Three-Dimensional Metamaterial for Plasmon-Enhanced Raman Scattering at any Excitation Wavelengths from the Visible to Near-Infrared Range.

Plasmonic materials with highly confined electromagnetic fields at resonance wavelengths have been widely used to enhance Raman scattering signals. To achieve the maximum enhancement, the resonance peaks of the plasmonic materials should overlap with the excitation and emission wavelengths of target molecules, which is difficult for most of the plasmonic materials possessing a few narrow resonance peaks. Here, we report an ultrabroadband plasmonic metamaterial absorber (BPMA) that can absorb 99% of the incident light energy and excite plasmon resonance from the ultraviolet to near-infrared range (250-1900 nm), which allows us to observe efficient plasmon-enhanced Raman scattering (PERS) with any excitation sources. As demonstrated by the investigation on a self-assembled monolayer of the nonresonant molecule 4-mercaptobenzonitrile, the BPMA exhibits high PERS performance with a detection limit of down to 10-12 M under any excitation sources of three different lasers and excellent uniformity (∼5.51%) and reproducibility (∼5.50%), which corroborates the potential for high-throughput production with low cost and at a large scale. This work offers a novel platform for anti-interference PERS analysis in dynamic and complex environments.

pH-Dependent Slipping and Exfoliation of Layered Covalent Organic Framework.

Layered/two-dimensional covalent organic frameworks (2D COF) are crystalline porous materials composed of light elements linked by strong covalent bonds. Interlayer force is one of the main factors directing the formation of a stacked layer structure, which plays a vital role in the stability, crystallinity, and porosity of layered COFs. The as-developed new way to modulate the interlayer force of imine-linked 2D TAPB-PDA-COF (TAPB = 1,3,5-tris(4-aminophenyl)benzene, PDA = terephthaldehyde) by only adjusting the pH of the solution. At alkaline and neutral pH, the pore size of the COF decreases from 34 Šdue to the turbostratic effect. Under highly acidic conditions (pH 1), TAPB-PDA-COF shows a faster and stronger turbostratic effect, thus causing the 2D structure to exfoliate. This yields bulk quantities of an exfoliated few/single-layer 2D COF, which was well dispersed and displayed a clear Tyndall effect (TE). Furthermore, nanopipette-based electrochemical testing also confirms the slipping of layers with increase towards acidic pH. A model of pH-dependent layer slipping of TAPB-PDA-COF was proposed. This controllable pH-dependent change in the layer structure may open a new door for potential applications in controlled gas adsorption/desorption and drug loading/releasing.

Graphene Plasmon-Enhanced IR Biosensing for in Situ Detection of Aqueous-Phase Molecules with an Attenuated Total Reflection Mode.

Graphene plasmon has attracted extensive interest due to the unprecedented electromagnetic confinement, long propagation distance, and tunable plasmonic frequency. Successful applications of graphene plasmon as infrared sensors have been recently demonstrated, yet they are mainly focused on solid/solid and solid/gas interfaces analysis. Herein, we, for the first time, propose a graphene plasmon-enhanced infrared sensor based on attenuated total reflection configuration for in situ analysis of aqueous-phase molecules. This IR sensor includes a boron-doped graphene (BG) nanodisk array fabricated on top of a ZnSe prism surface that supports attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRA). Our ATR-SEIRA platform is efficient and straightforward for in situ and label-free monitoring of the interaction of biomolecules without interference from the environments, allowing for the extraction of instant spectroscopic information in a complex biological event. Utilizing the near-field enhancement of graphene plasmon, the binding interaction of L-selectin with its aptamer as a demonstration has been investigated to evaluate the specific protein recognition process. The detection limit of the target protein reaches 0.5 nM. Our work demonstrates that chemical-doped graphene plasmon combined with ATR-SEIRA is a promising signal enhancement platform for in situ aqueous-phase biosensing.

Au/ZnSe-Based Surface Enhanced Infrared Absorption Spectroscopy as a Universal Platform for Bioanalysis.

