Interaction-Transferable Graphene-Isolated Superstable AuCo Nanocrystal-Enabled Direct Cyanide Capture

Advances in metal graphitic nanocapsules for biomedicine

Metal graphitic nanocapsules have the advantages of both graphitic and metal nanomaterials, showing great promise in biomedicine. On one hand, the chemically inert graphitic shells are able to protect the metal core from external environments, quench the fluorescence signal from the biological system, offer robust platform for targeted molecules or drugs loading, and act as stable Raman labels or internal standard molecule. On the other hand, the metal cores with different compositions, sizes, and morphologies show unique physicochemical properties, and further broaden their biomedical functions. In this review, we firstly introduce the preparation, classification, and properties of metal graphitic nanocapsules, then summarize the recent progress of their applications in biodetection, bioimaging, and therapy. Challenges and their development prospects in biomedicine are eventually discussed in detail. We expect the versatile metal graphitic nanocapsules will advance the development of future clinical biomedicine.

Metal Graphitic Nanocapsules for Theranostics in Harsh Conditions

Metal nanoparticles (NPs) with superior physicochemical properties and biocompatibility have shown great potential in theranostics. However, metal NPs show poor stability in some harsh conditions such as strong acid, oxidation, corrosion and high-temperature conditions, which limits their extensive bioapplications. To address such issue, a variety of superstable metal graphitic nanocapsules with the metal cores confined in the nanospace of few-layer graphitic shell have been developed for biodetection and therapy in harsh conditions. In this mini-review, we summarize the recent advances in metal graphitic nanocapsules for bioapplications in harsh conditions. Firstly, their theranostic performance in non-intrinsic physiological harsh environment, including oxidation, corrosion and high-temperature conditions, is systematically discussed. Then, we highlight their theranostic performance in the harsh stomach condition that is strong acidic and pepsin-rich. It is expected that this review will offer inspiration to facilitate the exploitation of novel theranostic agents that are stable in harsh conditions.

Assembling PVP-Au NPs as portable chip for sensitive detection of cyanide with surface-enhanced Raman spectroscopy

Cyanide (C≡N) can lead to blood, cardiovascular system, and nervous system disorders owing to the acute and chronic toxicity; thus, aiming at the group or individual poisoning incidents, it is necessary to develop the sensitive and credible method for rapid on-site detection of poisons cyanide. Surface-enhanced Raman spectroscopy (SERS) with the advantages of providing fingerprint information of target molecules and single-molecules sensitivity has been widely used in on-site analysis; however, the SERS measurements always suffer from the problem of the stability of substrates. Here, the polyvinylpyrrolidone (PVP)-stabilized Au NPs (PVP-Au NPs) have been assembled through the simple, convenient evaporation-induced strategy with the large-scale hotspots substrates. The presence of PVP can not only facilitate the assembly of Au NPs but also prevent the corrosion of CN^- towards the Au NPs with the formation of [Au (CN)₂]^-1, providing high stable and reproducible SERS signals. Moreover, the PVP-Au NPs have been assembled on the Si wafer to fabricate the portable SERS chip for rapid on-site detection of CN^- with an RSD of 5.8% and limitation of 100 ppb. Furthermore, by coupling a portable Raman spectrometer, the SERS spectra of CN^- spiked into different specimens to simulate the poison samples have been collected and analyzed on SERS chips with the recovery of 89-103% and RSD not higher than 11.3%. Consequently, the fabricated SERS chip with assembled PVP-Au NPs can provide sensitive and credible detection for CN^- in different specimens, and then would satisfy the rapid on-site evaluation of CN^- in poisoning incidents with the portable Raman spectrometer. Graphical Abstract.

Carbon dots and AuNCs co-doped electrospun membranes for ratiometric fluorescent determination of cyanide

Due to the extremely toxic nature of cyanide, the World Health Organization (WHO) has set 1.9 μM as the maximum acceptable level in drinking water. Therefore, methods for facile screening and on-site detection of cyanide is urgently needed. In this work, a ratiometric fluorescent method for cyanide detection was developed based on blue-emitting carbon dots (CDs) and red-emitting AuNCs. To suit an on-site detection, the two fluorophores were incorporated into a nanofibrous membrane through electrospinning, yielding the core-shell structure of CDs/AuNCs-PVA@CA. Upon reaction with cyanide, the red fluorescence of AuNCs was quenched but the blue fluorescence of CDs was retained, resulting in ratiometric fluorescence change. Besides, both CDs and AuNCs can be excited with a handheld UV lamp (365 nm), and the resultant visible fluorescence color change could be visualized with naked eye. The proposed ratiometric method provided a limit of detection (LOD) 0.15 μM for cyanide, which was far lower than 1.9 μM. The membrane was further employed for screening analysis of cyanide in tap water samples. After collection of 500 analytical results, only 5.6% of the results located outside the X¯±2s criteria, while for the X¯±3s criteria, there is no outlier. The statistical results indicated that the proposed method may be potentially useful for screening analysis of cyanide in water samples.