Carbon nano-dot for cancer studies as dual nano-sensor for imaging intracellular temperature or pH variation.

Cellular temperature and pH govern many cellular physiologies, especially of cancer cells. Besides, attaining higher cellular temperature plays key role in therapeutic efficacy of hyperthermia treatment of cancer. This requires bio-compatible, non-toxic and sensitive probe with dual sensing ability to detect temperature and pH variations. In this regard, fluorescence based nano-sensors for cancer studies play an important role. Therefore, a facile green synthesis of orange carbon nano-dots (CND) with high quantum yield of 90% was achieved and its application as dual nano-sensor for imaging intracellular temperature and pH was explored. CND was synthesized from readily available, bio-compatible citric acid and rhodamine 6G hydrazide using solvent-free and simple heating technique requiring purification by dialysis. Although the particle size of 19 nm (which is quite large for CND) was observed yet CND exhibits no surface defects leading to decrease in photoluminescence (PL). On the contrary, very high fluorescence was observed along with good photo-stability. Temperature and pH dependent fluorescence studies show linearity in fluorescence intensity which was replicated in breast cancer cells. In addition, molecular nature of PL of CND was established using pH dependent fluorescence study. Together, the current investigation showed synthesis of highly fluorescent orange CND, which acts as a sensitive bio-imaging probe: an optical nano-thermal or nano-pH sensor for cancer-related studies.

Rapid and selective magnetic separation of uranium in seawater and groundwater using novel phosphoramidate functionalized citrate-Fe3O4@Ag nanoparticles.

One-pot magnetic separation of uranium (U) in seawater and groundwater samples has been made possible by synthesizing phosphoramidate functionalized Ag coated citrate-Fe3O4 nanoparticles (NPs). The magnetic saturation value of these functionalized NPs is 27.1 emu g-1. The synergistic extraction mechanism of U(VI) ion by the surface-modified phosphoramidate and citrate molecules make these NPs highly selective towards U(VI). The adsorption kinetics follows a pseudo-second-order model and the adsorption isotherm fits successfully to the Langmuir adsorption model. The functionalized NPs show quantitative extraction efficiency in the pH range of 6.5-8 with a maximum loading capacity (Qm) of 108.7 mg g-1. The equilibration time required by these functionalized NPs to attain the Qm value is 120 s. The recycling of these NPs can be done up to 5-6 times with 1.0 mol L-1 of Na2CO3 or NH4OH for quantitative extraction of U(VI). These functionalized NPs show high resilience towards large number of naturally abundant metal ions.

Colorimetric and visual determination of ultratrace uranium concentrations based on the aggregation of amidoxime functionalized gold nanoparticles.

The authors describe the synthesis and characterization of 3-mercaptopropionylamidoxime functionalized gold nanoparticles (AuNPs) for visual detection of uranium (U) by cloud point extraction. The method is capable of quantifying U at the concentration limits set by the World Health Organization in drinking water i.e., 30.0 ng mL-1. The method is based on the gradual color change from red to blue that occurs as a result of the interaction between uranyl ion and the modified AuNPs leading to particle aggregation. Such analyte-triggered aggregation results in AuNP's peak absorbance quenching as well as red shift in the wavelength range of 520 to 543 nm. The colorimetric response at 520 nm is linear in the 2-100 ng mL-1 U concentration range, and the limit of detection is 0.3 ng mL-1. No interferences by other ions are found, and the relative standard deviation is ≤4% (for n = 5). The method is validated by analyzing a certified reference material (NIST SRM 1640a; natural water), and also applied to the quantification of U in four (spiked) water samples. Graphical abstract Schematic presentation of cloud point extraction (CPE) assisted coloirmetric and visual detection of uranium (U). In CPE of gold nanoparticles (AuNPs) the color of surfactant rich phase (SRP) turns red in absence of U(VI) and blue in presence of U(VI).

Synthesis and structure of [(Ph3P)2Cu(µ-SeCH2Ph)2In(SeCH2Ph)2] as a single-source precursor for the preparation of CuInSe2 nano-materials.

The reaction of freshly prepared Na[In(SeCH2C6H5)4] with the mixture of CuCl and triphenylphosphine in methanol yielded [(PPh3)2CuIn(SeCH2C6H5)4]. The X-ray structure of the complex revealed the monomeric form of [(Ph3P)2Cu(µ-SeCH2Ph)2In(SeCH2Ph)2] consisting of tetrahedral Cu(i) and In(iii) centers, bridged by two benzyl selenolate ligands. The complex on pyrolysis in a furnace or in oleylamine/HDA yielded tetragonal CuInSe2. The morphology and composition of nanostructures were investigated by pXRD, SEM, TEM and EDX analysis. The band gap of the CuInSe2 nanostructures, obtained from pyrolysis in HDA and OA has been deduced from DRS as 1.85 and 1.86 eV, respectively.

Controlling the phase and morphology of amorphous Se nanoparticles: their prolonged stabilization and anticancer efficacy.

Applications of amorphous Se nanoparticles (NPs) are limited due to their meticulous synthetic procedures and rapid phase transformation leading to low stability. A highly facile one-pot green method is being reported, wherein apart from tuning the morphology and the phase of the Se NPs, their stabilization could be prolonged to months as compared to a few minutes-to-days, known hitherto.

Green, Water-Dispersible Photoluminescent On-Off-On Probe for Selective Detection of Fluoride Ions.

