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Nowadays, the electromagnetic properties of artificial photonic materials can be well-tuned via designs over their composition and geometries. However, engineering the properties of artificial materials at the nanoscale is challenging and costly. Here we demonstrate a facile and low-cost method for fabricating large-area silver nanoparticle metasurfaces (AgNPMSs) by using the vectorial holography-mediated growth technique. The AgNPMS, which can be regarded as a hologram device, possesses excellent chiroptical properties. The vectorial holographic technique may open avenues for fabricating novel chiroptical metamaterials with large degrees of freedom, which can be further used for beam steering, photocatalysis, biosensing, etc.

A multi-point flexible straightening process characterized by reciprocating bending is proposed. Specifically, the process is analyzed in terms of deformation mechanism and verified by numerical simulations and physical experiments of the straightening of a series of metal profiles with different materials and initial shapes. Further, the relationship between the bending radius and the times of reciprocating bending required to unify the curvature is discussed, and the distribution of residual stress after straightening is analyzed. The results show that the reciprocating bending process can eliminate the difference of the initial curvature, make the curvature of each section tend to be uniform; the times of reciprocating bending to reach the uniform curvature decreases with the decrease of bending radius. The straightness of the straightened profile obtained from the experiment and simulation is less than 0.2%, demonstrating a good feasibility of this method.

Heavy metals, such as lead ions, are regarded as the main environmental contaminants and have a negative impact on human bodies, making detection technologies of lead ions critical. However, most existing detection methods suffer from time consumption, complicated sample pretreatment, and expensive equipment, which hinder their broad use in real-time detection. Herein, we show a new fluorescence sensor for detecting lead ions derived from liquid crystals doped with an aggregation-induced emission luminogen. The mechanism is based on the variation of fluorescence intensity caused by the disturbance of an ordered liquid crystal configuration in the presence of Pb2+, induced by DNAzyme and its catalytic cleavage. The proposed fluorescence sensor exhibits a low detection limit of 0.65 nM, which is 2 orders of magnitude lower than that previously reported in an optical sensor based on liquid crystals. The detection range of the Pb2+ fluorescence sensor is broad, from 20 nM to 100 μM, and it also selects lead ions from numerous metal ions exactly, resulting in a highly sensitive, highly selective, simple, and low-cost detection strategy of Pb2+ with potential applications in chemical and biological fields. This approach to designing a liquid crystal fluorescence sensor offers an inspiring stage for detecting biomacromolecules or other heavy metal ions by varying decorated molecules.

We demonstrate a simple, cost-effective method to enhance the photoluminescence intensity of monolayer MoS2. A hexagonal symmetric Au metasurface, made by polystyrene nanosphere lithography and metal coating, is developed to enhance the photoluminescence intensity of monolayer MoS2. By using nanospheres of different sizes, the localized surface plasmon resonances of the Au metasurfaces can be effectively tuned. By transferring monolayer MoS2 onto the Au metasurface, the photoluminescence signal of the monolayer MoS2 can be significantly enhanced up to 12-fold over a square-centimeter area. The simple, large-area, cost-effective fabrication technique could pave a new way for plasmon-enhanced light-mater interactions of atomically thin two-dimensional materials.

The rapid development of chiral inorganic nanostructures has greatly expanded from intrinsically chiral nanoparticles to more sophisticated assemblies made by organics, metals, semiconductors, and their hybrids. Among them, lots of studies concerning on hybrid complex of chiral molecules with achiral nanoparticles (NPs) and superstructures with chiral configurations were accordingly conducted due to the great advances such as highly enhanced biocompatibility with low cytotoxicity and enhanced penetration and retention capability, programmable surface functionality with engineerable building blocks, and more importantly tunable chirality in a controlled manner, leading to revolutionary designs of new biomaterials for synergistic cancer therapy, control of enantiomeric enzymatic reactions, integration of metabolism and pathology via bio-to nano or structural chirality. Herein, in this review our objective is to emphasize current research state and clinical applications of chiral nanomaterials in biological systems with special attentions to chiral metal- or semiconductor-based nanostructures in terms of the basic synthesis, related circular dichroism effects at optical frequencies, mechanisms of induced optical chirality and their performances in biomedical applications such as phototherapy, bio-imaging, neurodegenerative diseases, gene editing, cellular activity and sensing of biomarkers so as to provide insights into this fascinating field for peer researchers.

An all-solid organic semiconducting conjugated polymer poly(2-methoxy-5-(2ʹ-ethyl-hexyloxy)-p-phenylenevinylene) (MEH-PPV) activated polarisation grating (PG) laser was demonstrated for the first t...

