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Publications (10 of 101) Show all publications
Karlsson, M., Strandqvist, C., Jussi, J. I., Oberg, O., Petermann, I., Elmlund, L., . . . Wang, Q. (2019). Chemical Sensors Generated on Wafer-Scale Epitaxial Graphene for Application to Front-Line Drug Detection. Sensors, 19(10), Article ID 2214.
Open this publication in new window or tab >>Chemical Sensors Generated on Wafer-Scale Epitaxial Graphene for Application to Front-Line Drug Detection
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2019 (English)In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 19, no 10, article id 2214Article in journal (Refereed) Published
Abstract [en]

Generation of large areas of graphene possessing high quality and uniformity will be a critical factor if graphene-based devices/sensors are to be commercialized. In this work, epitaxial graphene on a 2" SiC wafer was used to fabricate sensors for the detection of illicit drugs (amphetamine or cocaine). The main target application is on-site forensic detection where there is a high demand for reliable and cost-efficient tools. The sensors were designed and processed with specially configured metal electrodes on the graphene surface by utilizing a series of anchors where the metal contacts are directly connected on the SiC substrate. This has been shown to improve adhesion of the electrodes and decrease the contact resistance. A microfluidic system was constructed to pump solutions over the defined graphene surface that could then act as a sensor area and react with the target drugs. Several prototypic systems were tested where non-covalent interactions were used to localize the sensing components (antibodies) within the measurement cell. The serendipitous discovery of a wavelength-dependent photoactivity for amphetamine and a range of its chemical analogs, however, limited the general application of these prototypic systems. The experimental results reveal that the drug molecules interact with the graphene in a molecule dependent manner based upon a balance of -stacking interaction of the phenyl ring with graphene (p-doping) and the donation of the amine nitrogens lone pair electrons into the *-system of graphene (n-doping).

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
epitaxial graphene, sensors, microfluidics, photoactivity, illicit drugs, forensics
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-255223 (URN)10.3390/s19102214 (DOI)000471014500001 ()31091664 (PubMedID)2-s2.0-85066874691 (Scopus ID)
Note

QC 20190903

Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-09-03Bibliographically approved
Fu, Y., Jussi, J. I., Elmlund, L., Dunne, S., Wang, Q. & Brismar, H. (2019). Intrinsic blinking characteristics of single colloidal CdSe-CdS/ZnS core-multishell quantum dots. Physical Review B, 99(3), Article ID 035404.
Open this publication in new window or tab >>Intrinsic blinking characteristics of single colloidal CdSe-CdS/ZnS core-multishell quantum dots
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 3, article id 035404Article in journal (Refereed) Published
Abstract [en]

Fluorescence blinking of single colloidal semiconductor quantum dots (QDs) has been extensively studied, and several sophisticated models have been proposed. In this work, we derive Heisenberg equations of motion to carefully study principal transition processes, i.e., photoexcitation, energy relaxation, impact ionization and Auger recombination, radiative and nonradiative recombinations, and tunneling between core states and surface states, of the electron-hole pair in single CdSe-CdS/ZnS core-multishell QDs and show that the on-state probability density distribution of the QD fluorescence obeys the random telegraph signal theory because of the random radiative recombination of the photoexcited electron-hole pair in the QD core, while the off-state probability density distribution obeys the inverse power law distribution due to the series of random walks of the photoexcited electron in the two-dimensional surface-state network after the electron tunnels from the QD core to the QD surface. These two different blinking characteristics of the single QD are resolved experimentally by properly adjusting the optical excitation power and the bin time.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-241317 (URN)10.1103/PhysRevB.99.035404 (DOI)000454766400012 ()2-s2.0-85059881217 (Scopus ID)
Note

QC 20190125

Available from: 2019-01-25 Created: 2019-01-25 Last updated: 2019-01-25Bibliographically approved
Karimi, M., Heurlin, M., Limpert, S., Jain, V., Zeng, X., Geijselaers, I., . . . Pettersson, H. (2018). Intersubband Quantum Disc-in-Nanowire Photodetectors with Normal-Incidence Response in the Long-Wavelength Infrared. Nano letters (Print), 18(1), 365-372
Open this publication in new window or tab >>Intersubband Quantum Disc-in-Nanowire Photodetectors with Normal-Incidence Response in the Long-Wavelength Infrared
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2018 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 1, p. 365-372Article in journal (Refereed) Published
Abstract [en]

