Hongyan Xia

Enantioselective synthesis of helical polydiacetylene by application of linearly polarized light and magnetic field

Magnetic optical activity, which can occur in all media and is induced by longitudinal magnetic field, causes the difference in absorption coefficients of left and right circularly polarized light and has the potential for magnetically induced enantioselectivity in chemical reactions. Compared with the well-established technique with circularly polarized light, there are few reports on the production of helical conjugated polymers in a photochemical reaction based on above magnetochiral anisotropy mechanism. Herein, we demonstrate experimentally that the enantioselective polymerization of diacetylene derivative can be achieved in the liquid crystal phase by application of linearly polarized light under a parallel or antiparallel magnetic field. The screw direction of predominant helical polydiacetylene chain can be rigorously controlled with the relative orientation of linearly polarized light and the magnetic field. Moreover, the prepared helical polydiacetylene assemblies can serve as a direct visual probe for the enantioselective recognition of D- or L-lysine.

Multifunctional Uniform Core–Shell Fe3O4@mSiO2 Mesoporous Nanoparticles for Bimodal Imaging and Photothermal Therapy

Multimodal imaging and simultaneous therapy is highly desirable because it can provide complementary information from each imaging modality for accurate diagnosis and, at the same time, afford an imaging-guided focused tumor therapy. In this study, indocyanine green (ICG), a near-infrared (NIR) imaging agent and perfect NIR light absorber for laser-mediated photothermal therapy, was successfully incorporated into superparamagnetic Fe(3)O(4)@mSiO(2) core-shell nanoparticles to combine the merit of NIR/magnetic resonance (MR) bimodal imaging properties with NIR photothermal therapy. The resultant nanoparticles were homogenously coated with poly(allylamine hydrochloride) (PAH) to make the surface of the composite nanoparticles positively charged, which would enhance cellular uptake driven by electrostatic interactions between the positive surface of the nanoparticles and the negative surface of the cancer cell. A high biocompatibility of the achieved nanoparticles was demonstrated by using a cell cytotoxicity assay. Moreover, confocal laser scanning microscopy (CLSM) observations indicated excellent NIR fluorescent imaging properties of the ICG-loaded nanoparticles. The relatively high r(2) value (171.6 mM(-1) s(-1)) of the nanoparticles implies its excellent capability as a contrast agent for MRI. More importantly, the ICG-loaded nanoparticles showed perfect NIR photothermal therapy properties, thus indicating their potential for simultaneous cancer diagnosis as highly effective NIR/MR bimodal imaging probes and for NIR photothermal therapy of cancerous cells.

Highly selective and reproducible detection of picric acid in aqueous media, based on a polydiacetylene microtube optical waveguide

Development of novel one-dimensional (1D) solid sensors for the highly selective and sensitive detection of 2,4,6-trinitrophenol (TNP) in aqueous media has attracted considerable attention. Herein, we describe how we fabricated a novel polydiacetylene (PDA) microtube and demonstrated that a single PDA microtube optical waveguide could serve as a novel optical sensor with fast response and high selectivity for TNP probing. The use of a single PDA microtube optical waveguide not only bestows the sensor with a small footprint, fast response and high sensitivity, but also enables its integration into the chip for real-time remote detection in the near future.

A Reversible Multi-Stimuli-Responsive Fluorescence Probe and the Design for Combinational Logic Gate Operations

Here, a novel multi-stimuli-responsive fluorescence probe is developed by incorporating spiropyran group into the coumarin-substituted polydiacetylene (PDA) vesicles. The fluorescence of PDA can be turned on upon heating, and can be quenched upon exposure to UV light irradiation or pH stimuli owing to the fluorescene resonance energy transfer (FRET) between the red-phase PDA and the open merocyanine (MC) form of spiropyran. Moreover, we have designed and experimentally realized a set of logic gate operations for the first time based on the fluorescence modulation of the designed system upon thermal, photo, and pH stimuli. This novel type of resettable logic gates augur well for practical applications in information storage, optical recording, and sensing in complicated microenvironments.

