The present article reports on a simple, economical, and green preparative strategy toward water-soluble, fluorescent carbon nanoparticles (CPs) with a quantum yield of approximately 6.9% by hydrothermal process using low cost wastes of pomelo peel as a carbon source for the first time. We further explore the use of such CPs as probes for a fluorescent Hg2+ detection application, which is based on Hg2+-induced fluorescence quenching of CPs. This sensing system exhibits excellent sensitivity and selectivity toward Hg2+, and a detection limit as low as 0.23 nM is achieved. The practical use of this system for Hg2+ determination in lake water samples is also demonstrated successfully.

Economical, Green Synthesis of Fluorescent Carbon Nanoparticles and Their Use as Probes for Sensitive and Selective Detection of Mercury(II) Ions

Recent advances in wide bandgap semiconductor biological and gas sensors

This review will focus on the synthesis, arrangement, structural assembly, for current and future applications, of 1D nanomaterials (tubes, wires, rods) in 2D and 3D ordered arrangements. The ability to synthesize and arrange one dimensional nanomaterials into ordered 2D or 3D micro or macro sized structures is of utmost importance in developing new devices and applications of these materials. Micro and macro sized architectures based on such 1D nanomaterials (e.g. tubes, wires, rods) provide a platform to integrate nanostructures at a larger and thus manageable scale into high performance electronic devices like field effect transistors, as chemo- and biosensors, catalysts, or in energy material applications. Carbon based, metal oxide and metal based 1D arranged materials as well as hybrid or composite 1D materials of the latter provide a broad materials platform, offering a perspective for new entries into fascinating structures and future applications of such assembled architectures. These architectures allow bridging the gap between 1D nanostructures and the micro and macro world and are the basis for an assembly of 1D materials into higher hierarchy domains. This critical review is intended to provide an interesting starting point to view the current state of the art and show perspectives for future developments in this field. The emphasis is on selected nanomaterials and the possibilities for building three dimensional arrays starting from one dimensional building blocks. Carbon nanotubes, metal oxide nanotubes and nanowires (e.g. ZnO, TiO2, V2O5, Cu2O, NiO, Fe2O3), silicon and germanium nanowires, and group III–V or II–VI based 1D semiconductor nanostructures like GaS and GaN, pure metals as well as 1D hybrid materials and their higher organized architectures (foremost in 3D) will be focussed. These materials have been the most intensively studied within the last 5–10 years with respect to nano–micro integration aspects and their functional and application oriented properties. The critical review should be interesting for a broader scientific community (chemists, physicists, material scientists) interested in synthetic and functional material aspects of 1D materials as well as their integration into next higher organized architectures.

Assembly of one dimensional inorganic nanostructures into functional 2D and 3D architectures. Synthesis, arrangement and functionality

The article reports on the microwave-assisted rapid green synthesis of photoluminescent carbon nanodots (C-dots) with diameters in the range of 1–4 nm using flour as the carbon source. It suggests that the resultant C-dots exhibit high sensitivity and selectivity toward Hg 2+ with a detection limit as low as 0.5 nM and a linear range of 0.0005–0.01 μM. The practical use of this system for Hg 2+ determination in real lake water samples is also demonstrated successfully.

Microwave-assisted rapid green synthesis of photoluminescent carbon nanodots from flour and their applications for sensitive and selective detection of mercury(II) ions

Heavy metal ions are highly toxic species which can cause long-term damage to biological systems These species are known to disrupt biological events at the cellular level, cause significant oxidative damage, and are carcinogens The production of simple, in-field detection methods that are highly sensitive for these cations is highly desirable in response to global pollution In that regard, bio-inspired colorimetric sensing systems have been developed to detect Hg2+ and Pb2+, and other cations, down to nmol L−1 concentrations The benefits of these systems, which are reviewed herein, include cost-effective production, facile usage, and a visual color change for the detection method Such advantages are significant positive steps for heavy metal ion detection, especially in regions where sophisticated laboratory studies are prohibited

Bio-inspired colorimetric detection of Hg2+ and Pb2+ heavy metal ions using Au nanoparticles

Bare Au gated and thioglycolic acid functionalized Au-gated AlGaN∕GaN high electron mobility transistors (HEMTs) were used to detect mercury (II) ions. Fast detection of less than 5s was achieved for thioglycolic acid functionalized sensors. This is the shortest response time ever reported for mercury detection. Thioglycolic acid functionalized Au-gated AlGaN∕GaN HEMT based sensors showed 2.5 times larger response than bare Au-gated based sensors. The sensors were able to detect mercury (II) ion concentration as low as 10−7M. The sensors showed an excellent sensing selectivity of more than 100 for detecting mercury ions over sodium or magnesium ions. The dimensions of the active area of the sensor and the entire sensor chip are 50×50μm2 and 1×5mm2, respectively. Therefore, portable, fast response, and wireless based heavy metal ion detectors can be realized with AlGaN∕GaN HEMT based sensors.

Fast electrical detection of Hg(II) ions with AlGaN∕GaN high electron mobility transistors

Bare Au-gated and thioglycolic acid functionalized Au-gated AlGaN/GaN high electron mobility transistors were used to detect mercury(II) and copper(II) ions. Fast detection of <5 s was achieved for thioglycolic acid functionalized sensors. The thioglycolic acid functionalization increased the sensitivity for detection of mercury by 2.5 times over the bare Au-gated surface. Both surfaces had a selectivity of approximately 100-fold over other contaminating ions of sodium, magnesium, and lead and can be easily recycled. Our results show that portable, selective, and fast Cu 2+ and Hg 2+ sensors can be realized by combining bare Au-gated and thioglycolic acid-functionalized surface in one sensor.

T. F. Chancellor

Papers

Fast electrical detection of Hg(II) ions with AlGaN∕GaN high electron mobility transistors

Selective Detection of Hg"II… Ions from Cu"II… and Pb"II… Using AlGaN/GaN High Electron Mobility Transistors