AbstractCarbon nanomaterials, predominantly carbon nanofibers, carbon nanotubes, graphene, graphene nanoplates, graphene oxide and reduced graphene oxide, possess superior chemical, physical and mechanical properties. They have been successfully introduced into ordinary Portland cement to give enhancements in terms of mechanical properties, durability and electrical/thermal conductivity, and to modify the functional properties, converting conventional cement-based materials into stronger, smarter and more durable composites. This paper provides a comprehensive review of the properties of carbon nanomaterials, current developments and novel techniques in carbon nanomaterials enhanced cement-based composites (CN-CBCs). Further study of the applications of CN-CBCs at industrial scale is also discussed.

Porous Co3O4 hexagonal nanosheets (PCHNSs) with a well-defined morphology have been synthesized successfully via a hydrothermal process and followed by calcinations. Co3O4 nanosheets immobilizing horseradish peroxidase (HRP), together with reduced graphene oxide, have been used to modify glassy carbon electrode to fabricate a mediator-free biosensor. The morphology and structure of PCHNSs are studied by XRD, FESEM, and HRTEM techniques. Spectroscopic and electrochemical results reveal that Co3O4/rGO composite film is an excellent immobilization matrix with biocompatibility for enzymes, affording good enzymes' bioactivity and stability. Meanwhile, due to the unique structure of the modified electrode, the direct electron transfer of HRP is facilitated and the prepared nitrite biosensors display good performance---a wide linear range of 1 to 5400 μM, an extremely low limit of detection (LOD) as 0.21 μM and a limit of quantification as (LOQ) as 0.58 µM. This work suggests that Co3O4/rGO composite film is a potential matrix for enzymes' immobilization and biosensors' preparation.

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