Luminescence-based optical sensors fabricated by means of the layer-by-layer nano-assembly technique

Luminescence-based sensing applications range from agriculture to biology, including medicine and environmental care, which indicates the importance of this technique as a detection tool. Luminescent optical sensors are required to be highly stable, sensitive, and selective, three crucial features that can be achieved by fabricating them by means of the layer-by-layer nano-assembly technique. This method permits us to tailor the sensors0 properties at the nanometer scale, avoiding luminophore aggregation and, hence, self-quenching, promoting the diffusion of the target analytes, and building a barrier against the undesired molecules. These characteristics give rise to the fabrication of custom-made sensors for each particular application.This work was supported by the Spanish State Research Agency (AEI) through the TEC2016- 79367-C2-2-R project and the European Regional Development Fund (ERDF-FEDER). Nerea de Acha would also like to acknowledge her pre-doctoral fellowship (reference BES-2014-069692) funded by the Spanish Ministry of Economy and Competitiveness through the TEC2013-43679-R project

Comparative study of polymeric matrices embedding oxygen-sensitive fluorophores by means of Layer-by-Layer nanosassembly

In this work, a comparative study of luminescent optical fiber oxygen sensors fabricated by means of Layer-by-Layer nanoassembly technique (LbL) has been carried out. The oxygen-sensitive fluorophore is the same in all the cases, the metalloporphyrin platinum tetrakis pentafluorophenylporphin (Pt-TFPP), which was deposited using LbL method by entrapping it into anionic micelles formed with a surfactant. As cationic counterpart to form the anionic-cationic bilayer, different polyelectrolytes acting as the polymeric matrices embedding the sensing material have been studied: poly(diallyldimethylammonium chloride) (PDDA), polyethyleneimine (PEI) and poly(allylamine hydrochloride) (PAH). Absorbance spectra, contact angle, Atomic Force Microscope and Scanning Electronic Microscope analysis were performed on the sensing films. The kinetics, resolution and sensitivity of the sensors for different number of bilayers were also determined. It has been found a remarkable difference on these characteristics depending on the polymer used

Engineering Tunable Plasmonic Nanostructures To Enhance Upconversion Luminescence

Plasmonic nanostructures, which can confine and manipulate light below the diffraction limit, are becoming increasingly important in many areas of optical physics and devices. One of the areas that can greatly benefit from surface-plasmon mediated confinement of optical fields is the enhancement of emission in low quantum yield materials. The resonant wavelength for plasmonic structures used for emission enhancement is either the excitation or emission wavelengths of the luminescent material. Therefore, a key component in designing plasmonic structures used in luminescent enhancement applications is the ability to engineer and tune plasmonic building blocks to create structures resonant at the desired wavelength. In this thesis, we have used two approaches to build tunable structures for luminescent enhancement: 1) using already synthesized metallic nanocrystals resonant at the desired wavelengths as building blocks, we designed structures that would result in maximum emission enhancement. 2) Designing arrays of plasmonic nanostructures with the help of simulation software to be resonant at the desired wavelength and then fabricating them with top-down nanoscale fabrication techniques. In either approach, the resulting large area structures were macroscopically studied by steady state and time-resolved photoluminescence measurements to quantify the plasmonic effects on enhancement. We were able to achieve high enhancement factors in almost all of the structures and designs. Furthermore, we were able to identify and study various effects that play a role in plasmonic enhancement processes

Classification of analytics, sensorics, and bioanalytics with polyelectrolyte multilayer capsules

Polyelectrolyte multilayer (PEM) capsules, constructed by LbL (layer-by-layer)-adsorbing polymers on sacrificial templates, have become important carriers due to multifunctionality of materials adsorbed on their surface or encapsulated into their interior. They have been also been used broadly used as analytical tools. Chronologically and traditionally, chemical analytics has been developed first, which has long been synonymous with all analytics. But it is not the only development. To the best of our knowledge, a summary of all advances including their classification is not available to date. Here, we classify analytics, sensorics, and biosensorics functionalities implemented with polyelectrolyte multilayer capsules and coated particles according to the respective stimuli and application areas. In this classification, three distinct categories are identified: (I) chemical analytics (pH; K+, Na+, and Pb2+ ion; oxygen; and hydrogen peroxide sensors and chemical sensing with surface-enhanced Raman scattering (SERS)); (II) physical sensorics (temperature, mechanical properties and forces, and osmotic pressure); and (III) biosensorics and bioanalytics (fluorescence, glucose, urea, and protease biosensing and theranostics). In addition to this classification, we discuss also principles of detection using the above-mentioned stimuli. These application areas are expected to grow further, but the classification provided here should help (a) to realize the wealth of already available analytical and bioanalytical tools developed with capsules using inputs of chemical, physical, and biological stimuli and (b) to position future developments in their respective fields according to employed stimuli and application areas

Nanoantennas for visible and infrared radiation

Nanoantennas for visible and infrared radiation can strongly enhance the interaction of light with nanoscale matter by their ability to efficiently link propagating and spatially localized optical fields. This ability unlocks an enormous potential for applications ranging from nanoscale optical microscopy and spectroscopy over solar energy conversion, integrated optical nanocircuitry, opto-electronics and density-ofstates engineering to ultra-sensing as well as enhancement of optical nonlinearities. Here we review the current understanding of optical antennas based on the background of both well-developed radiowave antenna engineering and the emerging field of plasmonics. In particular, we address the plasmonic behavior that emerges due to the very high optical frequencies involved and the limitations in the choice of antenna materials and geometrical parameters imposed by nanofabrication. Finally, we give a brief account of the current status of the field and the major established and emerging lines of investigation in this vivid area of research.Comment: Review article with 76 pages, 21 figure

