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Carbon dots (CDs) that showed strong blue fluorescence were successfully synthesised from sodium alginate via furnace pyrolysis. The single step pyrolytic synthesis was simple to perform while yielded CDs with high photostability, good water solubility and minimum by-products. In order to design the probe with “turn-on” sensing capability, the CDs were screened against a series of metal cations to first “turn-off” the fluorescence. It was found that ferric ions (Fe 3+ ) were most responsive and effective in quenching the fluorescence of CDs. Based on this observation, the conditioning of the probe was performed to ensure the fluorescence was completely quenched, while not overloading the system with Fe 3+ . At the optimised condition, the CDs-Fe 3+ mixture served as a highly specific detection probe for ascorbic acid (AA). The analytical potential of the probe was evaluated and showed a good linear range of response for AA concentration of 24–40 μg/mL. The selectivity study against other possible co-existing species was carried out and proved that our unique “turn-on” fluorescence signalling strategy was highly effective and selective towards AA as the target analyte. The probe was demonstrated for quantification of AA in real samples, which was the commercially available vitamin C supplement. The result showed good accuracy with minimum deviation from standard method adopted for validation purpose. [ABSTRACT FROM AUTHOR]

The services provided to users in the environment associated with the Internet of Things (hereinafter referred to as IoT) begin with the information collected from sensors. It is imperative to transmit high-quality sensor data for providing better services. It is also required to collect data only from those authenticated sensors. Moreover, it is imperative to collect high-quality data on a sustainable and continuous basis in order to provide services anytime and anywhere in the IoT environment. Therefore, high-quality, authenticated sensor networks should be constructed. The most prominent routing protocol to enhance the energy consumption efficiency for the sustainable data collection in a sensor network is the LEACH routing protocol. The LEACH routing protocol transmits sensor data by measuring the energy of sensors and allocating sensor groups dynamically. However, these sensor networks have vulnerabilities such as key leakage, eavesdropping, replay attack and relay attack, given the nature of wireless network communication. A large number of security techniques have been studied in order to solve these vulnerabilities. Nonetheless, these studies still cannot support the dynamic sensor group allocation of the LEACH routing protocol. Furthermore, they are not suitable for the sensor nodes whose hardware computing ability and energy resources are limited. Therefore, this paper proposed a group sensor communication protocol that utilizes only the four fundamental arithmetic operations and logical operation for the sensor node authentication and secure data transmission. Through the security analysis, this paper verified that the proposed scheme was secure to the vulnerabilities resulting from the nature of wireless network communication. Moreover, this paper verified through the performance analysis that the proposed scheme could be utilized efficiently. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) are a unique class of fascinating carbon-based fluorescent sensors with strong photoluminescence, chemical stability and good biocompatibility. In this work, new copper-doped carbon dots (Cu-CDs) were successfully synthesized from citric acid, ammonium tartrate and CuCl 2 via a household microwave. The Cu-CDs exhibit excitation-independent emissions, high fluorescence quantum yield (~34.74%) and excellent fluorescence stability. The fluorescence of Cu-CDs can be directly quenched by ascorbic acid (AA) linearly in the range of 0.1–3.0 μM based on the inner filter effect (IFE). The limit of detection (LOD) can be determined to 27 nM. Meanwhile, an "on-off-on" sensing system based on the complex of Cu-CDs and Fe3+ is designed and served as highly specific detection probes for AA through the fluorescence resonance energy transfer (FRET) with a lower LOD of 6 nM, which is one of the best reports. The proposed methods provide obvious advantages of convenience, simplicity, rapid response, high selectivity and sensitivity. Besides, good results also have been acquired for AA detection in real medicine samples. • Cu2+ functionalized carbon dots were synthesized through an efficient microwave-assisted method. • Two systems of direct detection and "on-off-on" detection exhibit high sensitivity to AA. • Both the two systems show high selectivity and excellent anti-interference to AA. • Good results of the two systems also have been acquired for AA detection in real medicine samples. [ABSTRACT FROM AUTHOR]