Optical Modulation of Waveguiding in Spiropyran-Functionalized Polydiacetylene Microtube

Optical modulation of waveguiding and logic operations play significant roles in highly integrated optical communication components, optical computing, and photonic circuits. Herein, we designed and synthesized spiropyran-functionalized polydiacetylene (SFPDA) microtubes, and realized reversible optical modulation of waveguiding in SFPDA microtubes through fluorescence resonance energy transfer (FRET) between the PDA matrix and spiropyran in open merocyanine (MC) form within the surface of the microtubes. Because of the reversible isomerization characteristics of spiropyran units, we have realized resettable, multireadout logic system that includes OR and INHIBIT logic operations in SFPDA microtube.

Bloch surface waves confined in one dimension with a single polymeric nanofibre

Polymeric fibres with small radii (such as ≤125 nm) are delicate to handle and should be laid down on a solid substrate to obtain practical devices. However, placing these nanofibres on commonly used glass substrates prevents them from guiding light. In this study, we numerically and experimentally demonstrate that when the nanofibre is placed on a suitable dielectric multilayer, it supports a guided mode, a Bloch surface wave (BSW) confined in one dimension. The physical origin of this new mode is discussed in comparison with the typical two-dimensional BSW mode. Polymeric nanofibres are easily fabricated to contain fluorophores, which make the dielectric nanofibre and multilayer configuration suitable for developing a large range of new nanometric scale devices, such as processor–memory interconnections, devices with sensitivity to target analytes, incident polarization and multi-colour BSW modes.

Photo‐controlled Hierarchical Assembly and Fusion of Coumarin‐containing Polydiacetylene Vesicles

Herein, we synthesize a coumarin-substituted diacetylene monomer (CODA) and report the novel photo-controlled reversible assembly and disassembly behavior of the polymerized CODA (PCODA) vesicles. The photo-triggered dimerization and cleavage reactions of the coumarin groups within the surface of the adjacent PCODA vesicles can be utilized as the driving force to induce assembly and disassembly of PCODA vesicles. Moreover, the boundary of PCODA vesicles in the aggregates becomes more obscure when the irradiation time exceeds 30 min. Fusion occurs upon close docking of target membranes, driven by sufficient dimerization of the coumarin groups within the surface of PCODA vesicles.

Multiconfigurable logic gate operation in 1D polydiacetylene microtube waveguide

Recently, multiconfigurable logic gate operation in one-dimensional (1D) nano/micrometer-sized waveguide materials have attracted enormous attention due to their potential applications in ultrafast information processing and optical computing systems, since 1D nano/micrometer-sized waveguides can directly act as the key building blocks of miniaturized optoelectronics. Herein, we designed and fabricated viologen-functionalized polydiacetylene (VFPDA) microtubes via a thiol–ene based ‘click’ reaction, and the tip emission of the VFPDA microtube exhibited a strong dependence on thermal or electrical stimuli, and the polarization of the excited linearly polarized light. Various basic logic gates (NOR, AND, INH) and combinational logic circuits (INH–INH, AND–INH) were constructed successfully by using two or three of the above triggers as the input signals, and the tip emission of a VFPDA microtube as the output signal. We expected this novel resettable multiconfigurable logic gate operation in micrometer-sized waveguides to show promising new opportunities in miniaturized electro-optical switches, smart integrated optical devices and circuits for future information technology.

Near-Infrared Circularly Polarized Light Triggered Enantioselective Photopolymerization by Using Upconversion Nanophosphors

Circularly polarized light (CPL) is considered to be a true chiral entity and has been suggested as an explanation for the introduction of initial chiral biases into key biomolecular building blocks. CPL used recently asymmetric photochemical reactions is of wavelengths mainly in the UV and visible regions, whereas natural CPL observed in star-forming regions of the Orion constellation falls in the IR region. Whether CPL in the IR or near-IR region could be utilized to trigger asymmetric photochemical reactions remains to be determined. Herein, it is demonstrated that enantioselective photopolymerization can be realized by using λ=980 nm CPL as the only chiral source. By incorporating NaYF4 nanophosphors as the antenna species, the enantioselective photopolymerization of achiral benzaldehyde-substituted diacetylene monomer can be realized based on an upconversion mechanism upon exposure to λ=980 nm CPL. The screw direction of the helical PDA chains can be completely controlled by the handedness of incident λ=980 nm CPL.