NIR-emissive Alkynylplatinum(II) Terpyridyl Complex as a turn-on selective probe for heparin quantification by induced helical self-assembly behaviour

The extent of self-assembly viametal–metal and π-π stacking interactions, induced by the polyanionic biopolymers, enables the class of alkynylplatinum(II) terpyridyl complexes to be applicable for the sensing of important biomacromolecules through the monitoring of spectral changes. Strong demand arises for the design of selective and practical detection techniques for the quantification of heparin, a highly negative-charged polysaccharidethat can function as anticoagulant, due to the prevention of hemorrhagic complications upon overdose usage.Aconvenient sensing protocol for the detection of UFH and LMWH, two common forms of heparins in clinical use, in buffer and biological medium has been demonstrated with the spectral changes associated with the induced self-assembly of a NIR-emissive platinum(II) complex. The detection range has been demonstrated to cover clinical dosage levels and the structurally similar analogues can be effectively differentiated based on their anionic charge density and the formation of supramolecular helical assembly of the platinum(II) complex with them ...postprin

Enhanced upconversion photoluminescence by novel plasmonic structures

The emerging field of plasmon-enhanced upconversion photoluminescence has a significant impact on a variety of technologies, including high-efficiency solar energy systems and biotechnology. To date, the upconversion efficiency of best reported rare-earth doped upconversion nanoparticles cannot meet the requirements of practical utilizations in these fields. Therefore, it is of great significance to find new approaches for the enhancement of upconversion efficiency. This thesis mainly aims to explore the enhanced upconversion photoluminescence by several novel plasmonic nanostructures. In this PhD work, I first studied the properties of rare-earth doped upconversion nanomaterials, which are capable of the spectral conversion of the otherwise lost sub-band-gap photons from the solar spectrum. The extra Gd3+ ion doping strategy was introduced in the hydrothermal synthesis process, which can provide an approach to tune the geometry and upconversion efficiency of upconversion nanoparticles (UCNPs). To achieve higher upconversion efficiency, advances in the experimental improvements in plasmon-enhanced upconversion photoluminescence (UCPL) efficiency are explored, by using Au mesoporous film, Au nanotriangle array or nanohole array substrates for the enhancement of upconversion photoluminescence. It is demonstrated that the best plasmonic nanostructures can achieve about 360 times UCPL enhancement. These experimental results demonstrated the great potential of the plasmonic effect for UCPL enhancement. Furthermore, a triplet-triplet annihilation based upconversion nanoparticles (TTA-UCNPs) were synthesized, which have much higher intrinsic upconversion efficiency than the rare-earth based upconversion nanoparticles. A plasmon-enhanced upconversion photoluminescence substrate was designed for high performance photocatalysis applications under solar simulator (AM 1.5 G) irradiation. Five times faster photocatalytic activity rate was achieved by this plasmonic/TTA-UCNPs/Au@TiO2 system, which demonstrates great value of plasmonic and upconversion mechanisms. The combination of excellent plasmonic substrate and high efficiency TTA-UCNPs makes it possible for the realization of industrial level applications of the plasmonic and upconversion in the photocatalytic field.Open Acces

Nanoparticles in polyelectrolyte multilayer layer-by-layer (LbL) films and capsules : key enabling components of hybrid coatings

Originally regarded as auxiliary additives, nanoparticles have become important constituents of polyelectrolyte multilayers. They represent the key components to enhance mechanical properties, enable activation by laser light or ultrasound, construct anisotropic and multicompartment structures, and facilitate the development of novel sensors and movable particles. Here, we discuss an increasingly important role of inorganic nanoparticles in the layer-by-layer assembly—effectively leading to the construction of the so-called hybrid coatings. The principles of assembly are discussed together with the properties of nanoparticles and layer-by-layer polymeric assembly essential in building hybrid coatings. Applications and emerging trends in development of such novel materials are also identified

Fabrication and Characterization of Hybrid Nanocomposites by Matrix Assisted Pulsed Laser Evaporation

Different methods have been applied to deposit hybrid nanocomposites which can be applied in various fields due to their light weight and multifunctional properties. Here, matrix assisted pulsed laser evaporation (MAPLE) equipment with 532 nm Nd:YAG laser is applied to fabricate three types of hybrid nanocomposites on different substrates. Chemical synthesized FeCo nanoparticles were deposited on graphene sheets by MAPLE technique (laser fluence: 300 mJ/cm2). The effects of deposition time (t) on particle amount, shape and size have been investigated. Yttrium barium copper oxide (YBCO) materials are one type of high-temperature superconductive materials and could be applied in transportation. To fabricate superconductive materials/graphene hybrid nanocomposites, YBCO nanoparticles were deposited on graphene sheets by MAPLE techniques with a laser fluence at 150 mJ/cm2. The microstructures in terms of particle size, size distribution, and particle shape are studied as functions of the deposition time (t). In addition, up-conversion nanoparticles (NaGdF4: Yb3+, Er3+) which are able to be excited by low energy photons (λex = 980 nm) and emit high energy photons were deposited through MAPLE technique. Results indicate that 2 hours’ deposition can result in high-quality samples in terms of particle size and particle amount. No toxic effect is imposed on the cells by the deposited up-conversion nanoparticles with/without protein modification. Our results indicate that the MAPLE deposition technique demonstrates the good versatility of depositing different nanoparticles and preserving their chemical composition