With digital equipment becoming increasingly networked, either on wired or wireless networks, for personal and professional use alike, distributed software systems have become a crucial element in information and communications technologies. The study of these systems forms the core of the ARLES' work, which is specifically concerned with defining new system software architectures, based on the use of emerging networking technologies. In this context, we concentrate on the study of distributed systems which bring to life the vision of ubiquitous computing systems, also known as ambient intelligence.

반도체 공정 overview

Carbon dots: synthesis, formation mechanism, fluorescence origin and sensing applications

Two-dimensional (2D) nanostructures are highly attractive for fabricating nanodevices due to their high surface-to-volume ratio and good compatibility with device design. In recent years 2D nanostructures of various materials including metal oxides, graphene, metal dichalcogenides, phosphorene, BN and MXenes, have demonstrated significant potential for gas sensors. This review aims to provide the most recent advancements in utilization of various 2D nanomaterials for gas sensing. The common methods for the preparation of 2D nanostructures are briefly summarized first. The focus is then placed on the sensing performances provided by devices integrating 2D nanostructures. Strategies for optimizing the sensing features are also discussed. By combining both the experimental results and the theoretical studies available, structure-properties correlations are discussed. The conclusion gives some perspectives on the open challenges and future prospects for engineering advanced 2D nanostructures for high-performance gas sensors devices.

Two-Dimensional Nanostructured Materials for Gas Sensing

Truly fluorescent excitation-dependent carbon dots are prepared, and the relationship between their chemical composition and fluorescent emission is discussed. Furthermore, potential applications of the as-prepared carbon dots to multicolor bio-labeling and multidimodal sensing are demonstrated.

Truly Fluorescent Excitation-Dependent Carbon Dots and Their Applications in Multicolor Cellular Imaging and Multidimensional Sensing

Sulfur-doped carbon dots (S-doped C-dots)were synthesized using a simple and straightforward hydrothermal method. The as-prepared S-doped C-dots exhibit significant fluorescence quantum yield (67%) and unique emission behavior. The spherical S-doped C-dots have an average diameter of 4.6 nm and the fluorescence of S-doped C-dots can be effectively and selectively quenched by Fe3+ ions. Thus, S-doped C-dots were applied as probes toward Fe3+ detection, exhibiting a limit of detection of 0.1 μM.

Preparation of highly photoluminescent sulfur-doped carbon dots for Fe(III) detection

Graphene-based gas/vapor sensors have attracted much attention in recent years due to their variety of structures, unique sensing performances, room-temperature working conditions, and tremendous application prospects, etc. Herein, we summarize recent advantages in graphene preparation, sensor construction, and sensing properties of various graphene-based gas/vapor sensors, such as NH3, NO2, H2, CO, SO2, H2S, as well as vapor of volatile organic compounds. The detection mechanisms pertaining to various gases are also discussed. In conclusion part, some existing problems which may hinder the sensor applications are presented. Several possible methods to solve these problems are proposed, for example, conceived solutions, hybrid nanostructures, multiple sensor arrays, and new recognition algorithm.

/pdf/a-review-on-graphene-based-gas-vapor-sensors-with-unique-3yvc87wwd5.pdf

A Review on Graphene-Based Gas/Vapor Sensors with Unique Properties and Potential Applications

Compared with traditional semiconductor quantum dots (QDs) and organic dyes, photoluminescent carbon dots (CDs) are superior because of their high aqueous solubility, robust chemical inertness, facile functionalization, high resistance to photobleaching, low toxicity and good biocompatibility. Herein, a green, large-scale and high-output heterogeneous synthesis of N-doped CDs was developed by reacting calcium citrate and urea under microwave irradiation without the use of any capping agents. The obtained N-doped CDs with a uniform size distribution exhibit good aqueous solubility and yellowish-green fluorescence in the solid and aqueous states. These unique luminescence properties of N-doped CDs inspire new thoughts for applications as fluorescent powders, fluorescent inks, the growth of fluorescent bean sprouts, and fingerprint detection tools.

http://yfzhang.sjtu.edu.cn/en/publications/2014/3.pdf

A green heterogeneous synthesis of N-doped carbon dots and their photoluminescence applications in solid and aqueous states.

