scholarly journals Silver Nanowires as Electron Transfer Mediators in Electrochemical Catechol Biosensors

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 899
Author(s):  
Coral Salvo-Comino ◽  
Fernando Martin-Pedrosa ◽  
Cristina Garcia-Cabezon ◽  
Maria Luz Rodriguez-Mendez
Keyword(s):  
Electron Transfer ◽  
Limit Of Detection ◽  
Silver Nanowires ◽  
High Surface ◽  
Volume Ratio ◽  
Homogeneous Distribution ◽  
Electron Mediator ◽  
Force Microscopy ◽  
Voltammetric Detection ◽  
Order Of Magnitude

The integration of nanomaterials as electron mediators in electrochemical biosensors is taking on an essential role. Due to their high surface-to-volume ratio and high conductivity, metallic nanowires are an interesting option. In this paper, silver nanowires (AgNWs) were exploited to design a novel catechol electrochemical biosensor, and the benefits of increasing the aspect ratio of the electron mediator (nanowires vs. nanoparticles) were analyzed. Atomic force microscopy (AFM) studies have shown a homogeneous distribution of the enzyme along the silver nanowires, maximizing the contact surface. The large contact area promotes electron transfer between the enzyme and the electrode surface, resulting in a Limit of Detection (LOD) of 2.7 × 10−6 M for tyrosinase immobilized onto AgNWs (AgNWs-Tyr), which is one order of magnitude lower than the LOD of 3.2 × 10−5 M) obtained using tyrosinase immobilized onto silver nanoparticles (AgNPs-Tyr). The calculated KM constant was 122 mM. The simultaneous use of electrochemistry and AFM has demonstrated a limited electrochemical fouling that facilitates stable and reproducible detection. Finally, the biosensor showed excellent anti-interference characteristics toward the main phenols present in wines including vanillin, pyrogallol, quercetin and catechin. The biosensor was able to successfully detect the presence of catechol in real wine samples. These results make AgNWs promising elements in nanowired biosensors for the sensitive, stable and rapid voltammetric detection of phenols in real applications.

Effect of current density on the porous silicon preparation as gas sensors**

2021 ◽  
Vol 30 (1) ◽  
pp. 257-264
Author(s):  
Muna H. Kareem ◽  
Adi M. Abdul Hussein ◽  
Haitham Talib Hussein
Keyword(s):  
Porous Silicon ◽  
Gas Sensors ◽  
Current Density ◽  
Room Temperature ◽  
Low Cost ◽  
High Surface ◽  
Volume Ratio ◽  
Etching Time ◽  
Force Microscopy ◽  
Materials Used

Abstract In this study, porous silicon (PSi) was used to manufacture gas sensors for acetone and ethanol. Samples of PSi were successfully prepared by photoelectrochemical etching and applied as an acetone and ethanol gas sensor at room temperature at various current densities J= 12, 24 and 30 mA/cm2 with an etching time of 10 min and hydrofluoric acid concentration of 40%. Well-ordered n-type PSi (100) was carefully studied for its chemical composition, surface structure and bond configuration of the surface via X-ray diffraction, atomic force microscopy, Fourier transform infrared spectroscopy and photoluminescence tests. Results showed that the best sensitivity of PSi was to acetone gas than to ethanol under the same conditions at an etching current density of 30 mA/cm2, reaching about 2.413 at a concentration of 500 parts per million. The PSi layers served as low-cost and high-quality acetone gas sensors. Thus, PSi can be used to replace expensive materials used in gas sensors that function at low temperatures, including room temperature. The material has an exceptionally high surface-to-volume ratio (increasing surface area) and demonstrates ease of fabrication and compatibility with manufacturing processes of silicon microelectronics.

scholarly journals A highly sensitive safrole sensor based on polyvinyl acetate (PVAc) nanofiber-coated QCM

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Kuwat Triyana ◽  
Aditya Rianjanu ◽  
Doni Bowo Nugroho ◽  
Ahmad Hasan As’ari ◽  
Ahmad Kusumaatmaja ◽  
...  
Keyword(s):  
Response Time ◽  
Polyvinyl Acetate ◽  
Limit Of Detection ◽  
High Surface ◽  
High Surface Area ◽  
Average Diameter ◽  
Promising Alternative ◽  
Force Microscopy ◽  
Atomic Force ◽  
Highly Sensitive

