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Wani, Ishtiaq HassanORCID iD iconorcid.org/0000-0001-8978-0477
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Publications (10 of 12) Show all publications
Wani, I. H., Jafri, S. H., Wärnå, J., Hayat, A., Li, H., Shukla, V. A., . . . Leifer, K. (2019). A sub 20 nm metal-conjugated molecule junction acting as a nitrogen dioxide sensor. Nanoscale, 11(14), 6571-6575
Open this publication in new window or tab >>A sub 20 nm metal-conjugated molecule junction acting as a nitrogen dioxide sensor
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2019 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 14, p. 6571-6575Article in journal (Refereed) Published
Abstract [en]

The interaction of a gas molecule with a sensing material causes the highest change in the electronic structure of the latter, when this material consists of only a few atoms. If the sensing material consists of a short, conductive molecule, the sensing action can be furthermore probed by connecting such molecules to nanoelectrodes. Here, we report that NO2 molecules that adhere to 4,4'-biphenyldithiol (BPDT) bound to Au surfaces lead to a change of the electrical transmission of the BPDT. The related device shows reproducible, stable measurements and is so far the smallest (<20 nm) gas sensor. It demonstrates modulation of charge transport through molecules upon exposure to nitrogen dioxide down to concentrations of 55 ppb. We have evaluated several devices and exposure conditions and obtained a close to linear dependence of the sensor response on the gas concentration.

National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-381056 (URN)10.1039/c8nr08417c (DOI)000464454400007 ()30916070 (PubMedID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationGöran Gustafsson Foundation for Research in Natural Sciences and MedicineCarl Tryggers foundation Swedish Energy AgencySwedish Foundation for Strategic Research
Available from: 2019-04-03 Created: 2019-04-03 Last updated: 2019-05-03Bibliographically approved
Wani, I. H. (2018). Fabrication, functionalization and electrical conductance modulation of nanoparticle based molecular electronic Nano-devices. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Fabrication, functionalization and electrical conductance modulation of nanoparticle based molecular electronic Nano-devices
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Over the years many techniques have been proposed for the purpose of the formation of electrically conducting metal-molecule-metal junctions. One such technique utilizes gold-nanoparticles (AuNPs) that could assist in contacting small molecules between large gaps. The Ideal device structure then comprises of one nanoparticle and two molecules that are aligned as electrode1-molecule-AuNP-molecule-electrode2.

In present work these AuNP-molecule hybrids were fabricated inside sub 20 nm sized nanogaps between nanoelectrodes. The nanogaps were fabricated by milling of thin gold wires using focused ion beam. The tuning of the ion dosage resulted in the tuning of the gap size and the smallest nanogap of 2.3 nm was achieved.

The nano molecular electronic device (nanoMoED) platform comprised of the AuNPs that were assembled inside the nanogaps via dielectrophoresis. Two types of the AuNPs were used that were different from each other due to their functionalization chemistry. The low bias resistance 'RLB' of the nanoMoED platform was (i) reduced as compared to the nanogaps (ii) remained stable in toluene and air, and (iii) was reduced when exposed to the electron beam.

The nanoMoED platform was functionalized with various molecules using the molecular place exchange method. The successful functionalization resulted in the reduction of the 'RLB'. The smallest value of the 'RLBof the nanoMoED devices was achieved when the inserted molecule was not only highly conducting but also its length was same as the initial spacing between the AuNPs.

The nitrogen dioxide (NO2) molecules reduced the 'RLBof the nanoMoED devices that were made with 4,4'-biphenyl dithiol. The theoretical simulations showed that this reduction was due to the induced states at Fermi energy of the junction. The nanoMoED devices made with 1,8-octanedithiol showed conductance switching between two levels because of different geometries of the Au-S contact. This switching vanished when these devices were exposed to NO2 and a strong enhancement of signal to noise ratio was observed.

