Detection of DMF and NH₃ at Room Temperature Using a Sensor Based on a MoS₂/Single-Walled Carbon Nanotube Composite

Sukhwinder Singh,Mark T. Swihart,Sandeep Sharma,Hyoun Woo Kim 한국표면공학회 2023 한국표면공학회 학술발표회 초록집 Vol.2023 No.11-1

Silicon nanoparticle size-dependent open circuit voltage in an organiceinorganic hybrid solar cell

김성범,이재희,Mark T. Swihart,이정철,김진영 한국물리학회 2014 Current Applied Physics Vol.14 No.1

We have incorporated silicon nanoparticles (Si-nps) into organiceinorganic hybrid solar cells in place of the chalcogenide nanocrystals that are commonly employed in such devices. Poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) and phenyl-C61-butyric acid methyl ester (PCBM) were employed as hole and electron transport layers, respectively. We used transmission electron microscopy, Raman spectroscopy, and ultravioletevisible spectroscopy to fully characterize the Si-nps and relate their characteristics to the performance of the hybrid solar cells. We show that the open circuit voltage (VOC) was largely dependent on the size and amorphous volume fraction of Si-nps. Our findings imply that the amorphous phase and small size of Si-nps produce band gap widening that increases the VOC when coupled with PCBM as acceptor. The maximum VOC was up to 0.634 V in a hybrid device with 5.7 nm Sinps.

Silicon nanoparticle size-dependent open circuit voltage in an organic-inorganic hybrid solar cell

Kim, S.,Lee, J.H.,Swihart, M.T.,Lee, J.C.,Kim, J.Y. Elsevier 2014 CURRENT APPLIED PHYSICS Vol.14 No.1

We have incorporated silicon nanoparticles (Si-nps) into organic-inorganic hybrid solar cells in place of the chalcogenide nanocrystals that are commonly employed in such devices. Poly(3,4-ethylenedioxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS) and phenyl-C<SUB>61</SUB>-butyric acid methyl ester (PCBM) were employed as hole and electron transport layers, respectively. We used transmission electron microscopy, Raman spectroscopy, and ultraviolet-visible spectroscopy to fully characterize the Si-nps and relate their characteristics to the performance of the hybrid solar cells. We show that the open circuit voltage (V<SUB>OC</SUB>) was largely dependent on the size and amorphous volume fraction of Si-nps. Our findings imply that the amorphous phase and small size of Si-nps produce band gap widening that increases the V<SUB>OC</SUB> when coupled with PCBM as acceptor. The maximum V<SUB>OC</SUB> was up to 0.634 V in a hybrid device with 5.7 nm Si-nps.

Enhanced Performance of a Polymer Solar Cell upon Addition of Free-Standing, Freshly Etched, Photoluminescent Silicon Nanocrystals

Kim, S.,Jeon, K.,Lee, J.C.,Swihart, M.T.,Yang, M. JAPAN SOCIETY OF APPLIED PHYSICS 2012 Applied physics express Vol.5 No.2

Electrosprayed graphene decorated with ZnO nanoparticles for supercapacitors

Samuel, Edmund,Londhe, Priyanka U.,Joshi, Bhavana,Kim, Min-Woo,Kim, Karam,Swihart, Mark T.,Chaure, Nandu B.,Yoon, Sam S. Elsevier 2018 Journal of alloys and compounds Vol.741 No.-

<P><B>Abstract</B></P> <P>A binder-free nanocomposite consisting of ZnO nanoparticles (NPs) grown directly on graphene sheets by electrospraying was fabricated for use as an electrode material in supercapacitors. The optimal concentrations of graphene and ZnO NPs were determined from the capacitive characteristics of the composite. Scanning electron microscopy confirmed that the ZnO NPs grew in a uniformly distributed manner on the graphene sheets and that they exhibited negligible agglomeration. Further, X-ray diffraction analysis confirmed that ZnO growth was preferentially oriented along (100) plane in the ZnO/graphene composite. A symmetric supercapacitor fabricated using this composite exhibited an energy density of 67 mWh·cm<SUP>−3</SUP> and power density of 6000 mW·cm<SUP>−3</SUP>. The composite also showed good long-term cycling performance, retaining 90% of its capacitance after 1000 galvanostatic charge/discharge cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ZnO/graphene electrodes for supercapacitor applications have been fabricated using electrospraying. </LI> <LI> A symmetric supercapacitor exhibited an energy density of 67 mWh·cm-3 and power density of 6000 mW·cm<SUP>−3</SUP>. </LI> <LI> The composite retained 90% of its capacitance after 1000 galvanostatic charge and discharge cycles. </LI> <LI> The graphene sheets prevented agglomeration of the ZnO nanoparticles. </LI> </UL> </P>

