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On-Chip Stochastic Detection of Silver Nanoparticles without a Reference Electrode Pedro G. Figueiredo, Leroy Grob, Philipp Rinklin, Kay J. Krause, and Bernhard Wolfrum ACS Sens., Just Accepted Manuscript • DOI: 10.1021/acssensors.7b00559 • Publication Date (Web): 25 Dec 2017 Downloaded from http://pubs.acs.org on December 26, 2017
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On-Chip Stochastic Detection of Silver Nanoparticles without a Reference Electrode ‡Pedro G. Figueiredo1, ‡Leroy Grob1, Philipp Rinklin1, Kay J. Krause3, Bernhard Wolfrum*1,2 1 Neuroelectronics group, Department of Electrical and Computer Engineering, Munich School of Bioengineering, Technical University of Munich, Boltzmannstraße 11, D-85749, Garching, Germany 2 Forschungszentrum Jülich, Institute of Complex Systems-Bioelectronics (ICS-8) 3 Niederrhein University of Applied Science, Department of Food Science and Nutrition, Rheydter Str. 277, 41065 Mönchengladbach KEYWORDS: Nanoparticle detection, microelectrode array, reference-free, open-circuit potential, impact electrochemistry ABSTRACT: We report the electrochemical detection of 20 nm silver nanoparticles at a chip-based microelectrode array (MEA) without the need for a conventional reference electrode. This is possible due to the system’s open-circuit potential allowing the oxidation of silver nanoparticles in the presence of phosphate-buffered saline (PBS). The hypothesis is confirmed by modulating the open-circuit potential via addition of ascorbic acid in solution, effectively inhibiting the detection of silver nanoparticle events. Employing the reference-free detection concept, we observe a linear relationship between the nanoparticle impact frequency at the microelectrodes and the nanoparticle concentration. This allows for viable quantification of silver nanoparticle concentrations in situ. The presented concept is ideal for the development of simple lab-on-a-chip or point-of-use systems enabling fast and low-cost screening of nanoparticles.
In the past decade, there has been a considerable increase in nanoparticle applications in various consumer and industrial products.1 In particular, silver nanoparticles (AgNPs) have increased in popularity1 mainly due to their antimicrobial properties.2 As a result, a large amount of these silver nanoparticles are either held in a variety of fluid suspensions or coated onto surfaces of potential consumables. As an example, Jain et.al showed the use of coating common polyurethane foams with silver nanoparticles for antibacterial water filters.3 Once in use, the silver nanoparticles are challenging to locate and their fate becomes unclear. In particular, the size of nanoparticles in solution is of considerate interest as it has been shown that cytotoxic effects of AgNPs are size dependent.4–6 Through a chain of events, the random introduction of silver nanoparticles can influence our environment7–9 which can sprout negative biological effects10 within ecosystems.11,12 While many different methods exist for trace analysis, electron microscopy (SEM and TEM) imaging still remains the most reliable method in quantifying the size of nanoparticles. However, these techniques are expensive and have a limited throughput, which is not ideal for screening large sample numbers. In particular, sizing nanoparticles using TEM does require additional preparation, where the samples are dried, which can cause agglomeration, biasing the sample’s end concentration.13 Apart from electron microscopy, there are a variety of optical techniques, which exploit the nanoparticle’s absorption and scattering properties to determine the size of nanoparticles in situ14,15 or ex situ16. Dynamic light scattering (DLS) is one such common in situ technique. As an example, Zheng et al. demonstrated the method for correctly sizing gold nanoparticles.17 This technique is applicable when spherical
and monodisperse particles in clear solutions are under examination.18,19 However, actual nanoparticles have a tolerance in size and shape leading to a varying backscatter for all particles in the detection volume, which ultimately blurs the desired result.20 In addition, once the introduction of different salt solutions are combined with silver nanoparticles, agglomeration of nanoparticle will further perturb concrete DLS measurements.21 The agglomeration of nanoparticles can be described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory22, which considers Van der Waals and electrostatic interactions between nanoparticles within a colloidal suspension. As an alternative to optical methods, impact electrochemistry23 has become a rapidly developing tool for quantitatively identifying the number and size of silver nanoparticles in situ. To date, a number of different research groups have shown the possibility to electrochemically detect nanoparticle impacts at an appropriately biased microelectrode. Novel research from the group of Lemay in 2004 reported the use of an electrical detection method for individual quantum dots adsorbing at a gold microelectrode surface in situ.24 This concept was further advanced by the group of Bard in identifying platinum citrate nanoparticle collisions at an ultramicroelectrode.25,26 In succession, the Compton group developed a method for the direct detection of silver nanoparticles in aqueous solution.27–30 By analyzing the resulting current-time traces, noticeable transients due to the electro-oxidation of silver nanoparticles upon contact with a positively biased microelectrode were shown.27 These stochastic events are able to relay particle concentration and size distribution of nanoparticles calculated by recording the number of particle impacts and the charge
