Ultrafast and Energy-saving Synthesis of Nitrogen and Chlorine Co-doped Carbon Nanodots via Neutralization Heat for Selective Detection of Cr(VI) in Aqueous Phase

Quantum Dots Based Fluorescent Probe for the Selective Detection of Heavy Metal Ions

Heavy metal ions are one of the primary causes of environmental pollution. A marshal effect of heavy metal ions is a paramount ultimatum to humans, aquatic animals and other organisms present in nature. Multitude arrays of materials have been proclaimed for sensing of heavy metal ions and also many methodologies are applied for heavy metal ion sensing. Due to their toxicity and non-biodegradability, it is required to be perceived immediately prior to its manifestation of harmful effects. Quantum Dots (QDs) are zero-dimensional nanomaterial particles and owing to their distinctive optical and electronic properties, they are utilized as nanosensors. QDs have enriched fluorescence properties which includes broad excitation spectrum, narrow emission spectrum and photostability. QDs offer eclectic and sensitive detection of heavy metal ions due to presence of discrete capping agents and different functional groups present on the surface of the QDs. These capping layers and functional groups attune the sensing capability of the QDs, which leverages the interactions of QDs with various analytes by different mechanisms. This review, comprising of papers from 2011 to 2020,focuses on heavy metal ions sensing potential of various quantum dots and its applicability as a nanosensor for on field heavy metal ions detection in water. Quantum Dots (QDs) based Heavy Metal Detection.

The exploitation of thermophile resources in hot springs: fluorescent carbon dots derived from Ureibacillus thermosphaericus for multicolour cellular imaging and selectivity detection of heavy metals

Microbial biomass, as an environmentally friendly resource, has attracted considerable attention as a green biomaterial for the production of unique and functionalised CDs; however, further exploration is required to characterise CDs derived from bacteria. In this study, a green biomaterial (fluorescence CDs-HS18) was successfully synthesised via a hydrothermal method from Ureibacillus thermosphaericus HS-18 specimens isolated from a hot spring. The prepared CDs-HS18 possess excellent photo-physical properties, outstanding fluorescence capabilities, and high biocompatibility, which make them desirable candidates for multi-mode imaging applications. Our results demonstrate that the prepared CDs can selectively stain the membrane of the biological cells tested and can be rapidly distributed to all parts of the leaf via the veins and intercellular interstitium through transpiration. Additionally, CDs-HS18 are likely to enter the digestive tract of Microworms through ingestion and spread rapidly through the entire body and may finally be excreted through the anus. Furthermore, the rapid and highly selective detection platform based on CDs-HS18 exhibited an excellent linear response for Cr6+ between 0 and 9 μM, with a detection limit of 36 nM. This research will expand the understanding of the characteristics of green biomaterials derived from bacteria and widen the application scope of hot spring resources.

You Don't Learn That in School: An Updated Practical Guide to Carbon Quantum Dots

Carbon quantum dots (CQDs) have started to emerge as candidates for application in cell imaging, biosensing, and targeted drug delivery, amongst other research fields, due to their unique properties. Those applications are possible as the CQDs exhibit tunable fluorescence, biocompatibility, and a versatile surface. This review aims to summarize the recent development in the field of CQDs research, namely the latest synthesis progress concerning materials/methods, surface modifications, characterization methods, and purification techniques. Furthermore, this work will systematically explore the several applications CQDs have been subjected to, such as bioimaging, fluorescence sensing, and cancer/gene therapy. Finally, we will briefly discuss in the concluding section the present and future challenges, as well as future perspectives and views regarding the emerging paradigm that is the CQDs research field.

Novel fluorescent nitrogen-doped carbon dots derived from Panax notoginseng for bioimaging and high selectivity detection of Cr6

Carbon dots (CDs) and photoluminescent carbon dots (Pn-CDs) are promising nanomaterials due to their bioimaging applications and have attracted considerable attention because of their excellent stability, good biocompatibility, and low biotoxicity. Here, the Pn-CDs and highly fluorescent nitrogen-doped CDs (Pn N-CDs) derived from Panax notoginseng were successfully synthesized by a simple hydrothermal method. Pn N-CDs exhibit optical properties and stability superior to those of Pn-CDs and can be better used as fluorescent dyes and probes in biological imaging. The obtained Pn N-CDs can be effectively applied to the imaging of bacteria, fungi, plant cells, and protozoa. In addition, Pn N-CDs can perform specific staining on the membranes of all tested cells. The in vivo imaging of mice revealed that Pn N-CDs exhibit nontoxicity and good biocompatibility and biodistribution. Furthermore, Pn N-CDs can be utilized as fluorescent probes for the rapid and highly selective detection of Cr⁶⁺. Hence, a simple, cost-effective, scalable, and green synthetic approach based on traditional Chinese medicine-derived CDs can be used to develop biolabeling, membrane targeting, and optical sensing probes.