On the basis of these results this thesis suggests possible routes for the fabrication of highly conducting nanoMoED devices as well as elucidates the possibility of using the nanoMoED devices for gas sensing applications.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 98
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1667
Keywords
Molecular electronics, gas sensor, hybrid materials, place exchange, random telegraph signal
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-347161 (URN)978-91-513-0327-7 (ISBN)
Public defence
2018-05-30, Häggsalen, Ångström Laboratory, Regementsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2018-05-09 Created: 2018-04-12 Last updated: 2018-10-08
Qin, T., Zhang, P., Wani, I. H., Han, Y., LEIFER, K., Nikolajeff, F. & Engqvist, H. (2017). A general strategy for template-free and low-cost synthesis of inorganic hollow spheres. Powder Technology, 319, 163-171
Open this publication in new window or tab >>A general strategy for template-free and low-cost synthesis of inorganic hollow spheres
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2017 (English)In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 319, p. 163-171Article in journal (Refereed) Published
Abstract [en]

Inorganic hollow spheres have a great potential in many fields, such as calcium phosphate (Ca3(PO4)2) as carriers of active ingredients and local delivery. They are typically synthesized by the methods that reply on template-based strategies. However, the template residue and energy consumption during template removal are drawbacks. Currently developed template-free methods remain challenges such as time, cost and complicated procedures. In this paper, we introduce a general low-cost and template-free precipitation method with simple procedure. A series of inorganic hollow spheres, including calcium phosphate, calcium fluoride, strontium phosphate, strontium fluoride, barium phosphate and barium fluoride via magnesium were successfully synthesized, respectively. Based on these experimental results, a new model is proposed to explain the mechanism of the hollow inorganic spheres formation. This paper provides a general method to synthesize inorganic hollow spheres, which may have an important indication to other systems.

Keywords
Inorganic, Spheres, Hollow, Mechanism
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-333956 (URN)10.1016/j.powtec.2017.06.051 (DOI)000407982600016 ()
Available from: 2017-12-13 Created: 2017-12-13 Last updated: 2019-04-24Bibliographically approved
Calard, F., Wani, I. H., Hayat, A., Jarrosson, T., Lere-Porte, J.-P., Jafri, S. H., . . . Orthaber, A. (2017). Designing sterically demanding thiolate coated AuNPs for electrical characterization of BPDT in a NP-molecule-nanoelectrode platform. MOLECULAR SYSTEMS DESIGN & ENGINEERING, 2(2), 133-139
Open this publication in new window or tab >>Designing sterically demanding thiolate coated AuNPs for electrical characterization of BPDT in a NP-molecule-nanoelectrode platform
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2017 (English)In: MOLECULAR SYSTEMS DESIGN & ENGINEERING, ISSN 2058-9689, Vol. 2, no 2, p. 133-139Article in journal (Refereed) Published
Abstract [en]

Molecular electronics with single or few molecules requires a stable metal-molecule nanojunction platform. Herein, we report the design and synthesis of gold nanoparticles coated with sterically demanding thiol ligands that are essential to fabricate a versatile and stable nanoelectrode-molecule-nanoparticle platform suitable for electrical characterization of small organic molecules. By combining.-tetraphenylmethane ether functionalized alkyl thioacetate and alkyl thiols, we prepared highly stable gold nanoparticles in a one-phase reaction providing simple and efficient purification. This robust preparation gives highly pure nanoparticles in very high yields (up to 90%) with long-time shelf stability. The synthesis in this work has superior reproducibility compared to previous synthesis processes that are currently being used for such molecular electronics platforms. Electron microscopy confirms the formation of uniform and small nanoparticles in the range of 5 to 7 nm. These nanoparticles with different ligand surface coverages were placed in a 20 nm nanoelectrode setup using dielectrophoretic forces. This setup was utilized to characterize the conductivity of the molecular wire 4,4'-biphenyldithiol introduced via ligand placeexchange under ambient conditions.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-323512 (URN)10.1039/c6me00095a (DOI)000400987200003 ()
Available from: 2017-06-14 Created: 2017-06-14 Last updated: 2018-04-12Bibliographically approved
Li, H., Wani, I. H., Anumol, A., Han, Y., Jafri, S. H., Somobrata, A. & Leifer, K. (2017). Enhanced gas sensing performance of graphene/ZnS-CdS hetero-nanowires gas sensor synthesized by Langmuir-Blodgett self-assembly method. Paper presented at MME 2017 28th Micromechanics and Microsystems Europe workshop. Journal of Physics Conference Series, 922, Article ID 012023.
Open this publication in new window or tab >>Enhanced gas sensing performance of graphene/ZnS-CdS hetero-nanowires gas sensor synthesized by Langmuir-Blodgett self-assembly method
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2017 (English)In: Journal of Physics Conference Series, ISSN 1742-6588, Vol. 922, article id 012023Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