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transferred per collision. In general, different reactions occur depending on the electrode material, specific particle type, electrolyte conditions, and the applied electrode potential.31–41 In the absence of advection, the probability of detecting nanoparticles at a single microelectrode is limited by diffusion and the size of the detection site. Since the noise for amperometric measurements scales with the size of the electrode-electrolyte interface, small individual microelectrodes distributed over a large surface-area hold advantages for high-throughput detection.42 Such kind of sensors can be established using microfabrication techniques to create a chip-based microelectrode array (MEA). With any electrochemical experiment, the introduction of a reference and possibly a counter electrode is advised for controlling the potential of the working electrode(s). However, in the case of microelectrodes on chip, the integration of a conventional macroscale reference electrode for point-of-care systems can become challenging depending on the system layout. As a consequence, researchers have explored the miniaturization processes available for on-chip reference electrodes for future low cost senor applications.43 However, the lifetime of these down-scaled reference electrodes still remains an issue. In the case of Ag/AgCl reference electrodes, the deposited silver or silver-chloride deplete over time, which in turn, reduces the stability and reliability of the half-cell potential.43 In addition, the integration of microchannels for the reference solution adds unwanted complexity in the microfabrication procedure. As an alternative, miniaturized quasireference electrodes have increased in popularity due to their simpler manufacturing process, as demonstrated by the integration of planar Ag/AgCl reference electrode arrays.44–46 The array of quasi-reference electrodes were used to record ionic currents across cell membranes.44,45 However, even quasireference electrodes may vary in stability and can complicate the fabrication process in confined lab-on-a-chip designs. Ideally, a simple and affordable system can operate without any additional reference electrode. Such an implementation of lab-on-a-chip (LOC) systems could greatly improve the feasibility of on-site detection of nanoparticle impacts, for simple and fast screening prior to detailed laboratory alanytics.47,48 Here we investigate the possibility of detecting nanoparticle impacts at platinum microelectrode arrays without a reference electrode. Therefore, we study the influence of the system’s open-circuit potential during the oxidizing process of silver nanoparticles. Our results show that silver nanoparticles can be readily detected without a reference electrode depending on the electrolyte composition. This approach is interesting for designing simple sensor concepts, for instance lateral flow devices as future disposable nanoparticle sensor systems. Materials and methods: Chip fabrication The microelectrode arrays (MEAs) were produced in the clean room using standard photolithography methods. First, a metal stack of Ti/Pt/Ti (10/200/5 nm) was deposited onto a 500 µm thick Borofloat® substrate via electron beam evaporation. Subsequently, 62 working electrodes (diameter 24 µm) and feedlines were structured using a double-resist lift-off step (LOR B, Microchem, Newton, MA; AZ nLOF 2020, MicroChemicals, Ulm, Germany). In order to passivate this metal layer, a stack of silicon oxide (O) and silicon nitride (N) was deposited with plasma enhanced chemical vapor deposition
(PECVD) to a thickness of 0.8 µm (layer composition: ONONO with individual thicknesses of 200/100/200/100/200 nm). The electrode openings were then etched with reactive ion etching, whereby the top Ti layer was also removed. Detailed information on the chips’ fabrication process has been described previously.49 After fabrication, the chip was cleaned via sonication in acetone and isopropanol for 5 min each. Then, a glass reservoir of height 6 mm and inner diameter 15.6 mm was glued to the surface of the chip by curing PDMS at 110 °C for 30 min (1:10 base:curing agent, Sylgard 184, Dow Corning, Wiesbaden). Preparation of solutions An aqueous dispersion of citrate-stabilized silver nanoparticles (AgNPs) with an average size of 20 nm with a silver concentration of 0.02 mg/mL were bought from SigmaAldrich. This corresponds to a nanoparticle concentration of approximately 750 pM, from which further solutions with concentrations of 25, 50, 100, 150, 200, 250 and 300 pM were prepared via dilution in MilliQ water. Similarly, phosphatebuffered saline (PBS) with pH 7.4 (0.01 M phosphate buffer, 0.0027 M potassium chloride and 0.137 M sodium chloride) was purchased from Sigma-Aldrich with a measured conductivity of 1.55 S/m. Finally, L-ascorbic acid (200 mM prepared solution) was purchased from Carl Roth. All solutions were used without additional deoxygenation. Open-circuit potential measurements Open-circuit potential (OCP) measurements were carried out with a potentiostat (VSP-300, Bio-Logic Science