Supersonically blown nylon-6 nanofibers entangled with graphene flakes for water purification

Lee, J. G.,Kim, D. Y.,Mali, M.,Al-Deyab, S.,Swihart, M.,Yoon, S. Royal Society of Chemistry 2015 Nanoscale Vol.7 No.45

Thermally Induced Superhydrophilicity in TiO₂ Films Prepared by Supersonic Aerosol Deposition

Park, Jung-Jae,Kim, Do-Yeon,Latthe, Sanjay S.,Lee, Jong-Gun,Swihart, Mark T.,Yoon, Sam S. American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.13

<P>Superhydrophilic and superhydrophobic surfaces enable self-cleaning phenomena, either forming a continuous water film or forming droplets that roll off the surface, respectively. TiO<SUB>2</SUB> films are well-known for their extreme hydrophilicity and photocatalytic characteristics. Here, we describe nanostructured TiO<SUB>2</SUB> thin films prepared by supersonic aerosol deposition, including a thorough study of the effects of the annealing temperature on the crystal structure, surface morphology, surface roughness, and wetting properties. Powder X-ray diffraction showed that supersonic deposition resulted in fragmentation and amorphization of the micrometer-size anatase (60%)–rutile (40%) precursor powder and that, upon annealing, a substantial fraction of the film (∼30%) crystallized in the highly hydrophilic but metastable brookite phase. The film morphology was also somewhat modified after annealing. Scanning electron microscopy and atomic force microscopy revealed rough granular films with high surface roughness. The as-deposited TiO<SUB>2</SUB> films were moderately hydrophilic with a water contact angle (θ) of ∼45°, whereas TiO<SUB>2</SUB> films annealed at 500 °C became superhydrophilic (θ ∼ 0°) without UV illumination. This thermally induced superhydrophilicity of the TiO<SUB>2</SUB> films can be explained on the basis of the combined effects of the change in the crystal structure, surface microstructure, and surface roughness. Supersonic aerosol deposition followed by annealing is uniquely able to produce these nanostructured films containing a mixture of all three TiO<SUB>2</SUB> phases (anatase, rutile, and brookite) and exhibiting superhydrophilicity without UV illumination.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-13/am401083y/production/images/medium/am-2013-01083y_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am401083y'>ACS Electronic Supporting Info</A></P>

Supersonically sprayed gas- and water-sensing MIL-100(Fe) films

Lee, Jong-Gun,Joshi, Bhavana N.,Samuel, Edmund,An, Seongpil,Swihart, Mark T.,Lee, Ji Sun,Hwang, Young Kyu,Chang, Jong-San,Yoon, Sam S. ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.722 No.-

<P><B>Abstract</B></P> <P>Highly uniform, mechanically stable, dense, and water-adsorbing MIL-100(Fe) films were fabricated via supersonic spraying, a rapid, high-throughput, and scalable method compatible with roll-to-roll processing. The film surface area (1667 m<SUP>2</SUP> g<SUP>−1</SUP>) was comparable to that of the nanoparticles from which it was prepared (2009 m<SUP>2</SUP> g<SUP>−1</SUP>), and was higher than previously reported values for MIL-100(Fe) films. The gas and water adsorption abilities of the film were tested by nitrogen physisorption and water adsorption at 30 °C. The supersonically sprayed film was mechanically resistant up to a critical scratching load of 1.84 N, higher than the critical scratchability loads of dip-coated or spin-coated films. In humidity-sensing applications, films that incorporated conductive Ag nanowires were highly responsive to environmental humidity, demonstrating applicability as water vapor sensors. The fabricated films were characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly uniform, mechanically stable, dense, and water-adsorbing MIL-100(Fe) films were fabricated via supersonic spraying. </LI> <LI> The film surface area was the highest value reported in the literature. </LI> <LI> The supersonically sprayed film was mechanically resistant up to a critical scratching load of 1.84 N. </LI> <LI> The fabricated films were highly responsive to environmental humidity, demonstrating applicability as water vapor sensors. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Gravity-Driven Hybrid Membrane for Oleophobic–Superhydrophilic Oil–Water Separation and Water Purification by Graphene