Tricalcium silicate cement (TSC) has been widely used in dental materials because of its self-setting behavior, good bioactivity, biocompatibility, osteoinductivity, and antibacterial effect. Tricalcium silicate (C3S) powder was prepared by Pechini technique with a calcining temperature of 1300 °C for 3 h. The influence of liquid/powder (L/P) rate on the setting time and the mechanical property of TSC was studied. Characterization methods including XRD, FTIR, SEM-EDS, TEM, and ICP-AES were utilized to study the properties of C3S powder and its hydrated cement. The bioactivity and biocompatibility of the cement were investigated by soaking test and cell culture, respectively. The results show that the L/P rate plays an important role in the setting time and the compressive strength of TSC. The surface of TSC was covered by hydroxyapatite deposition during the immersion experiment and the cells attachment on the surface of TSC was well, which indicated that TSC has good bioactivity and biocompatibility. In addition, TSC has excellent antibacterial properties against Staphylococcus aureus. In conclusion, TSC is a promising candidate for root canal filling materials.

International audience; Homeotropic alignment of liquid crystals (LCs) is one of the key modes used in commercial liquid crystal displays (LCDs) due to its advantages, such as high contrast ratios and fast response speed. Here, we report stable homeotropic LC alignment with a small pretilt angle in a nematic, negative LC host doped with additives including self-aligning agents, photoresponsive azo dyes, and reactive mesogen via an in situ self-assembled, dual-wavelength photoalignment approach. The underlying mechanism of stable, pretilted homeotropic LC alignment was further analyzed in detail. The achieved pretilted homeotropic LC cells are very stable against heat and UV light exposure and demonstrate excellent electro-optical characteristics. The experimental results show that such a noncontact, simple homeotropic alignment technique has big potential in many applications, such as high-quality LCDs, spatial light modulators, and other optoelectronic devices.

Lanthanide-doped particles exhibit unique polarization-dependent luminescence due to the anisotropic crystalline local symmetry surrounding the emitter. Precise control of the orientation of particles shows great significance for exploiting the luminescent polarization and their potential applications. Here, we demonstrated a facile polypropylene-aided shear-driven method to obtain large-scale orientationally ordered upconversion nanorods, showing a liquid-crystalline nematic phase. Upconversion nanorods with low aspect ratios were well-aligned with the crystalline c-axis along the shearing direction using monodispersed colloid nanorods as the nanoink. The order parameter of aligned upconversion nanorods can reach up to 0.95. The nematic upconversion nanorods demonstrated strong polarization-dependent luminescence with the high degrees of polarization of the 4F9/2 sublevels at 657 and 661 nm being 0.47 and 0.59, respectively. Taking advantage of these mesoscopic well-aligned upconversion nanorods, their peculiar polarized emissions are potentially useful for some interdisciplinary applications such as polarization-sensitive bioprobes and anticounterfeiting.

International audience; Optical metasurfaces are 2D flat elements that consist of spatially arranged meta-atoms. By carefully designing the metasurface, it is possible to fully control the properties of light in amplitude, phase, and/or polarization. When merged with liquid crystals (LCs), a metasurface can act as a reconfigurable optical component enabling dynamical control of light. However, many reports ignore the influence of the meta-atom's geometry on the orientation of LCs. Here, it is proposed to synergistically merge LCs and specially designed gold metasurfaces for multiple optical functions. Gold metasurfaces are designed as a template to align the LC molecules in a resolution of ≤2 µm. Meanwhile, the aligned LCs are used to actively control the polarization of the incident light, further achieving active modulation of the plasmonic resonances of gold metasurfaces. The synergistic mergence of LCs and metasurfaces can enable a designed optical device to work simultaneously in both visible and near infrared ranges, which is highly promising for multiple applications simultaneously, such as high-resolution display, modulation, anti-counterfeiting, beam deflection, LiDAR, etc.

Recent efforts in stimuli‐responsive soft materials have enabled wirelessly controlled actuation with increasing degrees of freedom, yielding miniature robots capable of various locomotion in open environments such as on a plane or inside fluids. However, grand challenges remain in harnessing photomechanical deformation to induce locomotion and control of friction during the movement, especially for robotic actuations within constrained spaces. Here, the authors report a centimeter‐long polymer strip made of a liquid crystal network that is capable of versatile light‐fueled motions along a human hair. The soft polymer robot can translocate directionally upon temporally modulated excitation and climb vertically through friction control with light. A self‐oscillating strip is demonstrated to continuously translocate along the hair upon a constant light stimulus, and its gaiting is associated to the smoothness of the hair surface. The results offer new insights to small‐scale photo‐actuator, mechanical control, and automation in soft micro robotics., Soft robots are facing hurdles to navigate within constrained spaces that geometrically restrict their deformations. Here, the authors report a centimeter‐long robot made of liquid crystal polymer that is capable of inching, vertically climbing and self‐oscillating translocating along the human hair. The versatile locomotion modes are all fueled by light, thus offering new views for small soft robots and photo‐actuation.

