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Zhang, D., Solomon, P., Zhang, S.-L. & Zhang, Z. (2017). An impedance model for the low-frequency noise originating from the dynamic hydrogen ion reactivity at the solid/liquid interface. Sensors and actuators. B, Chemical.
Open this publication in new window or tab >>An impedance model for the low-frequency noise originating from the dynamic hydrogen ion reactivity at the solid/liquid interface
2017 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077Article in journal (Refereed) Epub ahead of print
Abstract [en]

Understanding the dynamics of hydrogen ion reactivity at the solid/liquid interface is of paramount importance for applications involving ion sensing in electrolytes. However, the correlation of this interfacial process to noise generation is poorly characterized. Here, the relationship is unveiled by characterizing the interfacial process with impedance spectroscopy assisted by a dedicated electrochemical impedance model. The model incorporates both thermodynamic and kinetic properties of the amphoteric hydrogen ion site-binding reactions with the surface OH groups. It further takes into consideration the distributed nature of the characteristic energy of the binding sites. The simulated impedance matches the experimental data better with an energy distribution of the kinetic parameters than with that of the thermodynamic ones. Since the potentiometric low-frequency noise (LFN) originating from the solid/liquid interface correlates excellently with the real part of its electrochemical impedance spectrum, this work establishes a method for evaluating sensing surface quality aimed at mitigating LFN.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-326714 (URN)10.1016/j.snb.2017.07.054 (DOI)
Available from: 2017-07-26 Created: 2017-07-26 Last updated: 2017-08-03Bibliographically approved
Netzer, N. L., Must, I., Qiao, Y., Zhang, S.-L., Wang, Z. & Zhang, Z. (2017). Biomimetic supercontainers for size-selective electrochemical sensing of molecular ions. Scientific Reports, 7, Article ID 45786.
Open this publication in new window or tab >>Biomimetic supercontainers for size-selective electrochemical sensing of molecular ions
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, 45786Article in journal (Refereed) Published
Abstract [en]

New ionophores are essential for advancing the art of selective ion sensing. Metal-organic supercontainers (MOSCs), a new family of biomimetic coordination capsules designed using sulfonylcalix[4] arenes as container precursors, are known for their tunable molecular recognition capabilities towards an array of guests. Herein, we demonstrate the use of MOSCs as a new class of size-selective ionophores dedicated to electrochemical sensing of molecular ions. Specifically, a MOSC molecule with its cavities matching the size of methylene blue (MB+), a versatile organic molecule used for bio-recognition, was incorporated into a polymeric mixed-matrix membrane and used as an ion-selective electrode. This MOSC-incorporated electrode showed a near-Nernstian potentiometric response to MB+ in the nano-to micro-molar range. The exceptional size-selectivity was also evident through contrast studies. To demonstrate the practical utility of our approach, a simulated wastewater experiment was conducted using water from the Fyris River (Sweden). It not only showed a near-Nernstian response to MB+ but also revealed a possible method for potentiometric titration of the redox indicator. Our study thus represents a new paradigm for the rational design of ionophores that can rapidly and precisely monitor molecular ions relevant to environmental, biomedical, and other related areas.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2017
National Category
Chemical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-321839 (URN)10.1038/srep45786 (DOI)000398960200001 ()28393841 (PubMedID)
Funder
Swedish Foundation for Strategic Research , SSF ICA 12-0047Swedish Research Council, VR 2014-5588Göran Gustafsson Foundation for Research in Natural Sciences and Medicine, GG 1459BCarl Tryggers foundation , CTS14-527
Available from: 2017-05-15 Created: 2017-05-15 Last updated: 2017-05-16Bibliographically approved
Zhang, D., Solomon, P., Zhang, S.-L. & Zhang, Z. (2017). Correlation of Low-Frequency Noise to the Dynamic Properties of the Sensing Surface in Electrolytes. ACS Sensors, 2(8), 1160-1166.
Open this publication in new window or tab >>Correlation of Low-Frequency Noise to the Dynamic Properties of the Sensing Surface in Electrolytes
2017 (English)In: ACS Sensors, E-ISSN 2379-3694, Vol. 2, no 8, 1160-1166 p.Article in journal (Refereed) Published
Abstract [en]

Low-frequency noise (LFN) is of significant implications in ion sensing. As a primary component of LFN for ion sensing in electrolytes, the solid/liquid interfacial noise remains poorly explored especially regarding its relation to the surface binding/debinding dynamic properties. Here, we employ impedance spectroscopy to systematically characterize this specific noise component for its correlation to the dynamic properties of surface protonation (i.e., hydrogen binding) and deprotonation (i.e., hydrogen debinding) processes. This correlation is facilitated by applying our recently developed interfacial impedance model to ultrathin TiO2 layers grown by means of atomic layer deposition (ALD) on a TiN metallic electrode. With an excellent fitting of the measured noise power density spectra by the model for the studied TiO2 layers, we are able to extract several characteristic dynamic parameters for the TiO2 sensing surface. The observed increase of noise with TiO2 ALD cycles can be well accounted for with an increased average binding site density. This study provides insights into how detailed surface properties may affect the noise performance of an ion sensor operating in electrolytes.

