Towards high-performance, low-cost quartz sensors with high-density, well-separated, vertically aligned ZnO nanowires by low-temperature, seed-less, single-step, double-sided growth

Abstract

Resonant sensors with nanostructured surfaces have long been considered as an emergent platform for high-sensitivity transduction because of the potentially very large sensing areas. Nevertheless, until now only complex, time-consuming, expensive and sub-optimal fabrication procedures have been described; in fact, especially with reference to in-liquid applications, very few devices have been reported. Here, we first demonstrate that, by immersing standard, ultra-low-cost quartz resonators with un-polished silver electrodes in a conventional zinc nitrate/HMTA equimolar nutrient solution, the gentle contamination from the metallic package allows direct growth on the electrodes of arrays of high-density (up to 10 μm⁻²) and well-separated (no fusion at the roots) ZnO nanowires without any seed layer or thermal annealing. The combination of high-density and good separation is ideal for increasing the sensing area; moreover, this uniquely simple, single-step process is suitable for conventional, ultra-low-cost and high-frequency quartzes, and results in devices that are already packaged and ready to use. As an additional advantage, the process parameters can be effectively optimized by measuring the quartz admittance before and after growth. As a preliminary test, we show that the sensitivity to the liquid properties of high-frequency (i.e. high sensitivity) quartzes can be further increased by nearly one order of magnitude and thus show the highest ever reported frequency shifts of an admittance resonance in response to immersion in both ethanol and water.

Real-time monitoring of the solution growth of ZnO nanorods arrays by quartz microbalances and in-situ temperature sensors

“…With reference to nanostructures, we focused on the synthesis of arrays of ZnO nanorods because of their wide applications including nanogenerators23242526, laser2728, piezotronics2930, piezo-photo-tronics303132 and sensors with superior performances203334. As an illustrative example, we have considered an extremely simple, single-step, double-sided method for growing high-density, well-separated, vertically aligned ZnO nanorods on quartz resonators by means of the most typical nutrient solution20, i.e.…”

“…As an illustrative example, we have considered an extremely simple, single-step, double-sided method for growing high-density, well-separated, vertically aligned ZnO nanorods on quartz resonators by means of the most typical nutrient solution20, i.e. DI water containing an equimolar concentrations of zinc nitrate and HMTA35.…”

Sensitivity to Heavy-Metal Ions of Unfolded Fullerene Quantum Dots

“…In the past decade, the research on nanomaterials has undergone a huge development in many different fields such as medicine, biology, energy and sensors [1][2][3][4][5][6]. In particular, innovative carbon-based nanomaterials such as graphene quantum dots (GQDs) and graphene oxide quantum dots (GOQDs) have attracted much interest as stable, nontoxic, photoluminescent nanomaterials with possible applications in chemical and biological sensors, drug delivery, bio-imaging and energy conversion [7][8][9][10][11][12][13].…”

Alignment nature of ZnO nanowires grown on polished and nanoscale etched lithium niobate surface through self-seeding thermal evaporation method

“…Accordingly, they are widely adopted as nanostructured sensing medium in chemical sensors [1][2][3][4][5]. For instance, 1-D ZnO nanostructures such as nanowires and nanorods have been used as sensing medium in acoustic wave devices like surface acoustic wave (SAW) devices [6][7][8][9][10][11] and quartz crystal microbalance (QCM) [12,13] for gas sensing and UV detection purposes. These kinds of acoustic devices are generally made of piezoelectric substrates such as quartz, lithium niobate, lithium tantalate, gallium orthophosphate and langasite.…”

“…However, all these methods require pre-deposition of a seed layer made of ZnO film to nucleate the growth of nanowires. The disadvantage of having a pre-deposited ZnO seed layer prior to the ZnO nanowire growth process is that it usually produces nanowires with fusion among their roots which in turn reduces the exposed surface area, thereby affecting the sensitivity of the nanowires [12]. Further, solution grown method is prone to contamination of the ZnO nanowires grown [17] which is unfavorable for sensor applications.…”