A sensitive, selective colorimetric Fe3+ detection method has been developed by using pyrophosphate functionalized gold nanoparticles (P2O74−–AuNPs). Gold nanoparticles were prepared by reducing HAuCl4 with sodium borohydride, in the presence of Na4P2O7. IR spectra suggested that pyrophosphates were capped on the surface of the gold nanoparticles. Aggregation of P2O74−–AuNPs was induced immediately in the presence of Fe3+ ions, yielding a color change from pink to violet. This Fe3+-induced aggregation of P2O74−–AuNPs was monitored using first the naked eye and then UV-vis spectroscopy with a detection limit of 5.6 μM. The P2O74−–AuNPs bound by Fe3+ showed excellent selectivity compared to other metal ions (Ca2+, Cd2+, Co2+, Fe2+, Hg2+, K+, Mg2+, Mn2+, Na+, Ni2+, Pb2+, and Zn2+). The best detection of Fe3+ was achieved in a pH range from 3 to 9. In addition, the P2O74−–AuNPs were also used to detect Fe3+ in lake water samples, with low interference.

Colorimetric detection of Fe3+ ions using pyrophosphate functionalized gold nanoparticles

The mixed-metal phases, (Li2Mn1−yFeyP2O7, 0 ≤ y ≤ 1), were synthesized using a “wet method”, and found to form a solid solution in the P21/a space group. Both thermogravimetric analysis and magnetic susceptibility measurements confirm the 2+ oxidation state for both the Mn and Fe. The electrochemical capacity improves as the Fe concentration increases, as do the intensities of the redox peaks of the cyclic voltammogram, indicating higher lithium-ion diffusivity in the iron phase. The two Li+ ions in the three-dimensional tunnel structure of the pyrophosphate phase allows for the cycling of more than one lithium per redox center. Cyclic voltammograms show a second oxidation peak at ∼5 V and ∼5.3 V, indicative of the extraction of the second lithium ion, in agreement with ab initio computation predictions. Thus, electrochemical capacities exceeding 200 Ah/kg may be achieved if a stable electrolyte is found.

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Iron and Manganese Pyrophosphates as Cathodes for Lithium-Ion Batteries

Efficient and Broadband LiGaP2O7:Cr3+ Phosphors for Smart Near-Infrared Light-Emitting Diodes

A sensitive and selective colorimetric assay method for the detection of Cr3+ has been developed using tripolyphosphate functionalized gold nanoparticles (P3O105−–AuNPs). Infrared (IR) spectra and energy dispersive X-ray spectroscopy (EDS) confirmed that tripolyphosphates capped on the surfaces of gold nanoparticles (AuNPs). Gold nanoparticles were prepared by reducing HAuCl4 with sodium borohydride (NaBH4) in the presence of sodium tripolyphosphate (Na5P3O10). Upon exposure to Cr3+, the color of the gold nanoparticle solution changed from red to violet, which was in response to the surface plasmon absorption of dispersed and aggregated nanoparticles. The P3O105−–AuNPs were bound by Cr3+ and showed excellent selectivity compared to other ions (Hg2+, Fe3+, Cr6+, Mn2+, Cd2+, Ni2+, Pb2+, Ba2+, Co2+, Cu2+, Ca2+, Mg2+, Zn2+, Al3+, Na+, Cl−, SO42−, PO43−, CO32−, NO3−, and all of the above interfering ions with the exception of Cr3+) and had a detection limit of 10−7 M by the naked eye in this way. Most importantly, the P3O105−–AuNPs can be stored at room temperature over half a year. In addition, the P3O105−–AuNPs were also used to detect Cr3+ in real environmental water samples, with low interference.

Colorimetric detection of Cr3+ using tripolyphosphate modified gold nanoparticles in aqueous solutions

DC conductivity and study of AC electrical conduction mechanisms by non-overlapping small polaron tunneling model in LiFeP2O7 ceramic

Crystal structure, magnetic and infrared spectroscopy studies of the LiCryFe1−yP2O7 solid solution

The lithium double diphosphates LiCr y Fe 1− y P 2 O 7 have been investigated by X-ray diffraction, SQUID measurements and vibrational spectroscopy. The Rietveld refinements based on the XRD patterns show the existence of a continuous solid solution over the whole composition range (0⩽ y ⩽1.0) with a continuous evolution of the monoclinic unit cell parameters (S.G. P 2 1 ). The transition metal ions connect the diphosphate anions forming a three-dimensional network with channels filled by Li + cations expected to exhibit high mobility. All compounds order magnetically at low temperatures due the Fe–Fe interactions. The ordering temperature decreases with increasing Cr content. The slope in Curie–Weiss fits to the 1/χ vs T data in the paramagnetic domain clearly shows the existence of Fe 3+ and Cr 3+ in their high spin states, and a ferromagnetic component is clearly detected for y =0, 0.2 and 0.4. IR spectra have been interpreted using factor group analysis. The small shift of the frequencies is due to the influence of the chromium amount. The POP angles were estimated using the Lazarev's relationship.

Hssain Bih

Papers

Crystal structure, magnetic and infrared spectroscopy studies of the LiCryFe1−yP2O7 solid solution

Crystal Structure, Magnetic and Infrared Spectroscopy Studies of the LiCryFe1‐yP2O7 Solid Solution.