There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Fluorescent carbon nanoparticles or carbon quantum dots (CQDs) are a new class of carbon nanomaterials that have emerged recently and have garnered much interest as potential competitors to conventional semiconductor quantum dots. In addition to their comparable optical properties, CQDs have the desired advantages of low toxicity, environmental friendliness low cost and simple synthetic routes. Moreover, surface passivation and functionalization of CQDs allow for the control of their physicochemical properties. Since their discovery, CQDs have found many applications in the fields of chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis. This article reviews the progress in the research and development of CQDs with an emphasis on their synthesis, functionalization and technical applications along with some discussion on challenges and perspectives in this exciting and promising field.

Carbon quantum dots and their applications

The emerging graphene quantum dots (GQDs) and carbon dots (C-dots) have gained tremendous attention for their enormous potentials for biomedical applications, owing to their unique and tunable photoluminescence properties, exceptional physicochemical properties, high photostability, biocompatibility, and small size. This article aims to update the latest results in this rapidly evolving field and to provide critical insights to inspire more exciting developments. We comparatively review the properties and synthesis methods of these carbon nanodots and place emphasis on their biological (both fundamental and theranostic) applications.

Glowing Graphene Quantum Dots and Carbon Dots: Properties, Syntheses, and Biological Applications

Robust dynamic surface trajectory tracking control for a quadrotor UAV via extended state observer

Carbon quantum dots (CQDs) were synthesized by heating various carbon sources in HNO3 solution at reflux, and the effects of HNO3 concentration on the size of the CQDs were investigated. Furthermore, the oxygen-containing surface groups of as-prepared CQDs were selectively reduced by NaBH4 , leading to new surface states. The experimental results show that the sizes of CQDs can be tuned by HNO3 concentration and then influence their photoluminescent behaviors; the photoluminescent properties are related to both the size and surface state of the CQDs, but the photocatalytic activities are determined by surface states alone. The different oxygen-containing groups on the surface of the CQDs can induce different degrees of the band bending upward, which determine the separation and combination of the electron-hole pairs. The high upward band bending, which is induced by C=O and COOH groups, facilitates separation of the electron-hole pairs and then enhances high photocatalytic activity. In contrast, the low upward band bending induced by C-OH groups hardly prevents the electron-hole pairs from surface recombination and then exhibits strong photoluminescence. Therefore, both the photocatalytic activities and optical properties of CQDs can be tuned by their surface states.

Chemical regulation of carbon quantum dots from synthesis to photocatalytic activity.

We demonstrate a method for fabricating nanoparticles in a line at the top of silver wrinkled structures by tilting the substrate. The center of gravity of the colloidal droplets was moved backward, resulting in a small volume of droplets at the front of the colloidal droplet. The droplet rapidly evaporated, and the nanoparticles that remained formed lines of highly ordered nanoparticles. The distance between the nanoparticles changed after stretching the PDMS substrate due to the Poisson effect. An optimal plasma effect was achieved by controlling the distance between the nanoparticles. Finally, the Surface-Enhanced Raman Scattering (SERS) effects of CV and R6G molecules in water were determined, and the detection limit was 10−20 M. This method provides an extremely high sensitivity SERS substrate for the detection of biomolecules.

Ordered gold nanoparticle arrays on the tip of silver wrinkled structures for single molecule detection

Dual-optimization for a MEMS-INS/GPS system during GPS outages based on the cubature Kalman filter and neural networks

To improve the seamless navigation ability of an integrated Global Positioning System (GPS)/inertial navigation system in GPS-denied environments, a hybrid navigation strategy called the self-learning square-root- cubature Kalman filter (SL-SRCKF) is proposed in this article. The SL-SRCKF process contains two innovative steps: 1) it provides the traditional SRCKF with a self-learning ability, which means that navigation system observations can be provided continuously, even during long-term GPS outages; and 2) the relationship between the current Kalman filter gains and the optimal estimation error is established, which means that the optimal estimation accuracy can be improved by error compensation. The superiority of the proposed SL-SRCKF strategy is verified via experimental results and prominent advantages of this approach include: 1) the SL-SRCKF comprises two cycle filtering systems that work in a tightly coupled mode, and this allows more accurate error correction results to be obtained during GPS outages; 2) the system's error prediction ability is effectively improved by introducing a long short-term memory, which provides much better performance than other neural networks, such as random forest regression or the recursive neural network; and 3) under different (30, 60, and 100 s) GPS outage conditions, the long-term stability of SL-SRCKF is much better than that of other error correction approaches.

Jun Liu

Papers

Robust dynamic surface trajectory tracking control for a quadrotor UAV via extended state observer

Chemical regulation of carbon quantum dots from synthesis to photocatalytic activity.

Ordered gold nanoparticle arrays on the tip of silver wrinkled structures for single molecule detection

Dual-optimization for a MEMS-INS/GPS system during GPS outages based on the cubature Kalman filter and neural networks

Seamless GPS/Inertial Navigation System Based on Self-Learning Square-Root Cubature Kalman Filter