule. Generally, the electromagnetic effect dominates and the chemical effect contributes to the enhancement
only on one or two orders of magnitude.
A key role for the magnification is given by the so-called “hot spots” [38]. Hot spots
are highly localized regions of intense local field enhancement caused by local surface
plasmon resonances. They are generally formed within the interstitial crevices present
G. Compagnini et al.
the size of the formed spheres also increases. This result agrees with our experimental
results regarding titania.
4.3 Case Studies
We want now to discuss two typical applications of nanomaterials produced by using
laser processing in liquids. In this respect, we want to stress both advantages and
problems in the use of such a kind of synthetic method relatively to each of the
applications proposed. The first example concerns with the use of laser-generated
silver nanoparticles for protein biosensing through the use of the so-called Surface
Enhanced Raman (SER) effect. The second is related to the possible modification of
TiO 2 NPs and graphene oxide by laser irradiation of a colloidal solution. In this case,
the modified nanoparticles are employed for several purpouses, such as the pollutant
removal from water and photocatalytic water splitting applications.
We want to stress that the processing of nanomaterials through lasers in liquid
environments can be considered as an added value with respect to other materials
manipulation by conventional methods.
4.3.1 SERS Biosensing of Proteins
Surface-enhanced Raman spectroscopy (SERS) was originally discovered in the
1970s [32–35]. Almost 30 years after the discovery of SERS, interest in SERS has
exploded. Thanks to exciting advances in techniques for preparing nanoparticles and
to the laser and optics technology associated with measuring the Raman spectra, a
number of important applications have been reported.
Under favorable circumstances, Raman enhancements as large as 14 orders of
magnitude can be achieved [36]. This is a very high degree of enhancement, capable of
single-molecule detection [37] and raises a great interest in creating an ultrasensitive
sensing platform with molecular identification capabilities, especially as a sensor for
biological molecules.
The large enhancement of the Raman scattering intensity has been explained
by two mechanisms: the electromagnetic and chemical mechanisms. The former is
attributed to the increase of the local electromagnetic field of the adsorbate because
of the excitation of the surface plasmon on the metal surface. On the other hand,
the chemical adsorption mechanism is attributed to short distance effects due to the
charge transfer between the metal and the adsorbed molecule. Generally, the electromagnetic effect dominates and the chemical effect contributes to the enhancement
only on one or two orders of magnitude.
A key role for the magnification is given by the so-called “hot spots” [38]. Hot spots
are highly localized regions of intense local field enhancement caused by local surface
plasmon resonances. They are generally formed within the interstitial crevices present