A New Method for Measuring the Rotational Angles of a Precision Spherical Joint Using Eddy Current Sensors.

Precision spherical joint is a spherical motion pair that can realize rotation with three degrees of freedom. This joint is widely used in robots, parallel mechanisms, and high-end medical equipment, as well as in aerospace and other fields. However, the rotation orientation and angle cannot be determined when the joint is in passive motion. The real-time determination of the rotation orientation and angle is crucial to the improvement of the motion control accuracy of the equipment where the joint is installed in. In this study, a new measurement method that utilizes eddy current sensors is proposed to identify the special features of the joint ball and realize angle measurements indirectly. The basic idea is to manufacture the specific shape features on the ball without affecting its movement accuracy and mechanical performance. An eddy current sensor array is distributed in the ball socket. When the ball head rotates, the features on the ball opposite to the sensor, as well as the output signal of every eddy current sensor, change. The measurement model that establishes the relationship between the output signal of the eddy current sensor array and the rotation direction and angle of the ball head is constructed by learning and training an artificial neural network. A prototype is developed using the proposed scheme, and the model simulation and feasibility experiment are subsequently performed. Results show that the root mean square angular error of a single axis within a range of ±14° is approximately 20 min, which suggests the feasibility of the proposed method.

Drift Reduction of a 4-DOF Measurement System Caused by Unstable Air Refractive Index.

Laser beam drift greatly influences the accuracy of a four degrees of freedom (4-DOF) measurement system during the detection of machine tool errors, especially for long-distance measurement. A novel method was proposed using bellows to serve as a laser beam shield and air pumps to stabilize the refractive index of air. The inner diameter of the bellows and the control mode of the pumps were optimized through theoretical analysis and simulation. An experimental setup was established to verify the feasibility of the method under the temperature interference condition. The results indicated that the position stability of the laser beam spot can be improved by more than 79% under the action of pumping and inflating. The proposed scheme provides a cost-effective method to reduce the laser beam drift, which can be applied to improve the detection accuracy of a 4-DOF measurement system.

Photoelectrochemical aptasensor for sulfadimethoxine using g-C3N4 quantum dots modified with reduced graphene oxide.

A novel photoelectrochemical (PEC) aptasensor with graphitic-phase carbon nitride quantum dots (g-C3N4; QDs) and reduced graphene oxide (rGO) was fabricated. The g-C3N4 QDs possess enhanced emission quantum yield (with an emission peak at 450 nm), improved charge separation ability and effective optical absorption, while rGO has excellent electron transfer capability. Altogether, this results in improved PEC performance. The method is making use of an aptamer against sulfadimethoxine (SDM) that was immobilized on electrode through π stacking interaction. Changes of the photocurrent occur because SDM as a photogenerated hole acceptor can further accelerate the separation of photoexcited carriers. Under optimized conditions and at an applied potential of +0.2 V, the aptasensor has a linear response in the 0.5 nM to 80 nM SDM concentration range, with a 0.1 nM detection limit (at S/N = 3). The method was successfully applied to the analysis of SDM in tap, lake and waste water samples. Graphical abstract Graphitic-phase carbon nitride (g-C3N4) quantum dots (QDs) and reduced graphene oxide (rGO) were used to modify fluorine-doped SnO2 (FTO) electrodes for use in a photoelectrochemical (PEC) aptasensor. SDM oxidized by the hole on valance band (VB) of g-C3N4 QDs promote the separation of electron in the conductive band (CB), which made the changes of photocurrent signal.

Bioprotective Respirator Assembled by Defective Carbon Nitride for Long-Term Light Triggered Health Protection.

Wearing face masks is the best way to stop the spread of respiratory infections. However, if masks are not sterilized, changing them too frequently can actually increase the risk of cross-contamination. Herein, the construction of an antipathogen photocatalytic mask with carbon vacancy-modified carbon nitride nanosheets (g-C3N4-VC Ns) coated on the non-woven fabrics of the out layer of the mask, offering effective and long-term protection against damaging pathogens when exposed to light is reported. The introduced carbon vacancies are found capable of creating energy-disordered sites and inducing energetic electric force to overcome the Coulomb interactions between electron-hole pairs, thus promoting the electron-hole separation to achieve a high generation of reactive oxygen species (ROS). Thanks to its high activity in generating ROS upon exposure to light, the as-prepared photocatalytic mask shows high pathogen sterilization performance. This, in turn, prolongs the mask's protective lifetime, decreases the need for regular replacement, and decreases medical waste production. The work demonstrated here opens new viewpoints in designing pathogens biocidal protective devices for health protection, offering significant promise in specific environment self-protection.

