Nano/Micromotors in (Bio)chemical Science Applications

Nano/Micromotors in (Bio)chemical Science Application

Screen-Printed Electroluminescent Lamp Modified with Graphene Oxide as a Sensing Device

A screen-printed electroluminescent display with different sensing capabilities is presented. The sensing principle is based on the direct relationship between the light intensity of the lamp and the conductivity of the external layers. The proposed device is able to detect the ionic concentration of any conductive species. Using both top and bottom emission architectures, for the first time, a humidity sensor based on electroluminescent display functionalized by a graphene oxide nanocomposite is introduced. In this regard, just by coupling the display to a smartphone camera sensor, its potential was expanded for automatically monitoring human respiration in real time. Besides, the research includes a responsive display in which the light is spatially turned on in response to pencil drawing or any other conductive media. The above mentioned features together with the easiness of manufacturing and cost-effectiveness of this electroluminescent display can open up great opportunities to exploit it in sensing applications and point-of-care diagnosis

Screen-Printed Electroluminescent Lamp Modified with Graphene Oxide as a Sensing Device

A screen-printed electroluminescent display with different sensing capabilities is presented. The sensing principle is based on the direct relationship between the light intensity of the lamp and the conductivity of the external layers. The proposed device is able to detect the ionic concentration of any conductive species. Using both top and bottom emission architectures, for the first time, a humidity sensor based on electroluminescent display functionalized by a graphene oxide nanocomposite is introduced. In this regard, just by coupling the display to a smartphone camera sensor, its potential was expanded for automatically monitoring human respiration in real time. Besides, the research includes a responsive display in which the light is spatially turned on in response to pencil drawing or any other conductive media. The above mentioned features together with the easiness of manufacturing and cost-effectiveness of this electroluminescent display can open up great opportunities to exploit it in sensing applications and point-of-care diagnosis

All-Integrated and Highly Sensitive Paper Based Device with Sample Treatment Platform for Cd²⁺ Immunodetection in Drinking/Tap Waters

Nowadays, the development of systems, devices, or methods that integrate several process steps into one multifunctional step for clinical, environmental, or industrial purposes constitutes a challenge for many ongoing research projects. Here, we present a new integrated paper based cadmium (Cd²⁺) immunosensing system in lateral flow format, which integrates the sample treatment process with the analyte detection process. The principle of Cd²⁺ detection is based on competitive reaction between the cadmium–ethylenediaminetetraacetic acid–bovine serum albumin–gold nanoparticles (Cd–EDTA–BSA–AuNP) conjugate deposited on the conjugation pad strip and the Cd–EDTA complex formed in the analysis sample for the same binding sites of the 2A81G5 monoclonal antibody (mAb), specific to Cd–EDTA but not Cd²⁺ free, which is immobilized onto the test line. This platform operates without any sample pretreatment step for Cd²⁺ detection thanks to an extra conjugation pad that ensures Cd²⁺ complexation with EDTA and interference masking through ovalbumin (OVA). The detection and quantification limits found for the device were 0.1 and 0.4 ppb, respectively, these being the lowest limits reported up to now for metal sensors based on paper. The accuracy of the device was evaluated by addition of known quantities of Cd²⁺ to different drinking water samples and subsequent Cd²⁺ content analysis. Sample recoveries ranged from 95 to 105% and the coefficient of variation for the intermediate precision assay was less than 10%. In addition, the results obtained here were compared with those obtained with the well-established inductively coupled plasma emission spectroscopy (ICPES) and the analysis of certificate standard samples

Medium Dependent Dual Turn-On/Turn-Off Fluorescence System for Heavy Metal Ions Sensing

A dual turn-on/turn-off fluorescence sensing system based on <i>N</i>-alkylaminopyrazole ligands for heavy metal ions, where the response can be tuned upon medium change, is developed. The synthesis and characterization of Zn^II, Cd^II and Hg^II complexes with two <i>N</i>-alkylaminopyrazole ligands, used as metal receptors, are first presented. The acidity and complexation constants for a selected ligand (1-[2-(octylamino)ethyl]-3,5-diphenylpyrazole ligand (<b>L2</b>)) with Zn^II, Cd^II, and Hg^II are also determined. The fluorescent behavior of these complexes can be tuned by the different medium used (e.g., MeOH or HCl) giving rise to two different sensing mechanisms. The <b>L2</b> ligand can be applied as a global heavy metal warning chemosensor (for Pb^II, Zn^II, Cd^II, or Hg^II ions) for water samples achieving detection limits lower than the maximum concentration recommended by the environmental agencies (detection limit lower than 0.3 ng/mL for any of the mentioned metal ions). The utility of the developed sensing system for Hg^II detection in seawater without any previous sample pretreatment with interest for future in-field sensing kit like applications is also discussed

Water Activated Graphene Oxide Transfer Using Wax Printed Membranes for Fast Patterning of a Touch Sensitive Device