International audience; Metasurface-based structural coloration is a promising enabling technology for advanced optical encryption with a high-security level. Herein, we propose a paradigm of electrically switchable, polarization-sensitive optical encryption based on designed metasurfaces integrated with polymer-dispersed liquid crystals. The metasurfaces consist of anisotropic and isotropic aluminum nanoaperture arrays. Optical images can be encrypted by elaborately arranging anisotropic and isotropic nanoapertures based on their polarization-dependent plasmonic resonance characteristics. We demonstrate high-quality encrypted images and QR codes with electrically switchable, polarization-sensitive properties based on PDLC-integrated aluminum nanoaperture arrays. The proposed technique can be applied to many fields including high-security optical encryption, security tags, anticounterfeiting, multichannel imaging, and dynamic displays

Fluorescent semiconductor quantum nanocrystals have received much attention due to their high brightness and color purity. Fabrication of semiconductor quantum nanocrystals with optical activity is of particular interest recently due to the potential applications in the fields of chemistry, pharmacology, biology and physics. Several approaches have been developed to induce circular dichroism and circularly polarized luminescence of semiconductor quantum nanocrystals, but only resulted in very weak signals. Herein, we demonstrate a circularly polarized luminescent solid film by doping CdSe/CdS quantum rods into the self-assembled left-handed helical structure of the earth-abundant and renewable cellulose nanocrystals. The degree of circularly polarized luminescence can be tuned by adjusting the photonic band gap of the helical structure relative to the photoluminescent band. A significant right-handed circularly polarized luminescence has been demonstrated, offering an easy and powerful platform to produce circularly polarized luminescence of semiconductor quantum materials.

A mechanistic understanding of perovskite degradation is one of the most urgent issues to push perovskite devices toward commercial applications. Surface coverings will lower the electrical injection and light extraction efficiency of perovskites. Therefore, structural modification of Zn doped perovskites has been proposed herein. The Zn doping will induce local lattice strain due to smaller ionic radius. It is interesting that the lattice structure at atomic resolution has been observed directly through cryo-TEM. Under light illumination, the photostriction will compensate for the local lattice strain, which leads to structural stability as evidence suggests no phase transition in temperature ranges of the temperature-dependent photoluminescence spectra. In addition, MPZB also shows less than 3% decrease in PL intensity after 60 days. This is because the Zn doping induced the lowest defect density in the MPZB SC (density of trap-states ntrp = 6.33 × 108 cm−3), which has been confirmed by the high performance of the photodetector. Such strain compensation is expected to fundamentally improve the stability of photoelectric devices.

A unique type of refractive index (RI) sensor is proposed using a dual Mach-Zehnder interferometer (MZI) structure based on side-hole fibers (SHFs). The MZI structure contains two single-mode fibers (SMFs), two coreless fiber (CLF) sections and an SHF section, which are spliced together in the order of SMF-CLF-SHF-CLF-SMF. The SMFs and the CLFs enable light lead in/out and beam splitting/combining, respectively. As a special feature of the structure, one hole of SHF is exposed for liquid filling and to form two MZIs as well. Three types of sensors are fabricated, namely S1, S2 and S3. Numerical simulation and experimental studies have been conducted to characterize the sensing performance. The RI sensitivity of the S1 using the ∼550 μm long SHF section reaches 14,000 nm/RIU. When a shorter SHF section is used in S2, the detectable RI range is broadened due to larger FSR. When the closed hole of SHF in S3 is filled with liquid to introduce the Vernier effect, the sensitivity can be further enhanced to over 44,000 nm/RIU (i.e., Refractive Index Unit), which corresponds to the detection limit at the level of 1.0 × 10−5 RIU. This sensor design is original and easy to package, which gives it potential for label-free biochemical analyses.

We demonstrate a spatially and electrically tunable random lasing based on polymer-stabilized blue phase liquid crystal (PS-BPLC)-wedged cell. The spatially tunable random lasers can be obtained fr...

Flexible low-power reflective photonics and display devices with high stability to environmental stimuli such as temperature and mechanical stress have attracted significant attention. Alth...

The polymer/liquid-crystal composite materials have been extensively studied for their potential applications. Various optical devices based on this composite material have been proposed an...

