Research Article Issue
Deep-elliptical-silver-nanowell arrays (d-EAgNWAs) fabricated by stretchable imprinting combining colloidal lithography: A highly sensitive plasmonic sensing platform
Nano Research 2019, 12 (4): 845-853
Published: 01 February 2019

Elliptical metallic nanohole arrays possess much higher transmission and enhanced sensitivity compared with circular nanohole arrays. However, fabricating elliptical metallic nanohole arrays in large area with highly tunable aspect ratio remains a challenge. Herein, a brand-new method combining stretchable imprinting with colloidal lithography is figured out to fabricate deep-elliptical-silver-nanowell arrays (d-EAgNWAs). In this method, large area highly ordered silicon nanopillar arrays fabricated by colloidal lithography were taken as a master to transfer large area polydimethylsiloxane (PDMS) nanohole arrays. Benefit from the high elasticity of PDMS mold, the aspect ratio of d-EAgNWAs achieved can be facilely regulated from 1.7 to 5.0. Through optimization of polarization direction and the structural parameters including nanowell depth, aspect ratio, and hole size, the sensing performance of d-EAgNWAs was finally improved up to 1, 414.1 nm/RIU. The best sensing behaved d-EAgNWAs were employed as an immunoassay platform finally to prove their great potential in label-free biosensing.

Research Article Issue
Highly sensitive deep-silver-nanowell arrays (d-AgNWAs) for refractometric sensing
Nano Research 2017, 10 (3): 908-921
Published: 07 December 2016

Large-area deep-silver-nanowell arrays (d-AgNWAs) for plasmonic sensing were manufactured by combining colloidal lithography with metal deposition. In contrast to most previous studies, we shed light on the outstanding sensitivity afforded by deep metallic nanowells (up to 400 nm in depth). Using gold nanohole arrays as a mask, a silicon substrate was etched into deep silicon nanowells, which acted as a template for subsequent Ag deposition, resulting in the formation of d-AgNWAs. Various geometric parameters were separately tailored to study the changes in the optical performance and further optimize the sensing ability of the structure. After several rounds of selection, the best sensing d-AgNWA, which had a Ag thickness of 400 nm, template depth of 400 nm, hole diameter of 504 nm, and period of 1 μm, was selected. It had a sensitivity of 933 nm·RIU–1, which is substantially higher than those of most common thin metallic nanohole arrays. As a proof of concept, the as-prepared structure was employed as a substrate for an antigen-antibody recognition immunoassay, which indicates its great potential for label-free real-time biosensing.

Research Article Issue
An effective poly(p-phenylenevinylene) polymer adhesion route toward three-dimensional nitrogen-doped carbon nanotube/reduced graphene oxide composite for direct electrocatalytic oxygen reduction
Nano Research 2016, 9 (11): 3364-3376
Published: 30 August 2016

Heteroatom-doped nanocarbons have excellent potential for use in the oxygen reduction reaction (ORR). However, construction of three-dimensional (3D) N-doped carbon materials with good electrocatalytic performance remains a challenge. Herein, a poly(p-phenylenevinylene) (PPV)-precursor adhesion route was developed for construction of 3D N-doped reduced graphene oxide-PPV calcined-carbon nanotubes (N-RGO-PPV(c)-CNTs). In the synthesis, the PPV-precursor plays the role of a "glue" for strong adhesion of the RGO and CNTs. At high temperature, PPV can undergo transformation from the glassy state to a viscous state. Thus, the N-RGO-PPV(c)-CNT composite with multi-porous structure and ridge-like folded graphene flakes could be formed during nitridation at high temperature, which was favorable for production of more active sites for the ORR. As an ORR catalyst, the N-RGO-PPV(c)-CNT composites exhibited superior catalytic activity in alkaline electrolyte. The obtained onset potential (Eonset) of 0.92 V and catalytic current density of 5.7 mA·cm–2 at 0.6 V (vs. RHE) are comparable to those of the 20% Pt/C composite (0.98 V and 5.2 mA·cm–2). The electron transfer number for the N-RGO-PPV(c)-CNT catalyst was about 3.99, which is close to that of the 20% Pt/C (4.01) catalyst. Notably, the optimal N-RGO-PPV(c)-CNT catalyst shows better durability and methanol tolerance than commercial 20% Pt/C. The good performance of the N-RGO-PPV(c)-CNT catalyst for the ORR may be attributed to the synergistic effects of the unique 3D structure for effective mass-transfer, the effective N-doping for production of more active sites, and the good contact between the RGO and CNTs for easy charge-transfer.

