Graphene as an Electron Shuttle for Silver Deoxidation: Removing a Key Barrier to Plasmonics and Metamaterials for SERS in the Visible

The role of graphene in enabling deoxidation of silver nanostructures, thereby contributing to enhance plasmonic properties and to improve the temporal stability of graphene/silver hybrids for both general plasmonic and meta‐materials applications, as well as for surface enhanced Raman scattering (SERS) substrates, is demonstrated. The chemical mechanism occurring at the graphene–silver oxide interface is based on the reduction of silver oxide triggered by graphene that acts as a shuttle of electrons and as a kind of catalyst in the deoxidation. A mechanism is formulated, combining elements of electron transfer, role of defects in graphene, and electrochemical potentials of graphene, silver, and oxygen. Therefore, the formulated model represents a step forward from the simple view of graphene as barrier to oxygen diffusion proposed so far in literature. Single layer graphene grown by chemical vapor deposition is transferred onto silver thin films, a periodic silver fishnet structure fabricated by nanoimprint lithography, and onto silver nanoparticle ensembles supporting a localized surface plasmon resonance in the visible range. Through the study of these nanostructured graphene/Ag hybrids, the effectiveness of graphene in preventing and reducing oxidation of silver plasmonic structures, keeping silver in a metallic state over months at air exposure, is demonstrated. The enhanced and stable plasmonic properties of the silver‐fishnet/graphene hybrids are evaluated through their SERS response for detecting benzyl mercaptane.     

Microstructure of shear-induced thixoformed Al-4.5Cu-1.5Mg alloy via RAP and SSTT processes

In this research, the effect of the thixoforming temperature on the microstructure and mechanical properties was investigated in the thixoforming of the feedstock produced by the RAP(recrystallization and partial melting) and SSTT(semi-solid thermal transformation) processes for Al-4.5Cu-1.5Mg alloy. In the RAP process, the percentage reduction in area was approximately 35%. Thixoforming was done at 610, 620, and 630 °C. Globular microstructure was observed at all temperatures and conditions. The minimum average globule size was 39 μm, and it was obtained in the thixoforming of the feedstock produced by the RAP process in the section of 4 mm in diameter at 620 ° C after applying shear. Its corresponding compressive strength was-877.44 MPa. The maximum average globule size was 136 μm, and it was obtained in the thixoforming of the feedstock produced by the SSTT process in the section of 10 mm in diameter at 630 °C before applying shear. Its corresponding compressive strength was-769.18 MPa. The finest and most spherical globules, as well as the highest compressive strength were obtained at 620 °C in both RAP and SSTT states.     

Direct and Residual Effects of Water Deficit Stress,Different Sources of Silicon and Plant-Growth Promoting Bacteria on Silicon Fractions in the Soil

Silicon - Silicon (Si) and plant growth promoting bacteria (PGPB) can effectively reduce the negative effects of water deficit stress and augment plant growth. Few studies have simultaneously...     

Robotic date fruit harvesting using machine vision and a 5-DOF manipulator

Date fruits can be found at the highest point of the palm tree, so harvesting can be a dangerous task for humans. In this study, a robotic arm is presented to harvest date fruits. A manipulator, traveling on a U-shaped rail with four prismatic joints and one revolute joint, was designed and constructed to approach the fruits efficiently. The end-effector of the manipulator was an electric chainsaw capable of cutting the date bunch. Two cameras were located on the manipulator in perpendicular directions to capture images, which were then transmitted to a decision-making unit to control the speed of the manipulator links. The decision-making unit included three fuzzy inference systems that used the location data of the fruit bunch stems and the area of tree leaves in the images to determine the speed of electromotors of the trolley, horizontal link, and vertical link. An artificial palm tree with dimensions similar to a real palm tree was constructed to evaluate the performance of the robot. The performance of the robot was evaluated in various lighting conditions. The results showed that the introduced image processing algorithm could adequately detect the stems of the date bunches with accuracy, precision, and recall of 0.88, 0.92, and 0.96, respectively, in suitable lighting, that is, when there was sufficient natural lighting. Moreover, the experimental results revealed that the accuracy of the control system in cutting the stems was 87%, with a production loss of 5%. The proposed robot makes it possible to improve the capacity of using mechanized harvesting in date palm fields.     

Correction to: Direct and Residual Effects of Water Deficit Stress,Different Sources of Silicon and Plant-Growth Promoting Bacteria on Silicon Fractions in the Soil

Silicon - A Correction to this paper has been published: https://doi.org/10.1007/s12633-021-01161-w