Molybdenum disulfide (MoS2), as a promising gas-sensing material, has gained intense interest because of its large surface-to-volume ratio, air stability, and various active sites for functionalization. However, MoS2-based gas sensors still suffer from low sensitivity, slow response, and weak recovery at room temperature, especially for NO2. Fabrication of heterostructures may be an effective way to modulate the intrinsic electronic properties of MoS2 nanosheets (NSs), thereby achieving high sensitivity and excellent recovery properties. In this work, we design a novel p-n hetero-nanostructure on MoS2 NSs using interface engineering via a simple wet chemical method. After surface modification with zinc oxide nanoparticles (ZnO NPs), the MoS2/ZnO hetero-nanostructure is endowed with an excellent response (5 ppm nitrogen dioxide, 3050%), which is 11 times greater than that of pure MoS2 NSs. To the best of our knowledge, such a response value is much higher than the response values reported for MoS2 gas sensors. Moreover, the fabricated hetero-nanostructure also improves recoverability to more than 90%, which is rare for room-temperature gas sensors. Our optimal sensor also possesses the characteristics of an ultrafast response time of 40 s, a reliable long-term stability within 10 weeks, an excellent selectivity, and a low detection concentration of 50 ppb. The enhanced sensing performances of the MoS2/ZnO hetero-nanostructure can be ascribed to unique 2D/0D hetero-nanostructures, synergistic effects, and p-n heterojunctions between ZnO NPs and MoS2 NSs. Such achievements of MoS2/ZnO hetero-nanostructure sensors imply that it is possible to use this novel nanostructure in ultrasensitive sensor applications.

Design of Hetero-Nanostructures on MoS2 Nanosheets To Boost NO2 Room-Temperature Sensing.

In this work, SnO2 nanoparticles with Ni doping were synthesized via a facile one-step hydrothermal route. The addition of Ni to SnO2 lead to significant enhanced response to formaldehyde (HCHO). The Ni-doped SnO2 materials were used to fabricate HCHO gas sensors and the comprehensive HCHO-sensing properties under diverse working temperatures were tested and studied. With suitable Ni concentration, the SnO2 nanoparticles exhibited a 10 times sensing enhancement with high gas response, excellent selectivity and good stability. Furthermore, the limit of detection (LOD) was experimentally figured out to be as low as 120 ppb, which is much lower than the threshold exposure limit of HCHO proposed by American Conference of Governmental Industrial Hygienists. Importantly, the excellent performances of the as-fabricated gas-sensing devices make Ni-doped SnO2 a promising candidate for HCHO sensing applications. This synthesis strategy here can also give guidance for designing high-performance HCHO gas sensors.

Enhanced formaldehyde detection based on Ni doping of SnO2 nanoparticles by one-step synthesis

The desired control of particle size, doping element composition, and surface structure of carbon dots (CDs) are vital for understanding the fluorescence mechanism and exploring their potential applications. Herein, nitrogen-doped CDs (N-doped CDs) have been synthesized with tartaric acid and various alkylol amines (monoethanolamine, biethanolamine and triethanolamine) under microwave irradiation. A systematic investigation was performed to characterize the N-doped CDs. It is found that with increasing nitrogen proportion, the fluorescent quantum yield and lifetime of N-doped CDs increases, whereas cell toxicity decreases. In other words, N-doped CDs synthesized by tartaric acid and monoethanolamine have the highest nitrogen content, the highest fluorescent quantum yield, the longest lifetime and the lowest cell toxicity. A corresponding mechanism has been proposed. Moreover, as-synthesized N-doped CDs have been applied for selectively detecting the Fe(3+) ion and writing letters as a fluorescent ink.

Guili He

Papers

A Review on Graphene-Based Gas/Vapor Sensors with Unique Properties and Potential Applications

A green heterogeneous synthesis of N-doped carbon dots and their photoluminescence applications in solid and aqueous states.

Design of Hetero-Nanostructures on MoS2 Nanosheets To Boost NO2 Room-Temperature Sensing.

Enhanced formaldehyde detection based on Ni doping of SnO2 nanoparticles by one-step synthesis

Hydrophilic and blue fluorescent N-doped carbon dots from tartaric acid and various alkylol amines under microwave irradiation.