Adsorption performance and its mechanism of aqueous As(III) on polyporous calcined oyster shell-supported Fe-Mn binary oxide.

Fe-Mn binary oxide (FMBO) is a promising adsorbent for As(III) removal through combined adsorption and oxidation. The calcined oyster shell-supported Fe-Mn binary oxide (FMBO/OS) adsorbent was synthesized by the co-precipitation method. Results indicated that the calcined oyster shell, as a carrier, improved the stability of FMBO and its adsorption capacity for As(III). The maximum adsorption capacity of FMBO/OS on As(III) reached 140.5 mg·g-1 . Under pH 5.0 and 25°C, the removal efficiency of FMBO/OS to As(III) solution (C0 = 10 mg·L-1 ) reached 87% within 12 h. Moreover, based on the characterization analyses, the removal mechanisms of As(III) were deduced to include the combined adsorption and oxidation process of FMBO and the synergistic effect of oyster shells. This work provides new insights into synthesizing efficient and green adsorbents to remove aqueous As(III). Meanwhile, it provides technical support for reusing waste biomass materials such as the oyster shell. PRACTITIONER POINTS: FMBO/OS was prepared by a simple hydrothermal co-precipitation method. The carrier alleviates the agglomeration of Fe-Mn oxides. The adsorbent shows a strong adsorption capacity of As(III) and good selectivity. The good results benefit from the synergistic effect of calcium arsenate generation. The prepared adsorbent can adsorb arsenic in real samples.

3D V2O5-MoS2/rGO nanocomposites with enhanced peroxidase mimicking activity for sensitive colorimetric determination of H2O2 and glucose.

In this work, we reported a novel nanozyme (3D V2O5-MoS2/rGO) by decorating MoS2 nano-flowers and V2O5 nanoparticles on reduced graphene oxide (rGO). The 3D V2O5-MoS2/rGO nanocomposites exhibited intrinsic peroxidase mimicking activity and catalyzed the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) to produce a blue colored product in the presence of H2O2. Compared with horseradish peroxidase (HRP), 3D V2O5-MoS2/rGO nanocomposites displayed high catalytic velocity (Vmax) and affinity (Km) for substrates (H2O2 and TMB). The study of the catalytic mechanism showed that the reduction of V5+ and the oxidation of S2- in the 3D V2O5-MoS2/rGO nanocomposites accelerate electron transfer between H2O2 and TMB, which enhanced the peroxidase mimicking activity of 3D V2O5-MoS2/rGO nanocomposites. The as-synthetized 3D V2O5-MoS2/rGO could be used for the colorimetric detection of H2O2 in the range of 20.00-800.00 µM with the LOD of 12.40 µM (3σ/S). Moreover, the 3D V2O5-MoS2/rGO could also be used for the detection of glucose in the range of 4.00-300.00 µM with the LOD of 3.99 µM (3σ/S). In addition, the as-synthetized novel peroxidase mimics has good applicability for sensitive colorimetric determination of glucose in human blood samples and artificial urine samples, and has broad application prospects as a multi-functional sensing platform in clinical diagnosis.

Bimetallic Fe/Mn metal-organic-frameworks and Au nanoparticles anchored carbon nanotubes as a peroxidase-like detection platform with increased active sites and enhanced electron transfer.

A hybrid of metal-organic frameworks (Fe, Mn) and Au nanoparticles anchored carbon nanotubes (Au/MOFs(Fe, Mn)/CNTs) was fabricated by a facile one-step hydrothermal process. The Au/MOFs(Fe, Mn)/CNTs exhibit highly enhanced peroxidase-like activity, because of the increased active sites, the enhanced partial charge density and electron transfer among the Fermi level of MOFs, Au and CNTs, as well as the synergistic action of Fe and Mn. The hybrid nanomaterials with high catalytic velocity (Vmax = 17.65 × 10-7 M s-1) and affinity (Km = 0.33 mM) for substrates of H2O2 display a great detection performance in the range of 0.34-53.05 nM with a limit of detection (LOD) of 0.18 nM (S/N = 3). Based on the cascade reaction of the artificial peroxidase and glucose oxidase (GOx), the glucose was further better detected in a linear range of 0.005-0.3 µM with a LOD of 0.002 µM (S/N = 3). Notably, considering the regulated peroxidase-like activity by sulfadimethoxine (SDM) aptamer, the concentration of SDM ranging from 0.54 to 41.58 µg L-1 was also detected with a LOD of 0.35 µg L-1 (S/N = 3). The as-synthesized hybrid nanozymes hold promising applications as the multifunctional sensing platform in environmental and biologic target detection with the combination of corresponding enzyme or specific aptamer.