Liping Song

Functionalization of Biodegradable PLA Nonwoven Fabric as Superoleophilic and Superhydrophobic Material for Efficient Oil Absorption and Oil/Water Separation

Although the construction of superwettability materials for oil/water separation has been developed rapidly, the postprocess of the used separation materials themselves is still a thorny problem due to their nondegradation in the natural environment. In this work, we reported the functionalization of polylactic acid (PLA) nonwoven fabric as superoleophilic and superhydrophobic material for efficient treatment of oily wastewater with eco-friendly post-treatment due to the well-known biodegradable nature of PLA matrix.

Underwater superoleophobic carbon nanotubes/core–shell polystyrene@Au nanoparticles composite membrane for flow-through catalytic decomposition and oil/water separation

A hierarchical composite membrane, consisting of an underwater superoleophobic carbon nanotube film and core–shell polystyrene@Au nanoparticle-assembled membrane, is fabricated to achieve simultaneous flow-through degradation of water-miscible toxic organic molecules and effective separation of oil/water emulsion. This multifunctional composite membrane allows continuous treatment of polluted oily wastewater, making it a promising candidate for water purification.

Engineering Gold Nanoparticles in Compass Shape with Broadly Tunable Plasmon Resonances and High-Performance SERS.

We present the uniform and high-yield synthesis of a novel gold nanostructure of compass shape composed of a Au sphere at the central and two gradually thinning conical tips at the opposed poles. The Au compass shapes were synthesized through a seed-mediated growth approach employing a binary mixture of cetyltrimethylammonium bromide (CTAB) and sodium oleate (NaOL) as the structure-directing agents. Under the condition of single surfactant (CTAB), the spherical seeds tend to grow into larger spherical Au nanoparticles (NPs); while the spherical seeds favor the formation of Au compass shaped NPs using two mixed surfactants (CTAB/NaOL). The reaction kinetics clearly shows a growth mechanism of Au compass shaped NPs. Interestingly, due to their anisotropic structure, Au compass shaped NPs show two distinctive plasmonic resonances, similar to those from Au nanorods. Particularly, the longitudinal surface plasmon resonances of Au compass shaped NPs exhibit a broadly tunable range from 600 to 865 nm. In addition, the obtained Au compass shaped NPs can be self-assembled into a two-dimensional monolayer with closely packed and highly aligned NPs, which results in periodic arrays of overlapped Au tips, generating hot spots for high-performance surface-enhanced Raman scattering.

Heterogemini surfactant assisted synthesis of monodisperse icosahedral gold nanocrystals and their applications in electrochemical biosensing

Icosahedral nanocatalysts (NCs) have shown very interesting physical and chemical properties owing to their multiply twinned nanostructures. Herein, we introduce a novel heterogemini surfactant (C10OhpNC8) assisted seed mediated growth approach for the synthesis of monodisperse icosahedral gold (Au) NCs in aqueous solution at room temperature. Very small shape impurities were observed in the resultant icosahedral Au NCs. Significantly improved monodispersity (relative standard deviation (RSD) of <10%) has been achieved by using a binary mixture of C10OhpNC8 and PVP as structure directing agents. Interestingly, the size of icosahedral Au NCs can be tuned ranging from 40 nm to 190 nm, which guides the surface plasmon resonance (SPR) peak to be tuned throughout the whole visible region and even to the near infrared (NIR) region. Furthermore, the developed icosahedral Au NCs specific probe has been designed to be applied as an easy electrochemical biosensor and successfully used to detect the bacteria Escherichia coli O157:H7 (E. coli O157:H7) with a detection limit of ∼10 colony forming units (CFU) mL−1. Notably, a much higher sensitivity of these icosahedral Au NCs probes has been achieved compared to the traditional colloidal gold immunochromatography (detection limit ∼103 CFU mL−1).

Amplifying the signal of localized surface plasmon resonance sensing for the sensitive detection of Escherichia coli O157:H7

Gold nanorods (Au NRs) based localized surface plasmon resonance (LSPR) sensors have been widely employed in various fields including biology, environment and food safety detection, but their size- and shape-dependent sensitivity limits their practical applications in sensing and biological detection. In our present work, we proposed an approach to maximally amplify the signal of Au NRs based LSPR sensing by coating an optimized thickness of mesoporous silica onto Au NRs. The plasmonic peaks of Au NRs@SiO2 with different shell thickness showed finely linear response to the change of surrounding refractive index. The optimized thickness of mesoporous silica of Au NRs@SiO2 not only provided high stability for LSPR sensor,but also displayed much higher sensitivity (390 nm/RIU) than values of Au NRs from previous reports. The obtained Au NRs@SiO2 based LSPR sensor was further used in practical application for selectively detection of the E. coli O157:H7, and the detection limit achieved 10 CFU, which is much lower than conventional methods such as electrochemical methods and lateral-flow immunochromatography.

First synthesis of unexpected functionalized trifluoromethylated 8-oxa-2,4-diazaspiro[5.5]undecanes via one-pot MCRs

Ethyl-7,11-diaryl-9-hydroxy-1,3,5-trioxo-9-(trifluoromethyl)-8-oxa-2,4-diazaspiro[5.5]undecane-10-carboxylate derivatives (4) were synthesized from barbituric acid, aromatic aldehydes and ethyl 4,4,4-trifluoro-3-oxobutanoate via a one-pot, multi-component reaction catalyzed by Et3N. The effect of catalyst and temperature on reaction efficiency and yield was investigated. In addition, the treatment of 4 with SOCl2/pyridine in the solvent CH3CN afforded the corresponding dehydrated products 5. A plausible reaction mechanism for the formation of compounds 4 was presented.