Research Article Issue
Functional interface based on silicon artificial chamfer nanocylinder arrays (CNCAs) with underwater superoleophobicity and anisotropic properties
Nano Research 2016, 9 (10): 3141-3151
Published: 25 July 2016

A functional interface based on silicon chamfer nanocylinder arrays (CNCAs) was successfully fabricated by carrying out secondary etching of silicon nanopillar arrays via a facile inclined etching method. The structure of the novel CNCAs was finely modulated by varying the nanopillar array structure and the etching conditions. The underwater oil wetting behavior of this CNCAs-based interface can be easily modulated from superoleophilic (oil contact angle (OCA) of ~8.13°) state to superoleophobic (OCA of ~163.79°) state by modifying the surface using different substances. Moreover, a reversible transformation of underwater oil wetting behavior from superoleophobic (OCA of ~155.67°) state to oleophilic (OCA of ~31.27°) state was achieved by grafting a temperature-responsive polymer onto this specific asymmetric structure. The functional interface exhibited isotropic wetting behavior under certain oleophilic conditions. Chemically heterogeneous structures, obtained via asymmetry modification of CNCAs, exhibited amphiphobic properties while maintaining their anisotropic wetting ability.

Review Article Issue
The photoluminescence mechanism in carbon dots (graphene quantum dots, carbon nanodots, and polymer dots): current state and future perspective
Nano Research 2015, 8 (2): 355-381
Published: 19 February 2015

At present, the actual mechanism of the photoluminescence (PL) of fluorescent carbon dots (CDs) is still an open debate among researchers. Because of the variety of CDs, it is highly important to summarize the PL mechanism for these kinds of carbon materials; doing so can guide the development of effective synthesis routes and novel applications. This review will focus on the PL mechanism of CDs. Three types of fluorescent CDs were involved: graphene quantum dots (GQDs), carbon nanodots (CNDs), and polymer dots (PDs). Four reasonable PL mechanisms have been confirmed: the quantum confinement effect or conjugated π-domains, which are determined by the carbon core; the surface state, which is determined by hybridization of the carbon backbone and the connected chemical groups; the molecule state, which is determined solely by the fluorescent molecules connected on the surface or interior of the CDs; and the crosslink-enhanced emission (CEE) effect. To give a thorough summary, the category and synthesis routes, as well as the chemical/physical properties for the CDs, are briefly introduced in advance.

Open Access Research Article Issue
An Effective Method to Prepare Polymer/Nanocrystal Composites with Tunable Emission over the Whole Visible Light Range
Nano Research 2010, 3 (7): 496-505
Published: 12 June 2010

Materials with emission over the whole visible range (400–800 nm) have been obtained through incorporating single-colored CdTe nanocrystals (NCs) into a poly(p-phenylene vinylene) (PPV) precursor [the sulfonium polyelectrolyte precursor of PPV]. Firstly, the quantum yield (QY) of the PPV precursor was improved to ~50% via heat treatment of a mixed solution of the PPV precursor and poly(vinyl alcohol) (PVA) at 100 ℃ for 3 min. Then, single-colored CdTe NCs were incorporated into the mixed solution. The introduction of the PVA was necessary to reduce the electrostatic interaction between the PPV precursor and CdTe NCs, which improved their compatibility. The reduced electrostatic interaction eliminated Förster resonance energy transfer (FRET) processes between NCs, as well as between NCs and the PPV precursor, which allowed the functional integration of the polymer and NCs. Consequently, polymer/NC composites with almost any Commission Internationale de L'Eclairage (CIE) coordinates can be achieved by simply changing the size and amount of the NCs. In particular, when the emission wavelength of the CdTe NCs was 559 nm, a pure white-light emitting material with CIE coordinates (0.337, 0.332) was obtained.

Open Access Research Article Issue
From Two-Dimensional Metal—Organic Coordination Networks to Near-Infrared Luminescent PbS Nanoparticle/Layered Polymer Composite Materials
Nano Research 2008, 1 (3): 195-202
Published: 01 March 2008

Two-dimensional (2-D) layered metal-organic coordination (lead methacrylate (LDMA)) networks have been prepared in aqueous solution under mild conditions and their structure determined by single crystal diffraction. As the ligand used in our experiments is easily polymerized, these metal-organic coordination layers are therefore employed as precursors to fabricate cross-linked polymer layered materials through γ-irradiated polymerization. The stabilities of the samples are significantly improved after γ-irradiation. To our knowledge, this is the first time that covalent bonded polymer layered structures have been fabricated without the assistance of added surfactant or template. Such layered polymer materials cannot only act as alternatives to layered inorganic materials in some caustic environments, but also allow the generation of PbS nanoparticles (NPs) without aggregation in the polymer matrix. By exposing the polymer layer to H2S gas at room temperature, uniform PbS nanoparticles with an average size of about 6 nm are generated in situ. In addition, the resulting PbS NPs exhibit near-infrared (NIR) luminescent properties, which suggests the composite materials may be useful as active optical elements at communication wavelengths from 1300 to 1550 nm.

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