Chenxu Wang

SERS-encoded nanogapped plasmonic nanoparticles: growth of metallic nanoshell by templating redox-active polymer brushes.

We report a new strategy to synthesize core-shell metal nanoparticles with an interior, Raman tag-encoded nanogap by taking advantage of nanoparticle-templated self-assembly of amphiphilic block copolymers and localized metal precursor reduction by redox-active polymer brushes. Of particular interest for surface-enhanced Raman scattering (SERS) is that the nanogap size can be tailored flexibly, with the sub-2 nm nanogap leading to the highest SERS enhancement. Our results have further demonstrated that surface functionalization of the nanogapped Au nanoparticles with aptamer targeting ligands allows for specific recognition and ultrasensitive detection of cancer cells. The general applicability of this new synthetic strategy, coupled with recent advances in controlled wet-chemical synthesis of functional nanocrystals, opens new avenues to multifunctional core-shell nanoparticles with integrated optical, electronic, and magnetic properties.

Interfacial Assembly of Mussel‐Inspired Au@Ag@ Polydopamine Core–Shell Nanoparticles for Recyclable Nanocatalysts

Recyclable nanocatalysts of core-shell bimetallic nanocrystals are developed through polydopamine coating-directed one-step seeded growth, interfacial assembly, and substrate-immobilization of Au@Ag core-shell nanocrystals. This strategy provides new opportunities to design and optimize heterogeneous nanocatalysts with tailored size, morphology, chemical configuration, and supporting substrates for metal-catalyzed reactions.

Versatile Core–Shell Nanoparticle@Metal–Organic Framework Nanohybrids: Exploiting Mussel-Inspired Polydopamine for Tailored Structural Integration

We report a versatile strategy based on the use of multifunctional mussel-inspired polydopamine for constructing well-defined single-nanoparticle@metal-organic framework (MOF) core-shell nanohybrids. The capability of polydopamine to form a robust conformal coating on colloidal substrates of any composition and to direct the heterogeneous nucleation and growth of MOFs makes it possible for customized structural integration of a broad range of inorganic/organic nanoparticles and functional MOFs. Furthermore, the unique redox activity of polydopamine adds additional possibilities to tailor the functionalities of the nanohybrids by sandwiching plasmonic/catalytic metal nanostructures between the core and shell via localized reduction. The core-shell nanohybrids, with the molecular sieving effect of the MOF shell complementing the intrinsic properties of nanoparticle cores, represent a unique class of nanomaterials of considerable current interest for catalysis, sensing, and nanomedicine.

Graphene Paper Decorated with a 2D Array of Dendritic Platinum Nanoparticles for Ultrasensitive Electrochemical Detection of Dopamine Secreted by Live Cells.

Abstract To circumvent the bottlenecks of non‐flexibility, low sensitivity, and narrow workable detection range of conventional biosensors for biological molecule detection (e.g., dopamine (DA) secreted by living cells), a new hybrid flexible electrochemical biosensor has been created by decorating closely packed dendritic Pt nanoparticles (NPs) on freestanding graphene paper. This innovative structural integration of ultrathin graphene paper and uniform 2D arrays of dendritic NPs by tailored wet chemical synthesis has been achieved by a modular strategy through a facile and delicately controlled oil–water interfacial assembly method, whereby the uniform distribution of catalytic dendritic NPs on the graphene paper is maximized. In this way, the performance is improved by several orders of magnitude. The developed hybrid electrode shows a high sensitivity of 2 μA cm−2 μm −1, up to about 33 times higher than those of conventional sensors, a low detection limit of 5 nm, and a wide linear range of 87 nm to 100 μm. These combined features enable the ultrasensitive detection of DA released from pheochromocytoma (PC 12) cells. The unique features of this flexible sensor can be attributed to the well‐tailored uniform 2D array of dendritic Pt NPs and the modular electrode assembly at the oil–water interface. Its excellent performance holds much promise for the future development of optimized flexible electrochemical sensors for a diverse range of electroactive molecules to better serve society.

Incorporating nanoporous polyaniline into layer-by-layer ionic liquid-carbon nanotube-graphene paper: towards freestanding flexible electrodes with improved supercapacitive performance.

The growing demand for lightweight and flexible supercapacitor devices necessitates innovation in electrode materials and electrode configuration. We have developed a new type of three-dimensional (3D) flexible nanohybrid electrode by incorporating nanoporous polyaniline (PANI) into layer-by-layer ionic liquid (IL) functionalized carbon nanotube (CNT)-graphene paper (GP), and explored its practical application as a freestanding flexible electrode in a supercapacitor. Our results have demonstrated that the surface modification of graphene nanosheets and CNTs by hydrophilic IL molecules makes graphene and CNTs well-dispersed in aqueous solution, and also improves the hydrophility of the assembled graphene-based paper. Furthermore, the integration of highly conductive one-dimensional (1D) CNTs with two-dimensional (2D) graphene nanosheets leads to 3D sandwich-structured nanohybrid paper with abundant interconnected pores, which is preferred for fast mass and electron transport kinetics. For in situ electropolymerization of PANI on paper electrodes, the IL functionalized CNT-GP (IL-CNT-GP) offers large surface area and interlayer spacing and the unique π surface of graphene and CNTs for efficient and stable loading of PANI. A key finding is that the structural integration of multiple components in this 3D freestanding flexible sheet electrode gives rise to a synergic effect, leading to a high capacitance of 725.6 F g(-1) at a current density of 1 A g(-1) and good cycling stability by retaining 90% of the initial specific capacitance after 5000 cycles.

Robust Nanoparticle–DNA Conjugates Based on Mussel-Inspired Polydopamine Coating for Cell Imaging and Tailored Self-Assembly

We have demonstrated that mussel-inspired polydopamine can serve as an intermediate coating layer for covalently attaching oligonucleotides on nanostructures of diverse chemical nature, which are made possible by the universal adhesion and spontaneous reactivity of polydopamine. Our results have shown that polydopamine can strongly bond to representative nanoparticles (i.e., Au nanoparticles and magnetic polymer nanobeads) and form a thin layer of coating that allows for attachment of commercially available DNA with thiol or amine end functionality. The resulting DNA-nanoparticle conjugates not only show excellent chemical and thermal stability and high loading density of DNA, but the linked DNA also maintain their biological functions in directing cancer cell targeting and undergo DNA hybridization to form multifunctional magnetic core-plasmonic satellite assemblies. The generally applicable strategy opens new opportunities for easy adoption of DNA-nanoparticle conjugates for broad applications in biosensors and nanomedicine.