Nanotechnology Applications for Clean Water

Solutions for Improving Water Quality

Anita Street, Richard Sustich, Jeremiah Duncan, Nora Savage

• Publisher: William Andrew
• Year: 2014
• ISBN:
  9781455731855
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

Nanotechnology is already having a dramatic impact on improving water quality and the second edition of Nanotechnology Applications for Clean Water highlights both the challenges and the opportunities for nanotechnology to positively influence this area of environmental protection. This book presents detailed information on cutting-edge technologies, current research, and trends that may impact the success and uptake of the applications.

Recent advances show that many of the current problems with water quality can be addressed using nanosorbents, nanocatalysts, bioactive nanoparticles, nanostructured catalytic membranes, and nanoparticle enhanced filtration. The book describes these technologies in detail and demonstrates how they can provide clean drinking water in both large scale water treatment plants and in point-of-use systems. In addition, the book addresses the societal factors that may affect widespread acceptance of the applications.

Sections are also featured oncarbon nanotube arrays and graphene-based sensors forcontaminant sensing, nanostructured membranes for water purification, and multifunctional materials incarbon microspheresfor the remediation of chlorinated hydrocarbons.

• Addresses both the technological aspects of delivering clean water supplies and the societal implications that affect take-up
• Details how the technologies are applied in large-scale water treatment plants and in point-of-use systems
• Highlights challenges and the opportunities for nanotechnology to positively influence this area of environmental protection

Part 1

Contaminant Sensing Technologies

Outline

Chapter 1 Sensors Based on Carbon Nanotube Arrays and Graphene for Water Monitoring

Chapter 2 Advanced Nanosensors for Environmental Monitoring

Chapter 3 Electrochemical Biosensors Based on Nanomaterials for Detection of Pesticides and Explosives

Chapter 4 Dye Nanoparticle-Coated Test Strips for Detection of ppb-Level Ions in Water

Chapter 5 Functional Nucleic Acid-Directed Assembly of Nanomaterials and Their Applications as Colorimetric and Fluorescent Sensors for Trace Contaminants in Water

Chapter 1

Sensors Based on Carbon Nanotube Arrays and Graphene for Water Monitoring

Dan Du^1,3, Weiying Zhang^1,3, Abdullah Mohamed Asiri² and Yuehe Lin^3,4, ¹Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, PR China, ²Chemistry Department, King Abdulaziz University, Jeddah, Saudi Arabia, ³School of Mechanical and Materials Engineering, Washington State University, Pullman, WA, USA, ⁴Pacific Northwest National Laboratory, Richland, WA, USA

Nanomaterials, particularly carbon nanomaterials, have shown great promise in environmental applications. In this chapter, we focus only on the use of two carbon nanomaterials, carbon nanotubes (CNTs) and graphene-based sensors for water monitoring and detection of hazardous chemicals. The excellent electrochemical behaviors of CNTs and graphene indicate that they are promising electrode materials in electroanalysis. Sensors based on CNTs and graphene have shown excellent performance in electrochemical detection of metal ions, pesticides, and other pollutants.

Keywords

Sensors; carbon nanotubes; arrays; graphene; metals; pesticides

Outline

1.1 Introduction 3

1.2 CNT-based electrochemical sensors 5

1.2.1 Various methods for preparation of CNT-based sensors 5

1.2.2 Fabrication of aligned CNT NEA 6

1.2.3 Applications of CNT-based sensors for metal ion monitoring 7

1.3 Graphene-based sensors 8

1.3.1 Graphene-based electrochemical sensors 8

1.3.2 Graphene sensors for pesticides 10

1.3.3 Graphene sensors for other pollutants 14

1.4 Conclusions and future work 15

Acknowledgments 16

References 16

1.1 Introduction

Environmental monitoring of toxic pollutants in surface and subsurface water sources and wastewaters presently relies on the collection of discrete liquid samples for subsequent laboratory analysis. Sensors that are field-deployable and able to measure part-per-billion (ppb) or nanomolar levels of toxic pollutants will reduce time and costs associated with environmental monitoring of hazardous chemicals. Electrochemical sensors appear to be a very promising technique that offers desired characteristics such as field-deployability, selectivity, sensitivity, robustness, and inexpensiveness [1–3].

