Photonic Crystals for Chemical Sensing and Biosensing

This Review covers photonic crystals (PhCs) and their use for sensing mainly chemical and biochemical parameters, with a particular focus on the materials applied. Specific sections are devoted to a) a lead‐in into natural and synthetic photonic nanoarchitectures, b) the various kinds of structures of PhCs, c) reflection and diffraction in PhCs, d) aspects of sensing based on mechanical, thermal, optical, electrical, magnetic, and purely chemical stimuli, e) aspects of biosensing based on biomolecules incorporated into PhCs, and f) current trends and limitations of such sensors.     

胶体晶体微球及其生物医学应用

光子晶体(PhCs)是由单分散纳米粒子周期性排列形成的材料,具有光子禁带,频率落在光子禁带内的光被禁止传播,这个特性激起了研究者对其制备和应用的研究热情。然而,一般的光子晶体材料都具有角度有偏性质,限制了其在宽视角光学材料和设备上的应用。近几年有一系列围绕球形胶体光子晶体材料的研究成果问世,由于球形的对称性,球形胶体晶体的衍射峰不会随着光的入射角变化而发生变化,从而拓宽了胶体晶体的应用范围。随着微流控技术被用于制备液滴模板,球形胶体晶体的制备取得了巨大的进步。微流控技术不仅保证了液滴模板的单分散性,还增加了胶体晶体微球的结构与功能的多样性。胶体晶体微球这些特有的性质,可以很好地将光子晶体材料与编码、非标记检测、细胞培养以及载药等生物医学领域连接起来,为其应用提供了广阔的前景。本文总结了球形光子晶体的研究进展,包括球形光子晶体的设计、制备及其生物医学应用,最后,对球形光子晶体未来的发展方向作了展望。     

Electrochemical Technologies to Decrease the Chemical Risk of Hospital Wastewater and Urine

The inefficiency of conventional biological processes to remove pharmaceutical compounds (PhCs) in wastewater is leading to their accumulation in aquatic environments. These compounds are characterized by high toxicity, high antibiotic activity and low biodegradability, and their presence is causing serious environmental risks. Because much of the PhCs consumed by humans are excreted in the urine, hospital effluents have been considered one of the main routes of entry of PhCs into the environment. In this work, a critical review of the technologies employed for the removal of PhCs in hospital wastewater was carried out. This review provides an overview of the current state of the developed technologies for decreasing the chemical risks associated with the presence of PhCs in hospital wastewater or urine in the last years, including conventional treatments (filtration, adsorption, or biological processes), advanced oxidation processes (AOPs) and electrochemical advanced oxidation processes (EAOPs).     

Amphibian-like Flexible Organic Crystal Optical Fibers for Underwater/Air Micro-Precision Lighting and Sensing

Visible light guiding optical fibers with underwater operational capability are highly desired for subaquatic communication and sensing technologies. Herein, we present mechanically flexible, blue-violet fluorescent (4,4′-bis(2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)biphenyl) (BPP) crystal waveguides with high-aspect ratio. These milli-meter-long BPP crystals guide light actively and passively in ambient and underwater conditions demonstrating their amphibian-like character. Due to the crystal's high flexibility, the optical fiber's output light direction in submerged and ambient states can be altered mechanically for high-precision lighting and sensing applications. The development of such multi-environment-compatible and mechanically flexible organic optical fibers acting as sensing materials possess enormous potential for short-range underwater photonic technologies.     

Sol–gel-derived photonic structures: fabrication,assessment, and application

Sol–gel is a handy, very flexible, and cheap method to fabricate, study, and apply innovative photonic structures. The possibility of starting from molecular precursors and elementary building blocks permits to tailor structures at the molecular level and to create new materials with enhanced performances. Of specific interest for the study of important physical effects as well as for application in light management are confined structures on the nano-micro scale as photonic crystal and planar waveguides. Activation by luminescent species and in particular by rare earth ions allows results in the integrated optics area covering application in sensing, biomedical diagnostic, telecommunication, lightning, and photon management. The present review is focused on some recent results obtained by the authors in Sol–gel photonics. The first part presents colloidal structures including single nano-micro spheres and photonic crystal structures. The second part of the review deals with amorphous and transparent glass–ceramic employed for the fabrication of confined structures in planar format. Some specific application are also reported to highlight the role of sol gel photonics in the development of high performance optical sensors, waveguide lasers, and nanostructured materials.     

Mechanochromic Fibers with Structural Color

Responsive photonic crystals have been widely developed to realize tunable structural colors by manipulating the flow of light. Among them, mechanochromic photonic crystals attract increasing attention due to the easy operation, high safety and broad applications. Recently, mechanochromic photonic crystal fibers were proposed to satisfy the booming wearable smart textile market. In this Concept, the fundamental mechanism, fabrication, and recent progress on mechanochromic photonic crystals, especially in fiber shape, are summarized to represent a new direction in sensing and displaying.     

