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

Sabri YM, Kandjani AE, Ippolito SJ, Bhargava SK - Sci Rep (2016)

Bottom Line: 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 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.

View Article: PubMed Central - PubMed

Affiliation: Centre for Advanced Materials and Industrial Chemistry (CAMIC), School of Applied Sciences, RMIT University, GPO Box 2476V, Melbourne, VIC 3001 (Australia).

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 (Hg(0)) 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 Hg(0) 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.

No MeSH data available.


Electrochemical characterization data showing (a) cyclic voltammograms (CVs) obtained at an Au electrode for the reduction of gold from an electrolyte containing 2.718 g/L HAuCl4•3H2O and 0.177 g/L Pb(CH3COO)2•3H2O recorded at 50 mV s−1; (b) the current stability during the formation of Au-NU with different nanospike sizes; (c) Linear sweep voltammograms (LSVs) for the Au-control and Au-NU-6 min samples obtained in 1 M H2SO4 at 100 mV s−1 (d) the electrochemical surface area (ESA) calculate from the reduction of one oxide monolayer formed on the Au surfaces during the reduction phase of the cyclic voltammogram recorded in 1 M H2SO4. The geometric surface area of each substrate was 0.196 cm2.
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f3: Electrochemical characterization data showing (a) cyclic voltammograms (CVs) obtained at an Au electrode for the reduction of gold from an electrolyte containing 2.718 g/L HAuCl4•3H2O and 0.177 g/L Pb(CH3COO)2•3H2O recorded at 50 mV s−1; (b) the current stability during the formation of Au-NU with different nanospike sizes; (c) Linear sweep voltammograms (LSVs) for the Au-control and Au-NU-6 min samples obtained in 1 M H2SO4 at 100 mV s−1 (d) the electrochemical surface area (ESA) calculate from the reduction of one oxide monolayer formed on the Au surfaces during the reduction phase of the cyclic voltammogram recorded in 1 M H2SO4. The geometric surface area of each substrate was 0.196 cm2.

Mentions: The cyclic voltammogram (CV) of the Au3+/Pb2+ electrolyte used to deposit the Au-nanospikes directly on the Au-MNM is shown Fig. 3a. The Pb2+ ions work as an inorganic shape-directing additive for the growth of nanospikes in order to form the NU structures while it does not alter the surface chemistry of the deposited gold4254. The deposition of the Au nanospikes was carried out at a constant potential (0.05 V) for periods of 6, 8, 10, 12 and 15 minutes, the current profiles (current-time curve) of which are presented in Fig. 3b. It can be observed that the current is increased and reaches stable state following the first 30 seconds of deposition, where the current is observed to reach a constant value ranging from −250 to −50 μA, depending on the sample. This fast transition to the steady stage is attributed to the uniform growth of nanospikes forming the NU nanostructures, the size of which depends on the deposition period. The electrochemically active surface area of the Au-NUs and Au-control were determined by using the linear sweep voltammetry (LSV) technique that was developed by Rand and Woods425455. This involved recording the CVs for each sample at 100 mVs−1 in a 1 M H2SO4 solution vs Ag/AgCl auxiliary electrode. The CVs for the Au-control and Au-NU-6 min samples are shown in Fig. 3c. The increase observed at the cathodic peak (ca. 0.93 V) is indicative of oxide removal that was formed at the electrode surface during the forward sweep. The onset for this oxide formation is found to be at ~0.98 V and ~1.2 V for the Au-NU-6 min and Au-control, respectively. Similarly the CVs for the Au-MNM, Au-NU-8 min, Au-NU-10 min, Au-NU-12 min and Au-NU-15 min presented in the Supplementary information (Fig. S3) also show lower onset potentials for oxide formation thereby indicating that highly active Au nanostructures are present on the modified Au-NU surfaces. The shoulder observed at ca. 1.1 V before the main oxidation peak further confirms that the Au-NU-6 min have active surface defect sites54. When the active electrochemical surface areas of the samples were calculated using the reduction peak, it was observed that the Au-NU-6 min sample had over 6 times the surface area of Au-control sample. The difference in surface area is observed to increase with increasing electrodeposition time (see Supplementary information, Fig. S3) with the 15 minute electrodeposition of nanospikes (Au-NU-15 min) having ~10 times the surface area of the Au-control sample and more than 25 times higher than the geometrical surface area as shown in Fig. 3d. High surface area based gold nanostructures are of particular interest in numerous applications such as catalysis, batteries and bio-sensors56.


