The manipulation of polymers and biological molecules or the control of chemical reactions on a nanometer scale by means of laser pulses shows great promise for applications in modern nanotechnology, biotechnology, molecular medicine or chemistry. A controllable, parallel, highly efficient and very local heat conversion of the incident laser light into metal nanoparticles without ablation or fragmentation provides the means for a tool like a 'nanoreactor', a 'nanowelder', a 'nanocrystallizer' or a 'nanodesorber'. In this paper we explain theoretically and show experimentally the interaction of laser radiation with gold nanoparticles on a polymethylmethacrylate (PMMA) layer (one-photon excitation) by means of different laser pulse lengths, wavelengths and pulse repetition rates. To the best of our knowledge this is the first report showing the possibility of highly local (in a 40 nm range) regulated heat insertion into the nanoparticle and its surroundings without ablation of the gold nanoparticles. In an earlier paper we showed that near-infrared femtosecond irradiation can cut labeled DNA sequences in metaphase chromosomes below the diffraction-limited spot size. Now, we use gold as well as silver-enhanced gold nanoparticles on DNA (also within chromosomes) as energy coupling objects for femtosecond laser irradiation with single-and two-photon excitation. We show the results of highly localized destruction effects on DNA that occur only nearby the nanoparticles.
Metal nanoparticle constructs of particles of different sizes and materials were prepared, using DNA as connecting element. Therefore, gold and silver nanoparticles were functionalized with complementary DNA sequences that enabled a controlled coupling. The well-established system based on thiolated DNA was thereby complemented with amino-functionalized DNA. The realization of specific DNA-DNA bonds due to hybridization was controlled by the ionic strength. The results demonstrate the potential of the combination of different particle sizes, composition as well as coupling chemistry in order to realize controlled conjugates of nanoparticles.
The spectral shape of the phosphorescence emission of organometallic porphyrin molecules is shown to be altered when these chromophores are incorporated into hybrid nanostructures with gold nanorods. This result shows that triplet-singlet transitions, which are (at least partially) dipolar forbidden, can be modified by the dipolar resonances of gold nanoparticles. By choosing nanorods of increasing aspect ratios, it is possible to match the long axis plasmon resonance of the nanorods to a specific phosphorescence transition. Consequently, the emission colour of the hybrids can be tuned.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.