6 research outputs found
Self-Assembled Nanocube-Based Plasmene Nanosheets as Soft Surface-Enhanced Raman Scattering Substrates toward Direct Quantitative Drug Identification on Surfaces
We report on self-assembled nanocube-based
plasmene nanosheets
as new surface-enhanced Raman scattering (SERS) substrates toward
direct identification of a trace amount of drugs sitting on topologically
complex real-world surfaces. The uniform nanocube arrays (superlattices)
led to low spatial SERS signal variances (ā¼2%). Unlike conventional
SERS substrates which are based on rigid nanostructured metals, our
plasmene nanosheets are mechanically soft and optically semitransparent,
enabling conformal attachment to real-world solid surfaces such as
banknotes for direct SERS identification of drugs. Our plasmene nanosheets
were able to detect benzocaine overdose down to a parts-per-billion
(ppb) level with an excellent linear relationship (<i>R</i><sup>2</sup> > 0.99) between characteristic peak intensity and
concentration.
On banknote surfaces, a detection limit of ā¼0.9 Ć 10<sup>ā6</sup> g/cm<sup>2</sup> benzocaine could be achieved. Furthermore,
a few other drugs could also be identified, even in their binary mixtures
with our plasmene nanosheets. Our experimental results clearly show
that our plasmene sheets represent a new class of unique SERS substrates,
potentially serving as a versatile platform for real-world forensic
drug identification
Free-Standing Bilayered Nanoparticle Superlattice Nanosheets with Asymmetric Ionic Transport Behaviors
Natural cell membranes can directionally and selectively regulate the ion transport, which is critical for the functioning of living cells. Here, we report on the fabrication of an artificial membrane based on an asymmetric nanoparticle superlattice bilayered nanosheet, which exhibits similar ion transport characteristics. The superlattice nanosheets were fabricated <i>via</i> a drying-mediated self-assembly of polystyrene-capped gold nanoparticles at the liquidāair interface. By adopting a layer-by-layer assembly process, an asymmetric nanomembrane could be obtained consisting of two nanosheets with different nanoparticle size. The resulting nanomembranes exhibit an asymmetric ion transport behavior, and diode-like currentāvoltage curves were observed. The asymmetric ion transport is attributed to the cone-like nanochannels formed within the membranes, upon which a simulation map was established to illustrate the relationship between the channel structure and the ionic selectivity, in consistency with our experimental results. Our superlattice nanosheet-based design presents a promising strategy for the fabrication of next-generation smart nanomembranes for rationally and selectively regulating the ion transport even at a large ion flux, with potential applications in a wide range of fields, including biosensor devices, energy conversion, biophotonics, and bioelectronics
Two-Dimensional Bipyramid Plasmonic Nanoparticle Liquid Crystalline Superstructure with Four Distinct Orientational Packing Orders
Anisotropic plasmonic nanoparticles
have been successfully used
as constituent elements for growing ordered nanoparticle arrays. However,
orientational control over their spatial ordering remains challenging.
Here, we report on a self-assembled two-dimensional (2D) nanoparticle
liquid crystalline superstructure (NLCS) from bipyramid gold nanoparticles
(BNPs), which showed four distinct orientational packing orders, corresponding
to horizontal alignment (H-NLCS), circular arrangement (C-NLCS), slanted
alignment (S-NLCS), and vertical alignment (V-NLCS) of constituent
particle building elements. These packing orders are characteristic
of the unique shape of BNPs because all four packing modes were observed
for particles with various sizes. Nevertheless, only H-NLCS and V-NLCS
packing orders were observed for the free-standing ordered array nanosheets
formed from a drying-mediated self-assembly at the air/water interface
of a sessile droplet. This is due to strong surface tension and the
absence of particleāsubstrate interaction. In addition, we
found the collective plasmonic coupling properties mainly depend on
the packing type, and characteristic coupling peak locations depend
on particle sizes. Interestingly, surface-enhanced Raman scattering
(SERS) enhancements were heavily dependent on the orientational packing
ordering. In particular, V-NLCS showed the highest Raman enhancement
factor, which was about 77-fold greater than the H-NLCS and about
19-fold greater than C-NLCS. The results presented here reveal the
nature and significance of orientational ordering in controlling plasmonic
coupling and SERS enhancements of ordered plasmonic nanoparticle arrays
Shape Transformation of Constituent Building Blocks within Self-Assembled Nanosheets and Nano-origami
Self-assembly of
nanoparticles represents a simple yet efficient
route to synthesize designer materials with unusual properties. However,
the previous assembled structures whether by surfactants, polymer,
or DNA ligands are āstaticā or āfrozenā
building block structures. Here, we report the growth of transformable
self-assembled nanosheets which could enable reversible switching
between two types of nanosheets and even evolving into diverse third
generation nanosheet structures without losing pristine periodicity.
Such <i>in situ</i> transformation of nanoparticle building
blocks can even be achieved in a free-standing two-dimensional system
and three-dimensional origami. The success in such <i>in situ</i> nanocrystal transformation is attributed to robust āplant-cell-wall-likeā
ion-permeable reactor arrays from densely packed polymer ligands,
which spatially define and confine nanoscale nucleation/growth/etching
events. Our strategy enables efficient fabrication of nanocrystal
nanosheets with programmable building blocks for innovative applications
in adaptive tactile metamaterials, optoelectronic devices, and sensors
Large-Scale Self-Assembly and Stretch-Induced Plasmonic Properties of CoreāShell Metal Nanoparticle Superlattice Sheets
We report on a facile interfacial
self-assembly approach to fabricate large-scale metal nanoparticle
superlattice sheets from nonspherical coreāshell nanoparticles,
which exhibited reversible plasmonic responses to repeated mechanical
stretching. Monodisperse Au@Ag nanocubes (NCs) and Au@Ag nanocuboids
(NBs) could be induced to self-assembly at the hexane/water interface,
forming uniform superlattices up to at least ā¼13 cm<sup>2</sup> and giving rise to mirror-like reflection. Such large-area mirror-like
superlattice sheets exhibited reversible plasmonic responses to external
mechanical strains. Under stretching, the dominant plasmonic resonance
peak for both NB and NC superlattice sheets shifted to blue, following
a power-law function of the applied strain. Interestingly, the power-law
exponent (or the decay rate) showed a strong shape dependence, where
a faster rate was observed for NB superlattice sheets than that for
NC superlattice sheets
Giant Plasmene Nanosheets, Nanoribbons, and Origami
We introduce <i>Plasmene</i>īø in analogy to grapheneīøas free-standing, one-particle-thick, superlattice sheets of nanoparticles (āmeta-atomsā) from the āplasmonic periodic tableā, which has implications in many important research disciplines. Here, we report on a general bottom-up self-assembly approach to fabricate giant plasmene nanosheets (<i>i.e.</i>, plasmene with nanoscale thickness but with macroscopic lateral dimensions) as thin as ā¼40 nm and as wide as ā¼3 mm, corresponding to an aspect ratio of ā¼75ā000. In conjunction with topādown lithography, such robust giant nanosheets could be milled into one-dimensional nanoribbons and folded into three-dimensional origami. Both experimental and theoretical studies reveal that our giant plasmene nanosheets are analogues of graphene from the plasmonic nanoparticle family, simultaneously possessing unique structural features and plasmon propagation functionalities