Abstract
Nanoparticles with tunable localized surface plasmon resonance have been prepared by synthesis in helium nanodroplets. Subsequent surface deposition allows for the formation of substrates which can be employed for surface-enhanced Raman spectroscopy (SERS). The assembly of Ag@Au core@shell clusters of about 5 nm diameter in helium droplets with different Ag:Au ratio allows to tune the surface plasmon resonance between the plain Ag resonance at 447 nm and the Au resonance at 555 nm. For the fabricated substrates only a single plasmon resonance is observed in the UV/vis absorption spectra. The prepared nanostructures have been functionalized with 4-methylbenzenethiol (4-MBT) molecules and SERS spectra have been recorded. The results demonstrate the potential of the helium droplet synthesis approach, opening up a new route to the formation of tailored plasmonic nanoparticles and functional nanostructures.Graphical abstract
Highlights
Nano-sized particles have paved the way for exciting new research and applications in science and technology
The advantages that come with the helium droplet approach are the (i) intrinsic inertness of the synthesis environment that does not involve any solvents, surfactants or other chemicals, (ii) the large variety of dopants that can be combined and (iii) the cold environment (0.37 K) [7,8] that enables the production of nanoparticles with a core@shell configuration indepen
Note that the ratio refers to the estimated ratio of the number of atoms, which can be controlled by adjusting the temperatures of the pickup-ovens [31]
Summary
Nano-sized particles have paved the way for exciting new research and applications in science and technology. We introduce the helium nanodroplet synthesis method as a novel approach for the production of functional hybrid nanoparticles with tailored plasmonic properties. With the helium droplet synthesis approach nanoparticles are formed when the droplets pass a pickup region, typically a cell in which a resistively heated oven establishes an increased vapor pressure of the desired dopant material. Decrease of the 4He yield in the quadrupole mass spectrometer at the end of the machine [30], which, provides a convenient way to monitor the doping level When applying this method to multiple dopants added subsequently to the droplets, differences in the binding energies have to be accounted for, which can be estimated by the bulk cohesive energies. The slide is subsequently taken out of the vacuum and placed into the spectrophotometer to acquire the spectra shown in Figure 4, using a second fused silica slide as reference
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