Bistable light shutter based on dual frequency cholesteric liquid crystals (LCs) have attracted intensive interests due to low energy consumption. Herein, we demonstrated an electrically switchable...

Electrochromic devices can modulate their light absorption under a small driving voltage, but the requirement for external electrical supplies causes response-lag. To address this problem, self-powered electrochromic devices have been studied recently. However, insensitivity to the surrounding light and unsatisfactory stability of electrochromic devices have hindered their critical applications. Herein, novel perovskite solar cell-powered all-in-one gel electrochromic devices have been assembled and studied in order to achieve automatic light adjustment. Two alkynyl-containing viologen derivatives are synthesized as electrochromic materials, the devices with very high stability (up to 70000 cycles) serves as the energy storage and smart window, while the perovskite solar cell with power-conversion-efficiency up to 18.3% serves as the light detector and power harvester. The combined devices can automatically switch between bleached and colored state to adjust light absorption with variable surrounding light intensity in real-time swiftly, which establish significant potentials for applications as modern all-day intelligent windows., The requirement for external electric supplies has significantly limited the application of electrochromic devices in modulating light absorption as smart windows. Here, the authors report automatic switching perovskite solar cells-powered all-in-one gel electrochromic device in response to surrounding light intensity in real-time.

Transparent wood with high optical transmittance, excellent thermal insulation and high toughness has attracted significant attention as an energy-saving building material. Many research efforts were dedicated to functional transparent wood, from luminescent to electrochromic transparent wood. However, photochromic transparent wood that is highly desirable and critical for smart window applications has been rarely studied. Herein, we experimentally demonstrate photochromic transparent wood with photo-switching of transmittance in the visible light region and color tuning properties. The photochromic transparent wood was obtained by infiltrating the lignin modified wood template with a mixture of photochromic material 3′,3′-dimethyl-6-nitro-spiro[2H-1-benzopyran-2,2′-indoline]-1′-ethanol (DNSE) and pre-polymerized methyl methacrylate (MMA). This photochromic transparent wood exhibits a vibrant purple-to-colorless color change under the illumination of light. In addition, dichroic dye material doped photochromic woods were studied for providing more color change choices. The proposed photochromic transparent wood shows potential applications in mechanically robust, energy-efficient, photo-switchable, and colorful smart windows on a large scale.

We demonstrate a photo-switchable and photo-tunable microlens based on chiral liquid crystals doped with an azobenzene chiral dopant immersed in water. A bi-stable microlens, which can be switched between a focusing state and scattering state through UV or green light, has been fabricated. The tuning properties of the microlens have also been demonstrated under light illumination. This bi-stable microlens possesses features including simple fabrication, low-cost, photo-switchability, and photo-tunability, and shows potential applications in dynamic imaging systems, biomimetic devices, wave-front sensors, micro-displays, light shaping etc.

Development of hydrogels with high mechanical and recoverable properties under physiological conditions is of great importance for broadening and improving their potential applications in load-bearing artificial soft tissues. Inspired by the self-assembly of chemical entities, homogeneous network hydrogels, which contain over 90 wt% water, were synthesized via covalent cross-linking of poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) triggered by microwave-assisted treatment. A structurally homogeneous network results in an evenly distributed stress that endures high strains with minimal energy dissipation, which enable the hydrogels to withstand up to 1.16 MPa of tensile stress, over seven-fold stretch length with negligible hysteresis, and sustain cyclic compression following high amplitude deformation. It is of importance for tissue replacement that the hydrogels retain these excellent properties under physiological conditions.

Recently, photochemical synthesis has attracted wide interest on in situ preparing the surface-enhanced Raman scattering (SERS) substrate with excellent performance, especially in a compact space and microfluidic channel. Herein, a facile, green and cost-effective approach to in situ photochemically synthesize silver nanoaggregates is demonstrated for SERS applications. By adjusting the photo-irradiation conditions, the morphologies and sizes of the silver nanoaggregates can be deliberately tailored. The synthesized silver nanoaggregates-based substrates exhibit a highly sensitive and reproducible SERS activity with a low detection limit of 10&minus, 8 M for 4-Aminothiophenol detection and relative standard deviation of 12.3%, paving an efficient and promising route for in situ SERS-based rapid detection in the environmental monitoring and food quality control.