Keyword
impedance, ion-sensing, low frequency noise, site-binding model, solid/liquid interface
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-326716 (URN)10.1021/acssensors.7b00285 (DOI)000408702500011 ()28745041 (PubMedID)
Funder
Swedish Research Council, VR 2014-5588Göran Gustafsson Foundation for Research in Natural Sciences and Medicine, GG 1459BCarl Tryggers foundation , CTS14-527Stiftelsen Olle Engkvist Byggmästare, 2016/39Swedish Foundation for Strategic Research
Available from: 2017-07-26 Created: 2017-07-26 Last updated: 2017-12-11Bibliographically approved
Jablonka, L., Kubart, T., Primetzhofer, D., Abedin, A., Hellstrom, P.-E., Ostling, M., . . . Zhang, Z. (2017). Formation of nickel germanides from Ni layers with thickness below 10 nm. Journal of Vacuum Science & Technology B, 35(2), Article ID 020602.
Open this publication in new window or tab >>Formation of nickel germanides from Ni layers with thickness below 10 nm
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2017 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 35, no 2, 020602Article in journal (Refereed) Published
Abstract [en]

The authors have studied the reaction between a Ge (100) substrate and thin layers of Ni ranging from 2 to 10 nm in thickness. The formation of metal-rich Ni5Ge3 was found to precede that of the monogermanide NiGe by means of real-time in situ x-ray diffraction during ramp-annealing and ex situ x-ray pole figure analyses for phase identification. The observed sequential growth of Ni5Ge3 and NiGe with such thin Ni layers is different from the previously reported simultaneous growth with thicker Ni layers. The phase transformation from Ni5Ge3 to NiGe was found to be nucleationcontrolled for Ni thicknesses < 5 nm, which is well supported by thermodynamic considerations. Specifically, the temperature for the NiGe formation increased with decreasing Ni (rather Ni5Ge3) thickness below 5 nm. In combination with sheet resistance measurement and microscopic surface inspection of samples annealed with a standard rapid thermal processing, the temperature range for achieving morphologically stable NiGe layers was identified for this standard annealing process. As expected, it was found to be strongly dependent on the initial Ni thickness.

Place, publisher, year, edition, pages
A V S AMER INST PHYSICS, 2017
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-320866 (URN)10.1116/1.4975152 (DOI)000397858500029 ()
Funder
Swedish Foundation for Strategic Research , SE13-0033 RIF14-0053Swedish Research Council, C0514401
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2017-11-29Bibliographically approved
Wen, C., Zeng, S., Arstila, K., Sajavaara, T., Zhu, Y., Zhang, Z. & Zhang, S.-L. (2017). Generalized Noise Study of Solid-State Nanopores at Low Frequencies. ACS Sensors, 2(2), 300-307.
Open this publication in new window or tab >>Generalized Noise Study of Solid-State Nanopores at Low Frequencies
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2017 (English)In: ACS Sensors, ISSN 2379-3694, Vol. 2, no 2, 300-307 p.Article in journal (Refereed) Published
Abstract [en]

Nanopore technology has been extensively investigated for analysis of biomolecules, and a success story in this field concerns DNA sequencing using a nanopore chip featuring an array of hundreds of biological nanopores (BioNs). Solid-state nanopores (SSNs) have been explored to attain longer lifetime and higher integration density than what BioNs can offer, but SSNs are generally considered to generate higher noise whose origin remains to be confirmed. Here, we systematically study lowfrequency (including thermal and flicker) noise characteristics of SSNs measuring 7 to 200 nm in diameter drilled through a 20-nmthick SiNx membrane by focused ion milling. Both bulk and surface ionic currents in the nanopore are found to contribute to the flicker noise, with their respective contributions determined by salt concentration and pH in electrolytes as well as bias conditions. Increasing salt concentration at constant pH and voltage bias leads to increase in the bulk ionic current and noise therefrom. Changing pH at constant salt concentration and current bias results in variation of surface charge density, and hence alteration of surface ionic current and noise. In addition, the noise from Ag/AgCl electrodes can become predominant when the pore size is large and/or the salt concentration is high. Analysis of our comprehensive experimental results leads to the establishment of a generalized nanopore noise model. The model not only gives an excellent account of the experimental observations, but can also be used for evaluation of various noise components in much smaller nanopores currently not experimentally available.

