Electrical Switching of the Off-Resonance Room-Temperature Valley Polarization in Monolayer MoS by a Double-Resonance Chiral Microstructure.

Enhancing and expanding the manipulated range of room-temperature valley polarization at off-resonance wavelength is extremely crucial to developing various functional valleytronic devices. Although these have been realized through the double-resonance strategy or twist-angle engineering, the demand for electrical control over the concepts remains elusive. Here, we fabricate a gate-tunable double-resonance chiral microstructure using a molybdenum disulfides (MoS) monolayer.

Broadband and compact polarization beam splitter in LNOI hetero-anisotropic metamaterials.

In this paper, theoretical modeling and numerical simulations of a high-performance polarization beam splitter (PBS) based on hetero-anisotropic metamaterials are proposed on the lithium-niobate-on-insulator (LNOI) platform. The hetero-anisotropic metamaterials constructed by sub-wavelength gratings (SWGs) can be regarded as effective anisotropy medium, which exhibits strong birefringence without breaking the geometrical symmetry, contributing to the formation of PBS. Rather than the principle of PBS based on beat-length difference of transverse electric (TE) polarization and transverse magnetic (TM) polarization, the device can realize polarization beam splitting in single beat length, and the footprint of the proposed PBS can be reduced to 8 µm × 160 µm (with S-bend).

A straightforward and sensitive "ON-OFF" fluorescence immunoassay based on silicon-assisted surface enhanced fluorescence.

A straightforward immunoassay based on silicon-assisted surface enhanced fluorescence (SEF) has been demonstrated using a silicon-based fluorescent immune substrate and silver-antibody nanoconjugate (SANC). The P-doped, (100) oriented silicon wafers are used for both fluorophore attachment and antigen immobilization. The silicon substrate offers a very low blank signal in the "OFF" state, due to its fluorescence quenching effect.

Silicon-assisted surface enhanced fluorescence toward improved assay performances.

A novel scheme of silicon-assisted surface enhanced fluorescence (SEF) is presented for SEF-based assays, where the blank signal suppression and the fluorescence signal enhancement is combined. The P-doped, (100) oriented silicon substrate is used to quench the fluorescence of Rose Bengal (RB) molecules attached to it, resulting in an effectively suppressed background signal, which is useful for a lower limit of detection (LOD). When a proper quantity of silver nanoparticles (AgNPs) is deposited on the RB-attached silicon substrate, a significant fluorescence enhancement of up to around 290 fold is obtained, which helps to improve the sensitivity in fluorescence-based assays.

Highly efficient and controllable photoluminescence emission on a suspended MoS-based plasmonic grating.

Being a new class of materials, transition metal dichalcogenides are paving the way for applications in atomically thin optoelectronics. However, the intrinsically weak light-matter interaction and the lack of manipulation ability has lead to poor light emission and tunable behavior. Here, we investigate the fluorescence characteristic of monolayer molybdenum disulfide on a metal narrow-slit grating, where a highly efficient, 471 times photoluminescence enhancement are realized, based on the hybrid surface plasmon polaritons resonances and the decreased influence of substrate.

An online pH detection system based on a microfluidic chip.

An online pH detection system is very critical in monitoring the sudden change of pH, especially in strongly acidic and alkaline conditions. We developed a pH sensing chip which works in the range of 5 M [H]-pH 3.0 and pH 6.

Manipulating "Hot Spots" from Nanometer to Angstrom: Toward Understanding Integrated Contributions of Molecule Number and Gap Size for Ultrasensitive Surface-Enhanced Raman Scattering Detection.

Narrower gaps between metal nanoparticles (so-called "hot spots") in surface-enhanced Raman scattering (SERS) substrates contribute to stronger electromagnetic (EM) enhancement; however, the accompanying steric effect hinders analyte molecules entering hot spots to access the benefit. To comprehensively understand integrated contributions of the gap size and molecule number accommodated in hot spots and then optimize design of SERS substrates, the thermal shrinking method was employed to manipulate hot spots and the "hottest zone" was defined to evaluate the integrated contributions to SERS intensity of the two factors. In the conventional shrink-adsorption mode, the contributions of the molecule number and gap size are competitive when the gap width is comparable with the target molecule size, which leads to oscillating behavior of SERS intensity versus gap size, and it is analyte molecule size dependent.

Performance improvements of a tunable bandpass microwave photonic filter based on a notch ring resonator using phase modulation with dual optical carriers.

A tunable bandpass microwave photonic filter can be achieved by using a notch ring resonator with optical phase modulation. However, the filter's out of band rejection ratio and shape factor are limited due to the ring resonator's residual phase, which can seriously degrade the filter's performance. By using dual optical carriers and setting their wavelengths oppositely detuned from two resonant frequencies of a notch ring resonator, the residual phase induced by the ring resonator at radio frequencies falling outside the region of the notch stopband is reduced, thus the out-of-band rejection ratio and shape factor of the microwave photonic filter are greatly improved.