We report stretchable metal-mesh transparent electrodes (TEs) with excellent electrical conductivity (2 Ω/sq) and optical transparency (80%) under up to 55% strain. The figures of merit on these electrodes, as defined as the ratio between electrical conductivity and optical conductivity, are among the highest reported for stretchable TEs under moderate stretching. Moreover, we demonstrate their application in a stretchable electroluminescent (EL) light-emitting film as top and bottom electrodes. EL lighting devices require low-resistance electrodes to unleash their potential for large-area low-power-consumption applications, in which our highly conductive and transparent stretchable TEs provide an edge on other competitor approaches. Importantly, our stretchable metal-mesh electrodes are fabricated through a vacuum-free solution-processed approach that is scalable for cost-effective mass production. We also investigate the fracture and fatigue mechanisms of stretchable metal-mesh electrodes with various mesh patterns and observe different behaviors under one-time and cyclic stretching conditions. Our solution-processed fabrication method, failure mechanism investigation, and device demonstration for metal-mesh stretchable TEs will facilitate the adoption of this promising high-performance approach in stretchable and wearable electronics applications.

Recently, biological materials have attracted more and more attentions on preparing the surface-enhanced Raman spectroscopy (SERS) substrate with the conspicuous SERS performance. Herein, we demonstrate a simply facile and inexpensive approach to fabricate a novel natural SERS substrate based on graphene oxide-Ag nanoparticles-Mytilus coruscus (GO-AgNPs-M.c.). The surface-enhanced resonance Raman spectroscopy (SERRS) signals of the Rhodamine 6G (R6G) on the GO-AgNPs-M.c. hybrids exhibit the much better SERRS performances in terms of the sensitivity, the signal reproducibility and the antioxidant stability than that on the AgNPs-M.c. one. The well electric field enhancement contribution is likewise confirmed in theory via the COMSOL software. Moreover, the successful detection of trace malachite green (MG) and methylene blue (MB) indicates the well feasibility for multi-molecules detection on the GO-AgNPs-M.c. hybrids. Thus, this inexpensive and high-efficiency natural SERS substrate have great potential for the considerable biochemical SERS applications and broaden the way for preparing multiple SERS platforms derived from other natural materials.

Dark solitons, which have good stability, long transmission distance and strong anti-interference ability. By using a coprecipitation method, the high quality indium tin oxide (ITO) were prepared with an average diameter of 34.1 nm. We used a typical Z-scan scheme involving a balanced twin-detector measurement system to investigated nonlinear optical properties of the ITO nanoparticles. The saturation intensity and modulation depths are 13.21 MW/cm2 and 0.48%, respectively. In an erbium-doped fiber (EDF) lasers, we using the ITO nanoparticles as saturable absorber (SA), and the formation of dark soliton is experimentally demonstrated. The generated dark solitons are centered at the wavelength of 1561.1 nm with a repetition rate of 22.06 MHz. Besides, the pulse width and pulse-to-pulse interval of the dark solitons is ∼1.33ns and 45.11 ns, respectively. These results indicate that the ITO nanoparticles is a promising nanomaterial for ultrafast photonics.

Hot spots have been considered as a dominant role in surface enhancement Raman scattering (SERS). Its generation cannot be separated from the ultra-small nanogaps, which will tremendously contribute to the strong electromagnetic field. We propose a AgNPs/graphene@AuNPs system with three-dimensional hot spots and tunable nanometer gap by changing the layer of graphene with a simple and facile method. The excellent SERS behaviors of the proposed AgNPs/graphene@AuNPs substrate are demonstrated experimentally using rhodamine 6G (R6G) and crystal violet (CV) as probe molecules and theoretically using commercial COMSOL software. The excellent SERS behaviors can be attributed to the electromagnetic mechanism (EM) in all three dimensions introduced by the lateral nanogaps (AgNP-AgNP) and the vertical nanogaps (AgNP-AuNPs), and the chemical enhancement mechanism (CM) induced by the graphene film. For practical application, the prepared sensitive AgNPs/graphene@AuNPs SERS substrate was used to detect Malachite green (MG) in sea water, which provides a bran-new avenue for the detection of biological and chemical molecule.

Electrochromic devices (ECDs) can alter their optical transmittances under external electrical power but are unable to spontaneously modulate the light flow in real-time along with the intensity change of surrounding light. To address this problem, a module of smart perovskite solar cell (PSC)-powered all-in-one gel ECDs was reported. The PSC-powered ECDs could modulate their transmittance swiftly in visible-infrared regions, hence regulating the photo energy flow in real time according to the surrounding light intensity. The ECD based on 4, 4′-(thiophene- 2, 5-diyl)bis(1-ethylpyridin-1-ium) diiodide (TEV) showed large optical contrast (79.7% at 570 nm, 64.9% at 908 nm), excellent coloration efficiency (231.2 cm2/C), and outstanding stability (only 1.1% ΔT change after 60,000 cycles). The PSC-powered ECDs showed fast response time (≤5 s) and high stability (negligible degradation after 5000 s consecutive switching between bright and dark conditions in air). Meanwhile, the stored power accompanied with the electrochromic process could drive a red LED with high cyclic stability (95.6% of areal capacitance maintained after 10,000 charging-discharging cycles), indicating that ECDs can serve as ideal electrochromic supercapacitors (ECSs). In addition, the fabricated ECD with large area (5.0 cm × 5.4 cm) showed excellent thermal regulation (7 °C of temperature difference between colored and bleached states). We expect this work would pave a new way to save energy and improve energy efficiency in modern buildings and automobiles.

