Green Chemistry is a relatively new emerging field that strives to work at the molecular level to achieve sustainability. The field has received widespread interest in the past decade due to its ability to harness chemical innovation to meet environmental and economic goals simultaneously. Green Chemistry has a framework of a cohesive set of Twelve Principles, which have been systematically surveyed in this critical review. This article covers the concepts of design and the scientific philosophy of Green Chemistry with a set of illustrative examples. Future trends in Green Chemistry are discussed with the challenge of using the Principles as a cohesive design system (93 references).

Green Chemistry: Principles and Practice

Antibacterial activity of zinc oxide nanoparticles (ZnO-NPs) has received significant interest worldwide particularly by the implementation of nanotechnology to synthesize particles in the nanometer region. Many microorganisms exist in the range from hundreds of nanometers to tens of micrometers. ZnO-NPs exhibit attractive antibacterial properties due to increased specific surface area as the reduced particle size leading to enhanced particle surface reactivity. ZnO is a bio-safe material that possesses photo-oxidizing and photocatalysis impacts on chemical and biological species. This review covered ZnO-NPs antibacterial activity including testing methods, impact of UV illumination, ZnO particle properties (size, concentration, morphology, and defects), particle surface modification, and minimum inhibitory concentration. Particular emphasize was given to bactericidal and bacteriostatic mechanisms with focus on generation of reactive oxygen species (ROS) including hydrogen peroxide (H2O2), OH− (hydroxyl radicals), and O2 −2 (peroxide). ROS has been a major factor for several mechanisms including cell wall damage due to ZnO-localized interaction, enhanced membrane permeability, internalization of NPs due to loss of proton motive force and uptake of toxic dissolved zinc ions. These have led to mitochondria weakness, intracellular outflow, and release in gene expression of oxidative stress which caused eventual cell growth inhibition and cell death. In some cases, enhanced antibacterial activity can be attributed to surface defects on ZnO abrasive surface texture. One functional application of the ZnO antibacterial bioactivity was discussed in food packaging industry where ZnO-NPs are used as an antibacterial agent toward foodborne diseases. Proper incorporation of ZnO-NPs into packaging materials can cause interaction with foodborne pathogens, thereby releasing NPs onto food surface where they come in contact with bad bacteria and cause the bacterial death and/or inhibition.

/pdf/review-on-zinc-oxide-nanoparticles-antibacterial-activity-2smaigi8sc.pdf

Review on Zinc Oxide Nanoparticles: Antibacterial Activity and Toxicity Mechanism.

https://eva.fing.edu.uy/pluginfile.php/55828/mod_resource/content/1/kalogiru.pdf

Solar thermal collectors and applications

An introduction to heat transfer

Band bending in semiconductors: chemical and physical consequences at surfaces and interfaces.

Experimental Study on Operating Characteristics of Nitrate Salt-Based Latent Heat Thermal Energy Storage Unit

Macro encapsulation techniques have gained considerable attention in latent heat storage systems for solar energy applications in order to improve the overall energy conversion efficiency in solar thermal power plants. However the heat transfer mechanisms that govern the charging and discharging processes at high operating temperatures are still under development and represent an important aspect in the thermal energy storage design process. This study presents a numerical solution of the heat transfer and phase change that occurs during the solidification process of a phase change material (PCM) encapsulated in a spherical container. A transient two-dimensional axisymmetric mathematical model was solved using the control volume discretization approach along with the enthalpy-porosity method to track the melting front. A spherical shell of thickness t, under the gravitational field is completely filled with liquid PCM. For time t>0, a constant temperature boundary condition Tw, which is lower than the phase change temperature of the PCM, is imposed at the outer surface of the shell. A comprehensive analysis is presented in order to assess the role of the capsule size, buoyancy-driven flow in the liquid phase, and shell outer surface temperature on the thermal performance of the system. Results show that with the increase of Stefan number the solidification rate is enhanced. A reduction of 39.25% in total solidification time is predicted when the Stefan number changed from 0.095 to 0.143. Finally a generalized correlation for the solid mass fraction during solidification is obtained based on a combination of Fourier and Stefan numbers and a dimensionless material parameter.Copyright © 2013 by ASME

Numerical Solution of Heat Transfer During Solidification of an Encapsulated Phase Change Material

Robert McConnell National Renewable Energy Laboratory 23.1 Photovoltaics ..................................................................... 23-

Photovoltaics Fundamentals, Technology and Application

The present study numerically investigates the process of melting in a hollow vertical cylinder, filled with a phase change material (PCM). The PCM used is sodium nitrate, which expands upon melting. Therefore, the cylindrical shell is partially filled with the PCM and the remaining volume is occupied by air. The influence of cylinder shape on the melting and heat transfer rate is analyzed. The numerical model takes both conductive and convective heat transfer into account during the melting process. For the problem being considered here, the dimensionless numbers that characterized the process are the Grashof, Stefan, and Prandtl numbers. The Aspect Ratio (AR) is used to characterize the shape of the cylinder, which is defined as the ratio of the height to the diameter of the cylinder. In this study, a range of AR values from 0.25 to 10 are investigated. Cylinders with small AR, corresponding to high Grashof numbers, lead to lower melting times compared with cylinders with high AR. The partially melted PCM shape differed between the high and low AR cases. The molten PCM stream function was also influenced greatly by the variation in solid PCM shape.Copyright © 2013 by ASME

Melting in Vertical Cylinders During Thermal Energy Storage

Metal-insulator-metal (MIM) diodes play significant role in high speed electronics where high frequency rectification is needed Quantum based tunneling mechanism helps MIM diodes to rectify at high frequency signals Rectenna, antenna coupled MIM diodes are becoming popular due to their potential use as IR detectors and energy harvesters Because of small active area, MIM diodes could easily be incorporated into integrated circuits (IC's) The objective of the work is to design and develop MIM diodes for high frequency rectification In this work, thin insulating layer of ZnO was fabricated using Langmuir-Blodgett (LB) technique which facilitates ultrathin thin, uniform and pinhole free fabrication of insulating layer The ZnO layer was synthesized from organic precursor of zinc acetate layer The optimization in the LB technique of fabrication process led to fabricate MIM diodes with high non-linearity and sensitivity Moreover, the top and bottom electrodes as well as active area of the diodes were patterned using UV-tunneling conduction mechanism The highest sensitivity of the diode was measured around 37 (A/W), and the rectification ratio was found around 36 under low applied bias at ±100 mV

D. Yogi Goswami

Papers

Experimental Study on Operating Characteristics of Nitrate Salt-Based Latent Heat Thermal Energy Storage Unit

Numerical Solution of Heat Transfer During Solidification of an Encapsulated Phase Change Material

Photovoltaics Fundamentals, Technology and Application

Melting in Vertical Cylinders During Thermal Energy Storage

Design and fabrication of metal-insulator-metal diode for high frequency applications