Semiconductor nanowires have great potential for realizing broadband photodetectors monolithically integrated with silicon. However, the spectral range of such detectors has so far been limited to selected regions in the ultraviolet, visible, and near-infrared regions. Here, we report on the first intersubband nanowire heterostructure array photodetectors exhibiting a spectrally resolved photoresponse from the visible to long-wavelength infrared. In particular, the infrared response from 3 to 20 μm is enabled by intersubband transitions in low-bandgap InAsP quantum discs synthesized axially within InP nanowires. The intriguing optical characteristics, including unexpected sensitivity to normal incident radiation, are explained by excitation of the longitudinal component of optical modes in the photonic crystal formed by the nanostructured portion of the detectors. Our results provide a generalizable insight into how broadband nanowire photodetectors may be designed and how engineered nanowire heterostructures open up new, fascinating opportunities for optoelectronics.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
infrared photodetectors, intersubband photodetectors, Nanowires, photonic crystals, quantum discs
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-221689 (URN)10.1021/acs.nanolett.7b04217 (DOI)000420000000049 ()29256612 (PubMedID)2-s2.0-85040312470 (Scopus ID)
Funder
Swedish Research CouncilSwedish Agency for Economic and Regional GrowthKnut and Alice Wallenberg Foundation, 2016.0089Swedish Foundation for Strategic Research Swedish Energy Agency, P38331-1Carl Tryggers foundation EU, Horizon 2020, 641023Science for Life Laboratory - a national resource center for high-throughput molecular bioscience
Note

QC 20180122

Available from: 2018-01-22 Created: 2018-01-22 Last updated: 2018-01-29Bibliographically approved
Lu, W. & Fu, Y. (2018). Introduction to physics and optical properties of semiconductors. Springer series in optical sciences, 215, 23-71
Open this publication in new window or tab >>Introduction to physics and optical properties of semiconductors
2018 (English)In: Springer series in optical sciences, ISSN 0342-4111, Vol. 215, p. 23-71Article in journal (Refereed) Published
Abstract [en]

As the theoretical basis for the whole book, we introduce fundamental physics and optical properties of semiconductors in this chapter. We start the chapter by describing the electrons and their energy band structures in semiconductors based on quantum mechanics, then the electromagnetic field by the Maxwell’s equations. The focus of the chapter, and actually the central theme of the book, namely, the light-matter interaction, is studied in terms of first quantizing the electromagnetic field in terms of the number of photons and the energy carried per photon then calculating the optical transition of the electron between energy bands in semiconductors after either absorbing or emitting one photon. We also describe the phonon spectrum of the semiconductor which is responsible for many key features in the infrared spectra of the semiconductors.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-236403 (URN)10.1007/978-3-319-94953-6_2 (DOI)2-s2.0-85051238097 (Scopus ID)
Note

QC 20181031

Available from: 2018-10-31 Created: 2018-10-31 Last updated: 2018-10-31Bibliographically approved
Lu, W. & Fu, Y. (2018). Modulation spectroscopy. Springer series in optical sciences, 215, 159-183
Open this publication in new window or tab >>Modulation spectroscopy
2018 (English)In: Springer series in optical sciences, ISSN 0342-4111, Vol. 215, p. 159-183Article in journal (Refereed) Published
Abstract [en]

Optical spectroscopy is studied when a periodic external perturbation, such as an electromagnetic field, temperature, and static pressure or uniaxial stress, is applied to the semiconductor during the process of experimental measurement. The modulation spectroscopy, i.e., the change of the optical spectrum produced by the external perturbation, rather than the absolute spectrum itself, reveals many fine structures in the electronic energy diagram of the semiconductor.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-236416 (URN)10.1007/978-3-319-94953-6_5 (DOI)2-s2.0-85051199169 (Scopus ID)
Note

QC 20181026

Available from: 2018-10-26 Created: 2018-10-26 Last updated: 2018-10-26Bibliographically approved
Lu, W. & Fu, Y. (2018). Optical properties of fluorescent colloidal quantum dots. In: Spectroscopy of Semiconductors: (pp. 207-235). Springer
Open this publication in new window or tab >>Optical properties of fluorescent colloidal quantum dots
2018 (English)In: Spectroscopy of Semiconductors, Springer, 2018, p. 207-235Chapter in book (Refereed)
Abstract [en]

In the last chapter of the book we introduce the latest applications and developments of semiconductor spectroscopy in the field of bio-nano-photonics where semiconductor colloidal quantum dots are researched and developed as biomarkers using standard absorbance, fluorescence, time-resolved fluorescence (in ns time domain), fluorescence blinking (ms time domain) spectra, as well as bioimaging.