Heavy metal, such as Pb 2+ , detection technologies are quite important in environment monitoring and human health protection. However, most existing technologies are often time consuming, expensive with sophisticated equipment, and requirement of complicated sample pre-treatment, which limit the useful range of real-time application. Here, we report the development of a “turn-on” fluorescence sensor for Pb 2+ detection based on graphene quantum dots and gold nanoparticles. We achieved an extremely broad detection range of Pb 2+ from 50 nM to 4 μM, with a detection limit of 16.7 nM. This sensing system is highly sensitive and selective for determination of Pb 2+ . The proposed strategy is expected to provide considerable implication for other heavy metal, antigen, or DNAs by modifying sensing molecules, and fast examination in chemical and biological applications.

Blue phase liquid crystal films are quite useful in reflective displays, flexible photonic devices, and optical sensors. However, the effects of refractive index properties of refilled liquid crystals and environment temperature on reflection properties of blue phase liquid crystal films are far from fully exploration. Herein, we demonstrate blue phase liquid crystal films refilled with different nematic liquid crystals. The effects of birefringence and average refractive index of refilled nematic liquid crystals on the reflection properties such as reflectance, central wavelength, and linewidth of photonic band have been studies. The temperature effect on reflectance and central wavelength has been studied. A narrow linewidth (19.4 nm) and temperature insensitivity blue phase liquid crystal film has been fabricated by refilling liquid crystals of DYX8013 with small birefringence. The narrow linewidth and excellent temperature insensitivity properties of BPLC film can be applied in color reflective display and flexible photonic devices.

The rapid development of self-assembled plasmonic chiral nanostructures has proven its promising potential in many applications. The underlying mechanism lies in the localized surface plasmon resonance properties of plasmonic colloids with respect to induced chirality via chiral molecules or chiral geometries. In this review, we summarize recent advances in both experimental phenomena and theoretical modellings, in particular to plasmonic chirality based on geometric motives, to elucidate the underlying origin of chirogenesis so as to provide insights into this fascinating field.

We propose a liquid-crystal-based reconfigurable chiral metasurface absorber and numerically investigate its chiro-optical properties. The chiral metasurface absorber consists of a metal-insulator-metal structure with the substrate, which can strongly absorb a circularly polarized wave of one spin state and reflects that of the opposite spin, resulting a strong circular dichroism (CD). A birefringent liquid crystal (LC) is exploited to serve as the insulator layer in the metal-insulator-metal structure. We could then vary the circular state of the incident light by controlling the alignment of the LC molecules, hence inversing the CD. The simulation results show that the CD will change the sign as the LC molecules are realigned from 0° to 90°. The absorption efficiency for the specific circularly polarized wave is larger than 80% and the CD is nearly 70%. The simple and compact design of our proposed chiral metasurface absorber is especially favorable for integration, and such a reconfigurable chiral absorber could find many potential applications in biological detection/sensing, polarimetric imaging, and optical communications.

Superhydrophobic coatings have broad applications owing to their excellent water-resisting and self-cleaning properties. In this study, we have successfully fabricated coated meshes with robust and superhydrophobic surface (i.e., water-repellent magnesium stearate powders on substrates made of phenol-formaldehyde resin). These coated meshes showed superhydrophobicity with water contact angles exceeding 150° and excellent self-cleaning property both in air and oil circumstances. Additionally, the superhydrophobic surfaces also exhibited prominent mechanical stability, thermal stability, corrosion resistance, and oil/water separation properties (>92%). Therefore, it is believed that the facile fabrication presented in this study may provide a novel methodology and these robust and superhydrophobic coated meshes have potential applications in oil/water separation.