Nanomaterials, particularly carbon nanomaterials, have a significant role to play in new developments in each of the biosensor size domains [4–6]. They have shown great promise in many applications, such as bioscience and biotechnology, energy storage and conversion, environmental and biomedical applications. In this chapter, we focus only on the use of two carbon nanomaterials, carbon nanotubes (CNTs) and graphene-based sensors for water monitoring and environmental applications.

CNTs are well-ordered, hollow graphitic nanomaterials made of cylinders of sp²-hybridized carbon atoms. They have high aspect ratios, high mechanical strength, high surface areas, excellent chemical and thermal stabilities, and rich electronic and optical properties [7]. The latter properties make CNTs important transducer materials in biosensors: high conductivity along their length means they are excellent nanoscale electrode materials [8–10]. These materials are classed as single-walled carbon nanotubes (SWCNTs) (Figure 1.1A), which are single sheets of graphene “rolled” into tubes, or multiwalled carbon nanotubes (MWCNTs), each of which contains several concentric tubes that share a common longitudinal axis [11]. As one-dimensional (1D) carbon allotropes, CNTs have lengths that can vary from several hundred nanometers to several millimeters, but their diameters depend on their class: SWCNTs are 0.4–2 nm in diameter and MWCNTs are 2–100 nm in diameter. An important part of the success of CNTs for these applications is their ability to promote electron transfer in electrochemical reactions.

Figure 1.1 (A) The ideal structures of an SWCNT and (B) a graphene sheet. From Ref. [4], reproduced by permission of Wiley-VCH.

Graphene is a 2D sheet of carbon atoms in a hexagonal configuration with atoms bonded by sp² bonds. These bonds and this electron configuration are the reasons for the extraordinary properties of graphene, which include a very large surface area (at 2630 m²/g, it is double that of SWCNTs), a tunable band gap, room-temperature Hall effect, high mechanical strength (200 times greater than steel), and high elasticity and thermal conductivity [12]. Graphene is the most recent member of the multidimensional carbon-nanomaterial family, starting with fullerenes as a 0D material, SWCNTs as 1D nanomaterials, and ending with graphite as a 3D material. Graphene fills the gap for 2D carbon nanomaterials (Figure 1.1B). Isolation of individual graphene sheets was long sought, but only in 2004, it was achieved by a surprisingly simple technique [13]. Since then, fundamental research and research on applications have increased rapidly. Graphene is an ideal material for electrochemistry [14–17] because of its very large 2D electrical conductivity, large surface area, and low cost. The use of graphene in electrochemical sensors and biosensors is particularly interesting, with the first articles emerging in 2008. Since then, their number has grown explosively.

1.2 CNT-based electrochemical sensors

1.2.1 Various methods for preparation of CNT-based sensors

Although CNTs are relatively new in analytical fields, their unique electronic (electron transfer rate similar to edge-plane graphite), chemical (biocompatibility and ability to be covalently functionalized), and mechanical properties (3 times stronger than steel) make them extremely attractive for chemical and biochemical sensors [18,19]. Various methods have been used to prepare CNT-based sensors: (a) casting of CNT thin films, from the suspensions of CNTs in solvents [20–28], such as sulfuric acid [21], Nafion [25], dihexadecyl hydrogen phosphate (DHP) [26], DMF [27], and acetone [28], prior to being coated on electrode surfaces, (b) using CNTs as paste electrodes or electrode composites [29–31], and (c) using aligned CNT as electrode substrates [32–40]. With specific to metal ion sensors, DHP [26] and Nafion [25] have been used to disperse MWCNTs under ultrasonication prior to being drop-coated on glassy carbon electrodes. The CNT film enables the development of mercury-free electrodes that can detect from 10⁻⁹ to 10⁻⁶ M of Cd and Pb.

Most CNT-based sensors take advantage of the bulk properties of CNTs, including increased electrode surface area [41], fast electron transfer rate [42], and good electrocatalytivity in promoting electron transfer reactions of many important species [43,44]. Using CNTs as nanoelectrod...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Foreword
• Preface
• Acknowledgment
• Introduction: Water Purification in the Twenty-First Century—Challenges and Opportunities
• Part 1: Contaminant Sensing Technologies
• Part 2: Separation Technologies
• Part 3: Transformation Technologies
• Part 4: Stabilization Technologies
• Part 5: Societal Issues
• Part 6: Outlook