Keyword
flicker noise, nanopore, electrical double layer, model, power spectrum density, low frequency range, Hooge’s theory
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-315230 (URN)10.1021/acssensors.6b00826 (DOI)000395047000017 ()
Funder
Swedish Research Council, 621-2014-6300Stiftelsen Olle Engkvist Byggmästare, 2016/39Swedish Foundation for Strategic Research
Note

Chenyu Wen and Shuangshuang Zeng contributed equally to this work.

Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2017-04-21Bibliographically approved
Makaraviciute, A., Xu, X., Nyholm, L. & Zhang, Z. (2017). Systematic approach to the development of microfabricated biosensors: relationship between the gold surface pretreatment and thiolated molecule binding. ACS Applied Materials and Interfaces, 9(31), 26610-26621.
Open this publication in new window or tab >>Systematic approach to the development of microfabricated biosensors: relationship between the gold surface pretreatment and thiolated molecule binding
2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 31, 26610-26621 p.Article in journal (Refereed) Published
Abstract [en]

Despite the increasing popularity of microfabricated biosensors due to advances in technologic and surface functionalization strategies, their successful implementation is partially inhibited by the lack of consistency in their analytical characteristics. One of the main causes for the discrepancies is the absence of a systematic and comprehensive approach to surface functionalization. In this article microfabricated gold electrodes aimed at biosensor development have been systematically characterized in terms of surface pretreatment, thiolated molecule binding, and reproducibility by means of X-ray photoelectron scattering (XPS) and cyclic voltammetry (CV). It has been shown that after SU-8 photolithography gold surfaces were markedly contaminated, which decreased the effective surface area and surface coverage of a model molecule mercaptohexanol (MCH). Three surface pretreatment methods compatible with microfabricated devices were compared. The investigated methods were (i) cyclic voltammetry in dilute H2SO4, (ii) gentle basic piranha followed by linear sweep voltammetry in dilute KOH, and (iii) oxygen plasma treatment followed by incubation in ethanol. It was shown that all three methods significantly decreased the contamination and increased MCH surface coverage. Most importantly, it was also revealed that surface pretreatments may induce structural changes to the gold surfaces. Accordingly, these alterations influence the characteristics of MCH functionalization.

National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:uu:diva-326715 (URN)10.1021/acsami.7b08581 (DOI)000407540400106 ()28726367 (PubMedID)
Funder
Swedish Foundation for Strategic Research , SSF ICA 12-0047, FFL15-0174Swedish Research Council, VR 2014-5588Carl Tryggers foundation
Available from: 2017-07-26 Created: 2017-07-26 Last updated: 2017-12-28Bibliographically approved
Chen, X., Zhang, T., Constantoudis, V., Zhang, S.-L. & Zhang, Z. (2016). Aged hydrogen silsesquioxane for sub-10 nm line patterns. Microelectronic Engineering, 163, 105-109.
Open this publication in new window or tab >>Aged hydrogen silsesquioxane for sub-10 nm line patterns
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2016 (English)In: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 163, 105-109 p.Article in journal (Refereed) Published
Abstract [en]

Hydrogen silsesquioxane (HSQ) has been used as a negative tone resist in electron beam lithography to define sub-10 nm patterns. The spontaneous polymerization in HSQ usually called aging in this context, sets a restricted period of time for a vendor-warranted use in patterning such small features with satisfactory line-edge roughness (LER). Here, we study the effect of HSQ aging on sensitivity and LER by focusing on exposing line patterns of 10 nm width in various structures. The results show that the 10 nm lines are easily achievable and the LER of the patterned lines remains unaltered even with HSQ that is stored 10 months beyond the vendor-specified expiration date. However, an increasingly pronounced decrease with time of the threshold electron dose (D-th), below which the line width would become less than 10 nm, is observed. After the HSQ expiration for 10 months, the 10 nm lines can be manufactured by reducing D-th to a level that is technically manageable with safe margins. In addition, the inclusion of a prebaldng step at 220 degrees C to accelerate the aging process results in a further reduced D-th for the 10 nm lines and thereby leads to a shortened writing time. The time variation of D-th with respect to the vendor-specified production date of HSQ is found to follow an exponential function of time and can be associated to the classical nucleation-growth polymerization process in HSQ.