A versatile and sensitive platform for label-free bioanalysis has been proposed on the basis of attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) using Au/ZnSe as the enhancement substrate that allows a wide spectral range down to 700 cm-1. Au nanoparticles are stably deposited on the surface of a ZnSe prism due to the formation of Au-Se bonds via electroless deposition, and the enhancement factor of the resultant Au/ZnSe substrate is about 2 times larger than that of the commonly used Au/Si substrate. As a demonstration, the Au/ZnSe-based SEIRAS has been applied to obtain abundant structural information in the fingerprint region and quantitative analysis of various biomolecular interactions such as DNA hybridization and immunoreaction without any labeling process.

In Situ Monitoring of DNA-Hg2+ Binding Reaction within Confined Nanospace of Metamaterial Nanochannel by Plasmon-Enhanced Raman Scattering.

Nanochannel-based plasmon-enhanced Raman scattering (PERS) substrates can simulate biological environments, revealing the recognition and conformation information on biomolecules in confined spaces. In this work, a metamaterial nanochannel-based PERS platform was constructed for highly sensitive analysis of DNA recognition to Hg2+ with the lowest Hg2+ concentration down to 1.0 pM. The established platform enables in situ monitoring of the thermodynamics and kinetics of DNA-Hg2+ recognition reaction in a confined nanospace. The recognition reaction in a nanospace shows good reversibility and specificity, and the isotherm follows well the Freundlich adsorption model. Compared to its folding on a rough Au nanofilm, the folding time of ssDNA-Rox decorated in nanochannels is remarkably increased, and the folding process can be tuned through varying the pore size and ionic strength. The presented PERS platform is promising for studying biomolecule-ion binding events and biomolecule conformation change under nanochannel-confined conditions.

Ultrasensitive plasmon enhanced Raman scattering detection of nucleolin using nanochannels of 3D hybrid plasmonic metamaterial.

Detection of cancer biomarker is of great significance in cancer diagnostics. In this work, we propose an ultrasensitive and in situ method for plasmon enhanced Raman scattering (PERS) detection of nucleolin (NCL) using a 3D hybrid plasmonic metamaterial (PM). In this aptasensor, thiolated complementary DNA (cDNA) immobilized on PM can hybridize with Rox-labeled NCL-binding aptamer (AS1411-Rox) to form a rigid double-stranded DNA (dsDNA). When NCL passes through the PM nanochannels under a transmembrane voltage bias, it interacts with AS1411-Rox to form G-quadruplexes (G4-AS1411-Rox), resulting in the release of AS1411-Rox from the nanochannels surface and the decrease in PERS signal of the reporter Rox. This change in PERS signals can be recorded in situ without the interference of external environment. With the help of the enrichment function of nanochannel, the present method is able to achieve fast NCL detection within 10 min with a detection limit as low as 71 pM. Furthermore, our method shows excellent specificity, reversibility, uniformity (relative standard deviation of ~6.86%) and reproducibility (~6.65%), providing a new platform for reliable cancer auxiliary diagnosis and drug screening.

[Study on skin sensitization as well as liver and kidney impairment in guinea pigs treated with trichloroethylene].

OBJECTIVE: To study skin sensitization as well as liver and kidney impairment in guinea pigs treated with trichloroethylene (TCE). METHODS: Guinea pig maximization test (GPMT) was applied in this study, guinea pigs were divided into 3 groups, namely negative control, positive control and TCE treatment. Animals of 3 groups were administrated with olive oil, 2, 4-dinitrochlorobenzene (DNCB), and TCE, respectively, by intradermal injection. The animal skin was observed and blood was collected after various treatment, the liver function tests were conducted, including detection of activities of ALT, AST, LDH and levels of creatinine, uric acid, and urea with automatic biochemical analyzer. RESULTS: Obvious skin impairment was observed in the groups of positive control and TCE treatment, the skin impairment included erythema and edema, the sensitization rate was 100% in positive control and 83.3% in TCE treatment group. Additionally, the activities of ALT, AST and LDH increased significantly in the groups of positive control and TCE treatment when compared with the negative control. CONCLUSIONS: Trichloroethylene is one of the strong hypersensitizing substances, it could induce skin allergic reaction and liver impairment in guinea pigs.