Abstract A novel, highly sensitive and selective safrole sensor has been developed using quartz crystal microbalance (QCM) coated with polyvinyl acetate (PVAc) nanofibers. The nanofibers were collected on the QCM sensing surface using an electrospinning method with an average diameter ranging from 612 nm to 698 nm and relatively high Q–factors (rigid coating). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the PVAc nanofiber surface morphology, confirming its high surface area and roughness, which are beneficial in improving the sensor sensitivity compared to its thin-film counterpart. The as-spun PVAc nanofiber sensor could demonstrate a safrole limit of detection (LOD) of down to 0.7 ppm with a response time of 171 s and a sensitivity of 1.866 Hz/ppm. It also showed good reproducibility, rapid response time, and excellent recovery. Moreover, cross-interference of the QCM sensor response to non-target gases was investigated, yielding very low cross-sensitivity and high selectivity of the safrole sensor. Owing to its high robustness and low fabrication cost, this proposed sensing device is expected to be a promising alternative to classical instrumental analytical methods for monitoring safrole-based drug precursors.

Development of Diclofenac Sodium Releasing Bio-Erodible Polymeric Nanomats

2006 ◽  
Vol 6 (9) ◽  
pp. 3310-3320 ◽  
Author(s):  
A. M. Piras ◽  
L. Nikkola ◽  
F. Chiellini ◽  
N. Ashammakhi ◽  
E. Chiellini
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Release Kinetics ◽  
Diclofenac Sodium ◽  
High Surface ◽  
Active Agent ◽  
Volume Ratio ◽  
Homogeneous Distribution ◽  
Scanning Calorimetry ◽  
Nano Structure

Application of nanofiber-based nanomats in medicine is attractive and thanks to the 3D nano-structure and the high surface to volume ratio they are excellent for local controlled drug delivery. The use of bioactive bioerodible polymers for developing drug delivery nanomats may allow for drug release and targeting control. Objective of the current study was to evaluate the suitability of bioerodible polymeric material based on n-butyl hemiester of [poly(maleic anhydride-alt-2-methoxyethyl vinyl ether)] (PAM14) for the preparation of nanomats for controlled administration of anti-inflammatory, diclofenac sodium (DS) drug. Samples were prepared using different polymer concentrations (5–10%) in either ethanol or acetic acid as solvent. Morphology was investigated by using scanning electron microscopy (SEM). Thermal analysis such as differential scanning calorimetry (DSC) was performed to detect effect on polymer arrangement. DS localization in electrospun nanomats was evaluated by using electron back scattering microanalysis, based on the detection of chlorine, and drug release kinetics was assessed using UV-Vis. Average fiber diameter resulted in the range of 100 nm to 1.0 μm and a homogeneous distribution of the loaded drug into the fibers was observed. The DS release was immediate and despite the preliminary nature of the performed electrospinning experiments, the achieved results appear promising for the future development of a novel system for the controlled and targeted administration of drug and active agent.

Improvement of electrocatalytic effect in voltammetric sensors based on phthalocyanines

2016 ◽  
Vol 20 (01n04) ◽  
pp. 413-420 ◽  
Author(s):  
María L. Rodríguez-Méndez ◽  
Cristina Medina-Plaza ◽  
Celia García-Hernández ◽  
Silvia Rodríguez ◽  
Cristina García-Cabezón ◽  
...  
Keyword(s):  
Arachidic Acid ◽  
Volume Ratio ◽  
Layer By Layer ◽  
Carbon Paste ◽  
Electron Mediator ◽  
Limits Of Detection ◽  
Carbon Paste Electrodes ◽  
Voltammetric Sensors ◽  
Electrocatalytic Effect ◽  
Order Of Magnitude