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

Sabri YM, Kandjani AE, Ippolito SJ, Bhargava SK - Sci Rep (2016)

Electrochemical characterization data showing (a) cyclic voltammograms (CVs) obtained at an Au electrode for the reduction of gold from an electrolyte containing 2.718 g/L HAuCl4•3H2O and 0.177 g/L Pb(CH3COO)2•3H2O recorded at 50 mV s−1; (b) the current stability during the formation of Au-NU with different nanospike sizes; (c) Linear sweep voltammograms (LSVs) for the Au-control and Au-NU-6 min samples obtained in 1 M H2SO4 at 100 mV s−1 (d) the electrochemical surface area (ESA) calculate from the reduction of one oxide monolayer formed on the Au surfaces during the reduction phase of the cyclic voltammogram recorded in 1 M H2SO4. The geometric surface area of each substrate was 0.196 cm2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835752&req=5

f3: Electrochemical characterization data showing (a) cyclic voltammograms (CVs) obtained at an Au electrode for the reduction of gold from an electrolyte containing 2.718 g/L HAuCl4•3H2O and 0.177 g/L Pb(CH3COO)2•3H2O recorded at 50 mV s−1; (b) the current stability during the formation of Au-NU with different nanospike sizes; (c) Linear sweep voltammograms (LSVs) for the Au-control and Au-NU-6 min samples obtained in 1 M H2SO4 at 100 mV s−1 (d) the electrochemical surface area (ESA) calculate from the reduction of one oxide monolayer formed on the Au surfaces during the reduction phase of the cyclic voltammogram recorded in 1 M H2SO4. The geometric surface area of each substrate was 0.196 cm2.
Mentions: The cyclic voltammogram (CV) of the Au3+/Pb2+ electrolyte used to deposit the Au-nanospikes directly on the Au-MNM is shown Fig. 3a. The Pb2+ ions work as an inorganic shape-directing additive for the growth of nanospikes in order to form the NU structures while it does not alter the surface chemistry of the deposited gold4254. The deposition of the Au nanospikes was carried out at a constant potential (0.05 V) for periods of 6, 8, 10, 12 and 15 minutes, the current profiles (current-time curve) of which are presented in Fig. 3b. It can be observed that the current is increased and reaches stable state following the first 30 seconds of deposition, where the current is observed to reach a constant value ranging from −250 to −50 μA, depending on the sample. This fast transition to the steady stage is attributed to the uniform growth of nanospikes forming the NU nanostructures, the size of which depends on the deposition period. The electrochemically active surface area of the Au-NUs and Au-control were determined by using the linear sweep voltammetry (LSV) technique that was developed by Rand and Woods425455. This involved recording the CVs for each sample at 100 mVs−1 in a 1 M H2SO4 solution vs Ag/AgCl auxiliary electrode. The CVs for the Au-control and Au-NU-6 min samples are shown in Fig. 3c. The increase observed at the cathodic peak (ca. 0.93 V) is indicative of oxide removal that was formed at the electrode surface during the forward sweep. The onset for this oxide formation is found to be at ~0.98 V and ~1.2 V for the Au-NU-6 min and Au-control, respectively. Similarly the CVs for the Au-MNM, Au-NU-8 min, Au-NU-10 min, Au-NU-12 min and Au-NU-15 min presented in the Supplementary information (Fig. S3) also show lower onset potentials for oxide formation thereby indicating that highly active Au nanostructures are present on the modified Au-NU surfaces. The shoulder observed at ca. 1.1 V before the main oxidation peak further confirms that the Au-NU-6 min have active surface defect sites54. When the active electrochemical surface areas of the samples were calculated using the reduction peak, it was observed that the Au-NU-6 min sample had over 6 times the surface area of Au-control sample. The difference in surface area is observed to increase with increasing electrodeposition time (see Supplementary information, Fig. S3) with the 15 minute electrodeposition of nanospikes (Au-NU-15 min) having ~10 times the surface area of the Au-control sample and more than 25 times higher than the geometrical surface area as shown in Fig. 3d. High surface area based gold nanostructures are of particular interest in numerous applications such as catalysis, batteries and bio-sensors56.

Bottom Line: 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 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.

View Article: PubMed Central - PubMed

Affiliation: Centre for Advanced Materials and Industrial Chemistry (CAMIC), School of Applied Sciences, RMIT University, GPO Box 2476V, Melbourne, VIC 3001 (Australia).

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 (Hg(0)) 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 Hg(0) 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.

No MeSH data available.