Instruments, Seyssinet-Pariset, France) in a grounded Faraday cage. To this end, the glass reservoir was filled with 600 µL PBS and the OCP was measured at the microelectrode versus a Ag/AgCl reference electrode (3M NaCl) (RE-6, BASi®, West Lafayette, USA). The potential was recorded for a total of 10 min. After an equilibration phase of approximately 2 min either 150 µL of 250 pM silver nanoparticles (final concentration 50 pM) or 4 µL of 200 mM L-ascorbic acid (final concentration 1.3 mM) was inserted. Nanoparticle measurements Nanoparticle measurements were performed with a custombuilt amplifier in a grounded Faraday cage adopted from our previous investigation.49 Further, information about the amplifier system is given in the supporting information. Two different classes of experiments were performed. The first set of experiments recorded individual nanoparticle impacts using 64 working electrodes with a single (shared) Ag/AgCl reference electrode (3M NaCl) (RE-6, BASi®) or with a reference-free configuration. 600 µL PBS was firstly pipetted into the glass reservoir of the MEA, followed by the recording of amperometric traces. After four seconds 150 µL of AgNP suspension was inserted. A nanoparticle concentration of 50 pM was measured at electrode potentials of 160 mV, 130 mV and 100 mV vs. the Ag/AgCl reference potential. In addition, a set of reference-free experiments, was recorded with different end bulk silver nanoparticle concentrations, varying from 5 to 60 pM. The second class of experiments analyzed the influence of L-ascorbic acid on the detection of AgNPs in the two previ-
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ACS Sensors ously mentioned configurations, with and without a reference electrode. The glass reservoir was filled with a 600 µL volume of PBS with a bulk concentration of 1.3 mM L-ascorbic acid. Nanoparticle recordings were started and after four seconds, 150 µL of 250 pM silver nanoparticle suspension was inserted, resulting in a final bulk concentration of 50 pM AgNP and 1 mM L-ascorbic acid. For the configuration including the reference electrode a potential of 160 mV vs. Ag/AgCl was applied. Data analysis After the measurements, the data was analyzed with a selfwritten algorithm in MatLab®. In particular, the frequency of events per electrode was evaluated as follows. First, electrodes showing irregular noise behavior, as well as those that could not detect any events at all, were neglected. From the remaining channels the median of the total number of spikes with an amplitude exceeding 40 pA (approx. tenfold RMS noise) was calculated. After that, the number of events was normalized to one electrode by calculating the mean and standard deviation. For this normalization, the channels with a number of spikes within 50 to 150% of the median were evaluated. Finally, this result was divided by the total evaluation time, which was 10 s starting 2 s after insertion, to convert the number of events into the average frequency per electrode. The number of electrodes per chip contributing to the above described evaluation varied between 40 and 55. The varying amount of electrodes was most likely caused by dysfunctional contacts or impurities on the electrode surface arising from the fabrication procedure. In the experimental process, the MEA chips are cleaned with MilliQ water and pressurized air between each measurement. Chips are used only if the number of working electrodes is above approximately 50% of the original 62 microelectrodes.
Results and discussion: Influence of the reference electrode’s potential on AgNP detection The present work presents an approach to detect silver nanoparticles (AgNPs) in a reference-free electrode setup. In a standard electrochemical cell, the reference electrode is used to reliably define the working electrodes’ potential. In this context, Figures 1a-c show current traces of AgNP oxidation events in dependence of the working electrode’s potential. Each trace is an overlay of the simultaneously recorded current at the different microelectrodes of one chip. We see the appearance of many short current transients (spikes) caused by the nanoparticle impacts at the microelectrodes. The shape of an individual spike at a single microelectrode is shown in the supporting information (Figure S-1). As the potential of the electrodes is set to 160 mV (a) and 130 mV (b) vs Ag/AgCl, spikes can be readily observed. The frequency of the detected spikes decreases over time but is approximately the same for both current traces. However, at a potential of 100 mV vs Ag/AgCl, no spikes are visible in the current traces since either no particle oxidation takes place or the corresponding spikes are indistinguishable from the background noise. Overall, this data indicates that a threshold potential between 100 mV and 130 mV vs Ag/AgCl is necessary to reliably detect AgNPs electrochemically in our system. Similar values have been reported previously for the detection of silver nano-
particles at gold microelectrode arrays depending on the chloride concentration in the bulk solution.34
Figure 1. Current traces recorded in PBS with a) 160 mV, b) 130 mV, c) 100 mV vs a Ag/AgCl reference electrode (3M NaCl) and d) without any reference electrode. AgNP with a final concentration of 50 pM were inserted after 4 s. Each trace shows the combined response of multiple microelectrodes on the same chip. The traces are shifted by 3 nA for better illustration.