Yoon, Hyun,Na, Seung-Heon,Choi, Jae-Young,Latthe, Sanjay S.,Swihart, Mark T.,Al-Deyab, Salem S.,Yoon, Sam S. American Chemical Society 2014 Langmuir Vol.30 No.39

<P>We prepared a simple, low-cost membrane suitable for gravity-driven oil–water separation and water purification. Composite membranes with selective wettability were fabricated from a mixture of aqueous poly(diallyldimethylammonium chloride) solution, sodium perfluorooctanoate, and silica nanoparticles. Simply dip-coating a stainless steel mesh using this mixture produced the oil–water separator. The contact angles (CAs) of hexadecane and water on the prepared composite membranes were 95 ± 2° and 0°, respectively, showing the oleophobicity and superhydrophilicity of the membrane. In addition, a graphene plug was stacked below the membrane to remove water-soluble organics by adsorption. As a result, this multifunctional device not only separates hexadecane from water, but also purifies water by the permeation of the separated water through the graphene plug. Here, methylene blue (MB) was removed as a demonstration. Membranes were characterized by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy to elucidate the origin of their selective wettability.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2014/langd5.2014.30.issue-39/la5031526/production/images/medium/la-2014-031526_0015.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la5031526'>ACS Electronic Supporting Info</A></P>

Hierarchical zeolitic imidazolate framework-derived manganese-doped zinc oxide decorated carbon nanofiber electrodes for high performance flexible supercapacitors

Samuel, Edmund,Joshi, Bhavana,Kim, Min-Woo,Kim, Yong-Il,Swihart, Mark T.,Yoon, Sam S. Elsevier 2019 Chemical Engineering Journal Vol.371 No.-

<P><B>Abstract</B></P> <P>We demonstrate freestanding, flexible, and cost-effective supercapacitor electrodes comprising carbon nanofibers (CNFs) decorated with metal oxide framework (MOF)-derived manganese-doped zinc oxide (Mn@ZnO). Nanoparticles of manganese-doped zeolitic imidazolate framework (ZIF-8) were grown directly on electrospun polyacrylonitrile nanofibers by a simple solution-phase synthesis. Carbonization of these composite fibers produced high surface area dodecahedral Mn@ZnO on core CNFs that provide fast electron-transfer pathways. The synergy between Mn@ZnO (active sites for Faradaic reactions) and the highly electrically conductive carbon nanofiber improves the performance of the supercapacitor electrode. The Mn@ZnO/CNF electrodes exhibit a high specific capacitance of 501 F·g<SUP>−1</SUP> and retain >92% of their initial capacitance after 10,000 cycles. The optimized Mn@ZnO/CNF electrodes deliver impressive energy densities of 72.1 W·h·kg<SUP>−1</SUP> and 33.3 W·h·kg<SUP>−1</SUP> at power densities of 500 W·kg<SUP>−1</SUP> and 5000 W·kg<SUP>−1</SUP>, respectively. This electrochemical performance demonstrates that the Mn@ZnO/CNF nanostructured composite is a robust electrode material for long-lifetime high-rate energy storage/delivery devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrospun nanofiber mats are surface-decorated with Mn-doped ZIF-8 nanoparticles. </LI> <LI> Freestanding flexible Mn@ZnO/CNF is demonstrated as a promising supercapacitor electrode. </LI> <LI> Enhanced capacitance of 501 F·g<SUP>−1</SUP> and 92% capacitance retention after 10,000 cycles are obtained. </LI> </UL> </P>