Considering the high toxicity and widespread availability of fluoride ions in different environmental matrices, it is imperative to design a probe for its detection. In view of this, a selective fluorescent on-off-on probe based on carbon quantum dots (CQDs) and Eu3+ has been designed. We have synthesized water-soluble carboxylic acid-functionalized CQDs and monitored their interaction with Eu3+. Luminescence quenching in the CQD emission was observed (switch-off) on adding Eu3+ ions. We investigate the reason for this luminescence quenching using time-resolved emission and high-resolution transmission electron microscopy (HRTEM) studies and observed that both electron transfer from CQDs to Eu3+ and aggregation of CQDs are responsible for the luminescence quenching. ζ-Potential and X-ray photoelectron spectroscopy studies confirm Eu3+ binding with the COOH groups on CQD surface. Interestingly, luminescence regains after the addition of fluoride ions to the CQDs/Eu3+ system (switch-on). This has been assigned to the removal of Eu3+ from the CQD surface due to the formation of EuF3 and is confirmed by X-ray diffraction and HRTEM measurements. The sensitivity of the probe was tested by carrying out experiments with other competing ions and was found to be selective for fluoride ions. Experiments with variable concentrations of fluoride ions suggest that the working range of the probe is 1-25 ppm. The probe has been successfully tested for the detection of fluoride ions in a toothpaste sample and the results were compared to those of ion chromatography. To the best of our knowledge, this is the first report based on CQDs and Eu3+ for the detection of fluoride ions, wherein a clear mechanism of the detection has been demonstrated, which, in turn, will help to develop better detection methods. The suggested probe is green, economical, rapid, efficient, and, most importantly, selective and can be used for the detection of fluoride ions in real environmental samples.

Rapid extraction of uranium from sea water using Fe3O4 and humic acid coated Fe3O4 nanoparticles.

Uranium is one of the most toxic elements present in the environment and a number of methods have been developed for its extraction. Herein we have demonstrated a new method using magnetic nanoparticles (NPs) that can be used for uranium extraction from water and sea water matrix. Fe3O4 and humic acid (HA) coated Fe3O4 NPs with different amount of HA coating were synthesized and uranium sorption from water and sea water matrix was demonstrated. It was observed that sorption increases with increase in amount of HA coating. NPs settlement in presence of magnetic field was monitored where only bare Fe3O4 and Fe3O4/HA 1 NPs settles while no settlement was observed for Fe3O4/HA 2 and Fe3O4/HA 3 NPs. Considering both sorption and particle separation from the matrix Fe3O4/HA 1 NPs are the best among synthesized ones with maximum sorption capacity of 10.5mg of U/g of NPs. The results presented here reveal the exceptional potential of magnetic NPs and functionalized magnetic NPs for environmental remediation of uranium and to extract uranium from sea water on which to the best of our knowledge no report is available till now.

Molecular Origin and Self-Assembly of Fluorescent Carbon Nanodots in Polar Solvents.

Despite numerous efforts, there are several fundamental ambiguities regarding the photoluminescence of carbon dots (CDs). Spectral shift measurements display characteristic of both π-π* and n-π* transitions for the main absorption or excitation band at ∼350 nm, contrary to common assignment of exclusive n-π* transition. Additionally, the generally perceived core-state transition at ∼250 nm, involving sp2-networked carbogenic domains shielded from external environments, needs to be reassessed because it fails to explain the observed fluorescence quenching and spectral shift. These results have been explained based on the molecular origin of PL in CDs invoking the similarity between CD and citrazinic acid. Fluorescent derivatives of the latter are recognized to be produced during citric-acid-based CD synthesis. Concentration-dependent spectral splitting of the main excitation band in combination with the temperature-dependent PL results has been envisioned assuming self-assembly of CDs into various H-aggregates.

Size Selective Green Synthesis of Silver and Gold Nanoparticles: Enhanced Antibacterial Efficacy of Resveratrol Capped Silver Sol.

In view of potential biomedical application of the noble metal nanoparticles, we report a size controlled yet simple and green synthesis of resveratrol stabilized silver and gold nanoparticles having low polydispersity of size. Here, resveratrol plays two simultaneous roles, reducing the metal ions and providing efficient capping of the small nanoparticles. This gives rise to specific size of silver and gold nanoparticles at specific ratios of metal to resveratrol. The particles have been characterized by XRD and transmission electron microscopy. The nanoparticle sols are stable for months. The UV Visible absorption spectra of the silver sol show the plasmon peak of spherical nanoparticles, presence of which is further reflected in the TEM images. Size of the silver particles obtained is in between 11 to 21 nm depending on the ratio of resveratrol to metal ion used. Resveratrol capped silver nanoparticles exhibit high antibacterial activity against Gram negative wild type E coli BW (25113). The minimum inhibitory concentration (MIC) of nano-silver against the bacterium has been estimated to be 6.48 µg/ml, which is significantly lower than that reported in some earlier as well as recent publications. Reaction of gold ions with resveratrol, on the other hand, produces gold nanoparticles of sizes varying from 7 to 29 nm at different ratios of resveratrol to the metal ions. Particles with higher size and aspect ratio are formed at lower concentration of the capping agent whereas particles with very small size and pseudo-spherical morphology are formed at higher capping concentration. Difference in the formation kinetics of silver and gold nanoparticles has been attributed to the different growth mechanisms in the two cases. Possible modes of anchorage of resveratrol to silver nanoparticles have been investigated using surface enhanced resonance Raman spectroscopy (SERS) which shows that the silver nanoparticles are capped by resveratrol molecule primarily through O-Ag linkages of the p-OH aromatic ring. This, in turn, demonstrates the feasibility of using these nanoparticles as SERS templates.