Voltammetric sensors based on phthalocyanines have been used to detect a variety of compounds. In this paper, the state of the art of sensors prepared using classical techniques will be revised. Then, new strategies to improve the performance of the sensors will be described using as example sensors chemically modified with lutetium bisphthalocyanine (LuPc[Formula: see text] dedicated to the detection of phenols of interest in the food industry. Classical LuPc2 carbon paste electrodes can detect phenols such as catechol, caffeic acid or pyrogallol with limits of detection in the range of 10[Formula: see text]–10[Formula: see text] M. The performance can be improved by using nanostructured Langmuir–Blodgett (LB) or Layer by Layer (LbL) films. The enhanced surface to volume ratio produce an increase in the sensitivity of the sensors. Limits of detection of 10[Formula: see text]–10[Formula: see text] M are attained, which are one order of magnitude lower than those obtained using conventional carbon paste electrodes. Moreover, these techniques can be used to co-immobilize two electrocatalytic materials in the same device. The limits of detection obtained in LB sensors combining LuPc2/AuNPs or LuPc2/CNT are further improved. Finally, the LB technique has been used to prepare biosensors where a phenol oxydase (such as tyrosinase or lacasse) is immobilized in a biomimetic environment that preserves the enzymatic activity. Moreover, LuPc2 can be co-immobilized with the enzyme in a lipidic film formed by arachidic acid (AA). LuPc2 can act as an electron mediator facilitating the electron transfer. These biomimetic sensors formed by LuPc2/AA/enzyme show Limits of detection of 10[Formula: see text] M and an enhanced selectivity.

scholarly journals Inkjet Printing of Controlled ZnO Nanoparticles Layering

2019 ◽  
Vol 8 (1) ◽  
pp. 34-40
Author(s):  
N. Spinella ◽  
C. Galati ◽  
L. Renna
Keyword(s):  
Zno Nanoparticles ◽  
Gas Sensing ◽  
High Surface ◽  
Volume Ratio ◽  
Specific Chemical ◽  
Force Microscopy ◽  
Electron Microscopies ◽  
Atomic Force ◽  
Preliminary Study

 Controlled layering of functional material can produced a versatile film with specific chemical and physical proprieties for desirable applications. This article presented inkjet multilayer structures of ZnO nanoparticles of specific layer morphology and thickness for the development of devices where a high surface-to-volume ratio is required (e.g. micro gas sensors). Stacked multilayers were stratified through a multi-run printing process suitable to produce large-square pattern on flat silicon support. The formation of a multilayer structure was demonstrate through an extended structural characterization of the resulting film. Printed layer morphology was investigated with optical and scanning electron microscopies; atomic force microscopy profiling characterizations were conducted over the entire printed area to evaluate the pattern reproducibility. Finally, a preliminary study as gas sensing film was performed, using the alcohol/ZnO interaction experiments.

Superficial and electrical characterization of thin films based on Chitosan/polypyrrole/MWCNT

2016 ◽  
Vol 1819 ◽  
Author(s):  
A. Olarte-Paredes ◽  
R. Salgado-Delgado ◽  
A. M. Salgado-Delgado ◽  
E. Rubio-Rosas ◽  
E. García-Hernández ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Surface Characterization ◽  
Electrochemical Impedance ◽  
High Surface ◽  
Electrical Characterization ◽  
Volume Ratio ◽  
Homogeneous Distribution ◽  
Multilayer Carbon Nanotubes ◽  
Mechanical And Electrical Properties ◽  
The Matrix

ABSTRACTIn recent decades conducting polymers have attracted attention due to their promising and versatile applications in different fields. There is a considerable interest in the application of nanotubes multilayer carbon (MWCNT) because of their unique structure, high electrical conductivity, high chemical stability, and high surface-to-volume ratio. These properties make MWCNT extremely attractive for fabricating sensors. Composites based on a matrix of a biopolymer such as the chitosan (CS) with a lot of conductive polymers or (MWCNT), have received increasing attention due to their attractive structural, mechanical and electrical properties that could have applications in different fields such as tissue engineering, biomedicine, and manufacture of sensors and biosensors. Have been reported conducting polymer composites with an extensive range of interesting mechanical and electrical properties, which is reported in this paper to obtain films by ultrasonic bath mixing of Chitosan 3% w/v using polypyrrole (PPy) and multilayer carbon nanotubes. Surface characterization was performed using scanning electron microscopy (SEM). The electrical properties were analyzed using electrochemical impedance spectroscopy (EIS) in a frequency range 0.01 - 10E+5 Hz to 10 mV AC. The results show that the films of CS/PPy/MWCNT have a homogeneous distribution where the chitosan envelops the loads, while for EIS retention load was observed within the matrix observing these materials in accordance with the equivalent circuit of Warburg showing diffusional process.

