Site-selective surface enhanced Raman scattering study of ligand exchange reactions on aggregated Ag nanocubes.

Surface modification of ligand protected nanoparticles (NPs) can be driven by ligand exchange reactions (LER). Little is known about the mechanism of this reaction, especially when the particles are not spherical. Here, we use the intrinsic hot spots generated on the corners/edges of 40 nm silver nanocubes (AgNCs) and the extrinsic hot spots generated by the aggregation of AgNCs to obtain strong enhancements in surface enhanced Raman scattering (SERS) to monitor the displacement of poly(vinylpyrrolidone) with either a hydrophilic (sodium 11-mercapto-1-undecanesulfonate, MUS) or a hydrophobic ligand (1-octanethiol, OT).

Synthesis of a thermoresponsive crosslinked MEOMA polymer coating on microclusters of iron oxide nanoparticles.

Encapsulation of magnetic nanoparticles (MNPs) of iron (II, III) oxide (FeO) with a thermopolymeric shell of a crosslinked poly(2-(2-methoxyethoxy)ethyl methacrylate) P(MEOMA) is successfully developed. Magnetic aggregates of large size, around 150-200 nm are obtained during the functionalization of the iron oxide NPs with vinyl groups by using 3-butenoic acid in the presence of a water soluble azo-initiator and a surfactant, at 70 °C. These polymerizable groups provide a covalent attachment of the P(MEOMA) shell on the surface of the MNPs while a crosslinked network is achieved by including tetraethylene glycol dimethacrylate in the precipitation polymerization synthesis.

Carbon Dots as Sensing Layer for Printed Humidity and Temperature Sensors.

This work presents an innovative application of carbon dots (Cdots) nanoparticles as sensing layer for relative humidity detection. The developed sensor is based on interdigitated capacitive electrodes screen printed on a flexible transparent polyethylene terephthalate (PET) film. Cdots are deposited on top of these electrodes.

Optimization of Cost-Effective and Reproducible Flexible Humidity Sensors Based on Metal-Organic Frameworks.

In this letter, we present the extension of a previous work on a cost-effective method for fabricating highly sensitive humidity sensors on flexible substrates with a reversible response, allowing precise monitoring of the humidity threshold. In that work we demonstrated the use of three-dimensional metal-organic framework (MOF) film deposition based on the perylene-3,4,9,10-tetracarboxylate linker, potassium as metallic center and the interspacing of silver interdigitated electrodes (IDEs) as humidity sensors. In this work, we study one of the most important issues in efficient and reproducible mass production, which is to optimize the most important processes' parameters in their fabrication, such as controlling the thickness of the sensor's layers.

Evaluation of a reconfigurable portable instrument for copper determination based on luminescent carbon dots.

A portable reconfigurable platform for copper (Cu(II)) determination based on luminescent carbon dot (Cdots) quenching is described. The electronic setup consists of a light-emitting diode (LED) as the carbon dot optical exciter and a photodiode as a light-to-current converter integrated in the same instrument. Moreover, the overall analog conditioning is simply performed with one integrated solution, a field-programmable analog array (FPAA), which makes it possible to reconfigure the filter and gain stages in real time.

Microsystem-assisted synthesis of carbon dots with fluorescent and colorimetric properties for pH detection.

The present paper describes the use of a microfluidic system to synthesize carbon dots (Cdots) and their use as optical pH sensors. The synthesis is based on the thermal decomposition of ascorbic acid in dimethyl sulfoxide. The proposed microsystem is composed of a fluidic and a thermal platform, which enable proper control of synthesis variables.

Carbon dots for copper detection with down and upconversion fluorescent properties as excitation sources.

Carbon dots were synthesized by a simple and green strategy for selective and sensitive Cu(2+) ion detection using both down and upconversion fluorescence. These fluorescent nanosensors show low cytotoxicity and are applied for intracellular sensing and imaging of Cu(2+) in biological systems.

Behaviour of Au-citrate nanoparticles in seawater and accumulation in bivalves at environmentally relevant concentrations.

The degree of aggregation and/or coalescence of Au-citrate nanoparticles (AuNPs, mean size 21.5 ± 2.9 nm), after delivery in simulated seawater, are shown to be concentration-dependent.

Photographing the synergy between magnetic and colour properties in spin crossover material [Fe(NH2trz)3](BF4)2: a temperature sensor perspective.

We introduce the first method for imaging colour changes related to a spin crossover phenomenon induced by thermal variation which can be determined with the naked eye or with a photographic digital camera in a solid phase sensor.

Magnetic core-shell fluorescent pH ratiometric nanosensor using a Stöber coating method.

We describe the use of a modified Stöber method for coating maghemite (γ-Fe(2)O(3)) nanocrystals with silica shells in order to built magnetic fluorescent sensor nanoparticles in the 50-70nm diameter range. In detail, the magnetic cores were coated by two successive silica shells embedding two fluorophores (two different silylated dye derivatives), which allows for ratiometric pH-measurements in the pH range 5-8. Silica coated magnetic nanoparticles were prepared using maghemite nanocrystals as cores (5-10nm in diameter) coated by tetraethoxyorthosilicate via hydrolysis/condensation in ethanol, catalyzed by ammonia.

