A nature-inspired 'tree'-like 3D hierarchical titania/TiO 2 architecture was prepared as a façade to strategically assemble reduced graphene oxide/RGO (a facile charge transporter) and cadmium sulfide/CdS (a visible light harvester) is presented for the first time. The core 3D TiO 2 heterostructure was prepared using a TiCl 3 mediated surface treatment of titania nanorods on fluorine-doped tin oxide (FTO) coated glass-slides. The performance of the 3D TiO 2 , which varies as a function of the treatment time, was first examined to achieve optimal photoelectrochemical response.Subsequently, the architecture was tested for its (i) theoretical water-splitting potential and (ii) ability to immobilize chalcogenide nonocrystals (CdS) with and without RGO.The best 'applied bias to photoconversion efficiency' (% ABPE) was noted to be 0.36% (-0.15 V versus Ag/AgCl) for the TiO 2 architecture. A 140% increase with CdS deposition on the branched TiO 2 indicated the structures' ability to effectively immobilize the chalcogenide. The effect of RGO on the photoelectrochemical response was explored and an optimum loading (1 mg.mL -1 ) of RGO was noted to boost the photoresponse by an additional 150% compared to 'CdS-only' photoanodes. Further, stability analysis performed over 3h showed that the presence of RGO significantly delays CdS corrosion-driven deactivation. Finally, the fundamental insights on the impact of RGO in the 3D TiO 2 /RGO/CdS photoanode and its effect on the charge transportation mechanism was examined using electrochemical impedance spectroscopy.

Flexible sensors with low fabrication cost, high sensitivity, and good stability are essential for the development of smart devices for wearable electronics, soft robotics, and electronic skins. Herein, we report a nanocomposite material based on carbon nanotube and metal oxide semiconductor for ultraviolet (UV) sensing applications, and its sensing behavior. The sensors were prepared by a screen-printing process under a low-temperature curing condition. The formation of a conducting string node and a sensing node could enhance a UV sensing response, which could be attributed to the uniform mixing of functionalized multi-walled carbon nanotubes and zinc oxide nanoparticles. A fabricated device has shown a fast response time of 1.2 s and a high recovery time of 0.8 s with good mechanical stability.

A novel bismuth (Bi)-biopolymer (chitosan) nanocomposite screen-printed carbon electrode was developed using a Bi and chitosan co-electrodepositing technique for detecting multiple heavy metal ions. The developed sensor was fabricated with environmentally benign materials and processes. In real wastewater, heavy metal detection was evaluated by the developed sensor using square wave anodic stripping voltammetry (SWASV). The nanocomposite sensor showed the detection limit of 0.1 ppb Zn2+, 0.1 ppb Cd2+ and 0.2 ppb Pb2+ in stock solutions. The improved sensitivity of the Bi-chitosan nanocomposite sensor over previously reported Bi nanocomposite sensors was attributed to the role of chitosan. When used for real wastewater samples collected from a mining site and soil leachate, similar detection limit values with 0.4 ppb Cd2+ and 0.3 ppb Pb2+ were obtained with relative standard deviations (RSD) ranging from 1.3% to 5.6% (n = 8). Temperature changes (4 and 23 °C) showed no significant impact on sensor performance. Although Zn2+ in stock solutions was well measured by the sensor, the interference observed while detecting Zn2+ in the presence of Cu2+ was possibly due to the presence of Cu-Zn intermetallic species in mining wastewater. Overall, the developed sensor has the capability of monitoring multiple heavy metals in contaminated water samples without the need for complicated sample preparation or transportation of samples to a laboratory.

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We have grown crystals of solid argon doped with rubidium atoms. The spectrum of the implanted atoms depends on the crystal-growth temperature and annealing history. We have used optical pumping to polarize the spin state of the implanted atoms and polarization spectroscopy to detect the spin state and measure the spin-relaxation time. In addition to the desired optical pumping, we also observed modification of the absorption spectrum of the rubidium due to the applied light.

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Lead sulfide quantum dot nanocrystal (QDNC) sensitized TiO 2 nanotubes have been fabricated using a simple, wet chemical method that is both time-and cost-effective. A single precursor source containing both Pb and S has been employed, with oleylamine as a linker molecule to synthesize the PbS under an ambient pressure based approach. This approach serves to assemble the QDNCs on a TiO 2 nanotube surface. Surface characterization was performed using electron microscopy, X-ray diffraction, and elemental analysis, indicating the formation of PbS quantum dots along the nanotube walls and intertubular spacing. The optoelectronic, photoelectrochemical, and photocatalytic properties of the composite heterostructure have been characterized using absorbance spectroscopy, electrochemical studies (including efficiency measurements), and methylene blue conversion as a probe. A 24-fold increase in the photocurrent of TiO 2 −PbS heterostructure over bare TiO 2 nanotube has been observed. Electrochemical impedance measurements of the TiO 2 nanotube sample indicate donor density of ∼4.5 × 10 19 cm −3 while TiO 2 /PbS heterostructure shows an n-n photoactive heterojunction with a donor density of ∼2.3 × 10 20 cm −3 . A 12% increase in photocatalytic activity and theoretical estimates suggesting almost 40-fold enhancement toward value-added product synthesis with PbS inclusion are presented.

Deposition of 0D CdS on 1D TiO2 nanotubes.