scholarly journals Graphene/Silver Nanowires/Graphene Sandwich Composite for Stretchable Transparent Electrodes and Its Fracture Mechanism

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 512
Author(s):  
Chi-Hsien Huang ◽  
Hong-Cing Wu ◽  
Bo-Feng Chen ◽  
Yen-Cheng Li
Keyword(s):  
Sandwich Structure ◽  
Silver Nanowires ◽  
High Surface ◽  
Chemical Vapor ◽  
Electrical Performance ◽  
Sandwich Composite ◽  
Transparent Electrodes ◽  
Graphene Layers ◽  
Force Microscopy ◽  
Conductivity Loss

Polycrystalline graphene grown by chemical vapor deposition (CVD) is characterized by line defects and disruptions at the grain boundaries and nucleation sites. This adversely affects the stretchability and conductivity of graphene, which limits its applications in the field of flexible, stretchable, and transparent electrodes. We demonstrate a composite electrode comprised of a graphene/silver nanowires (AgNWs)/graphene sandwich structure on a polydimethylsiloxane substrate to overcome this limitation. The sandwich structure exhibits high transparency (>90%) and excellent conductivity improvement of the graphene layers. The use of AgNWs significantly suppresses the conductivity loss resulting from stretching. The mechanism of the suppression of the conductivity loss was investigated using scanning electron microscopy, atomic force microscopy, and lateral force microscopy. The results suggest that the high surface friction of the sandwich structure causes a sliding effect between the graphene layers would produce low crack or hole formation to maintain the conductivity. In addition to acting as conductive layers, the top and bottom graphene layers can also protect the AgNWs from oxidation, thereby enabling maintenance of the electrical performance of the electrodes over a prolonged period. We also confirmed the applicability of the sandwich structure electrode to the human body, such as on the wrist, finger, and elbow.

Cauliflower polyaniline/multiwalled carbon nanotube electrode and its applications to hydrogen peroxide and glucose detection*

2012 ◽  
Vol 84 (10) ◽  
pp. 2055-2063 ◽  
Author(s):  
Sujittra Poorahong ◽  
Chongdee Thammakhet ◽  
Panote Thavarungkul ◽  
Proespichaya Kanatharana
Keyword(s):  
Chemical Sensor ◽  
Limit Of Detection ◽  
High Surface ◽  
Volume Ratio ◽  
Deposition Process ◽  
Glucose Biosensor ◽  
Pani Film ◽  
Scanning Electron Micrographs ◽  
Multiwalled Carbon ◽  
Relative Standard

Vertically aligned polyaniline (PANI) structures were prepared by controlling the deposition current density during a stepwise template-free electrochemical deposition process of aniline on a glassy carbon electrode (GCE). Scanning electron micrographs (SEMs) showed the formation of cauliflower PANI structures, each with a diameter of approximately 2–3 and 10 μm in length. The cauliflower-like PANI electrode was modified with multiwalled carbon nanotubes (cauliflower PANI/MWCNTs) and used as the working electrode for electrochemical detections where H2O2 and glucose were used as the models for the chemical sensor and biosensor, respectively. The sensor provided linearity in the range of 1.0 to 150 μM of H2O2 with the limit of detection (LOD) of 50 nM. This is 100-fold better than the LOD of the bare GCE. Moreover, this sensor exhibited remarkable operational stability, i.e., 50 μM H2O2 could be analyzed up to 140 times with a 2.7 % relative standard deviation (RSD). A glucose biosensor was prepared using the modified cauliflower PANI/MWCNT electrode. This had a 3.4 times higher sensitivity than an electrode modified with PANI film/MWCNTs. The regular size and high surface-to-volume ratio of the cauliflower PANI electrode will provide good opportunities for further biosensor applications.

