Carbon nanomaterial hybrids via laser writing for high-performance non-enzymatic electrochemical sensors: a critical review

Abstract

Non-enzymatic electrochemical sensors possess superior stability and affordability in comparison to natural enzyme-based counterparts. A large variety of nanomaterials have been introduced as enzyme mimicking with appreciable sensitivity and detection limit for various analytes of which glucose and H₂O₂ have been mostly investigated. The nanomaterials made from noble metal, non-noble metal, and metal composites, as well as carbon and their derivatives in various architectures, have been extensively proposed over the past years. Three-dimensional (3D) transducers especially realized from the hybrids of carbon nanomaterials either with metal-based nanocatalysts or heteroatom dopants are favorable owing to low cost, good electrical conductivity, and stability. In this critical review, we evaluate the current strategies to create such nanomaterials to serve as non-enzymatic transducers. Laser writing has emerged as a powerful tool for the next generation of devices owing to their low cost and resultant remarkable performance that are highly attractive to non-enzymatic transducers. So far, only few works have been reported, but in the coming years, more and more research on this topic is foreseeable.

Keywords: Carbon nanomaterials; Electrochemical detection; Laser-induced carbon; Nanocatalysts; Non-enzymatic sensor.

Fig. 1

Carbon nanomaterial-based electrocatalysts and their active sites or sources of catalytic activity for non-enzymatic sensors. Middle: graphene and its different structures [11]. a Acid-treated CNT and presence of oxygenated groups at the sidewall and tip [12]. b (i) SEM and (ii) TEM images of CNTs grown with 20 nm Fe/Ti underlayer [13]. c Nanographite impurities present in multi-walled CNT (MWCNT) powder [14]. d Introduction of metallic impurities during transferring CVD graphene onto other substrates [15]. e Introduction of impurities during common synthesis methods for the preparation of rGO using graphite as a starting material. Gray spheres represent carbon atoms, red spheres represent oxygen atoms, and other colors represent metallic impurities [16]. f Active catalytic sites in the graphene domain due to incorporation of heteroatoms [17]. a [12] reprinted with permission from Elsevier. Figure 1 in the middle [11] and c [14] reprinted with permission from John Wiley & Sons, Inc. d [15] reprinted with permission from the Royal Society of Chemistry. f reprinted with permission from [17]. Copyright (2013) American Chemical Society

Fig. 2

Heteroatom-doped carbon nanomaterials. a Structures of various heteroatom-doped carbon [33]. b Schematic representation of N-doped graphene. Gray for the carbon atom, blue for the nitrogen atom, and white for the hydrogen atom. A possible defect structure is shown in the middle of the ball-stick model (i), and its electrochemical performance for H₂O₂ detection in comparison to conventional electrodes (ii) [34]. c Preparation of N and S dual-doped graphene (NSG) (i) and its electrochemical performance for H₂O₂ detection in comparison to without N and S (microwave-exfoliated graphene, MEG) and individual atom doping (S-doped graphene, SG, and N-doped graphene, NG) [32]. d Electrocatalytic activity of P-doped graphene for dopamine (DA) detection (i), and the improved signal intensity realized by Au/P-doped graphene (ii) [35]. a [33] reprinted with permission from John Wiley & Sons, Inc. b adapted with permission from [34]. Copyright (2010) American Chemical Society. c [32] and d [35] adapted with permission from Elsevier

Fig. 3

3D carbon nanomaterials–electrocatalyst hybrids for non-enzymatic sensors. a SEM image of bare 3D graphene foam (i) where the inset shows the high-magnification SEM image. (ii) and (iii) low- and (iv) high-magnification SEM images of Ni(OH)₂/3D graphene foam [40]. b Hydrothermal preparation of holey nitrogen-doped graphene aerogel (HNGA) (i), SEM image of holey graphene aerogel (HGA) (ii), and electrochemical performance of the electrodes for simultaneous detection of AA, DA, and UA (iii) [41]. c Fabrication of bimetallic CoCu-carbon fiber (CuCo-CF) via electrospinning and thermal carbonization, and electrochemical performance of various bimetallic electrocatalysts (i), morphological structure of CuCo-CF after thermal carbonization (ii), and its energy dispersive X-ray (EDS) spectra (iii) [42]. d Patterning laser-scribed graphene (LSG) electrodes followed by drop-casting of Cu salt precursor solution (i–iii), reduction of Cu precursor via irradiation by focused sunlight (iv–vi), and SEM images of LSG-CuO nanoparticle hybrids prepared from different concentrations of Cu precursors (vii–ix) [39]. a [40] reprinted with permission from the Royal Society of Chemistry. b [41] and c [42] adapted with permission from Elsevier. d reprinted with permission from [39]. Copyright (2020) American Chemical Society

