A Novel Nanocomposite of Zn(II)-Protoporphyrin-Chitosan-Multi Walled Carbon Nanotubes and the Application to Caffeic Acid Sensing

Caffeic acid is an antioxidant that has been widely been related to the health benefits of people in recent years. In this paper, the amino side chains of chitosan (CS) were modified with protoporphyrin IX by amide cross-linking, and then Zn ions were chelated. The properties of metalloporphyrin-preparing functionalized multi-walled carbon nanotubes (MWCNTs) and Zn ions chelated by protoporphyrin IX composites were used as sensitive-selective electrochemical biosensors for the determination of caffeic acid. The morphology and structure of nanocomposite Zn–PPIX–CS–MWCNTs were observed by X-ray spectroscopy mapping (EDX mapping), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). The electrochemical behaviors of Zn–PPIX–CS–MWCNT-modified glassy carbon (GC) electrodes were evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results show that the modified electrode had good electrocatalytic activity towards caffeic acid with a wide linear range of 0.0008–1.6 mM, an excellent sensitivity of 886.90 µAmM−1cm−1, and a detection limit of 0.022 µM. In addition, the caffeic acid sensor had excellent reproducibility, stability, and selectivity to various interfering substances. Therefore, the modified electrode prepared by this experiment can also be applied to electrochemical sensors of other substances

Dynamics Modeling of a Delta Robot with Telescopic Rod for Torque Feedforward Control

This paper presents dynamics modeling of a Delta robot with three revolute legs and a telescopic rod. Firstly, two generalized coordinate systems are established to describe the relationship between the movement of the telescopic rod and the position of the moving platform, and the telescopic rod system kinematics are established through singularity analysis. Secondly, taking the telescopic rod as the research object, the corresponding dynamics model is established using the Euler–Lagrange method. Moreover, this paper proposes a method to convert the force exerted by the telescopic rod motion on the moving platform into actuator torques. Thirdly, the dynamics model of the Delta robot with a telescopic rod is established, and numerical simulations are performed to demonstrate this approach. Finally, the influence of the telescopic rod on the actuator torques is verified using an experiment. A comparison is drawn between the two dynamics models used in torque feedforward control to validate the proposed dynamics model

Dynamics Modeling of a Delta Robot with Telescopic Rod for Torque Feedforward Control

This paper presents dynamics modeling of a Delta robot with three revolute legs and a telescopic rod. Firstly, two generalized coordinate systems are established to describe the relationship between the movement of the telescopic rod and the position of the moving platform, and the telescopic rod system kinematics are established through singularity analysis. Secondly, taking the telescopic rod as the research object, the corresponding dynamics model is established using the Euler–Lagrange method. Moreover, this paper proposes a method to convert the force exerted by the telescopic rod motion on the moving platform into actuator torques. Thirdly, the dynamics model of the Delta robot with a telescopic rod is established, and numerical simulations are performed to demonstrate this approach. Finally, the influence of the telescopic rod on the actuator torques is verified using an experiment. A comparison is drawn between the two dynamics models used in torque feedforward control to validate the proposed dynamics model

Electrochemical Detection for Uric Acid Based on β-Lactoglobulin-Functionalized Multiwall Carbon Nanotubes Synthesis with PtNPs Nanocomposite

In this work, a simple and highly selective electrochemical biosensor for determination of uric acid (UA) is synthesized by using β-lactoglobulin (BLG)-functionalized multiwall carbon nanotubes (MWCNTs) and a platinum nanoparticles (PtNPs) nanocomposite. Urate oxidase (UOx) can oxidize uric acid to hydrogen peroxide and allantoin, which provides a good opportunity for electrochemical detection for UA. Under the optimized conditions, the current changes by the UOx/Bull Serum Albumin (BSA)/BLG-MWCNTs-PtNPs/Glassy Carbon (GC) electrode with the electrochemical method was proportional to the concentration of UA. According to experiments, we obtained a linear response with a concentration range from 0.02 to 0.5 mM and achieved a high sensitivity of 31.131 μA mM−1 and a low detection limit (0.8 μΜ). Meanwhile, nanoparticles improved the performance of the biosensor and combined with BLG not only prevented the accumulation of composite nanomaterials, but also provided immobilization of uricase through electrostatic adsorption. This improves the stability and gives the constructed electrode sensing interface superior performance in UA detection

Facile Synthesis of β-Lactoglobulin-Functionalized Reduced Graphene Oxide and Trimetallic PtAuPd Nanocomposite for Electrochemical Sensing

The use of graphene has leapt forward the materials field and the functional modification of graphene has not stopped. In this work, β-lactoglobulin (BLG) was used to functionalize reduced graphene oxide (RGO) based on its amphiphilic properties. Also, trimetallic PtAuPd nanoparticles were reduced to the surface of BLG-functionalized RGO and formed BLG-PtAuPd-RGO nanocomposite using facile synthesis. Transmission electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectra were used to characterize the nanocomposite. Electrocatalytic analysis was evaluated through cyclic voltammetry and chronoamperometry methods. We developed a glucose sensor by fabricating GOD-BLG-PtAuPd-RGO/glassy carbon (GC) electrode. It presented a remarkable sensitivity of 63.29 μA mM−1 cm−2 (4.43 μA mM−1), a wider linear range from 0.005 to 9 mM and a lower detection limit of 0.13 μM (S/N = 3). Additionally, the glucose sensor exhibited excellent testing capability in human serum samples

A Label-free Electrochemical Immunosensor Based on Gold Nanoparticles-poly(ferriporphyrin-co-acrylamide)-reduced Graphene Oxide and the Application in Prostate Specific Antigen Detection

Prostate specific antigen (PSA), as a biomarker, plays important roles in early diagnosis of male prostate diseases, especially prostate cancer. In this study, a novel electrochemical probe polymer of poly(ferriporphyrin-co-acrylamide) was synthesized, by further combined with reduced graphene oxide and gold nanoparticles, and oriented immobilization of PSA antibody, a label-free electrochemical immunosensor was obtained, and then successfully applied in the determination of PSA in 10 % non-antigen serum system. The prepared biosensor expressed high selectivity toward PSA, with a LOD of 0.001 ng mL−1, a linear range of 0.01–110 ng mL−1, and a sensitivity of 15.78 µA mL ng−1. What’s more, it showed good stability, well repeatability and high selectivity in the real PSA sample detection. This work provided certain references for the design of the new electrochemical probes and the detection of tumor markers