Ordered Monolayer Gold Nano-urchin Structures and Their Size Induced Control for High Gas Sensing Performance

Abstract

The synthesis of ordered monolayers of gold nano-urchin (Au-NU) nanostructures with controlled size, directly on thin films using a simple electrochemical method is reported in this study. In order to demonstrate one of the vast potential applications, the developed Au-NUs were formed on the electrodes of transducers (QCM) to selectively detect low concentrations of elemental mercury (Hg0) vapor. It was found that the sensitivity and selectivity of the sensor device is enhanced by increasing the size of the nanospikes on the Au-NUs. The Au-NU-12 min QCM (Au-NUs with nanospikes grown on it for a period of 12 min) had the best performance in terms of transducer based Hg0 vapor detection. The sensor had 98% accuracy, 92% recovery, 96% precision (repeatability) and significantly, showed the highest sensitivity reported to date, resulting in a limit of detection (LoD) of only 32 μg/m3 at 75 °C. When compared to the control counterpart, the accuracy and sensitivity of the Au-NU-12 min was enhanced by ~2 and ~5 times, respectively. The results demonstrate the excellent activity of the developed materials which can be applied to a range of applications due to their long range order, tunable size and ability to form directly on thin-films.

Silicon as a ubiquitous contaminant in graphene derivatives with significant impact on device performance

“…The highest purity GO sheets displayed an extremely low limit of detection (LOD) of 0.006% RH at 27 °C, which is equivalent to 1.5 mg/m 3 (2 ppm) absolute humidity; a level which has not been reported to date. This LOD is at least two orders of magnitude superior to the best-performing 2D MXenes (LOD of 0.8% RH) and around one order of magnitude better than the lowest reported LOD in the literature 46 . Similar trend was found when the effect of temperature is considered (Fig.…”

Long‐Range Ordered Crystals of 3D Inorganic–Organic Heterojunctions via Colloidal Lithography

“…The strategy employed for the preparation of ZnO/AgTCNQ heterojunction nanoarrays is illustrated in Figure . Briefly, a thin layer of zinc oxide was deposited on a silicon wafer, on which a uniform monolayer of polystyrene (PS) microspheres was assembled via an air/water interface strategy . This was followed by e‐beam deposition of a 300 nm thick Ag on the PS monolayer, subsequently followed by the removal of the PS template by sonication.…”

Galvanic-Cell-Reaction-Driven Deposition of Large-Area Au Nanourchin Arrays for Surface-Enhanced Raman Scattering

“…In order to tune their unique properties and further improve their performance, Au nanostructures with diverse geometric features, including plate [ 23 ], cube [ 24 ], cage [ 25 ], wire [ 26 ], sphere [ 27 ], decahedron [ 28 ], and branched nanostructures [ 29 ] have been synthesized through a rich variety of chemical methods. Recently, urchin-like Au nanostructures, such as Au nanostars [ 18 , 30 ] and Au nanourchins [ 31 , 32 , 33 , 34 , 35 , 36 , 37 ], a class of nanostructures with sharp protrusions, have aroused great interest, because of the strong relation between the fantastic morphology and their unique optical properties. The individual nanourchin is composed of many sharp nanotips serving as nanoantennas, where localized surface plasmons (LSPs) can be excited by the incident light to enhance the local electromagnetic (EM) field intensity by 2–5 orders of magnitude [ 35 ].…”

“…However, Au nanourchins achieved by the colloidal strategy are not the optimal option for wafer-based applications, including optics, electrocatalysis, chemical/biochemical sensing, and SERS substrates. On the other hand, large area Au nanourchin array, based wafer substrates could be produced via a two-step process combining a variety of prefabricated 3D templates, such as polyaniline (PANI) membrane [ 34 ], polystyrene (PS) nanospheres [ 33 ], Ag-nanohemisphere arrays [ 39 ] and then assembling or electrodepositing Au nanoparticles onto the 3D templates through electrochemical systems [ 40 , 41 ], which broaden application fields of the Au nanourchins. However, it is usually time-consuming and expensive to fabricate large-scale 3D Au nanourchin array-based wafer substrates.…”