Graphene is a promising material in the field of solid-state gas sensors due to the unique two-dimensional structure. Here, we have shown by fabricating graphene/ZnS-CdS hetero-nanowire structure, the gas sensor sensitivity has a two-fold increase to 20% under 15 ppm gaseous concentration compared to a 10% response in pristine graphene. Spectroscopy and microscopy analysis indicate that the semi-conducting ZnS-CdS hetero-nanowires are 2 nm wide and densely packed on top of graphene. By combining UV illumination, the device approaches a fast response/recovery and high gas sensitivity, thus has a potential to be used in a detection of wide range of gases. 

National Category
Analytical Chemistry Materials Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-334517 (URN)10.1088/1742-6596/922/1/012023 (DOI)000419231200023 ()
Conference
MME 2017 28th Micromechanics and Microsystems Europe workshop
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council
Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2019-04-24Bibliographically approved
Qin, T., Han, Y., Zhang, P., Wani, I. H., Nikolajeff, F., Leifer, K. & Engqvist, H. (2017). Template-free synthesis of phosphate-based spheres via modified supersaturated phosphate buffer solutions. Journal of materials science. Materials in medicine, 28(7), Article ID 99.
Open this publication in new window or tab >>Template-free synthesis of phosphate-based spheres via modified supersaturated phosphate buffer solutions
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2017 (English)In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 28, no 7, article id 99Article in journal (Refereed) Published
Abstract [en]

Modified supersaturated phosphate buffer solutions were used to synthesize phosphate-based spheres, including calcium phosphate (CaP), strontium phosphate (SrP) and barium phosphate (BaP). A series of ions concentrations in the modified phosphate buffer solutions were investigated in order to study their effects in precipitates morphologies. During synthesis, it was found that magnesium was the key factor in sphere formation. The morphologies of calcium phosphate, strontium phosphate and barium phosphate precipitates varied as the concentration of magnesium ions varied. When sufficient magnesium was provided, the precipitates appeared spherical, and the diameter was in range of 0.5-2 mu m. The morphologies, compositions and structure of spheres were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N-2 adsorption analysis. Moreover, the application of magnesium substituted calcium phosphate spheres in dentin tubules occlusion was investigated.

Place, publisher, year, edition, pages
SPRINGER, 2017
National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-329001 (URN)10.1007/s10856-017-5911-x (DOI)000403777800001 ()28534282 (PubMedID)
Available from: 2017-09-06 Created: 2017-09-06 Last updated: 2019-04-24Bibliographically approved
Li, H., Wani, I., Hayat, A., Jafri, S. & Leifer, K. (2015). Fabrication of reproducible sub-5 nm nanogaps by a focused ion beam and application in electrical characterization of single molecules. In: : . Paper presented at 2nd European Conference on Smart Inorganic Polymers.
Open this publication in new window or tab >>Fabrication of reproducible sub-5 nm nanogaps by a focused ion beam and application in electrical characterization of single molecules
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2015 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-268035 (URN)
Conference
2nd European Conference on Smart Inorganic Polymers
Available from: 2015-12-01 Created: 2015-12-01 Last updated: 2019-04-24
Li, H., Wani, I. H., Hayat, A., Jafri, S. H. & Leifer, K. (2015). Fabrication of reproducible sub-5 nm nanogaps by a focused ion beam and observation of Fowler-Nordheim tunneling. Applied Physics Letters, 107(10), Article ID 103108.
Open this publication in new window or tab >>Fabrication of reproducible sub-5 nm nanogaps by a focused ion beam and observation of Fowler-Nordheim tunneling
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2015 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 10, article id 103108Article in journal (Refereed) Published
Abstract [en]

