Shahid Ali

Sonochemical assisted hydrothermal synthesis of pseudo-flower shaped Bismuth vanadate (BiVO4) and their solar-driven water splitting application

Bismuth vanadate (BiVO4) is a well-known photocatalyst due to its lower bandgap (Eg) and visible electromagnetic light absorption capacity. Herein, we reported the pulse ultra-sonochemical assisted hydrothermal approach to synthesize S-BiVO4. For the comparison purpose, H-BiVO4 is also synthesized via conventional hydrothermal approach. The surface morphology of S-BiVO4 through scanning electron microscope (SEM) indicates condensed microarrays (MAs) having pseudo-flower shapes. The energy dispersive X-rays (EDX) spectrum also confirmed the elemental percent composition of Bi, V and O in BiVO4. X-rays diffraction (XRD) pattern further confirmed the monoclinic scheelite phase of S-BiVO4. Fourier transformed infrared (FTIR) spectrum showed Bi-O and Bi-V-O vibrational bands at 1382 and 1630cm-1, respectively. The diffuse reflectance spectroscopy (DRS) indicated absorption edge at ∼515nm, corresponds to bandgap value (Eg) of 2.41eV, which is suitable range for water splitting applications. The photocurrent density from water splitting under artificial 1 SUN visible light source found at 60 and 50μA/cm2 for S-BiVO4 and H-BiVO4, respectively. The stability test through chronoamperometry showed that S-BiVO4 was more stable than H-BiVO4. It can be depicted from the growth mechanism that ultrasonication played a definite role in the overall synthesis of pseudo-flower shaped S-BiVO4 MAs.

Fabrication of TiO2/Ag/Ag2O Nanoparticles to Enhance the Photocatalytic Activity of Degussa P25 Titania

A simple chemical reduction approach was used to synthesize Ag nanoparticles (NPs) over a reputed photocatalyst, Degussa P25 (TiO2). Silver doping extended the P25 absorption wavelength from the ultraviolet to the visible region. The synthesized silver NPs (Ag NPs) were of spherical shape and had an average size of ~4.6 nm. In the next stage, Ag NPs were partially oxidized by treatment with hydrogen peroxide. The resulting P25/Ag/Ag2O nanocomposites were characterized by X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray analysis, Brunauer–Emmett–Teller analysis, and UV-visible spectroscopy. The photocatalytic activities of the P25, P25/Ag, and P25/Ag/Ag2O catalysts were investigated for the degradation of non-biodegradable dyes, methylene blue and rhodamine 6G. The P25/Ag/Ag2O nanocomposite exhibited better photodegradation activity than P25, as well as the commonly used Ag3PO4, under visible light irradiation.

Visual Occam: Syntax and semantics

Visual Occam (VISO) is a visual programming language for concurrent programming. It uses message passing for interprocess communication and processes are disjoint. The VISO language uses a modular approach to visual programming which simplifies the specification of programs. It has a graphical syntax based on the language Occam. The petri net formalism is used to represent the semantics of the VISO language. This paper describes the design and implementation of the VISO language. It presents syntax, semantics, and a number of concurrent programs specified in the VISO language. Also, it discusses how synchronous communication can be expressed in petri nets.

Formal semantics of visual occam

Visual programming languages (VPLs) have been proposed to simplify the task of programming and to make better use of human capabilities. Visual Occam (VISO) is a visual programming language for concurrent programming. It uses message passing for interprocess communication and processes are disjoint. The VISO language uses a modular approach to visual programming which simplifies the specification of programs. It has a graphical syntax based the language occam. The main emphasis in this paper is to provide formal semantics of VISO using process calculus. The semantics of all programming constructs and icons in VISO are given as well as a number of complete example programs and their translation in process calculus.