In this paper, Ag@Fe3O4@cellulose nanocrystals (CNC) nanocomposites were synthesized by a facile and green microwave-assisted hydrothermal method. In the procedure, CNC was used as a reducing agent for the synthesis of Ag. During the whole synthesis process, there were no additional reducing agents or toxic solvents used. The nanocomposites were characterized by X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectrum, transmission electron microscopy, thermogravimetric analysis, and differential thermal analysis. In addition, Ag@Fe3O4@CNC nanocomposites were also synthesized by microwave-assisted method and hydrothermal method. Both the effects of reaction time and synthetic procedures on the reduction process of Ag+ by CNC were explored. The results showed that Fe3O4 was formed with sphere-like structure and dispersed uniformly. Ag@Fe3O4@CNC nanocomposites exhibited good adsorption of dye solution, which showed potential applications in water treatment. The antibacterial results showed that Ag@ Fe3O4@CNC nanocomposites had good antibacterial activities toward both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The green and facile strategy reported in this paper may be broadly used in synthesizing other metal nanoparticles, as well as organic–inorganic nanocomposites.

We developed an improved self-assembly method to obtain a large-area, high-quality templated monolayer mask using the polystyrene spheres. On the basis of the templated mask, hierarchically ordered Si metastructures with different nanosteps are fabricated using cyclic inductively coupled plasma etching technique. By evaporating a thin gold capping layer on these Si metastructures, their optical properties are comparatively studied using the surface-enhanced Raman scattering spectroscopy. Our proposed technique is highly promising for fabricating a variety of periodic three-dimensional hierarchically ordered metastructures, which could be further utilized for applications in SERS-based biosensors, optical absorbers, metamaterial/metasurface devices, etc.

Bio-chemical sensors are expected to offer high sensitivity and specificity towards the detection of an analyte. It has been found that optical sensors based on long period fiber gratings (LPFGs) meet most of these requirements, particularly when coated with thin and high-refractive index overlays with proper bio-functionalization. In this paper, the influence of properties of the overlay material on the sensitivity of LPFG sensors to bio-analytes is analyzed. It has been observed that the sensitivity of a particular cladding mode of LPFG can be changed drastically with the adhesion of few tens of ‘nm’ of bio-layers to the surface of LPFG. “Volume refractive index sensitivity” and “add-layer sensitivity” of a particular cladding mode, dynamic range, and limit of detection of the sensors have been investigated in the context of overlay materials, bio-functionalization steps, and surrounding buffer medium. The selection criteria of the thin-film deposition technique are discussed with the aim of designing highly sensitive sensors for biological and chemical applications. Concept of optimum overlay thickness has been redefined and an effective case-specific design methodology is proposed. Keywords: Long period fiber grating, Nano-layer coating, Mode transition, Multi-layer model, Coupled mode theory, Biological and chemical sensors

International audience; We report holographic fabrication of nanoporous distributed Bragg reflector (DBR) films with periodic nanoscale porosity via a single-prism configuration. The nanoporous DBR films result from the phase separation in a material recipe, which consists of a polymerizable acrylate monomer and nonreactive volatile solvent. By changing the interfering angle of two laser beams, we achieve the nanoporous DBR films with highly reflective RGB colors. The reflection band of the nanoporous DBR films can be tuned by further filling different liquids into the pores inside the films, resulting in the color change accordingly. Experimental results show that such kind of nanoporous DBR films could be potentially useful for many applications, such as color filters and refractive index sensors.

Greatly enhanced upconversion luminescence was demonstrated by integrating the core-shell upconversion nanorods with the Ag nanogratings. Both the Ag nanogratings and upconversion nanorods were fabricated/synthesized in a facile, cost-effective, high-throughput way. Experimental results showed that the upconversion luminescence intensity of Er

Lead ions (Pb2+) are one of the major environmental pollutants that are dangerous for human health, thus the detection methods of Pb2+ become very important as well. However, most reported techniques suffer from drawbacks such as long time, expensive equipment and complicated testing process, which prevent the use of real-time application. Herein, we demonstrate a novel liquid crystal optical sensor for detection of Pb2+ based on DNAzyme and its combined strand. The ordered and disordered configuration of liquid crystals, induced by complementary DNA strand and catalytically cleaved DNA in presence of lead ion separately, leads to dark and bright optical image under POM. The proposed naked-eye optical sensor possesses an extremely broad detection range of Pb2+ from 50 nM to 500 µM, with a low detection limit about 36.8 nM. The sensor also demonstrates high selectivity of Pb2+ from many other metal ions. The proposal LC sensor is highly sensitive and selective for Pb2+ detection, which provides a novel platform for other heavy metal, DNAs or antigen in biological and chemical fields by modifying sensing molecules.

In this paper, a novel high-energy mode-locked fiber laser based on the nonlinear polarization rotation (NPR) technique is presented to generate 331 nJ rectangular pulses. When pump power was 2659 mW, the maximum output power would be 102.3 mW; the maximum peak power was 41.74 W under the pump power of 1766 mW. In this study, the use of two homemade laser diodes and other common fiber devices was a vital step to achieve the low-cost and high-efficiency NPR mode-locked fiber laser. Based on these results, a novel approach could be developed to realize a high-energy rectangular pulse and promote the practical applications of the NPR mode-locked fiber laser in the field of ultrafast photonics.