A SERS fiber probe fabricated by layer-by-layer assembly of silver sphere nanoparticles and nanorods with a greatly enhanced sensitivity for remote sensing.

Remote sensing remains a challenge due to its demand for high sensitivity, convenient sampling and rapid response time. Surface enhanced Raman scattering (SERS) spectroscopy is a powerful analytical method for the detection of various samples. Here, aiming at increasing the sensitivity, a novel strategy for the preparation of a SERS probe is demonstrated by using hollow optical fiber tips decorated by layer-by-layer assembly of two kinds of nanoparticles.

Super blinking and biocompatible nanoprobes based on dye doped BSA nanoparticles for super resolution imaging.

As one of the super-resolved optical imaging techniques, single molecule localization microscopy (SMLM) received considerable attention due to its impressive spatial resolution. Compared with other fluorescence imaging techniques, SMLM has one particular request for the fluorophores, that is, continuous 'on' and 'off' behaviors of their signals (referred to as 'blinking'). Hence, we present here a kind of super blinking and biocompatible nanoprobes (denoted as SBNs) for SMLM.

Realization of mid-infrared broadband absorption in monolayer graphene based on strong coupling between graphene nanoribbons and metal tapered grooves.

In this paper, we theoretically propose an effective broadband absorption architecture in mid-infrared region based on strong coupling between the plasmonic resonance of graphene nanoribbons and the waveguide mode of a metal tapered groove. The special architecture facilitates two new hybrid modes splitting with very strong energy distribution on graphene ribbon, which results in the broadband absorption effect. To well explain these numerical results, an analytical dispersion relation of waveguide mode is obtained based on the classical LC circuit model.

Single molecule localization imaging of telomeres and centromeres using fluorescence in situ hybridization and semiconductor quantum dots.

Single molecule localization microscopy (SMLM) is a powerful tool for imaging biological targets at the nanoscale. In this report, we present SMLM imaging of telomeres and centromeres using fluorescence in situ hybridization (FISH). The FISH probes were fabricated by decorating CdSSe/ZnS quantum dots (QDs) with telomere or centromere complementary DNA strands.

Visualization and intracellular dynamic tracking of exosomes and exosomal miRNAs using single molecule localization microscopy.

Exosomes are small membrane vesicles secreted by a wide variety of cells. Studies have demonstrated that exosomal miRNAs can influence the biological processes of recipient cells. Therefore, direct imaging and tracking of exosomal miRNAs in living recipient cells are essential for exosome functional analysis.

Investigating the Intracellular Behaviors of Liposomal Nanohybrids SERS: Insights into the Influence of Metal Nanoparticles.

The recent proposition to combine liposomes with nanoparticles presents great opportunities to develop multifunctional drug delivery platforms. Although impressive progress has been made, attempts to elucidate the role nanoparticles play in the integral nanohybrids are still rather limited. Here, using surface-enhanced Raman scattering (SERS) technique, we investigate the influence of metal nanoparticles on the liposomal properties, ranging from drug release to intracellular movement.

Joint effect of ferromagnetic and non-ferromagnetic cations for adjusting room temperature ferromagnetism of highly luminescent CuNiInS quaternary nanocrystals.

In this work, highly luminescent quaternary CuNiInS nanocrystals (NCs) are put forward as a good prototype for investigating defect-induced room temperature ferromagnetism. A ferromagnetic Ni cation can preserve the strong luminescence of NCs without introducing intermediate energy levels in the center of the forbidden band. The strong luminescence of NCs is used as an indicator for monitoring the concentration of vacancy defects inside them, facilitating the investigation of the origin of room temperature ferromagnetism in CuNiInS NCs.

Design of a compact and high sensitive refractive index sensor base on metal-insulator-metal plasmonic Bragg grating.

A nanometric and high sensitive refractive index sensor based on the metal-insulator-metal plasmonic Bragg grating is proposed. The wavelength encoded sensing characteristics of the refractive index sensor were investigated by analyzing its transmission spectrum. The numerical results show that a good linear relationship between the Bragg wavelength and the refractive index of the sensing material can be obtained, which is in accordance with the analytical results very well.

Dual-mode tracking of tumor-cell-specific drug delivery using fluorescence and label-free SERS techniques.

We developed a dual-mode detection method for tumor cell specific targeting and intracellular delivery of the chemotherapeutic agent Doxorubicin (DOX) using folic acid functionalized mesoporous silica nanoparticles (FA-MSNs) as carrier systems. In this method, label free surface enhanced Raman scattering (SERS) spectra were utilized to monitor the dynamic release of DOX inside tumor cells in combination with fluorescence images. To investigate the targeting delivery performance of the carrier system, both normal cells (MRC-5) and tumor cells (HeLa) were used as the model cells.

