A Capacitive Ice-Sensor Based on Graphene Nano-Platelets Strips.

This paper investigates the possibility of realizing ice sensors based on the electrical response of thin strips made from pressed graphene nano-platelets. The novelty of this work resides in the use of the same graphene strips that can act as heating elements via the Joule effect, thus opening the route for a combined device able to both detect and remove ice. A planar capacitive sensor is designed and fabricated, in which the graphene strip acts as one of the armatures. The sensing principle is based on the high sensitivity of the planar capacitor to the change in electrical permittivity in the presence of ice, as shown in the experimental case study discussed here, can also be interpreted by means of a simple circuit and electromagnetic model. The properties of the sensor are analyzed, and the frequency range for its use as an ice detector has been established.

Graphene-based immunoassay for human lipocalin-2.

We have developed a highly sensitive immunoassay using graphene nano platelets (GNPs) for the rapid detection of human lipocalin-2 (LCN2) in plasma, serum, and whole blood. It has the dynamic range, linear range, limit of detection, and analytical sensitivity of 0.6 to 5120, 80 to 2560, 0.7, and 1pg/ml, respectively. It is the most sensitive assay for the detection of LCN2, which has 80-fold higher analytical sensitivity and 3-fold lesser immunoassay duration than the commercially available sandwich enzyme-linked immunosorbent assay (ELISA) kit. The functionalization of microtiter plate (MTP) with GNPs, dispersed in 3-aminopropyltriethoxysilane (APTES), provided the increased surface area that leads to higher immobilization density of capture antibodies. Moreover, the generation of free amino groups on MTP and GNPs by APTES enables the leach-proof covalent crosslinking of anti-human LCN2 capture antibody by its carboxyl groups using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) as the heterobifunctional crosslinker. The anti-LCN2 antibody-bound MTPs were highly stable given that they did not show any significant decrease in their functional activity when stored at 4°C in 0.1M phosphate-buffered saline (PBS) for 8weeks. The developed immunoassay correlated well with the conventional ELISA, thereby demonstrating its high precision and potential utility for highly sensitive analyte detection in industrial and clinical settings.

The effect of Co-encapsulated GNPs-CNTs nanofillers on mechanical properties, degradation and antibacterial behavior of Mg-based composite.

Magnesium (Mg)-based composites, as one group of the biodegradable materials, enjoy high biodegradability, biocompatibility, and non-toxicity making them a great option for implant applications. In this paper, by the semi powder metallurgy (SPM) technique, the graphene nano-platelets (GNPs) and carbon nanotubes (CNTs) nanosystems, as reinforcements, are dispersed homogenously in the Mg-Zn (MZ) alloy matrix. Subsequently, the composite is successfully produced employing the spark plasma sintering (SPS) process. Compared to the unreinforced MZ sample, GNPs + CNTs mixture reinforced composite exhibits higher compressive strength (∼75%). Notably, adding only 1 wt % of GNPs + CNTs to the MZ matrix reduces the rate of the degradation in the Mg-based composite by almost 2- fold. Examining the antibacterial activity demonstrate that the incorporation of GNPs + CNTs into the Mg-based matrix is likely to prevent the infiltration and development of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) significantly. While the MTT with 0.5 and 1 wt % GNPs + CNTs does not demonstrate cytotoxicity to the MG63 cells, the excessive GNPs + CNTs results in a certain degree of poisonousness. In general, the findings of the present research attest to the viable application of MZ/GNPs + CNTs composites for implants as well as bone infection treatment.

Screen-printed sensors for efficient potentiometric analysis of tolperisone hydrochloride in presence of its co-formulated drugs.

Researchers seeking for green chemistry to help safeguard and boost the economy and the environment by discovering unique ways to decrease waste and find substitutes for dangerous chemicals. In this study, a green potentiometric ion-selective electrode (ISE) was developed for measurement of tolperisone HCl (TOLP) in bulk and Pharmaceutical dosage forms in presence of diclofenac sodium and paracetamol as co-formulated drugs. This paper presents the manufacture and characterization of a disposable potentiometric ion-selective strip with an enhanced detection limit for (TOLP) measurement in its tablet dosage form either alone or in presence of the co-formulated drugs. Numerous ion pairs (IPs), such as TOLP-tetraphenylborate (TOLP-TPB), TOLP-phosphotungstic acid (TOLP-PTA), and TOLP-ammonium Reinecke (TOLP- RKT) are tested in presence of different plasticizers. The optimal potentiometric response with a near Nernstian slope of 55.949 mV/decade was achieved within a linear concentration range of 5 [Formula: see text] 10-5 - 1 [Formula: see text] 10-2 M using (PTA) and ortho nitrophenyl octyl ether (o-NPOE) as a plasticizer. The effect of the nanoparticles on the membrane stability was studied using the graphene nanoplatelets which have an effective role in the enhancement of some constructed sensors stability. Finally, the developed technique is validated for the estimation of TOLP with high accuracy and precision.

On the Multi-Functional Behavior of Graphene-Based Nano-Reinforced Polymers.