Keyword
Electron beam lithography (EBL); Hydrogen silsesquioxane (HSQ); 10 nm wide resist lines; Aging effect; Line edge roughness (LER); Prebaking
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-300188 (URN)10.1016/j.mee.2016.06.011 (DOI)000381837300015 ()
Funder
Swedish Foundation for Strategic Research , ICA 12-0047 SE13-0033Swedish Research Council, 2014-5588 2014-5591Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of Technology, GG 1459BCarl Tryggers foundation , CTS14-527
Available from: 2016-08-04 Created: 2016-08-04 Last updated: 2017-11-28Bibliographically approved
Zhang, D., Must, I., Netzer, N. L., Xu, X., Solomon, P., Zhang, S.-L. & Zhang, Z. (2016). Direct assessment of solid–liquid interface noise in ion sensing using a differentialmethod. Applied Physics Letters, 108(15), Article ID 151603.
Open this publication in new window or tab >>Direct assessment of solid–liquid interface noise in ion sensing using a differentialmethod
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2016 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 108, no 15, 151603Article in journal (Refereed) Published
Abstract [en]

This letter presents a microelectrode cell dedicated to direct assessment of the solid-liquid interface noise without recourse to a reference electrode. In the present design, two identical TiN electrodes of various sizes are used for differential measurements in KCl-based electrolytes. Measured noise of the TiN vertical bar electrolyte system is found to be of thermal nature. Scaling inversely with electrode area, the noise is concluded to mainly arise from the solid-liquid interface. This noise is comparable to or larger than that of the state-of-the-art MOSFETs. Therefore, its influence cannot be overlooked for the design of future ion sensors.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-283484 (URN)10.1063/1.4946857 (DOI)000374314000011 ()
External cooperation:
Funder
Swedish Foundation for Strategic Research , SSF ICA 12-0047Swedish Research Council, 2014-5588Swedish Research Council, 2014-5591Swedish Research Council, 2014-6300Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of Technology, GG 1459BCarl Tryggers foundation , CTS14-527
Available from: 2016-04-13 Created: 2016-04-13 Last updated: 2017-11-30Bibliographically approved
Wen, C., Zeng, S., Zhang, Z., Hjort, K., Scheicher, R. & Zhang, S.-L. (2016). On nanopore DNA sequencing by signal and noise analysis of ionic current. Nanotechnology, 27, Article ID 215502.
Open this publication in new window or tab >>On nanopore DNA sequencing by signal and noise analysis of ionic current
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2016 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 27, 215502Article in journal (Refereed) Published
Abstract [en]

DNA sequencing, i.e., the process of determining the succession of nucleotides on a DNA strand, has become a standard aid in biomedical research and is expected to revolutionize medicine. With the capability of handling single DNA molecules, nanopore technology holds high promises to become speedier in sequencing at lower cost than what are achievable with the commercially available optics-or semiconductor-based massively parallelized technologies. Despite tremendous progress made with biological and solid-state nanopores, high error rates and large uncertainties persist with the sequencing results. Here, we employ a nano-disk model to quantitatively analyze the sequencing process by examining the variations of ionic current when a DNA strand translocates a nanopore. Our focus is placed on signal-boosting and noise-suppressing strategies in order to attain the single-nucleotide resolution. Apart from decreasing pore diameter and thickness, it is crucial to also reduce the translocation speed and facilitate a stepwise translocation. Our best-case scenario analysis points to severe challenges with employing plain nanopore technology, i.e., without recourse to any signal amplification strategy, in achieving sequencing with the desired single-nucleotide resolution. A conceptual approach based on strand synthesis in the nanopore of the translocating DNA from single-stranded to double-stranded is shown to yield a 10-fold signal amplification. Although it involves no advanced physics and is very simple in mathematics, this simple model captures the essence of nanopore sequencing and is useful in guiding the design and operation of nanopore sequencing.

Keyword
nanopore; DNA sequencing; ionic current; model; series resistance; noise; signal
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-295968 (URN)10.1088/0957-4484/27/21/215502 (DOI)000374507600013 ()27095148 (PubMedID)
Funder
Swedish Research Council, 621-2014-6300
Available from: 2016-06-11 Created: 2016-06-11 Last updated: 2017-11-28Bibliographically approved
Jablonka, L., Kubart, T., Gustavsson, F., Primetzhofer, D., Abedin, A., Hellström, P.-E., . . . Zhang, Z. (2016). Scalability Study of Nickel Germanides. In: : . Paper presented at Materials for Advanced Metallization (MAM), Brussels, March 20-23, 2016. .
Open this publication in new window or tab >>Scalability Study of Nickel Germanides
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2016 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-284445 (URN)
External cooperation:
Conference
Materials for Advanced Metallization (MAM), Brussels, March 20-23, 2016
Funder
Swedish Foundation for Strategic Research
Available from: 2016-04-18 Created: 2016-04-18 Last updated: 2016-08-30
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4317-9701

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