Giant Vesicles with Anchored Tiny Gold Nanowires: Fabrication and Surface-Enhanced Raman Scattering

Sensitivity and reproducibility are two major concerns to improve the performance and extend the range of practical applications of surface-enhanced Raman scattering (SERS). A theoretical report reveals that hot spots formed by gold nanoparticles with a tip-to-tip configuration would generate the maximum electric field enhancement because of the lightning rod effect. In our present study, we constructed a giant vesicle consisting of anchored tiny gold nanowires to provide a high density of sharp tip-to-tip nanogaps for SERS application. The tiny gold nanowires were directly grown and anchored onto the surfaces of polystyrene (PS) microspheres by a seed-mediated method. Then, the removal of PS microspheres by tetrahydrofuran led to the formation of the giant gold vesicles with hierarchical cage structures, providing the sharp tips and high density of hot spots for improving SERS performance. Compared with the nonwire structure (island and inhibited nanoparticle), giant gold vesicles with tiny wires showed a higher SERS enhancement factor (9.90 × 107) and quantitative SERS analysis in the range of 10-4 to 10-7 M. In addition, the large-scale giant gold vesicle array on the silica substrate resulted in a high reproducibility of SERS signals with the variation of intensities less than 7.6%.

pH and Temperature Dual-Responsive Plasmonic Switches of Gold Nanoparticle Monolayer Film for Multiple Anticounterfeiting

Two-dimensional (2D) gold nanoparticle (Au NP) monolayer film possesses a lot of fascinating peculiarities, and has shown promising applications in photoelectrical devices, catalysis, spectroscopy, sensors, and anticounterfeiting. Because of the localized surface plasmon resonance (LSPR) property predetermined by the natural structure of metal nanoparticles, it is usually difficult to realize the reversible LSPR transition of 2D film. In this work, we report on the fabrication of a large-area free-standing Au NP monolayer film with dual-responsive switchable plasmonic property using a pH- or thermal-responsive dendronized copolymer as a stimuli-sensitive linker. In this system, an oligoethylene-glycol-based (OEG-based) dendronized copolymer (named PG1A) with pH or temperature sensitivity was first modified onto the surface of a Au NP. Then, polyethylene glycol dibenzyl aldehyde (PEG-DA) was introduced to interact with the amino moieties from PG1A before the process of oil-water interfacial self-assembly of NPs, resulting in an elastic, robust, pH- or temperature-sensitive interpenetrating network among Au NPs in monolayer films. In addition, the film could exhibit reversibly plasmonic shifts of about 77 nm and inherent color changes through varying temperature or pH. The obtained free-standing monolayer film also shows an excellent transferable property, which can be easily transferred onto substrates such as plastic molds, PDMS, copper grids, and silicon wafers. In virtue of these peculiarities of the free-standing property, special plasmonic signal, and homologous macroscopic color, the transferred film was primely applied to an anticounterfeiting security label with clear color change at the designed spots, providing a new avenue to plasmonic nanodevices with various applications.

Humidity-Responsive Gold Aerogel for Real-Time Monitoring of Human Breath

Humidity sensors have received considerable attention in recent years because of their significance and wide applications in agriculture, industries, goods stores, and medical fields. However, the conventional humidity sensors usually possessed a complex sensing mechanism and low sensitivity and required a time-consuming, labor-intensive process. The exploration for an ideal sensing material to amplify the sensitivity of humidity sensors is still a big challenge. Herein, we developed a simple, low-cost, and scalable fabrication strategy to construct a highly sensitive humidity sensor based on polymer/gold nanoparticle (AuNP) hybrid materials. The hybrid polymer/AuNP aerogel was prepared by a simple freeze-drying method. By taking advantage of the conductivity of AuNPs and high surface area of the highly porous structure, the hybrid poly- N-isopropylacrylamide (PNIPAm)/AuNP aerogel showed high sensitivity to water molecules. Interestingly, the hybrid PNIPAm/AuNP aerogel-based humidity sensor can be used to detect human breath in different states, such as normal breath, fast breath, and deep breath, or in different individuals such as persons with illness, persons who are smoking, and persons who are normal, which is promising in practical flexible wearable devices for human health monitoring. In addition, the humidity sensor can be used in whistle tune recognition.

Macroscopic Assembly of Gold Nanorods into Superstructures with Controllable Orientations by Anisotropic Affinity Interaction

Two-dimensional or three-dimensional highly ordered arrays of anisotropic nanoparticles provide attracting properties that are highly desired by the industry. Traditional assembly methods such as evaporation usually produces the nanostructure arrays only up to the millimeter scale with poor control of nanoparticle orientation, making them hardly applicable for industrial needs. Here, we report a facile method to assemble centimeter-scale gold nanorod (Au NR) arrays with highly controlled nanoparticle orientation and high reproducibility. We selectively functionalized the transverse or longitudinal facets of Au NRs with polyethylene glycol (PEG) molecules and utilized the interfacial polymeric affinity between the PEG domains on Au NRs and the PEGylated substrate to achieve the anisotropic self-assembly. The side-PEGylated Au NRs formed closely packed horizontal arrays, whereas the end-PEGylated Au NRs formed vertically standing arrays on the substrate, respectively. The obtained Au NR arrays with different orientations showed anisotropic surface-enhanced Raman scattering (SERS) performance. We showed that the vertically ordered Au NR arrays exhibited 3 times higher SERS signals than the horizontally ordered arrays.