Colloidal quantum dots (QDs) combined with a graphene charge transducer promise to provide a photoconducting platform with high quantum efficiency and large intrinsic gain, yet compatible with cost-efficient polymer substrates. The response time in these devices is limited, however, and fast switching is only possible by sacrificing the high sensitivity. Furthermore, tuning the QD size toward infrared absorption using conventional organic capping ligands progressively reduces the device performance characteristics. Here we demonstrate methods to couple large QDs (>6 nm in diameter) with organometal halide perovskites, enabling hybrid graphene phototransistor arrays on plastic foils that simultaneously exhibit a specific detectivity of 5 × 10 Jones and high video-frame-rate performance. PbI and CHNHI co-mediated ligand exchange in PbS QDs improves surface passivation and facilitates electronic transport, yielding faster charge recovery, whereas PbS QDs embedded into a CHNHPbI matrix produce spatially separated photocarriers leading to large gain.

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SummaryThe interactions of Pu(N) and Pu(VI) in alkaline media with some metal hydroxides and oxides commonly found in Hanford Site tank wastes were studied. The properties of mixed hydroxide systems of Pu(IV) with various metal ions mi@), Fe(III), C o o , Al(m), Cr(m>, Zr(IV), La(IlI), and U(VI)] were investigated at variable component ratios using physicalchemical methods. The interactions of P u O with Al(lII), Fe(III), and Cr(IlI) also were studied.It was shown by infrared (IR) spectroscopy that, except for the system Pu(IV)-Ni(II), Pu(IV) interacts with all the listed metal ions and affects their interatomic bonding. The locations of IR absorption bands of the mixed hydroxides change irregularly compared with the spectra of pure components, with change in the Pu:metal mole ratio of from 1:lO to 1O:l. The changes occur both for the valent and deformation vibration bands of hydroxyl ions and water at 3600 to 3100 and 1750 to 1250 cm-' and for the vibrations of metal-oxygen (M-0) bridging bonds in the range of 1050 to 850 cm-'. In the Pu(IV)/Ni(II) system, the IR spectra are equivalent to the sum of the individual components precipitated separately from alkaline solution.The separate precipitation of h(N) hydrous oxide and Ni(OH), upon adding NaOH solution to acidic solution containing both Pu(N) and Ni(II) nitrate was confirmed by studying the dissolution rate of the resulting precipitate in 3 M HCl at 60°C. No difference in plutonium dissolution behavior was found for pure PuO,-xH,O and the products obtained by alkaline precipitation of 1: 1 mole ratio Pu(N):Ni(II) mixtures, aged for 1 hour at 70"C, over a wide range of NaOH concentrations. Similar results were obtained for the Pu(IV)-Al(III) system. Only trace amounts of aluminum were detected in pUO,.xl&O precipitates formed even in relatively dilute NaOH solutions.

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