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Silver telluride nanotubes have been prepared by the hydrothermal process without a template or a surfactant. The as-prepared sample was characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectra, and Raman spectra. The structural phase transition of the sample was observed. A rolling-up mechanism is proposed to explain the formation of the silver telluride nanotubes based on the inherent crystal structure of low-temperature beta-Ag2Te. Raman spectra analysis revealed an interesting Raman scattering enhancement phenomenon.

Covellite copper sulfide submicron crystals in the shapes of ball-like, rodlike, and chrysanthemumlike architectures congregated from nanoslices with thickness of 20 to 100 nm have been prepared by a hydrothermal method without using any surfactant and characterized by X-ray diffraction, energy-dispersive X-ray spectrometer (EDX), UV-vis optical absorption spectra, and electron-microscopy techniques. A systematic investigation has been carried out to understand the factors influencing the evolution of the crystal morphology which was found to be predominant by the reactant molar ratio (Tu:Cu(NO 3 ) 2 , Tu ) thiourea), the hydrothermal reaction time, and the temperature. Possible crystal growth processes are also discussed.

Manganese ion (Mn2+) bonded nitrogen-doped graphene quantum dots (Mn(ii)-NGQDs) with water solubility have been successfully synthesized by a simple, one-pot hydrothermal carbonization, using sodium citrate, glycine and manganese chloride as raw materials.

Poly(ethylene glycol) passivated graphene quantum dots (PEG-GQDs) were synthesized based on a green and effective strategy of the hydrothermal treatment of cane molasses. The prepared PEG-GQDs, with an average size of 2.5 nm, exhibit a brighter blue fluorescence and a higher quantum yield (QY) (up to approximately 21.32%) than the QY of GQDs without surface passivation (QY = 10.44%). The PEG-GQDs can be used to detect and quantify paramagnetic transition-metal ions including Fe 3+ , Cu 2+ , Co 2+ , Ni 2+ , Pb 2+ , and Mn 2+ . In the case of ethylenediaminetetraacetic acid (EDTA) solution as a masking agent, Fe 3+ ions can be well selectively determined in a transition-metal ion mixture, following the lowest limit of detection (LOD) of 5.77 μM. The quenching mechanism of Fe 3+ on PEG-GQDs belongs to dynamic quenching. Furthermore, Fe 3+ in human serum can be successfully detected by the PEG-GQDs, indicating that the green prepared PEG-GQDs can be applied as a promising candidate for the selective detection of Fe 3+ in clinics.

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