A surface plasmon resonance (SPR) sensor with high sensitivity and symmetrical double channel is proposed. A side hole fiber has been considered as a platform of the proposed sensor. Detailed numerical calculation is carried out with the full-vector finite-element method. A polarization-maintaining single mode fiber considered for the simulation purposes two symmetrical holes introduced in the boundary of the core-cladding interface for dual-channel detection purpose. Metal layers are introduced in the inner wall of the hole. Numerically computed results show that the sensor can work in the range of different refractive index (RI) from 1.30 to 1.43. Sensitivity can be reached as high as 8800nm/RIU around 1.43. The average sensitivity of the developed sensors is 5160nm/RIU is obtained.

We have developed a method to fabricate freestanding highly ordered porous silver (Ag) superstructures by an "assembly-based nanoparticle (NP) coalescence" method. The synthesized superstructures have high-density mesopores periodically distributed over the entire structure, on which a highly enhanced electromagnetic field was observed by electron energy loss spectroscopy. Thus, the surface enhanced Raman scattering (SERS) signal of Rhodamine 6G in the ordered mesopores is 8.2 times higher compared to that in disordered porous superstructures. The results demonstrate that these freestanding mesoporous Ag superstructures are potentially good SERS substrates.

Holographic lithography is widely used as an effective approach for two-dimensional (2D) photonic crystal fabrication. However, for the fabrication of 2D polarization structures based on photoaligned liquid crystals (LCs), holographic lithography method is limited. The fabrication requires full coverage of light intensity, 2D chiral distribution and continuously varying polarization direction, which could be hardly guaranteed by multi-beam interference of circularly polarized light (CPL). Herein, we introduce a linearly polarized light (LPL) into a three-CPL interference configuration to improve the interference field and fulfill the critical requirement. The introduced LPL intensity is chosen to be 1/5 of the CPL to guarantee both full coverage of light intensity and well photoalignment defined LC directors. Moreover, the introduction of the weak LPL into multiple CPL interference is shown to give little disturbance to the desired diffraction properties.

We propose and demonstrate the versatile fabrication of optical subwavelength microcavities by using imaging holography. As a demonstration, a peculiar square optical microcavity with a periodicity of 400 nm is imaged from a micrometer-scale diffractive optical element, attributing to the interference by the refocusing of the multiple diffractive beams. By spin-coating an active conjugated polymer onto the microcavity, highly directional laser emission with a low pumping threshold of 0.5 kW/cm2 is achieved. The effect of the film thickness on the lasing performance is also investigated. This imaging holography technique can enable convenient and easy fabrication of optical microcavities with subwavelength features, hence providing significant flexibility and richness on engineering the optical response of photonic nanostructures.

International audience; Stiffness and anisotropy of culture substrates are important factors influencing the cell behavior and their responses to external stimuli. Herein, we report a fabrication method of oblique polymer pillars which allow modulating both stiffness and anisotropy of the substrate for spreading and elongation studies of Rat Mesenchymal Stem Cells (RMSCs). Poly (Lactic-co-Glycolic Acid) (PLGA) has been chosen to produce micro-pillars of different heights and different pitches using a combined method of soft-lithography and hot embossing. The stiffness of such pillar substrates varies over a large range so that RMSCs show effectively different spreading behaviors which are also sensitive to the inclining angle of the pillars. Our results showed that with the increase of the pillar height the area of cell spreading decreases but the cell elongation aspect ratio increases. Moreover, cells preferentially elongate along the direction perpendicular to that of the pillars' inclining, which is in agreement with the calculated anisotropy of the pillar substrate stiffness.

International audience; As opposed to traditional photoluminescence and ultra-violet based optical sensing, we present here a sensing system based on resolved optically active polarization with promising applications. It is based on the ultrathin CdSe nanoplatelets (NPLs) when modified with either L or D-cysteine molecules (L/D-cys) as bio-to-nano ligands. The chiral ligand transfers its chiroptical activity to the achiral nanoplatelets with an anisotropy factor of ∼10−4, which unlocks the chiral excitonic transitions and allows lead ion detection with a limit of detection (LOD) as low as 4.9 nM. Simulations and modelling based on time-dependent density functional theory (TD-DFT) reveal the chiral mechanism of L/D-cys capped CdSe NPLs. The presented CD-based sensing system illustrates an alternative possibility of using chiral CdSe NPLs as competitive chiral sensors for heavy metal ion detection.