We demonstrate a graphene oxide printing technology using wax printed membranes for the fast patterning and water activation transfer using pressure based mechanisms. The wax printed membranes have 50 μm resolution, longtime stability and infinite shaping capability. The use of these membranes complemented with the vacuum filtration of graphene oxide provides the control over the thickness. Our demonstration provides a solvent free methodology for printing graphene oxide devices in all shapes and all substrates using the roll-to-roll automatized mechanism present in the wax printing machine. Graphene oxide was transferred over a wide variety of substrates as textile or PET in between others. Finally, we developed a touch switch sensing device integrated in a LED electronic circuit

Time- and Size-Resolved Plasmonic Evolution with nm Resolution of Galvanic Replacement Reaction in AuAg Nanoshells Synthesis

The rational design of advanced nanomaterials with enhanced optical properties can be reached only with the profound thermodynamic and kinetic understanding of their synthetic processes. In this work, the synthesis of monodisperse AuAg nanoshells with thin shells and large voids is achieved through the development of a highly reproducible and robust methodology based on the galvanic replacement reaction. This is obtained thanks to the systematic identification of the role played by the different synthetic parameters involved in the process (such as surfactants, co-oxidizers, complexing agents, time, and temperature), providing an unprecedented control over the material’s morphological and optical properties. Thus, the time- and size-resolved evolution of AuAg nanoshells surface plasmon resonance band is described for 15, 30, 60, 80, 100, and 150 nm-sized particles spanning almost through the entire visible spectrum. Its analysis reveals a four-phase mechanism coherent with the material’s morphological transformation. Simulations based on Mie’s theory confirm the observed optical behavior in AuAg nanoshells formation and provide insights into the influence of the Au/Ag ratio on their plasmonic properties. The high degree of morphological control provided by this methodology represents a transferable and scalable strategy for the development of advanced-generation plasmonic nanomaterials

Simple On-Plastic/Paper Inkjet-Printed Solid-State Ag/AgCl Pseudoreference Electrode

A miniaturized, disposable, and low cost Ag/AgCl pseudoreference electrode based on inkjet printing has been developed. Silver ink was printed and chlorinated with bleach solution. The reference electrodes obtained in this work showed good reproducibility and stability during at least 30 min continuous measurement and even after 30 days storage without special care. Moreover, the strategy used in this work can be useful for large scale production of a solid-state Ag/AgCl pseudoreference electrode with different designs and sizes, facilitating the coupling with different electrical/electrochemical microsensors and biosensors

Electrochromic Molecular Imprinting Sensor for Visual and Smartphone-Based Detections

Electrochromic effect and molecularly imprinted technology have been used to develop a sensitive and selective electrochromic sensor. The polymeric matrices obtained using the imprinting technology are robust molecular recognition elements and have the potential to mimic natural recognition entities with very high selectivity. The electrochromic behavior of iridium oxide nanoparticles (IrOx NPs) as physicochemical transducer together with a molecularly imprinted polymer (MIP) as recognition layer resulted in a fast and efficient translation of the detection event. The sensor was fabricated using screen-printing technology with indium tin oxide as a transparent working electrode; IrOx NPs where electrodeposited onto the electrode followed by thermal polymerization of polypyrrole in the presence of the analyte (chlorpyrifos). Two different approaches were used to detect and quantify the pesticide: direct visual detection and smartphone imaging. Application of different oxidation potentials for 10 s resulted in color changes directly related to the concentration of the analyte. For smartphone imaging, at fixed potential, the concentration of the analyte was dependent on the color intensity of the electrode. The electrochromic sensor detects a highly toxic compound (chlorpyrifos) with a 100 fM and 1 mM dynamic range. So far, to the best of our knowledge, this is the first work where an electrochromic MIP sensor uses the electrochromic properties of IrOx to detect a certain analyte with high selectivity and sensitivity

Graphene Quantum Dots-based Photoluminescent Sensor: A Multifunctional Composite for Pesticide Detection

Due to their size and difficulty to obtain, cost/effective biological or synthetic receptors (e.g., antibodies or aptamers, respectively), organic toxic compounds (e.g., less than 1 kDa) are generally challenging to detect using simple platforms such as biosensors. This study reports on the synthesis and characterization of a novel multifunctional composite material, magnetic silica beads/graphene quantum dots/molecularly imprinted polypyrrole (mSGP). mSGP is engineered to specifically and effectively capture and signal small molecules due to the synergy among chemical, magnetic, and optical properties combined with molecular imprinting of tributyltin (291 Da), a hazardous compound, selected as a model analyte. Magnetic and selective properties of the mSGP composite can be exploited to capture and preconcentrate the analyte onto its surface, and its photoluminescent graphene quantum dots, which are quenched upon analyte recognition, are used to interrogate the presence of the contaminant. This multifunctional material enables a rapid, simple and sensitive platform for small molecule detection, even in complex mediums such as seawater, without any sample treatment