Design Analysis of a 3-D, Ultra-High Performance, Scalable, Micro Convective Heat Sink With NPCM

2003 ◽  
Author(s):  
Y.-X. Tao ◽  
R. Moreno ◽  
Y. Hao
Keyword(s):  
Phase Change ◽  
Heat Sink ◽  
High Performance ◽  
Phase Change Materials ◽  
High Surface ◽  
Volume Ratio ◽  
Cooling Capacity ◽  
System Level ◽  
Uniform Heat Flux ◽  
Order Of Magnitude

The paper proposes a new design of a scalable, heat sink containing 3-D micro/nano network, utilizing liquid mixed with nano phase change materials (NPCM) and having a high surface-to-volume ratio geometry. The conceptual design is capable of reaching 105 W/cm3 using encapsulated nano-size phase change materials, which would result in an order of magnitude higher cooling capacity than typical microchannel heat sink of the same volume and same pumping power. It is also scalable to submicron range, resulting even higher cooling capacity. An analysis for a working model (10 × 10 × 1 mm) is presented utilizing energy conservation principle and uniform temperature and uniform heat flux boundary conditions. The average phase change heat transfer coefficient is obtained using the numerical model results. A process of micro electrochemical deposition to fabricate the target model is illustrated, and the issues associated with system-level applications are discussed.

scholarly journals Steady state charge conduction through solution processed liquid crystalline lanthanide bisphthalocyanine films

2019 ◽  
Vol 23 (11n12) ◽  
pp. 1603-1615
Author(s):  
Chandana Pal ◽  
Isabelle Chambrier ◽  
Andrew N. Cammidge ◽  
A. K. Sharma ◽  
Asim K. Ray
Keyword(s):  
Metal Ions ◽  
Liquid Crystalline ◽  
Microscopy Study ◽  
Individual Characteristics ◽  
Central Metal ◽  
Force Microscopy ◽  
Atomic Force ◽  
Double Decker ◽  
Order Of Magnitude ◽  
Chain Lengths

In-plane electrical characteristics of non-peripherally octyl(C[Formula: see text]H[Formula: see text]- and hexyl(C[Formula: see text]H[Formula: see text]-substituted liquid crystalline (LC) double decker lanthanide bisphthalocyanine (LnPc[Formula: see text] complexes with central metal ions lutetium (Lu), and gadolinium (Gd) have been measured in thin film formulations on interdigitated gold (Au) electrodes for the applied voltage ([Formula: see text] range of [Formula: see text]. The conduction mechanism is found to be Ohmic within the bias of [Formula: see text] while the bulk limited Poole–Frenkel mechanism is responsible for the higher bias. The compounds show individual characteristics depending on the central metal ions, substituent chain lengths and their mesophases. Values of 67.55 [Formula: see text]cm[Formula: see text] and 42.31 [Formula: see text]cm[Formula: see text] have been obtained for room temperature in-plane Ohmic conductivity of as-deposited octyl lutetium (C[Formula: see text]LuPc[Formula: see text] and hexyl gadolinium (C[Formula: see text]GdPc[Formula: see text] films, respectively while C[Formula: see text]GdPc[Formula: see text] films exhibit nearly two orders of magnitude smaller conductivity. On annealing at 80[Formula: see text]C, Ohmic conductivities of C[Formula: see text]LuPc[Formula: see text] and C[Formula: see text]GdPc[Formula: see text] are found to have increased but the conductivity of C[Formula: see text]GdPc[Formula: see text] decreased by more than one order of magnitude to 1.5 [Formula: see text]cm[Formula: see text]. For physical interpretation of the charge transport behavior of these three molecules, their UV-vis optical absorption spectra in the solution and in as-deposited and annealed solid phases and atomic force microscopy study have been performed. It is believed that both orientation and positional reorganizations are responsible, depending upon the size of the central ion and side chain length.

Sign in / Sign up

Export Citation Format

Share Document