硫化镉反蛋白石光子晶体制备及光解水制氢

对硫化镉反蛋白石结构光子晶体薄膜进行了可控合成,用巯基乙酸修饰的纳米晶和P(St-MMA-SPMAP)高分子小球共组装,成功地构筑了反蛋白石结构并用于可见光光解水产氢。结果表明,在可见光(λ≥420 nm)照射下,Cd S-310反蛋白石结构薄膜的光解水产氢性能比硫化镉纳米颗粒提高了一倍。这主要是因为等级孔结构反蛋白石光子晶体特性对催化剂的光催化性能的提升:首先,反蛋白石的周期性结构增加了光子在材料中的传播,提高了催化剂对太阳光的利用率;同时,大孔孔壁是由纳米颗粒堆积而成的,在反应中提供了更多的反应活性位点;此外,孔结构有利于物质的传输和分子的吸附。     

Stimuli-responsive 2D polyelectrolyte photonic crystals for optically encoded pH sensing

A versatile photonic crystal sensing motif based on a two-dimensional (2D) inverse opal monolayer of stimuli-responsive polyelectrolyte gel with tunable optical properties is reported. The photonic membrane shows prompt response to pH and can be readily read out from either its optical spectra or interference colours.     

A general photonic crystal sensing motif: creatinine in bodily fluids

We developed a new sensing motif for the detection and quantification of creatinine, which is an important small molecule marker of renal dysfunction. This novel sensor motif is based on our intelligent polymerized crystalline colloidal array (IPCCA) materials, in which a three-dimensional crystalline colloidal array (CCA) of monodisperse, highly charged polystyrene latex particles are polymerized within lightly cross-linked polyacrylamide hydrogels. These composite hydrogels are photonic crystals in which the embedded CCA diffracts visible light and appears intensely colored. Volume phase transitions of the hydrogel cause changes in the CCA lattice spacings which change the diffracted wavelength of light. We functionalized the hydrogel with two coupled recognition modules, a creatinine deiminase (CD) enzyme and a 2-nitrophenol (2NPh) titrating group. Creatinine within the gel is rapidly hydrolyzed by the CD enzyme in a reaction which releases OH(-). This elevates the steady-state pH within the hydrogel as compared to the exterior solution. In response, the 2NPh is deprotonated. The increased solubility of the phenolate species as compared to that of the neutral phenols causes a hydrogel swelling which red-shifts the IPCCA diffraction. This photonic crystal IPCCA senses physiologically relevant creatinine levels, with a detection limit of 6 microM, at physiological pH and salinity. This sensor also determines physiological levels of creatinine in human blood serum samples. This sensing technology platform is quite general. It may be used to fabricate photonic crystal sensors for any species for which there exists an enzyme which catalyzes it to release H(+) or OH(-).     

反蛋白石结构光催化剂的制备与应用进展

光子晶体是一种具有光子禁带的周期性结构,在一定的波长范围内,光在晶体的某些方向上是不允许传播的;反蛋白石结构作为一种典型的光子晶体结构,具有慢光效应、多次散射效应和放大光子吸收、发射等特性,可以提高催化剂的传质效率、活性中心的曝光率和其集光性能,因此其在光催化领域受到越来越多的关注.我们综述了反蛋白石结构的光学性质;将反蛋白石结构光催化剂的制备方法归结为三步法和两步法两大类,列举了所包含的具体方法,总结了各自的优缺点;同时阐述了反蛋白石结构光催化剂的应用领域,最后对其在光催化领域的研究和发展趋势做出了展望.     

Cellulose ternary photonic crystal created by solution processing

For the first time, a multiplanar photonic crystal structure has been obtained using cellulose as a structural material. This all-polymer system, made of cellulose, polyvinyl alcohol and poly(N-vinylcarbazole) is a ternary planar photonic crystal composed by 7 repeated trilayers produced by spin coating. Trimethylsilyl cellulose is used as a precursor to be converted to cellulose. Transverse Transmission Electron Microscopy analysis of our systems confirms the multilayered structure whose optical response can be theoretically accounted for. Preliminary results on the response of the photonic crystal to water vapors envisage the use of this system for humidity optical sensing.     

