Preparation of porous carbon nanomaterials and their application in sample preparation: A review

Highlights

• Recent developments of advanced porous carbon nanomaterials (PCNMs) were reviewed.

• Application of PCNMs in sample preparation were summarized.

• New sample preparation methods based on porous carbon nanomaterials were introduced.

• Perspectives of PCNMs in sample preparation were outlooked.

Abstract

Porous carbon nanomaterials (PCNMs) have been favored by researchers because of their excellent properties, such as adjustable pore structure, high specific surface area, high porosity, good stability, and surface modifiability. At present, it has been widely used in the fields of adsorption, separation, catalysis, electrochemistry, and biomedicine. In recent years, new sample preparation methods based on porous carbon nanomaterials have emerged. This article outlines the preparation methods of PCNMs and their applications in solid phase extraction (SPE), dispersive solid phase extraction (DSPE), magnetic solid phase extraction (MSPE), solid phase microextraction (SPME), other sample preparation techniques, and prospects for them.

Introduction

Sample preparation is generally the first and key step in the process of sample analysis, especially in the trace analysis of complex samples. Due to the low concentration of analytes in these samples, it is necessary to pretreat the sample before detection to obtain reliable analysis results due to the existence of interferences and difficulties in direct detection. Pretreatment technology can improve the compatibility of samples and analytical instruments, purify samples, reduce the interference and pollution to analytical instruments, and pre-concentrate analytes to reduce the limit of detection/quantification [1]. So, sample preparation is widely used in the fields of environment analysis [2], food analysis [3,4], biological analysis [5] and other fields. At present, the commonly used pretreatment techniques include solid phase extraction (SPE), dispersive solid phase extraction (DSPE), magnetic solid phase extraction (MSPE), solid phase microextraction (SPME), etc. [6] Extraction materials play a vital role in these technologies, which are the key to achieve high extraction efficiency and high selective enrichment. In order to improve the reliability of sample detection results, researchers continue to explore extraction materials with excellent performance, such as metal organic frameworks (MOFs) [7], covalent organic frameworks (COFs) [8], carbon nanomaterials [9,10], molecularly imprinted polymers [11], organic polymer materials [12] and so on. At the same time, various porous carbon materials also become popular in different technologies of sample preparation.

Porous carbon nanomaterials (PCNMs) are carbon nanomaterials with different pore structures. According to the pore diameter, they can be divided into three categories: microporous (less than 2 nm), mesoporous (2–50 nm) and macroporous (more than 50 nm). The pore size can be adjusted according to the requirements of practical application. Generally speaking, the materials with smaller pore size have larger specific surface area. For most porous carbon materials, different pore structures will affect their capacity. In the past few decades, PCNMs have been developed continuously. A series of different kinds of PCNMs have been synthesized or derived from different materials, such as MOFs [13], COFs [14,15] and biomasses [16,17]. PCNMs are widely used in sample preparation, catalysis [18,19], electrochemistry [20,21] and biology [22], due to their large specific surface area (SSA) and pore volume, controllable porous structure, more active sites, good conductivity, and chemical stability [23]. Especially in the aspect of sample preparation, PCNMs as adsorbents can not only overcome the shortcomings of traditional adsorbents (graphitized carbon black, C8, C18), such as small specific surface area and low adsorption capacity, but also improve the adsorption performance through a variety of functions (hydrophobicity, hydrogen bonding, π-π conjugation). The performance of adsorbent directly affects the extraction efficiency, enrichment ability and anti-matrix interference ability of the whole method. Thus, several methods have been used to enhance the performance of PCNMs, such as doping of heteroatoms, surface functionalization, synthesis strategies, etc. [24,25].

So far, many articles and comments about porous carbon have been published, but they are mainly focused on supercapacitors, catalysis and integrated applications or the application of certain types of carbon nanomaterials in pretreatment. This review mainly focuses on the preparation of various PCNMs with ideal structures by different methods and their applications in sample preparation as adsorbent in recent years, and compares the advantages and disadvantages of the different approaches. In addition, the future prospective in the exciting and promising field will be discussed, which can provide a reference for future study.