In comparison, Figure 1d shows a current trace of a measurement without a reference electrode. Similar to the measurements at defined potentials of 130 and 160 mV vs Ag/AgCl, oxidation events were detected with no considerable change in frequency. On a first intuition, this result may be unexpected, since the circuit without reference electrode was technically open (apart from leakage currents) and no potential was applied to enable the particle oxidation. However, the experiment can be understood in terms of the microelectrode polarization during nanoparticle impacts as explained below.
Microelectrode polarization during nanoparticle impacts In the proposed reference-free design of AgNP detection, the OCP of the system plays a fundamental role. It is influenced by adsorption and electrochemical reactions at the electrode-electrolyte interface. As demonstrated in Figure 1, nanoparticles cannot be detected when the potential at the working electrode is at 100 mV vs. Ag/AgCl. However, current spikes are observed when the reference electrode is taken out and no potential is applied. This suggests that the OCP is high enough to cause the particle oxidation. Potential measurements were performed in order to characterize the OCP of our system in dependence of the experimental parameters in more detail. Figure 2 shows a representative graph of the OCP between a platinum microelectrode and a Ag/AgCl reference electrode. The plot demonstrates that the potential at the electrode is significantly above 130 mV vs Ag/AgCl, both before and after AgNP insertion. From this we can conclude that the potential is high enough to oxidize nanoparticles. The dominant method of nanoparticle oxidation at the microelectrode array in the presence of supporting chloride ions is given by the following reaction:34 ( → 1) In a typical 3-electrode electrochemical experiment, we can directly control the working electrode’s potential to facilitate
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particle oxidation. In an experiment without counter and reference electrode, the situation is different. Here, any charge transfer reaction between the electrode and the particles will directly influence the potential, prohibiting sustained unidirectional currents. To assess the influence of the silver nanoparticles we measured the OCP before and after insertion of particles (final concentration 50 pM) in a three-electrode setup. If particles are oxidized at the electrode, one might expect that the charge transfer events will lead to a decrease of the OCP over time. However, Figure 2 suggests that the insertion of the AgNPs into solution does not cause a rapid decay of the OCP. We evaluate this result, by first estimating an upper boundary of the transferred charge for a 20 nm-diameter silver nanoparticle assuming that the whole particle is oxidized: ( ~40 fC 2) where is the volume of the particle, Faraday’s constant, = 10490 kg/m3 is the density of silver, and M = 0.10787 kg/mol its molar mass. To calculate the influence of the oxidation reaction on the electrode potential we have to consider the capacitance of the electrode-electrolyte interface. For our electrodes (24 µm in diameter) we typically observe a capacitance at the electrode/electrolyte interface of ~ 100 pF. Therefore, the variation in potential due to the oxidation of a single nanoparticle is given by: ( ∆ !" ~ 0.4 mV 3) This small potential variation does not directly affect further nano-impacts at the microelectrode. Overall, the net charge transfer will depend on the individual charge transfer events and the mass flux of particles to the electrode. Concentrationdependent measurements of the impact rate of nanoparticles suggest a frequency of approximately 6 Hz/electrode at a concentration of 50 pM (see Figure 4). As a result, the average current caused by the particle oxidation over time amounts to ~0.24 pA. It is likely that this small input bias is partially compensated by leakage currents.
Figure 2. Open circuit potential recording of a single microelectrode vs Ag/AgCl with a final volume of 750 µL PBS and a silver nanoparticle concentration of 50 pM.
Influence of ascorbic acid In order to evaluate a chemically induced shift in the OCP and the consequential effects on the AgNP detection, we investigated a solution with PBS and ascorbic acid. Ascorbic acid is an important antioxidant in biological systems, which is known to reduce the OCP at a noble metal electrode in PBS.50 Figure 3a displays the OCP measured in PBS before and after
the insertion of ascorbic acid. Since the addition of ascorbic acid reduces the OCP of the microelectrodes to values below the threshold of approximately 100-130mV vs Ag/AgCl, we expect the oxidation of AgNP to be suppressed in this configuration. This is confirmed in the upper trace of Figure 3b, where no AgNP detection can be observed when measuring without a reference electrode in the presence of ascorbic acid.