Fig. 4

Laser-induced non-enzymatic carbon nanofiber hybrids. a Fabrication of nanofibers precursors via electrospinning and carbonization by irradiation using CO₂ laser (i and ii), and a photograph of a laser-induced carbon nanofiber (LCNF) electrode (iii) [88]. b SEM images show the side view of LIG, electrospun nanofibers before (ii) and after laser carbonization (iii), electrocatalytic activity of LCNFs containing Fe in comparison to screen-printed carbon (SPCE) and gold (SPGE) electrodes (iv and v) [88]. c TEM images from low- to high-magnification display the presence of Ni nanoparticles in LCNFs after laser writing (i–iii), stacked graphene sheets present within LCNFs (iv), morphological structure of as-spun nanofibers containinh Ni before (v) and after (vi), and distribution of Ni on LCNF electrode studied by EDS (viii) [89]. d Amperograms of glucose at various LCNF electrodes (i), and calibration plot of glucose obtained from LCNFs with 25% Ni (ii) [89]. a and b [88] adapted with permission from the Royal Society of Chemistry. c adapted and d reprinted with permission from [89]. Copyright (2020) American Chemical Society

Fig. 5

Various approaches for fabrication of laser-induced carbon nanomaterials and metal hybrids in sensing applications. a Modification of LIG with Cu NPs through substrate-assisted electroless deposition (SAED) (i), TEM images of cubic Cu NP decorated LIG with high (ii) and low (iii) magnifications [91]. b Modification of LIG via sputtering (i), and SEM images of LIG before (ii) and after (iii) Pt sputtering [92]. c The schematic illustration of electrodeposition of Ag onto LSG electrodes [93]. a [91] adapted and c [93] reprinted with permission from Elsevier. b [92] adapted with permission from John Wiley & Sons, Inc

Fig. 6

Multi-analyte detection realized by LIG electrodes. a Simultaneous detection of AA, DA, and UA by DPV (i) and CV (ii) on LIG electrodes [94]. b Sensing system setup (i) and alternating current impedance response for distilled water (ii). c PCA plot for impedance responses of (i) mixed solutions and enlarged views for the responses of the (ii) vinegar and sugar mixture, (iii) NaCl and vinegar mixture, and (iv) NaCl and sugar mixture [95]. a [94] reprinted with permission from Elsevier. b reprinted and c adapted with permission from [95]. Copyright (2018) American Chemical Society

Fig. 7

Molecular imprinted LIG. a The preparation process of molecular imprinted polymer (MIP) on LIG realized by polypyrrole (PPy) for BPA determination and the device integration. b Analytical performance with respect to reusability (i), selectivity (ii) by using 1 μM of BPA and other interferences (EPI: epinephrine GAA: gallic acid, CAA: caffeic acid, E2: estradiol, CP: chlorophenol, DBP: dibuthyl phatalathe), and stability (iii) [96]. a reprinted and b [96] adapted with permission from Elsevier

Fig. 8

Wearable sensing systems based on laser-induced graphene. a Scheme of transferring LIG generated on polyimide foil (i) by casting with PDMS (ii) and subsequent peeling off (ii). The LIG is now bound to PDMS (iv) which offers elastic properties (v) [100]. b Transfer of LIG to Scotch tape that can be taped to the body and monitor analytes directly in produced sweat [39]. c Transfer of LIG to gas-permeable silicone elastomeric sponges (i), and multi-sensing abilities and demonstration of the flexible behavior of the sensor (ii) [101]. a [100] and c [101] adapted with permission from John Wiley & Sons, Inc. b adapted with permission from [39]. Copyright (2020) American Chemical Society