The objective of the present study is the assessment of the impact performance and the concluded thermal conductivity of epoxy resin reinforced by layered Graphene Nano-Platelets (GNPs). The two types of used GNPs have different average thicknesses, <4 nm for Type 1 and 9-12 nm for Type 2. Graphene-based polymers containing different GNP loading contents (0.5, 1, 5, 10, 15 wt.%) were developed by using the three-roll mill technique. Thermo-mechanical (Tg), impact tests and thermal conductivity measurements were performed to evaluate the effect of GNPs content and type on the final properties of nano-reinforced polymers. According to the results, thinner GNPs were proven to be more promising in all studied properties when compared to thicker GNPs of the same weight content. More specifically, the glass transition temperature of nano-reinforced polymers remained almost unaffected by the GNPs inclusion. Regarding the impact tests, it was found that the impact resistance of the doped materials increased up to 50% when 0.5 wt.% Type 1 GNPs were incorporated within the polymer. Finally, the thermal conductivity of doped polymers with 15 wt.% GNPs showed a 130% enhancement over the reference material.

Investigation of the Impact of Graphene Nanoplatelets (GnP) on the Bond Stress of High-Performance Concrete Using Pullout Testing.

Efficient load transmission between concrete and steel reinforcement by bonding action is a key factor in the process of the design procedure of bar-reinforced concrete structures. To enhance the bond strength of steel/concrete composites, the impact of graphene nanoplatelets (GnP) on the bond stress and bond stress-slip response of deformed reinforcement bars, embedded in high-performance concrete (HPC), was investigated using bar pullout tests. In the current study, 36 samples were produced and examined. The main variables were the percentages of GnP, the steel reinforcement bar diameter, and embedded length. Bond behavior, failure mode, and bond stress-slip response were studied. Based on the experimental findings, the inclusion of GnP had a significant favorable influence on the bar-matrix interactions due to the bridging action of GnP as a nano reinforcement. For 0.02 wt.% of GnP, the bond strength was enhanced by more than 41.28% and 53.90% for steel bar diameters of 10 and 16 mm, respectively. The HPC-GnP mixture displayed a reduction in the initial slippage in comparison to the control sample. The test findings were compared to the prediction models created by other researchers and the ACI 408R-12 code.

Transmittance and Reflectance Effects during Thermal Diffusivity Measurements of GNP Samples with the Flash Method.

Thermal diffusivity of GNPs (graphene nano-platelets) is an important thermo-physical property as it is useful to predict the material behavior in many heat transfer applications. GNP samples were pressed at different loads to obtain different densities, and then thermal diffusivity was measured with the flash method. All samples were coated with a thin layer (~1 µm) of colloidal graphite (Aquadag®) on both sides to reduce reflectance of their surfaces and consequently increase the emissivity. Carrying out measurements on both samples with and without coating, a difference between the two series of measurements was found: This is attributed to a non-negligible transmittance of the uncoated samples due to the porosity of GNPs. Furthermore, assuming a spatial distribution of the light within the samples according to the Lambert-Bougert-Beer law, the extinction coefficient of GNP at different densities has been evaluated processing experimental data with a nonlinear least square regression, (NL-LSF, nonlinear least square fitting), whose model contains the extinction coefficient as unknown. The proposed method represents a further improvement of thermal diffusivity data processing, crucial to calculate the extinction coefficient when data with and without coating are available; or to correct biased thermal diffusivity data when the extinction coefficient is already known. Moreover, reflectance effects have been highlighted comparing asymptotic temperature reached during the tests on coated and uncoated samples at different densities. In fact, the decrease of asymptotic temperature of the uncoated samples gives the percentage of the light reflected and consequently an estimate of the reflectance of the GNP surface.

Thermal and Mechanical Behavior of Wood Plastic Composites by Addition of Graphene Nanoplatelets.

Wood plastic composites (WPCs) incorporating graphene nano-platelets (GNPs) were fabricated using hot-pressed technology to enhance thermal and mechanical behavior. The influences of thermal filler content and temperature on the thermal performance of the modified WPCs were investigated. The results showed that the thermal conductivity of the composites increased significantly with the increase of GNPs fillers, but decreased with the increase of temperature. Moreover, thermogravimetric analysis demonstrated that coupling GNPs resulted in better thermal stability of the WPCs. The limiting oxygen index test also showed that addition of GNPs caused good fire retardancy in WPCs. Incorporation of GNPs also led to an improvement in mechanical properties as compared to neat WPCs. Through a series of mechanical performance tests, it could be concluded that the flexural and tensile moduli of WPCs were improved with the increase of the content of fillers.

Physical properties of carboxymethyl cellulose based nano-biocomposites with Graphene nano-platelets.

Carboxymethyl cellulose (CMC) based bio-nanocomposite filled with graphene nano-platelets (GNPs) was prepared using casting technique. The morphology, thermal, light barrier, water vapor permeability (WVP), contact angle, moisture absorption and mechanical properties of the resulted bio-nanocomposites were investigated. The results indicated with addition of 0.5% w/w GNPs to polymer matrix, ultimate tensile strength (UTS) decreased from 7.74 MPa (in the pure film) to 5.69 MPa however, strain to break (SB) increased from 12.49% to 19.87%. The GNPs caused to reducing of light transmission and increasing of the water repelling nature of nano-biocomposites. However, it had not effect on melting point of CMC based nano-biocomposites.