Figure 3. a) Open circuit potential measurement of a single microelectrode vs Ag/AgCl in 600 µL PBS with ascorbic acid at a final concentration of 1.3 mM. b) Current traces of PBS and 1 mM ascorbic acid without reference electrode (top) and with a Ag/AgCl RE at a biased potential of 160 mV (bottom). Both traces show overlaid responses of multiple microelectrodes on the same chip. Silver nanoparticles were inserted after 4 s with a final bulk concentration of 50 pM. The signals are shifted by 3 nA for better illustration.
However, when a Ag/AgCl reference electrode is used to set the potential of the working electrode to 160 mV, current spikes can again be observed, as shown in the lower trace of Figure 3b. This indicates that the addition of ascorbic acid does not inhibit nanoparticle oxidation at a biased electrode but inhibits the detection of nanoparticles in reference-free measurements due to a change of the OCP. Frequency of event dependence on AgNP concentration Finally, we used our reference-free detection scheme, to validate the linear dependence of the spike frequency on the nanoparticle concentration. Figure 4 shows a plot of the recorded spike frequency per electrode versus the concentration of the nanoparticles. As the frequency of events decreases over time it is necessary to specify a fixed time interval for the comparison of impact rates at different concentrations. A similar decrease in the spike frequency has been reported previously and was attributed to the adsorption of particles at the passivation layer.42 Thus, the flux of particles to the electrode is changed from a radial diffusion profile, typically observed for microelectrodes, to a linear diffusion profile. The total flux will depend on the initial concentration distribution during particle insertion as well as possible advection contri-
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ACS Sensors butions. Overall, the approximately linear relation between the recorded spike frequency and the particle concentration suggests that our reference-free technique is useful for quantifying silver nanoparticles in electrolyte solution.
Author Contributions ‡These authors contributed equally.
Funding Sources We greatly appreciate the funding from the BCCN (grant number 01GQ1004A, BMBF).
ACKNOWLEDGMENT We acknowledge Norbert Wolters and Dieter Lomparski for the design and implementation of the silver nanoparticle detection hardware and software. In addition, we wish to thank Marko Banzet for the fabrication of the microelectrode arrays at the Helmholtz Nano Facility (HNF) and Enno Kätelhön for discussion on the manuscript.
ABBREVIATIONS Figure 4. Recorded spike frequency per electrode in dependence of AgNP concentration in PBS solution without a reference electrode. For each concentration the event frequency was averaged over all active microelectrodes for 20 s after the 2 s insertion interval.
Conclusion We demonstrated the electrochemical detection of AgNPs in aqueous electrolyte solution without the use of a reference electrode. In this approach, the oxidation of the particles is solely driven by the open-circuit potential of the system and the mass transport of particles to the electrode. We validated this assumption by reducing the open circuit potential via the addition of ascorbic acid. As expected, the presence of ascorbic acid inhibited the oxidation of the nanoparticles in a reference-free measurement. Biasing the working electrode’s potential via a reference electrode reestablished detectable particle oxidation events in the presence of ascorbic acid. Finally, we validated theoretical predictions of a linear dependence of the oxidation frequency on the nanoparticle concentration using the reference-free particle detection scheme. In summary, we demonstrated a simple electrochemical detection of AgNPs at a microelectrode array without a reference electrode. We believe that this methods presents an interesting approach for low-cost field-based sensing of nanoparticles as it greatly facilitates the sensor layout compared to classical two- or three-electrode setups, enabling easier integration of microfluidics for lab on a chip systems.
