There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Semiconductor photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials. We begin with a survey of efforts to explore suitable materials and to optimize their energy band configurations for specific applications. We then examine the design and fabrication of advanced photocatalytic materials in the framework of nanotechnology. Many of the most recent advances in photocatalysis have been realized by selective control of the morphology of nanomaterials or by utilizing the collective properties of nano-assembly systems. Finally, we discuss the current theoretical understanding of key aspects of photocatalytic materials. This review also highlights crucial issues that should be addressed in future research activities.

Nano‐photocatalytic Materials: Possibilities and Challenges

Rising atmospheric levels of carbon dioxide and the depletion of fossil fuel reserves raise serious concerns about the ensuing effects on the global climate and future energy supply. Utilizing the abundant solar energy to convert CO2 into fuels such as methane or methanol could address both problems simultaneously as well as provide a convenient means of energy storage. In this Review, current approaches for the heterogeneous photocatalytic reduction of CO2 on TiO2 and other metal oxide, oxynitride, sulfide, and phosphide semiconductors are presented. Research in this field is focused primarily on the development of novel nanostructured photocatalytic materials and on the investigation of the mechanism of the process, from light absorption through charge separation and transport to CO2 reduction pathways. The measures used to quantify the efficiency of the process are also discussed in detail.

Photocatalytic reduction of CO2 on TiO2 and other semiconductors.

Global warming and climate change concerns have triggered global efforts to reduce the concentration of atmospheric carbon dioxide (CO2). Carbon dioxide capture and storage (CCS) is considered a crucial strategy for meeting CO2 emission reduction targets. In this paper, various aspects of CCS are reviewed and discussed including the state of the art technologies for CO2 capture, separation, transport, storage, leakage, monitoring, and life cycle analysis. The selection of specific CO2 capture technology heavily depends on the type of CO2 generating plant and fuel used. Among those CO2 separation processes, absorption is the most mature and commonly adopted due to its higher efficiency and lower cost. Pipeline is considered to be the most viable solution for large volume of CO2 transport. Among those geological formations for CO2 storage, enhanced oil recovery is mature and has been practiced for many years but its economical viability for anthropogenic sources needs to be demonstrated. There are growing interests in CO2 storage in saline aquifers due to their enormous potential storage capacity and several projects are in the pipeline for demonstration of its viability. There are multiple hurdles to CCS deployment including the absence of a clear business case for CCS investment and the absence of robust economic incentives to support the additional high capital and operating costs of the whole CCS process.

https://www.elsevier.com/__data/assets/pdf_file/0005/96980/Current-status-carbon-capture.pdf

An overview of current status of carbon dioxide capture and storage technologies

A review on g-C3N4-based photocatalysts

Flow of a shear-thinning fluid over curved and moving geometries demands special attention owing to its industrial and biological relevance. The present study reports a numerical simulation of the motion of a Carreau fluid over a transversely oscillating cylinder for a range of oscillation amplitudes and frequencies at Reynolds number ). This difference in the flow structures is explained through the behaviour of the diffusion terms in the vorticity transport equation. Further, the effect of the Carreau fluid properties on the flow structures and vorticity dynamics are also discussed.

Numerical simulation of flow of a shear-thinning Carreau fluid over a transversely oscillating cylinder

Magnetic nanoparticles are of immense importance in various biological applications such as bio-imaging techniques, drug delivery, hematologic disease detection, biomolecules separation (Figure 1). However, one of the limitations faced while using magnetic nanoparticles is to synthesize small size, high surface to volume ratio particles via simple approach. Magnetic nanoparticles in general are synthesized using hydrothermal method, template based method or electrochemical methods. These conventional synthesis approaches are not only complex to carry out but are also time consuming. Herein, we report a wet chemical method to synthesize high aspect ratio magnetite (Fe3O4) nanowires. The benefit of this method is facile, rapid and cost-effective process. The method involves a chemical reduction of ferrous sulphate and ferric chloride. The resultant product was obtained in two portions – the precipitate and the supernatant. Physical appearance of both the precipitate and supernatant was observed as brown in colour. These synthesized magnetic nanoparticles in supernatant were light in weight and completely dispersible in water for more than 6h. Surface morphology analysis of these nanoparticles demonstrated that the precipitate was aggregate of nanoparticles whereas the particles present in the supernatant were observed to be thin nanowires of dimension approximately ranged from 200 to 275nm with calculated aspect ratio of approximately eleven (Figure 2). Magnetic property was observed in these nanowires using a simple bar magnet.  Further, to enhance its biocompatibility, a thin gold coating was carried out on its surface. A reaction was performed by citrate capping followed by reduction using sodium borohydride in presence of chloroauric acid[1]. Gold coating was confirmed by a UV-vis absorbance spectrum that showed a distinct plasmonic peak at 540 nm (Figure 3). The prospective application planned in this study is for efficient separation of exosomes from bodily fluids. Conventionally exosome isolation is challenging in terms of process complexity, cost and accuracy[2]. Gold coated magnetic nanowires will allow direct attachment of a large number of exosomes by affinity interactions which can significantly enhance the capture efficiency. The magnetic activity allows magnetic nanowire based mixing, separation and purification via magnetic isolation and purification steps[3]. Alongside the light weight and dispersible nature of these nanowires prevents their agglomeration in the cell suspension allowing easy separation after exosome attachment using the external magnetic field. Overall these as synthesized high aspect ratio magnetic nanowires can be used as highly efficient nanocarriers for direct isolation of bulk exosomes from bodily fluids via magnetic separation method and thus can avoid the use of expensive commercial kit based multi-step pre-extraction procedures.
                 Figure 1. Applications of magnetic nanoparticles
              
Figure 2. SEM image of nanowires      Figure 3. Absorption spectra of gold coated nanowires

Somnath C. Roy

Papers

Numerical simulation of flow of a shear-thinning Carreau fluid over a transversely oscillating cylinder

Facile synthesis of high aspect ratio gold coated magnetic nanowires