We report metallurgy on the nanoscale
to generate metal nanoparticles
and their simultaneous patterning in a single step. This is achieved
by the self-reduction of porous metal–organic framework crystals
using nanosecond pulsed laser irradiation. Metal nanoparticles of
Fe, Co, Ni, Cu, Zn, Cd, In, Bi, and Pb with uniform sizes (controllable
between 3 to 200 nm) and gaps (as narrow as 2 nm) are produced by
nine different metal–organic frameworks, where atomically dispersed
non-noble metal ions are reduced and gathered across the pores. The
instant light absorption and cooling at local positions by a laser
allows for precise and efficient patterning of metal nanoparticles.
This new method is suitable for device fabrication at a speed of 15
mm2 s–1 on glass, consuming only 1.5
W of power. A large variety of metal nanoparticle three-dimensional
architectures are demonstrated, among which one architecture exhibits
an enhanced plasmonic effect homogeneously across the entire pattern
for the detection of molecules at an extremely low concentration (10–12 M). These architectures are extremely stable under
air and humidity during production, use, and storage, without altering
the oxidation state, for 6 months.
Surface-enhanced Raman scattering (SERS) and magnetic resonance imaging (MRI)-guided phototherapy are new breakthroughs in cancer therapeutics due to their complementary advantages, such as enhanced imaging spatial resolution and depth.
The unique “tip spots” can simultaneously enhance SERS and the photothermal effect, facilitating label-free SERS intracellular imaging during cell apoptosis.
High-throughput
optical labeling technologies have become increasingly
important with the growing demands for molecular detection, disease
diagnosis, and drug discovery. In this thought, a series of CN-bridged
coordination polymer encapsulated gold nanoparticles have been developed
as a universal and interference-free optical label through a facile
and auxiliary agent-free self-assembly route. Moreover, surface-enhanced
Raman scattering (SERS) emissions of CN-bridge can be tuned flexibly
by simple replacement of Fe2+/Fe3+ with other
metal ions relying on the synthesis of three Prussian blue analogues
encapsulated gold nanoparticles (Au@PBA NPs). Thus, three distinct
Raman frequencies have been acquired, which merely replaced the metal
irons. On the basis of the potential supermultiplex optical label,
space-confined surface-enhanced Raman scattering (SERS) emissions
have been realized. Relying on “Abbe theorem”, the focused
laser allows the pure and single triple bond-coded SERS emissions
to be combined into a unique and independent output, so-called “combined
SERS emission” (c-SERS), if the Au@PBA NPs were confined into
one micrometer-scale object. This study demonstrated c-SERS may simultaneously
provide 2
n
– 1 optical labels only
using n single emissions in the Raman-silent region
for micrometer-size objects.
Materials
with surface wrinkles at a micro/nanoscale possess extraordinary
fascinating properties, and various techniques have been employed
to create controllable wrinkles. Herein, natural polysaccharide was
used to construct the surface wrinkled microsphere with controllable
wrinkling patterns. A robust microsphere with an average size of about
55 μm fabricated from chitosan in alkali/urea aqueous solution
was swelled and then coated orderly by introducing rigid silver nanoparticles
(Ag NPs) with an average size of about 5 nm as the shell onto the
surface through electrostatic layer-by-layer (LBL) self-assembly followed
by deswelling, resulting in a surface wrinkled microsphere. The significant
difference in the swelling behaviors between the stiff Ag shell and
swelled chitosan microsphere could generate enough driving forces
to form 3D micro- and nanoscale wrinkling surface topography. The
surface wrinkled microspheres exhibited the hierarchically porous
structure and hydrophobicity, and the topographical patterns could
be adjusted by controlling the thickness of the Ag NP layer to achieve
the sizes of wrinkling ranging from 60 to 300 nm. It was demonstrated
that the wrinkled microspheres were superior as 3D surface-enhanced
Raman spectroscopy (SERS) substrates, in which the wrinkled structure
with spatial periodicity was proved to be effective for enhancing
the SERS signal. The microsphere with controllable wrinkled surface
topography could be applied to be a miniature 3D device, which promises
potential technological applications in various areas.
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