ASSOCIATED CONTENT
MEA: microelectrode array PBS: phosphate-buffered saline AgNP: silver nanoparticles MEA: microelectrode array. SEM: scanning electron microscope TEM: transmitting electron microscope DLS: dynamic light scattering DLVO: Derjaguin-Landau-Verwey-Overbeek LOC: lab-on-a-chip PECVD: plasma enhanced chemical vapor deposition ONONO: silicon oxide-silicon nitride-silicon oxide-silicon nitride- silicon oxide PDMS: polydimethylsiloxane OCP: open-circuit potential RE: reference electrode RMS: root mean square
REFERENCES (1)
(2)
(3)
(4)
(5)
Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI:
(6)
Amplifier characteristics and silver nanoparticle impact signals (PDF). (7)
AUTHOR INFORMATION Corresponding Author
Vance, M. E.; Kuiken, T.; Vejerano, E. P.; McGinnis, S. P.; Hochella, M. F.; Rejeski, D.; Hull, M. S. Nanotechnology in the Real World: Redeveloping the Nanomaterial Consumer Products Inventory. Beilstein Journal of Nanotechnology 2015, 6, 1769–1780. Nowack, B.; Krug, H. F.; Height, M. 120 Years of Nanosilver History: Implications for Policy Makers. Environ. Sci. Technol. 2011, 45 (4), 1177–1183. Jain, P.; Pradeep, T. Potential of Silver Nanoparticle-Coated Polyurethane Foam as an Antibacterial Water Filter. Biotechnol. Bioeng. 2005, 90 (1), 59–63. Jiang, W.; Kim, B. Y. S.; Rutka, J. T.; Chan, W. C. W. Nanoparticle-Mediated Cellular Response Is SizeDependent. Nat Nano 2008, 3 (3), 145–150. Kim, T.-H.; Kim, M.; Park, H.-S.; Shin, U. S.; Gong, M.-S.; Kim, H.-W. Size-Dependent Cellular Toxicity of Silver Nanoparticles. J. Biomed. Mater. Res. 2012, 100A (4), 1033– 1043. Gliga, A. R.; Skoglund, S.; Odnevall Wallinder, I.; Fadeel, B.; Karlsson, H. L. Size-Dependent Cytotoxicity of Silver Nanoparticles in Human Lung Cells: The Role of Cellular Uptake, Agglomeration and Ag Release. Particle and Fibre Toxicology 2014, 11, 11. Blaser, S. A.; Scheringer, M.; MacLeod, M.; Hungerbühler, K. Estimation of Cumulative Aquatic Exposure and Risk Due to Silver: Contribution of Nano-Functionalized Plastics and Textiles. Science of The Total Environment 2008, 390 (2–3), 396–409.
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(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
(24)
Dobias, J.; Bernier-Latmani, R. Silver Release from Silver Nanoparticles in Natural Waters. Environ. Sci. Technol. 2013, 47 (9), 4140–4146. Schaumann, G. E.; Philippe, A.; Bundschuh, M.; Metreveli, G.; Klitzke, S.; Rakcheev, D.; Grün, A.; Kumahor, S. K.; Kühn, M.; Baumann, T.; et al. Understanding the Fate and Biological Effects of Ag- and TiO2-Nanoparticles in the Environment: The Quest for Advanced Analytics and Interdisciplinary Concepts. Science of The Total Environment 2015, 535, 3–19. Srivastava, V.; Gusain, D.; Sharma, Y. C. Critical Review on the Toxicity of Some Widely Used Engineered Nanoparticles. Ind. Eng. Chem. Res. 2015, 54 (24), 6209–6233. Metreveli, G.; Philippe, A.; Schaumann, G. E. Disaggregation of Silver Nanoparticle Homoaggregates in a River Water Matrix. Science of The Total Environment 2015, 535, 35– 44. Hinther, A.; Vawda, S.; Skirrow, R. C.; Veldhoen, N.; Collins, P.; Cullen, J. T.; van Aggelen, G.; Helbing, C. C. Nanometals Induce Stress and Alter Thyroid Hormone Action in Amphibia at or below North American Water Quality Guidelines. Environ. Sci. Technol. 2010, 44 (21), 8314– 8321. Loget, G.; Lee, T. C.; Taylor, R. W.; Mahajan, S.; Nicoletti, O.; Jones, S. T.; Coulston, R. J.; Lapeyre, V.; Garrigue, P.; Midgley, P. A.; et al. Direct Visualization of Symmetry Breaking During Janus Nanoparticle Formation. Small 2012, 8 (17), 2698–2703. Zhu, J.; Ozdemir, S. K.; Xiao, Y.-F.; Li, L.; He, L.; Chen, D.