An electrochemical DNAzyme sensor for sensitive and selective detection of lead ion (Pb(2+)) has been developed, taking advantage of catalytic reactions of a DNAzyme upon its binding to Pb(2+) and the use of DNA-Au bio-bar codes to achieve signal enhancement. A specific DNAzyme for Pb(2+) is immobilized onto an Au electrode surface via a thiol-Au interaction. The DNAzyme hybridizes to a specially designed complementary substrate strand that has an overhang, which in turn hybridizes to the DNA-Au bio-bar code (short oligonucleotides attached to 13 nm gold nanoparticles). A redox mediator, Ru(NH3)6(3+), which can bind to the anionic phosphate of DNA through electrostatic interactions, serves as the electrochemical signal transducer. Upon binding of Pb(2+) to the DNAzyme, the DNAzyme catalyzes the hydrolytic cleavage of the substrate, resulting in the removal of the substrate strand along with the DNA bio-bar code and the bound Ru(NH3)6(3+) from the Au electrode surface. The release of Ru(NH3)6(3+) results in lower electrochemical signal of Ru(NH3)6(3+) confined on the electrode surface. Differential pulse voltammetry (DPV) signals of Ru(NH3)6(3+) provides quantitative measures of the concentrations of Pb(2+), with a linear calibration ranging from 5 nM to 0.1 microM. Because each nanoparticle carries a large number of DNA strands that bind to the signal transducer molecule Ru(NH3)6(3+), the use of DNA-Au bio-bar codes enhances the detection sensitivity by five times, enabling the detection of Pb(2+) at a very low level (1 nM). The DPV signal response of the DNAzyme sensor is negligible for other divalent metal ions, indicating that the sensor is highly selective for Pb(2+). Although this DNAzyme sensor is demonstrated for the detection of Pb(2+), it has the potential to serve as a general platform for design sensors for other small molecules and heavy metal ions.

Recent progress in artificial nanomachines offers promising solutions to grand challenges in biochemical delivery and diagnostics. In this work, advances of micro/nanomachines made of synthesized micro/nanostructures for applications in delivery and detection of biomolecules are reviewed, along with a discussion of pros and cons of each type of machine. The review of micro/nanomachines is categorized according to their working mechanisms, including motion actuation realized by magnetic, electric, and acoustic fields and chemical reactions. The developments of micro/nanomachines are discussed in depth in the fabrication, propulsion, and motion control, loading and releasing of micro/nano-substances, and biochemical sensing. The rapid development of man-made miniaturized machines paves the road towards future intelligent nanorobots and nanofactories that could revolutionize society.

Keeping up: The fastest kinetic data for ion transfer at a liquid/liquid interface were evaluated by nanopipette voltammetry. The steady‐state voltammograms can be explained by theoretical models. In previous electrochemical measurements the systematic underestimation of k0 is probably a result of inefficient mass transfer to the relatively large interface.

The modification of glass nanopipettes with polyethyleneimines (PEIs) has been successfully achieved by a relatively simple method, and the smallest tip opening is around 3 nm. Thus, in a much wider range of glass pipettes with radii from several nanometers to a few micrometers, the ion current rectification (ICR) phenomenon has been observed. The influences of different KCl concentrations, pH values, and tip radii on the ICR are investigated in detail. The sizes of PEIs have been determined by dynamic light scattering, and the effect of the sizes of PEIs for the modification, especially for a few nanometer-pipettes in radii, is also discussed. These findings systemically confirm and complement the theoretical model and provide a platform for possible selectively molecular detection and mimic biological ion channels.

The development rotary nanomotors is an essential step towards intelligent nanomachines and nanorobots. In this article, we review the concept, design, working mechanisms, and applications of the state-of-the-art rotary nanomotors made from synthetic nanoentities. The rotary nanomotors are categorized according to the energy sources employed to drive the rotary motion, including biochemical, optical, magnetic, and electric fields. The unique advantages and limitations for each type of rotary nanomachines are discussed. The advances of rotary nanomotors is pivotal for realizing dream nanomachines for myriad applications including microfluidics, biodiagnosis, nano-surgery, and biosubstance delivery.

Sharp practice: A water/n‐octanol interface can be formed at the tip of a very short and sharp nanopipette, and can be polarized externally (see picture). This interface has been used to investigate various ion‐transfer processes and evaluate partition coefficients for ionizable species.

A widely applicable mechanism that facilely enables semicondutor micro/nanodevices with multifold mechanical reconfigurability.

SummaryA novel and simple strategy for the efficient synthesis of the corresponding tetrahydroquinolines from N,N-dimethylanilines and maleimides using visible light in an air atmosphere in the presence of Eosin Y as a photocatalyst has been developed. The metal-free protocol involves aerobic oxidative cyclization via sp3 C–H bond functionalization process to afford good yields in a one-pot procedure under mild conditions.