Environmental fate processes and biochemical transformations of chiral emerging organic pollutants

This review highlights the analytical chemistry, environmental occurrence, and environmental fate of individual stereoisomers of chiral emerging pollutants, which are modern current-use chemicals of growing environmental concern due to their presence in the environment and potential for deleterious effects. Comparatively little is known about individual stereoisomers of pollutants, which can have differential toxicological effects and can be tracers of biochemical weathering in the environment. Stereoisomers are resolved by gas chromatography (GC), high-performance liquid chromatography (HPLC), and capillary electrophoresis (CE). Separation techniques in environmental analysis are typically coupled to mass spectrometry (MS) and tandem mass spectrometry (MS/MS), as these provide the sensitivity and selectivity needed. The enantiomer composition of phenoxyalkanoic and acetamide herbicides, organophosphorus and pyrethroid pesticides, chiral polychlorinated biphenyl metabolites, synthetic musks, hexabromocyclododecane, and pharmaceuticals in the environment show species-dependent enantioselectivity from biotransformation and other biologically mediated processes affecting enantiomers differentially. These enantiomer compositions are useful in detecting biologically mediated environmental reactions, apportioning sources of pollutants, and gaining insight into the biochemical fate of chiral pollutants in the environment, which are needed for accurate risk assessment of such chemicals.     

流动控制沉积法制备PMMA叠层光子晶体薄膜及其光学性能研究

采用流动控制沉积法, 通过调控泵速和聚甲基丙烯酸甲酯(PMMA)胶体微球溶液的浓度, 制备出微球排列高度有序且薄膜紧密附着于基底的高质量光子晶体薄膜. 获得了制备高质量PMMA光子晶体薄膜的组装条件范围, 发现在该条件范围内, 当泵速或胶体微球溶液浓度一定时, PMMA光子晶体薄膜的厚度随胶体微球溶液浓度的增加或泵速的降低而增加. 研究了组装条件对PMMA光子晶体薄膜光学性能的影响, 发现光子禁带位置随光子晶体薄膜厚度增加或减少而红移或蓝移. 在此基础上, 控制组装条件得到了不同尺寸微球堆叠而成的叠层光子晶体薄膜, 并研究了其光学性能的变化规律. 结果显示, 叠层光子晶体薄膜的光子禁带峰为各层叠层光子晶体禁带峰的简单叠加, 且峰强度受光入射角方向影响.     

Recent advances in spherical photonic crystals: Generation and applications in optics

Spherical photonic crystals (PCs), generated by assembly of monodisperse colloidal nanospheres in a spherical confined geometry, attract great attention recently owing to their potential applications in the fields of displays, sensors, optoelectronic devices, and others. Compared to their conventional film or bulk counterparts, the optical stop band of the spherical PCs is independent of the rotation under illumination of the surface of a fixed incident angle of the light, broadening their applications. In this paper, we will review recent advances in the field of spherical PCs including design, preparation and potential applications. Various preparation strategies for spherical PCs, including solvent-evaporation induced crystallization method, microfluidic-assisted approach, and others are outlined. Their applications based on the unique optical properties (such as photonic band gaps and structural colors) for sensing and displaying are then presented, followed by the perspective of this emerging field.     

Recent progress in chiral photonic band‐gap liquid crystals for laser applications

This article describes a brief review of recent research advances in chiral liquid crystals (CLCs) for laser applications. The CLC molecules have an intrinsic capability to spontaneously organize supramolecular helical assemblages consisting of liquid crystalline layers through their helical twisting power. Such CLC supramolecular helical structures can be regarded as one‐dimensional photonic crystals (PhCs). Owing to their supramolecular helical structures, the CLCs show negative birefringence along the helical axis. Selective reflection of circularly polarized light is the most unique and important optical property in order to generate internal distributed feedback effect for optically‐excited laser emission. When a fluorescent dye is embedded in the CLC medium, optical excitation gives rise to stimulated laser emission peak(s) at the band edge(s) and/or within the CLC selective reflection. Furthermore, the optically‐excited laser emission peaks can be controlled by external stimuli through the self‐organization of CLC molecules. This review introduces the research background of CLCs carried out on the PhC realm, and highlights intriguing precedents of various CLC materials for laser applications. It would be greatly advantageous to fabricate active CLC laser devices by controlling the supramolecular helical structures. Taking account of the peculiar features, we can envisage that a wide variety of supramolecular helical structures of CLC materials will play leading roles in next‐generation optoelectronic molecular devices. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.201000013     

基于石墨烯光子晶体光纤的流体传感器

与传统的传感器设备阵列相比,由于结构更为简单,具有广泛检测兼容性的光纤系统逐渐成为分布式监测的有力候选者。然而,受工作机制的限制,大多数光纤传感器仍局限于对折射率等物理参数进行探测,一种用于环境化学监测的全光纤分布式传感系统亟待研发。本工作中,我们向化学气相沉积法生长的石墨烯光子晶体光纤(Gr-PCF)中引入了一种化学传感机制。初步结果表明,石墨烯光子晶体光纤可以选择性地检测浓度为ppb级的二氧化氮气体,并在液体中表现出离子敏感性。石墨烯光子晶体光纤与光纤通信系统的波分、时分复用技术结合后,将为实现分布式光学传感环境问题提供巨大的潜力和机会。     