-R.; Yang, L. On-Chip Single Nanoparticle Detection and Sizing by Mode Splitting in an Ultrahigh-Q Microresonator. Nat Photon 2010, 4 (1), 46–49. Martinez-Marrades, A.; Rupprecht, J.-F.; Gross, M.; Tessier, G. Stochastic 3D Optical Mapping by Holographic Localization of Brownian Scatterers. Opt. Express, OE 2014, 22 (23), 29191–29203. McFarland, A. D.; Van Duyne, R. P. Single Silver Nanoparticles as Real-Time Optical Sensors with Zeptomole Sensitivity. Nano Lett. 2003, 3 (8), 1057–1062. Zheng, T.; Bott, S.; Huo, Q. Techniques for Accurate Sizing of Gold Nanoparticles Using Dynamic Light Scattering with Particular Application to Chemical and Biological Sensing Based on Aggregate Formation. ACS Appl. Mater. Interfaces 2016, 8 (33), 21585–21594. Hoo, C. M.; Starostin, N.; West, P.; Mecartney, M. L. A Comparison of Atomic Force Microscopy (AFM) and Dynamic Light Scattering (DLS) Methods to Characterize Nanoparticle Size Distributions. J Nanopart Res 2008, 10 (1), 89–96. Khlebtsov, B. N.; Khlebtsov, N. G. On the Measurement of Gold Nanoparticle Sizes by the Dynamic Light Scattering Method. Colloid J 2011, 73 (1), 118–127. Tomaszewska, E.; Soliwoda, K.; Kadziola, K.; TkaczSzczesna, B.; Celichowski, G.; Cichomski, M.; Szmaja, W.; Grobelny, J. Detection Limits of DLS and UV-Vis Spectroscopy in Characterization of Polydisperse Nanoparticles Colloids. J. Nanomaterials 2013, 2013, 60:60–60:60. Huynh, K. A.; Chen, K. L. Aggregation Kinetics of Citrate and Polyvinylpyrrolidone Coated Silver Nanoparticles in Monovalent and Divalent Electrolyte Solutions. Environ. Sci. Technol. 2011, 45 (13), 5564–5571. Ninham, B. W. On Progress in Forces since the DLVO Theory. Advances in Colloid and Interface Science 1999, 83 (1), 1–17. H. Robbs, P.; V. Rees, N. Nanoparticle Electrochemistry. Physical Chemistry Chemical Physics 2016, 18 (36), 24812– 24819. Quinn, B. M.; van’t Hof, P. G.; Lemay, S. G. Time-Resolved Electrochemical Detection of Discrete Adsorption Events. J. Am. Chem. Soc. 2004, 126 (27), 8360–8361.
(25)
(26)
(27)
(28)
(29)
(30)
(31) (32)
(33)
(34)
(35)
(36)
(37)
(38)
(39)
(40)
(41)
Page 6 of 8 Xiao, X.; Bard, A. J. Observing Single Nanoparticle Collisions at an Ultramicroelectrode by Electrocatalytic Amplification. J. Am. Chem. Soc. 2007, 129 (31), 9610–9612. Xiao, X.; Fan, F.-R. F.; Zhou, J.; Bard, A. J. Current Transients in Single Nanoparticle Collision Events. J. Am. Chem. Soc. 2008, 130 (49), 16669–16677. Zhou, Y.-G.; Rees, N. V.; Compton, R. G. The Electrochemical Detection and Characterization of Silver Nanoparticles in Aqueous Solution. Angew. Chem. Int. Ed. 2011, 50 (18), 4219–4221. E. Stuart, E. J.; Zhou, Y.-G.; V. Rees, N.; G. Compton, R. Determining Unknown Concentrations of Nanoparticles : The Particle-Impact Electrochemistry of Nickel and Silver. RSC Advances 2012, 2 (17), 6879–6884. E. Stuart, E. J.; V. Rees, N.; T. Cullen, J.; G. Compton, R. Direct Electrochemical Detection and Sizing of Silver Nanoparticles in Seawater Media. Nanoscale 2013, 5 (1), 174– 177. Tschulik, K.; Cheng, W.; Batchelor‐McAuley, C.; Murphy, S.; Omanović, D.; Compton, R. G. Non‐Invasive Probing of Nanoparticle Electrostatics. ChemElectroChem 2015, 2 (1), 112–118. Pumera, M. Impact Electrochemistry: Measuring Individual Nanoparticles. ACS Nano 2014, 8 (8), 7555–7558. Bentley, C. L.; Kang, M.; Unwin, P. R. Time-Resolved Detection of Surface Oxide Formation at Individual Gold Nanoparticles: Role in Electrocatalysis and New Approach for Sizing by Electrochemical Impacts. J. Am. Chem. Soc. 2016, 138 (39), 12755–12758. V. Sokolov, S.; Eloul, S.; Kätelhön, E.; Batchelor-McAuley, C.; G. Compton, R. Electrode–particle Impacts: A Users Guide. Physical Chemistry Chemical Physics 2017, 19 (1), 