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Functionalized graphene oxide (GO), derived from pure graphite via the modified Hummer method, was used to modify commercially available ceramic ultrafiltration membranes using the vacuum method. The modified ceramic membrane functionalized with GO (ceramic) was characterized using a variety of analysis techniques and exhibited higher hydrophilicity and increased negative charge compared with the pristine ceramic membrane. Although the pure water permeability of the ceramic membrane (14.4-58.6 L/m h/bar) was slightly lower than that of the pristine membrane (25.1-62.7 L/m h/bar), the removal efficiencies associated with hydrophobic attraction and charge effects were improved significantly after GO coating. Additionally, solute transport in the GO nanosheets of the ceramic membrane played a vital role in the retention of target compounds: natural organic matter (NOM; humic acid and tannic acid), pharmaceuticals (ibuprofen and sulfamethoxazole), and inorganic salts (NaCl, NaSO, CaCl, and CaSO). While the retention efficiencies of NOM, pharmaceuticals, and inorganic salts in the pristine membrane were 74.6%, 15.3%, and 2.9%, respectively, these increased to 93.5%, 51.0%, and 31.4% for the ceramic membrane. Consequently, the improved removal mechanisms of the membrane modified with functionalized GO nanosheets can provide efficient retention for water treatment under suboptimal environmental conditions of pH and ionic strength.

The enhancement in electrical transport properties of exfoliated individual RuO NSs was systemically investigated for their application in flexible electronics and optoelectronics. Decoration of Ag NPs on the surface of the RuO NSs provides donor electrons and dramatically increases the electrical conductivity of the monolayer RuO NSs by up to 3700%. The n-type doping behavior was confirmed via Hall measurement analysis of the doped RuO NSs. The layer number- and temperature-dependence of the conductivity were also investigated. Moreover, carrier concentration and mobility were obtained from Hall measurements, indicating that the undoped RuO NSs had ambipolar transport and semi-metallic characteristics. Moreover, the Ag-doped RuO NS multilayer films on polycarbonate substrates were demonstrated by the Langmuir-Blodgett assembly methods, showing one-third reduction in the sheet resistance and extraordinarily high bending stability that the change in the resistance was less than 1% over 50 000 cycles.

Photoconductive PbSe thin films are highly important for mid-infrared imaging applications. However, the photoconductive mechanism is not well understood so far. Here we provide additional insight on the photoconductivity mechanism using transmission electron microscopy, x-ray photoelectron microscopy, and electrical characterizations. Polycrystalline PbSe thin films were deposited by a chemical bath deposition method. Potassium iodide (KI) was added during the deposition process to improve the photoresponse. Oxidation and iodization were performed to sensitize the thin films. The temperature-dependence Hall effect results show that a strong hole–phonon interaction occurs in oxidized PbSe with KI. It indicates that about half the holes are trapped by KI-induced self-trapped hole centers ( V k center), which results in increasing dark resistance. The photo Hall effect results show that the hole concentration increases significantly under light exposure in sensitized PbSe, which indicates the photogenerated electrons are compensated by trapped holes. The presence of KI in the PbSe grains was confirmed by I 3 d 5 / 2 core-level x-ray photoelectron spectra. The energy dispersive x-ray spectra obtained in the scanning transmission electron microscope show the incorporation of iodine during the iodization process on the top of PbSe grains, which can create an iodine-incorporated PbSe outer shell. The iodine-incorporated PbSe releases electrons to recombine with holes in the PbSe layer so that the resistance of sensitized PbSe is about 800 times higher than that of PbSe without the iodine-incorporated layer. In addition, oxygen found in the outer shell of PbSe can act as an electron trap. Therefore, the photoresponse of sensitized PbSe is from the difference between the high dark resistance (by KI addition and iodine incorporation) and the low resistance after IR exposure due to electron compensation (by electron traps at grain boundary and electron–hole recombination in KI hole traps).

PbSe thin films were deposited using the chemical bath deposition method and sensitized with iodine for enhanced IR photoconductivity. After sensitization, PbSe films showed a high photoresponse of 44.7% in terms of resistance change in the midinfrared wavelength range (3–5 μm). To investigate the origin of high photoresponse in sensitized PbSe films, the bandgap, work function, and valence band maximum were measured by photoluminescence (PL) and X-ray photoelectron spectroscopy secondary cutoff and valence spectra. Infrared photoluminescence spectra showed a PbSe bandgap of 0.29 eV. Visible PL spectra showed a PbI2 bandgap of 2.41 eV. Work functions of as-grown PbSe and PbI2 in sensitized PbSe were determined to be 4.30 eV and 4.50 eV, respectively. An Ag/PbSe/Ag band diagram shows a measured barrier height of 0.25 eV at the PbSe/Ag interface due to Fermi level pinning. When the Ag/PbI2/PbSe/PbI2/Ag structure is biased and exposed to midwavelength infrared illumination, the electron flow is limited due to high barriers at the interfaces. Therefore, the only hole can flow after charge separation such that the electrical resistance of PbSe film is dramatically reduced. The measured bandgap, work function, and valence band maximum along with measured barrier height for metal contacts should help in providing the understanding of the charge transport mechanism in PbSe photoconductors.

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PbSe thin films of one-micron thickness were deposited on SiO 2 /Si wafers using chemical bath deposition method for IR detector applications. To sensitize the PbSe films for efficient midwave IR detection in the spectral range from 3 to 5 μm, oxidation at 460 °C and subsequent iodization at 350 °C were performed. The x-ray diffraction for as-grown PbSe shows polycrystalline face-centered cubic NaCl type structure while Pb 3 O 2 (SeO 3 ) oxide peak develops as a function of oxidation time. The existence of Se-rich structure may lead to p-type conduction. Scanning electron microscope and cross-sectional energy dispersive x-ray depth profile measurements after oxidation show the top layer of the film contains primarily Pb-Se-oxide while film at the bottom layer was PbSe. After sensitization, polytype trigonal 12R PbI 2 , Pb 3 O 2 I 2 and PbSe were confirmed. The top layer of the sensitized PbSe film was found to be converted to primarily PbI 2 while the bottom layer remained PbSe. However, during sensitization without oxidation, little PbSe remained because most of the PbSe was converted into PbI 2 . Also, the presence of metallic Pb nano-crystals with 10 nm diameter was detected in the sensitized film.