Chromium speciation by isophthalic acid-doped polymer dots as sensitive and selective fluorescent probes

Hexavalent chromium is a known carcinogen, among all species of chromium ions, for the respiratory tract in humans. In the present work, a new facile probe is developed for rapid and sensitive determination of Cr(VI) based on utilizing highly fluorescent conjugated poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-(2,1',3) thiadiazole)] (PFBT) polymer dots (PDs). The PDs are easily functionalized by doping of isophthalic acid (IPA) into the target PDs during a single step preparation. The prepared PDs with an average diameter of 30 nm illustrated a strong fluorescence with an emission peak centered at 530 nm (photo-excited at 480 nm). The strong fluorescence of PDs is selectively and significantly quench with Cr(VI), while it does not change by Cr(III) ion and, thus, can facilitate a chromium speciation process. The proposed mechanism is an inner filter effect (IFE) mechanism, in which the absorption bands of Cr(IV) overlaps with the emission and excitation bands of the modified PDs. The prepared PDs revealed a good linear relationship from 0.1 to 1000 μmol L^-1 for Cr(VI) with a detection limit of 0.03 μmol L^-1, which further used to track the Cr distribution in water samples. Finally, the IPA-doped PDs with excellent optical properties, biocompatibility, and high quantum yield showed promising potential in tracking Cr species and specifying of different Cr ions inside the human cells, which opening a new door toward getting a better insight into the cell function and metabolism in the presence of heavy metal ions, and especially chromium ions.

Comparative study of Cl,N-Cdots and N-Cdots and application for trinitrophenol and ClO- sensor and cell-imaging

To understand the effect of Cl doping in carbon dots, nitrogen-doped carbon dots (N-Cdots) and nitrogen and chlorine dual-doped carbon dots (Cl,N-Cdots) were fabricated by high-temperature carbonization and low-temperature concentrated acid (HCl) acidification of dried shaddock peel, respectively. The quantum yield of Cl,N-Cdots is about four times of that of N-Cdots and the size of Cl,N-Cdots is smaller than that of N-Cdots. Furthermore, since trinitrophenol (PA) and ClO^- could effectively quench the fluorescence of Cl,N-Cdots, the fluorescence sensors for determining PA and ClO^- was constructed, respectively. The linear range of PA and ClO^- are 0.9-90 μM and 3.24-216 μM with the limit of detection of 37.1 nM and 2.88 μM, respectively. The proposed sensor was used to detect PA in Taiyuan tap water, Wutai tap water, Wutai rain water and Wutai river water samples with encouraging results. The as-constructed sensor was also used to detect ClO^- in Taiyuan tap water and commercial disinfectants. Last but not least, Cl,N-Cdots was employed as an agent for A549 and HeLa cell-imaging, possessing optimal imaging effect and ultra-low cytotoxicity. Our results suggested that Cl,N-Cdots has promising applications in sensing, water monitoring, commodity supervision and cell-imaging.

Carbon quantum dots doped with phosphorus and nitrogen are a viable fluorescent nanoprobe for determination and cellular imaging of vitamin B12 and cobalt(II)

Phosphorus and nitrogen dually-doped carbon quantum dots (PN-CQDs) were prepared from sucrose, 85% phosphoric acid and 1,2-ethylenediamine as the sources for carbon, phosphorus and nitrogen, respectively. The PN-CQDs possess good water solubility and favorable biocompatibility. The excitation/emission peaks are at 365/451 nm, but bright blue, green, or red emissions are found depending on whether the excitation wavelengths of the laser are set to 408 nm, 488 nm, or 543 nm, respectively. Fluorescence is quenched by both vitamin B₁₂ (VB₁₂) and Co(II) by a combination of inner filter effect and static quenching. The PN-CQDs are shown to be useful nanoprobes for determination of VB₁₂ and Co(II). Response to VB₁₂ is linear in the range of 2.0-31 μM. The response to Co(II) is linear in two ranges, viz. from 1.7-12 μM and from 28 to 141 μM. The limit of detection of VB₁₂ and Co(II) are 3.0 nM and 29.4 nM, respectively. The nanoprobe was successfully applied to the analyses of VB₁₂ in drug samples and of Co(II) in spiked water samples, and it gave satisfactory results. The nanoprobe was also applied to the determination of VB₁₂ and Co(II) in human hepatocarcinoma cells (type SMMC7721), human pulmonary epithelial cells (type BEAS-2B), human adenocarcinoma cells (type A549), and human pheochromocytoma cells (type PC12), respectively. Graphical abstract Schematic presentation of the quenching of the fluorescence of phosphorus and nitrogen dually-doped carbon quantum dots (PN-CQDs) by vitamin B₁₂ (VB₁₂) and Co(II).