The conversion of micro lignin to lignin nanoparticles (LNP) and their application in engineering and technology are potential steps towards global sustainability because lignin is obtained from industrial and agricultural waste and can be used in green chemistry. In the present study, we report the high-yield synthesis of lignin nanoparticles in different media, i.e., castor oil (CO), ethylene glycol (EG) and water (W) and evaluate their effect on the size and morphology of the LNP. The syntheses of LNP cover 9 out of 12 of the green chemistry principles; the synthesis was carried out via acid precipitation in a polyol medium, which acts as a stabilizing agent. From the results of the TEM, DLS, and SEM studies, it was observed that ≈15–20 nm LNP were successfully formed and spherical morphologies were observed when EG and CO were used as solvents. Furthermore, the anticorrosive behaviour of these nanoparticles was evaluated; the LNP acted as anticorrosive nanofillers for the protection of carbon steel (CS) in stringent corrosive conditions and was dispersed in an epoxy matrix to formulate epoxy nanocomposite coatings. Physicomechanical and electrochemical impedance spectroscopy (EIS) studies suggest that LNP-dispersed epoxy coatings potentially protect the underlying materials and show better protection as compared to the bare epoxy coatings.

Due to its remarkable impermeability to gases, vapours, and liquids, graphene (G) is used as an excellent coating for metal protection. However, due to its high conductivity, recent studies have reported that G fails to prevent metal corrosion under long-term air exposure. Here, we obtained B-doped graphene (BG) and N-doped graphene (NG) with electron donating/withdrawing elements and then used them to modify the waterborne polyurethane (PU) resin. Our work reveals that embedding BG into a PU matrix greatly improves anticorrosion performance. The results revealed that graphene (BG) doped with electron accepting dopants exhibits a long-term corrosion resistance based on the suppression of galvanic corrosion, while graphene (NG) doped with electron donating dopants exhibits corrosion promotion due to its enhanced conductivity. Typically, the impedance modulus of BG/PU at Z_f=0.01Hz was up to 10⁸ Ω cm², increasing by approximately three orders of magnitude compared to that of neat PU, G/PU, and NG/PU (∼10⁶ Ω cm²) after immersion for 240 h in 3.5 wt% NaCl_(aq). The present investigation provides important future implications for the fabrication of graphene-based anticorrosive coatings with excellent durability.

Although semiconductor transition metal dichalcogenides (TMDs) are expected to be applied for corrosion protection, few studies have focused on the interactions between TMDs and metal substrates. Herein, few layered TMD nanosheets of MoS₂ and WS₂ were prepared through a liquid exfoliation technique. And then, the TMD reinforced epoxy (TMD/EP) nanocomposite coatings were fabricated through incorporating MoS₂ and WS₂ nanosheets into an epoxy matrix. The corrosion behavior of the TMD/EP nanocomposite coatings was investigated by a series of electrochemical tests like EIS and polarization curve tests. And the corrosion-promotion activity of the MoS₂ and WS₂ was also studied through EIS measurements of the semiconductor/metal contacts at coating defects. Our work reveals that single layered TMDs and graphene accelerated the corrosion of metals, while few layered TMD nanosheets exhibited no promising effect. At the same time, we proposed different corrosion mechanisms according to the work function difference of nanomaterials as well as their oxygen reduction reaction activity to clarify the corrosion-promotion activity.

The unique properties of graphene are highly desired for printing electronics, coatings, energy storage, separation membranes, biomedicine, and composites. However, the high efficiency exfoliation of graphene into single- or few-layered nanoplates remains a grand challenge and becomes the bottleneck in essential studies and applications of graphene. Here, we report a scalable and green method to exfoliate graphene nanoplatelets (GNPs) from nature graphite in pure water without using any chemicals or surfactants. The essence of this strategy lies in the facile liquid exfoliation route with the assistance of vapor pretreatment for the preparation of edge hydroxylated graphene. The produced graphene consisted primarily of fewer than ten atomic layers. Such the water soluble graphene can be stored in the form of dispersion (~0.55 g L⁻¹) or filter cake for more than 6 months without the risk of re-stacking. This method paves the way for the environmentally friendly and cost-effective production of graphene-based materials.

Graphene nanosheets (GNSs) possess outstanding conductivity, good thermal and chemical stabilities and desirable mechanical strengths. However, the unfunctionalized GNSs are hydrophobic and insoluble in water, which limits their application in many technological areas. Herein, we report a design strategy to exfoliate few-layered aqueous dispersible graphene by a simple ball-milling technique. The modifier of sodium lignosulfonate (LS) enables to synthesize LS-decorated GNSs from natural graphite based on the strong π–π interaction, greatly improving GNSs dispersion in water. The resultant GNSs exhibit a high production yield (∼100%), high dispersion concentration and excellent film formation ability. The electrical and thermal conductivities of the as-prepared graphene paper were up to 2385 S cm⁻¹ and 1324 W m⁻¹ K⁻¹, respectively, superior to those of most previously reported graphene materials. This graphene paper with the superb electrical and thermal conduction properties also exhibits excellent mechanical flexibility and structure intensity during bending, which has potential usages in electronic packaging and high power thermal management.

Although numerous papers have reported that graphene is a superior anticorrosion nanofiller, it has also been demonstrated that graphene cannot be used as a long-term anticorrosion barrier due to its essential high conductivity. Herein, an anticorrosive nanofiller (BNQDs@hBN) combining the nanomaterial boron nitride quantum dots (BNQDs) with insulating hexagonal boron nitride (hBN) is put forward. The homogeneous dispersion of BNQDs@hBN in an epoxy matrix was achieved with the assistance of BNQDs, and was based on strong π–π interactions between h-BN and BNQDs, as confirmed via UV-vis spectra. Embedding a small percentage of BNQDs@hBN in a waterborne epoxy (WEP) coating effectively improves the barrier properties of the coating by inhibiting the penetration of corrosive ions. Polarization tests revealed that the protection efficiency and corrosion rate of an epoxy coating with 0.5 wt% BNQDs@hBN were 99.99% and 6.482 × 10⁻⁵ mm year⁻¹, respectively. Electrochemical impedance spectroscopy (EIS) results demonstrated that the 0.5 wt% BNQDs@hBN coating system showed a higher impedance modulus (>10⁷) than that of a blank specimen after immersion for 60 days in 3.5 wt% NaCl_(aq).