28–43. Krause, K. J.; Brings, F.; Schnitker, J.; Kätelhön, E.; Rinklin, P.; Mayer, D.; Compton, R. G.; Lemay, S. G.; Offenhäusser, A.; Wolfrum, B. The Influence of Supporting Ions on the Electrochemical Detection of Individual Silver Nanoparticles: Understanding the Shape and Frequency of Current Transients in Nano-Impacts. Chem. Eur. J. 2017, 23 (19), 4638–4643. Mun, S. K.; Lee, S.; Kim, D. Y.; Kwon, S. J. Various Current Responses of Single Ag Nanoparticle Collisions on Au Ultramicroelectrode Depending on Collision Condition. Chem. Asian J. 2017, No. 10.1002/asia.201700770. Ustarroz, J.; Kang, M.; Bullions, E.; R. Unwin, P. Impact and Oxidation of Single Silver Nanoparticles at Electrode Surfaces: One Shot versus Multiple Events. Chemical Science 2017, 8 (3), 1841–1853. Peng, Y.-Y.; Qian, R.-C.; Hafez, M. E.; Long, Y.-T. Stochastic Collision Nanoelectrochemistry: A Review of Recent Developments. ChemElectroChem 2017, 4 (5), 977–985. Sun, L.; Jiang, D.; Li, M.; Liu, T.; Yuan, L.; Wang, W.; Chen, H.-Y. Collision and Oxidation of Single LiCoO2 Nanoparticles Studied by Correlated Optical Imaging and Electrochemical Recording. Anal. Chem. 2017, 89 (11), 6050– 6055. Ma, W.; Ma, H.; Chen, J.-F.; Peng, Y.-Y.; Yang, Z.-Y.; Wang, H.-F.; Ying, Y.-L.; Tian, H.; Long, Y.-T. Tracking Motion Trajectories of Individual Nanoparticles Using Time-Resolved Current Traces. Chemical Science 2017, 8 (3), 1854–1861. Ngamchuea, K.; Clark, R. O. D.; Sokolov, S. V.; Young, N. P.; Batchelor-McAuley, C.; Compton, R. G. Single Oxidative Collision Events of Silver Nanoparticles: Understanding the Rate-Determining Chemistry. Chem. Eur. J. 2017, 23 (63), 16085–16096. Oja, S. M.; Robinson, D. A.; Vitti, N. J.; Edwards, M. A.; Liu, Y.; White, H. S.; Zhang, B. Observation of Multipeak Collision Behavior during the Electro-Oxidation of Single Ag Nanoparticles. J. Am. Chem. Soc. 2017, 139 (2), 708– 718.
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ACS Sensors (42)
(43)
(44)
(45)
(46)
Krause, K. J.; Yakushenko, A.; Wolfrum, B. Stochastic OnChip Detection of Subpicomolar Concentrations of Silver Nanoparticles. Anal. Chem. 2015, 87 (14), 7321–7325. Shinwari, M. W.; Zhitomirsky, D.; Deen, I. A.; Selvaganapathy, P. R.; Deen, M. J.; Landheer, D. Microfabricated Reference Electrodes and Their Biosensing Applications. Sensors 2010, 10 (3), 1679–1715. Baaken, G.; Sondermann, M.; Schlemmer, C.; Rühe, J.; C. Behrends, J. Planar Microelectrode-Cavity Array for High-Resolution and Parallel Electrical Recording of Membrane Ionic Currents. Lab on a Chip 2008, 8 (6), 938–944. Baaken, G.; Ankri, N.; Schuler, A.-K.; Rühe, J.; Behrends, J. C. Nanopore-Based Single-Molecule Mass Spectrometry on a Lipid Membrane Microarray. ACS Nano 2011, 5 (10), 8080–8088. Schnitker, J.; Afanasenkau, D.; Wolfrum, B.; Offenhäusser, A. Planar Reference Electrodes on Multielectrode Arrays for
(47)
(48)
(49)
(50)
Electrochemical Measurements of Ionic Currents. Phys. Status Solidi A 2013, 210 (5), 892–897. Yang, K.; Peretz-Soroka, H.; Liu, Y.; Lin, F. Novel Developments in Mobile Sensing Based on the Integration of Microfluidic Devices and Smartphones. Lab Chip 2016, 16 (6), 943–958. Tian, T.; Li, J.; Song, Y.; Zhou, L.; Zhu, Z.; Yang, C. J. Distance-Based Microfluidic Quantitative Detection Methods for Point-of-Care Testing. Lab Chip 2016, 16 (7), 1139– 1151. Yakushenko, A.; Kätelhön, E.; Wolfrum, B. Parallel OnChip Analysis of Single Vesicle Neurotransmitter Release. Anal. Chem. 2013, 85 (11), 5483–5490. Farghaly, A. A.; Lam, M.; Freeman, C. J.; Uppalapati, B.; Collinson, M. M. Potentiometric Measurements in Biofouling Solutions: Comparison of Nanoporous Gold to Planar Gold. J. Electrochem. Soc. 2016, 163 (4), H3083–H3087.
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