SERS-based DNA detection in aqueous solutions using oligonucleotide-modified Ag nanoprisms and gold nanoparticles.

Oligonucleotide-modified nanoparticle conjugates show highly promising potential for SERS-based DNA detection. However, it remains challenging to carry out the SERS-based DNA detection in aqueous solutions directly using oligonucleotide-modified nanoparticles, because the Raman reporters would exhibit lower signals when they are dispersed in aqueous solutions than laid on "dry" metal nanoparticles. Here, we synthesized stable oligonucleotide-modified Ag nanoprism conjugates, and performed SERS-based DNA detection in aqueous solution directly by using such conjugates in combination with Raman reporter-labeled, oligonucleotide-modified gold nanoparticles.

Intracellular surface-enhanced Raman scattering probe based on gold nanorods functionalized with mercaptohexadecanoic acid with reduced cytotoxicity.

A surface-enhanced Raman scattering (SERS) probe for intracellular detection was demonstrated by utilizing gold nanorods (GNRs) coated with p-aminothiophenol as the Raman reporters. In this probe, to reduce the cytotoxicity of GNRs, cetyltrimethylammonium bromide (CTAB) molecules adsorbed on the surfaces of GNRs as ligands were replaced by mercaptohexadecanoic acid via a "round-trip" phase change method. Such a ligand exchange can reduce the toxicity of the probe compared to the original CTAB-stabilized GNRs, which were confirmed by both 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and bright field view of HeLa cells.

A straightforward immunoassay applicable to a wide range of antibodies based on surface enhanced fluorescence.

A straightforward immunoassay based on surface enhanced fluorescence (SEF) has been demonstrated using a fluorescent immune substrate and antibody functionalized-silver nanoparticles. Unlike the conventional SEF-based immunoassay, which usually uses the dye-labeled antibodies and the metallic nanostructured-substrates, the presented immune system does not need the antibodies to be labeled with dye molecules. Thus, this immunoassay can be easily applied to the detection of a wide range of target antigens, which is of great importance for its practical application.

Toxicity evaluation of hydrophilic CdTe quantum dots and CdTe@SiO2 nanoparticles in mice.

Quantum dots have drawn tremendous attention in the field of in vitro and small animal in vivo fluorescence imaging in the last decade. However, concerns over the cytotoxicity of their heavy metal constituents have limited their use in clinical applications. Here, we report our comparative studies on the toxicities of quantum dots (QDs) and silica coated CdTe nanoparticles (NPs) to mice after intravenous injection.

A multiplex and straightforward aqueous phase immunoassay protocol through the combination of SERS-fluorescence dual mode nanoprobes and magnetic nanobeads.

A novel aqueous phase immunoassay protocol was demonstrated, using surface enhanced Raman scattering (SERS)-fluorescence dual mode nanoprobes combined with magnetic nanobeads (MBs). Here, the dual mode nanoprobes provide an excellent multiplexing ability while the MBs greatly simplify the immunoassay process. Basically, the nanoprobes were acquired by assembling the Raman reporter tagged Au@Ag core-shell nanorods and quantum dots onto the silica nanospheres.

A comparative study of CdTe quantum dots and CdTe@SiO2 nanoparticles: fabrication and cytotoxicity in HEK293 cells.

Quantum Dots have shown remarkable potentials in biomedical research. Herein, we reported the effects of CdTe quantum dots (QDs) and CdTe@SiO2 nanoparticles (NPs) on human embryonic kidney 293 (HEK 293A) cells with the aim of investigating their in vitro cytotoxicity. The CdTe@SiO2 particles were prepared by reverse microemulsion method.

Immunoassays based on surface-enhanced fluorescence using gap-plasmon-tunable Ag bilayer nanoparticle films.

A novel gap-plasmon-tunable Ag bilayer nanoparticle film for immunoassays is demonstrated. Different from a traditional Ag monolayer nanoparticle film, a desired number of polyelectrolyte (PEL) layers are deposited on the nanoparticles before the self-assembly of a second Ag nanoparticle layer. Interestingly, by controlling the number of the PEL interlayers, the gap plasmon between the two Ag nanoparticle layers can be tuned across the visible spectral range.

Tracking multiplex drugs and their dynamics in living cells using the label-free surface-enhanced Raman scattering technique.

Label free and real time detection of nonfluorescent drugs inside living cells has been realized by using surface-enhanced Raman scattering (SERS). For the first time, the characteristics of 6-mercapotopurine and methimazole, two different drugs, were monitored simultaneously by SERS in living cells. Particularly, the processes of diffusion and metabolism of drugs occurring in the intracellular matrix were investigated.