Place, publisher, year, edition, pages
Springer, 2018
Series
Springer Series in Optical Sciences, ISSN 0342-4111, E-ISSN 1556-1534 ; 215
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-236354 (URN)10.1007/978-3-319-94953-6_7 (DOI)2-s2.0-85051214403 (Scopus ID)978-3-319-94952-9 (ISBN)978-3-319-94953-6 (ISBN)
Note

QC 20181106

Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2018-11-06Bibliographically approved
Lu, W. & Fu, Y. (2018). Optical spectral measurement. Springer Series in Optical Sciences, 1-21
Open this publication in new window or tab >>Optical spectral measurement
2018 (English)In: Springer Series in Optical Sciences, ISSN 0342-4111, p. 1-21Article in journal (Refereed) Published
Abstract [en]

A monochromatic light is quantified by its brightness and color, i.e., its optical power and wavelength. And a light beam is normally composed of many monochromatic lights of different powers and wavelengths. In this chapter we discuss three optical dispersive devices, namely, prism, diffraction grating, and Fourier transform spectroscopy, to resolve the compositing monochromatic lights of a light beam. Prism and diffraction grating disperse the compositing monochromatic lights in the light beam into different spatial regions, and are therefore denoted as spatial dispersion, while Fourier transform spectroscopy disperses the light beam in the time domain.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-236440 (URN)10.1007/978-3-319-94953-6_1 (DOI)2-s2.0-85051199986 (Scopus ID)
Note

QC 20181023

Available from: 2018-10-23 Created: 2018-10-23 Last updated: 2018-10-23Bibliographically approved
Lu, W. & Fu, Y. (2018). Photocurrent spectroscopy. Springer Series in Optical Sciences, 185-205
Open this publication in new window or tab >>Photocurrent spectroscopy
2018 (English)In: Springer Series in Optical Sciences, ISSN 0342-4111, p. 185-205Article in journal (Refereed) Published
Abstract [en]

Applying an external electric bias on a semiconductor can produce an electric current. Impinging a light on a semiconductor already having an external electric bias can generate an extra electric current called photocurrent whose amplitude depends on the optical power and the wavelength of the light. In this chapter we study the photocurrent spectra of quantum well infrared photodetector and solar cells using quantum dots. We also study the photocurrent induced by multiphoton excitation.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-236426 (URN)10.1007/978-3-319-94953-6_6 (DOI)2-s2.0-85051187604 (Scopus ID)
Note

QC 20181026

Available from: 2018-10-26 Created: 2018-10-26 Last updated: 2018-10-26Bibliographically approved
Lu, W. & Fu, Y. (2018). Reflection and transmission. Springer Series in Optical Sciences, 215, 73-106
Open this publication in new window or tab >>Reflection and transmission
2018 (English)In: Springer Series in Optical Sciences, ISSN 0342-4111, Vol. 215, p. 73-106Article in journal (Refereed) Published
Abstract [en]

In this chapter we study how a material reflects and transmits a light beam in terms of the macroscopic effective dielectric coefficient of the material. The focus of the chapter is to extract the effective dielectric coefficient of the material using the harmonic oscillator model and the Kramers–Kronig relationship by properly designing the reflection and transmission spectroscopic measurements including the reflection and transmission spectra from and through a thin film and the reflection spectrum from a thin film on a substrate.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Textile, Rubber and Polymeric Materials
Identifiers
urn:nbn:se:kth:diva-236401 (URN)10.1007/978-3-319-94953-6_3 (DOI)2-s2.0-85051240780 (Scopus ID)
Note

QC 20181101

Available from: 2018-11-01 Created: 2018-11-01 Last updated: 2018-11-01Bibliographically approved
de Melo, F. M., Grasseschi, D., Brandao, B. B. N., Fu, Y. & Toma, H. E. (2018). Superparamagnetic Maghemite-Based CdTe Quantum Dots as Efficient Hybrid Nanoprobes for Water-Bath Magnetic Particle Inspection. ACS Applied Nano Materials, 1(6), 2858-2868
Open this publication in new window or tab >>Superparamagnetic Maghemite-Based CdTe Quantum Dots as Efficient Hybrid Nanoprobes for Water-Bath Magnetic Particle Inspection
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2018 (English)In: ACS Applied Nano Materials, ISSN 2574-0970, Vol. 1, no 6, p. 2858-2868Article in journal (Refereed) Published
Abstract [en]

Fluorescent water-based cadmium telluride quantum dots (QDs) and citrate-functionalized maghemite nanoparticles (MghNPs) were synthesized and assembled together (MghNPs@QDs) through electrostatic interactions by using cetyltrimethylammonium bromide (CTAB) as a linker and steric spacer to minimize the Forster resonance energy transfer (FRET) restriction. A whole family of hybrid and multifunctional nanoparticles has been successfully obtained, exhibiting good performance in nondestructive water-bath magnetic particle inspection (MPI) assays.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
quantum dots, magnetic nanoparticles, hybrid nanoparticles, magneto fluorescent nanoparticles, nanoprobes, magnetic particle inspection
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-249906 (URN)10.1021/acsanm.8b00502 (DOI)000461400700049 ()
Note

QC 20190422

Available from: 2019-04-23 Created: 2019-04-23 Last updated: 2019-04-23Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2442-1809

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