Reduced Graphene Oxide Conjugated Cu₂O Nanowire Mesocrystals for High-Performance NO₂ Gas Sensor

Abstract

Reduced graphene oxide (rGO)-conjugated Cu(2)O nanowire mesocrystals were formed by nonclassical crystallization in the presence of GO and o-anisidine under hydrothermal conditions. The resultant mesocrystals are comprised of highly anisotropic nanowires as building blocks and possess a distinct octahedral morphology with eight {111} equivalent crystal faces. The mechanisms underlying the sequential formation of the mesocrystals are as follows: first, GO-promoted agglomeration of amorphous spherical Cu(2)O nanoparticles at the initial stage, leading to the transition of growth mechanism from conventional ion-by-ion growth to particle-mediated crystallization; second, the evolution of the amorphous microspheres into hierarchical structure, and finally to nanowire mesocrystals through mesoscale transformation, where Ostwald ripening is responsible for the growth of the nanowire building blocks; third, large-scale self-organization of the mesocrystals and the reduction of GO (at high GO concentration) occur simultaneously, resulting in an integrated hybrid architecture where porous three-dimensional (3D) framework structures interspersed among two-dimensional (2D) rGO sheets. Interestingly, "super-mesocrystals" formed by 3D oriented attachment of mesocrystals are also formed judging from the voided Sierpinski polyhedrons observed. Furthermore, the interior nanowire architecture of these mesocrystals can be kinetically controlled by careful variation of growth conditions. Owing to high specific surface area and improved conductivity, the rGO-Cu(2)O mesocrystals achieved a higher sensitivity toward NO(2) at room temperature, surpassing the performance of standalone systems of Cu(2)O nanowires networks and rGO sheets. The unique characteristics of rGO-Cu(2)O mesocrystal point to its promising applications in ultrasensitive environmental sensors.

Facet‐Controlled Synthetic Strategy of Cu2O‐Based Crystals for Catalysis and Sensing

“…In this context, the inexpensive, non‐toxic and abundantly available Cu 2 O nanomaterials, with unique optical and electrical properties,4, 9, 10, 53, 54, 55, 56, 57, 58 have recently aroused general attention, due to their outstanding morphology‐dependent applications in catalysis (gas oxidation,2, 3, 17, 59, 60, 61 CO 2 reduction,62, 63, 64, 65 organocatalysis,14, 24, 32, 40, 50, 66 electrocatalysis,28, 67, 68 and photocatalysis36, 44, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, sensing (gas sensors,8, 79, 80, 81, 82, 83 ion detection,29 and surface‐enhanced Raman scattering (SERS)84, 85, 86, 87, 88, 89, as adsorbents,7, 90 biotoxicity,26, 91, 92 as chemical templates35, 38, 45, 4...…”

“…Compared to Cu 2 O nanowires72, 81, 104, 105, 106 or nanorods,83, 107 nanospheres,53, 64, 76, 82, 84, 87, 90, 108, 109 hollow structures,42, 57, 67, 73, 79, 94, 95, 101, 110, 111, 112, 113, 114 self‐assembled superstructures,8, 115, 116 and Cu 2 O polyhedra enclosed by high‐index planes,17, 117, 118, 119, 120, 121, 122 the preparation of Cu 2 O polyhedra enclosed by low‐index planes2, 3, 7, 8, 9, 14, 25, 26, 29, 32, 55, 57, 66, 68, 75, 91, 92, 123, 124, 125, 126, 127, 128, 129 is simple and large‐scale. Even more importantly, several novel facet‐controlled routes, including carving,…”

A nanocomposite superstructure of metal oxides with effective charge transfer interfaces

“…So far, a variety of mesocrystals of metal oxides (for example, TiO 2 , ZnO, Fe 2 O 3 and CuO) have been synthesized [6][7][8][9][10] . The method most commonly used to synthesize mesocrystal materials is based on hydrothermal/solvothermal treatments [11][12][13][14] , in which the solution should be maintained at a specific temperature and aged for a specific period of time. The resulting precipitates are then collected and washed to remove impurities, and, in some cases, the precipitates also require further annealing.…”

Human‐Like Sensing and Reflexes of Graphene‐Based Films

“…For instance, vertically aligned ZnO nanorods was utilized to prepare hybrid material with chemically converted graphene116 and CVD graphene,117 in order to maximize the surface area to achieve a fast and easy gas transport. In addition, Cu 2 O nanowire was also used as a hybrid source to compound with rGO sheets, which have enhanced the response for 2 ppm NO 2 from 22.5% to 67.8% 118. And its theoretically calculated LOD of 64 ppb was lower than the rGO and Cu 2 O, which showed a significantly enhanced sensitivity.…”