Environmental monitoring using a conventional photographic digital camera for multianalyte disposable optical sensors.

The primary interest of this study concerns the use of an inexpensive photographic digital camera as the detection system, using its own flash as the source of light to present a new analytical procedure to measure disposable multianalyte optical sensors for potassium, magnesium, hardness and conventional pH test strips. The camera arrangement was designed in a fixed position over an optical board with controllable ambient conditions. After acquiring the digital image, the analytical information contained in each test zone is analyzed using theRGB colour space.

Magnetic and fluorescent core-shell nanoparticles for ratiometric pH sensing.

This paper describes the preparation of nanoparticles composed of a magnetic core surrounded by two successive silica shells embedding two fluorophores, showing uniform nanoparticle size (50-60 nm in diameter) and shape, which allow ratiometric pH measurements in the pH range 5-8. Uncoated iron oxide magnetic nanoparticles (∼10 nm in diameter) were formed by the coprecipitation reaction of ferrous and ferric salts. Then, they were added to a water-in-oil microemulsion where the hydrophilic silica shells were obtained through hydrolysis and condensation of tetraethoxyorthosilicate together with the corresponding silylated dye derivatives-a sulforhodamine was embedded in the inner silica shell and used as the reference dye while a pH-sensitive fluorescein was incorporated in the outer shell as the pH indicator.

Multi-ion detection by one-shot optical sensors using a colour digital photographic camera.

The feasibility and performance of a procedure to evaluate previously developed one-shot optical sensors as single and selective analyte sensors for potassium, magnesium and hardness are presented. The procedure uses a conventional colour digital photographic camera as the detection system for simultaneous multianalyte detection. A 6.

Surface-functionalized fluorescent silica nanoparticles for the detection of ATP.

The design of two-dyed fluorescent silica nanoparticles for ATP detection is presented. The indicator dye possesses a dipicolyl-amine (DPA) unit complexed with Zn(II) as a receptor function for ATP while a rhodamine derivative is used as the reference dye. The nanoparticles were fully characterized regarding analytical performance, morphology and cytocompatibility.

On the design of fluorescent ratiometric nanosensors.

Advances in nanoparticle technology have recently offered new tools to the bioanalytical field of research. In particular, new nanoparticle-based sensors have appeared able to give quantitative information about different species (ions, metabolites, biomolecules) in biosamples through ratiometric measurements. This article describes the methodologies developed so far in the design of such nanosensors.

Fluorescent polyacrylamide nanoparticles for naproxen recognition.

We present the synthesis of fluorescent acrylamide nanoparticles (FANs) capable of recognizing non-steroidal anti-inflammatory drugs (NSAIDs) in buffered aqueous solutions. Within this important group, we selected naproxen, one of the 2-arylpropionic acids (profens), due to its use for the treatment of moderate pain, fever, and inflammation. The nanosensors were prepared under mild conditions of inverse microemulsion polymerization using aqueous acrylamide as the monomer and N,N'-methylenebisacrylamide as the cross-linker, employing the surfactants polyoxyethylene-4-lauryl ether (Brij 30) and sodium bis(2-ethylhexyl)sulfosuccinate in hexane.

Multianalyte imaging in one-shot format sensors for natural waters.

A one-shot multisensor based on ionophore-chromoionophore chemistry for optical monitoring of potassium, magnesium and hardness in water is presented. The analytical procedure uses a black and white non-cooled CCD camera for image acquisition of the one-shot multisensor after reaction, followed by data treatment for quantitation using the grey value pixel average from a defined region of interest from each sensing area to build the analytical parameter 1-alpha. In optimised experimental conditions, the procedure shows a large linear range, up to 6 orders using the linearised model and good detection limits: 9.

Colourimetric characterisation of disposable optical sensors from spectroradiometric measurements.

Spectroradiometric measurements of reflectance and CIELAB hue-angle, were tested for K(I) determination using disposable optical sensors based on ion exchange mechanism. The linearisation of the sigmoidal response function, using a logistic regression, increases the linear range noticeably to 7.65 x 10(-8)-1.

Portable light-emitting diode-based photometer with one-shot optochemical sensors for measurement in the field.

This report describes the electronics of a portable, low-cost, light-emitting diode (LED)-based photometer dedicated to one-shot optochemical sensors. Optical detection is made through a monolithic photodiode with an on-chip single-supply transimpedance amplifier that reduces some drawbacks such as leakage currents, interferences, and parasitic capacitances. The main instrument characteristics are its high light source stability and thermal correction.

Magnesium optical one-shot sensor based on a coumarin chromoionophore.

The characterization of a new irreversible optical absorption-based one-shot sensor for magnesium is described. The magnesium photoactive probe is 7-diethylamino-3-(3,4-ethylendioxybenzoyl)coumarin immobilized in a plasticized polymeric membrane. The magnesium selectivity can be explained in terms of size and charge density of magnesium and charge-separated resonance forms contribution in the excited state of coumarin.

A simplified measurement procedure and portable electronic photometer for disposable sensors based on ionophore-chromoionophore chemistry for potassium determination.

A field-portable photometer for potassium determination with disposable sensors has been developed. It can be applied to routine water and beverage analysis. The disposable sensor is based on ionophore-chromoionophore chemistry.