Standing wave enhancement of red absorbance and photocurrent in dye-sensitized titanium dioxide photoelectrodes coupled to photonic crystals

The light harvesting efficiency of dye-sensitized photoelectrodes was enhanced by coupling a TiO(2) photonic crystal layer to a conventional film of TiO(2) nanoparticles. In addition to acting as a dielectric mirror, the inverse opal photonic crystal caused a significant change in dye absorbance which depended on the position of the stop band. Absorbance was suppressed at wavelengths shorter than the stop band maximum and was enhanced at longer wavelengths. This effect arises from the slow group velocity of light in the vicinity of the stop band, and the consequent localization of light intensity in the voids (to the blue) or in the dye-sensitized TiO(2) (to the red) portions of the photonic crystal. By coupling a photonic crystal to a film of TiO(2) nanoparticles, the short circuit photocurrent efficiency across the visible spectrum (400-750 nm) could be increased by about 26%, relative to an ordinary dye-sensitized nanocrystalline TiO(2) photoelectrode.     

Photonics-on-a-chip: recent advances in integrated waveguides as enabling detection elements for real-world, lab-on-a-chip biosensing applications

By leveraging advances in semiconductor microfabrication technologies, chip-integrated optical biosensors are poised to make an impact as scalable and multiplexable bioanalytical measurement tools for lab-on-a-chip applications. In particular, waveguide-based optical sensing technology appears to be exceptionally amenable to chip integration and miniaturization, and, as a result, the recent literature is replete with examples of chip-integrated waveguide sensing platforms developed to address a wide range of contemporary analytical challenges. As an overview of the most recent advances within this dynamic field, this review highlights work from the last 2-3 years in the areas of grating-coupled, interferometric, photonic crystal, and microresonator waveguide sensors. With a focus towards device integration, particular emphasis is placed on demonstrations of biosensing using these technologies within microfluidically controlled environments. In addition, examples of multiplexed detection and sensing within complex matrices--important features for real-world applicability--are given special attention.     

Self-activating liquid crystal devices for smart laser protection

ABSTRACT

Lasers are now extensively used in a multitude of optical devices and photonic systems spanning from sensing, communication, entertainment, medical surgery to military applications. Direct accidental or intentional exposures to high power lasers may lead to severe temporary or even permanent harm of human eye, skin, or optical sensors. The effective laser protection and shielding are currently not only a subject of scientific research but also a potential public safety issue, therefore there is an urgent need to develop the intelligent laser protection devices for keeping human eyes, optical sensors, and other sensitive components from these unintended or intended damages by laser radiations without warning. Self-activating liquid crystal devices undoubtedly represent such an elegant example because they could be autonomously activated to block or attenuate the lasers when the laser intensity is higher than a maximum permissible exposure value. This review is devoted to summarising the up-to-date significant advances of self-activating liquid crystal devices for potential smart laser protection, including twist-aligned nematic liquid crystal devices, liquid crystal cored waveguide fibre arrays, and photovoltaic/pyroelectric-hybridised liquid crystal devices. Finally, the review concludes with the perspectives and challenges for the future development of self-activating liquid crystal devices. It is anticipated that this glimpse and further endeavours in the emerging field will help the researchers from different backgrounds towards the fabrication of highly efficient laser protection devices, their real-world widespread applications and beyond.     

Beam shaping via photopatterned liquid crystals

ABSTRACT

Due to the fantastic properties and diverse applications of specific beams, optical beam shaping has attracted intensive attentions recently. Generally, these beams can be converted from Gaussian beams via particular spatial amplitude or phase control. In this work, we present a liquid crystal photopatterning technique based on dynamic microlithography with a polarisation-sensitive photoalignment agent. This technique enables the accurate, arbitrary and reconfigurable azimuthal angle control of liquid crystals, thus providing a powerful approach for the manipulation of light. By this means, the tailoring of arbitrary fine microstructures with binary or continuously space-variant liquid crystal azimuthal orientations are demonstrated. We briefly review our recent work on some specially designed patterns and corresponding specific optical fields. High-quality vortex beams, vector beams and Airy beams are generated with unprecedented flexibility in the design and control of light wavefront. Besides high efficiency, good electrical switchability and broad wavelength tolerance, the proposed devices also exhibit merits of compact size, low cost, dynamic mode conversion and polarisation controllable energy distribution, and are available for short pulse and intense light modulation. This work may pave a bright way towards beam shaping and bring new possibilities for the design of novel advanced liquid crystal photonic devices.