Creating a stable high resistance sub-5 nm nanogap in between conductive electrodes is one of the major challenges in the device fabrication of nano-objects. Gap-sizes of 20 nm and above can be fabricated reproducibly by the precise focusing of the ion beam and careful milling of the metallic lines. Here, by tuning ion dosages starting from 4.6 x 10(10) ions/cm and above, reproducible nanogaps with sub-5 nm sizes are milled with focused ion beam. The resistance as a function of gap dimension shows an exponential behavior, and Fowler-Nordheim tunneling effect was observed in nanoelectrodes with sub-5 nm nanogaps. The application of Simmon's model to the milled nanogaps and the electrical analysis indicates that the minimum nanogap size approaches to 2.3 nm.

National Category
Physical Sciences Other Engineering and Technologies
Identifiers
urn:nbn:se:uu:diva-264851 (URN)10.1063/1.4930821 (DOI)000361640200043 ()
Available from: 2015-10-19 Created: 2015-10-19 Last updated: 2019-04-24Bibliographically approved
Wani, I. H., Jafri, S., Orthaber, A., Leifer, K. & Grigoriev, A. (2015). Synthesis of nanoscale electronic device by molecular place exchange reaction in the nanoparticle nanoelectrode bridge platform.: Synthesis of nanoscale electronic device by molecular place exchange reaction in the nanoparticle-nanoelectrodebridge platform. In: : . Paper presented at European Conference on Molecular Electronics (ECME) 2015.
Open this publication in new window or tab >>Synthesis of nanoscale electronic device by molecular place exchange reaction in the nanoparticle nanoelectrode bridge platform.: Synthesis of nanoscale electronic device by molecular place exchange reaction in the nanoparticle-nanoelectrodebridge platform
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2015 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

For reducing the size and power consumption of electronic devices, building components with molecules is one alternative1. This has not been a success yet due to difficulty in creating stable molecular junctions2, 3. In efforts of creating molecular devices, we have developed the nanoparticle-nanoelectrode-molecule-bridge platform4  which has been employed to prepare 1,8 octanedithiol based molecular devices with stable metal molecule junctions5 and enabled us to observe the vibrational signals from inelastic electron tunneling spectroscopy (IETS) measurements6. The platform is electrically and mechanically stable over periods of months7.

Nanoparticle-nanoelectrode-molecule bridge platform is fabricated by the standard cleanroom techniques; where 150 nm wide patterns are developed using combination of Electron beam lithography and Photolithography. Gold is deposited using standard resistive evaporation. A very fine cut is made in the gold line using Focused Beam of Gallium ions that results in less than 20 nm separation (nanogap) between the electrodes. Gold nanoparticles (AuNPs) coated with stopper ligands and alkane thiols are synthesized by wet chemistry. Proportions of stoppers and alkane monothiols is controlled and nano particles with 5% to 10% stopper coverage (90% to 95% monothiols)  are synthesized and used in present work. These functionalized AuNPs are trapped in the nanogaps using dielectrophoretic trapping technique.

Here we present fabrication of molecular electronic nano devices based on biphenyl-4,4′-dithiol  and TBTs by molecular place exchange reaction in nano sized devices. The devices are prepared by replacing the stopper ligand attached to the surface of the AuNPs with the active molecules, using ligand exchange reaction which is carried out in inert atmosphere by placing trapped nanogaps in solution of target molecules. The reaction can take upto 100 hours to reach equilibrium. Electrical characterization before and after ligand exchange shows resistance change of more than 2 orders of magnitude which is considered as a clear signature of success of formation of molecular electronic device. 

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-268685 (URN)
Conference
European Conference on Molecular Electronics (ECME) 2015
Projects
Molecular Electronics
Available from: 2015-12-09 Created: 2015-12-09 Last updated: 2019-04-24
Wani, I. H., Orthaber, A., Jafri, S. H., Grigoriev, A., Ahuja, R. & LEIFER, K.Change of random telegraph conductance signal in different gas atmospheres in a nano molecular electronic device.
Open this publication in new window or tab >>Change of random telegraph conductance signal in different gas atmospheres in a nano molecular electronic device
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(English)Manuscript (preprint) (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-348338 (URN)
Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2018-04-12
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8978-0477

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