Papers by Majid Mortazavi
The exhibition of plasmon resonances in twodimensional
(2D) semiconductor compounds is desirable ... more The exhibition of plasmon resonances in twodimensional
(2D) semiconductor compounds is desirable for
many applications. Here, by electrochemically intercalating
lithium into 2D molybdenum disulfide (MoS2) nanoflakes,
plasmon resonances in the visible and near UV wavelength
ranges are achieved. These plasmon resonances are controlled
by the high doping level of the nanoflakes after the
intercalation, producing two distinct resonance peak areas
based on the crystal arrangements. The system is also
benchmarked for biosensing using bovine serum albumin.
This work provides a foundation for developing future 2D
MoS2 based biological and optical units.
Two-dimensional (2D) transition metal dichalcogenide semiconductors
offer unique electronic and o... more Two-dimensional (2D) transition metal dichalcogenide semiconductors
offer unique electronic and optical properties, which are significantly
different from their bulk counterparts. It is known that the electronic
structure of 2D MoS2, which is the most popular member of the family, depends
on the number of layers. Its electronic structure alters dramatically at near
atomically thin morphologies, producing strong photoluminescence (PL).
Developing processes for controlling the 2D MoS2 PL is essential to efficiently
harness many of its optical capabilities. So far, it has been shown that this PL
can be electrically or mechanically gated. Here, we introduce an electrochemical approach to actively control the PL of liquid-phase-exfoliated 2D MoS2
nanoflakes by manipulating the amount of intercalated ions including Liþ, Naþ, and Kþ into and out of the 2D crystal structure. These ions are selected as
they are crucial components in many bioprocesses. We show that this controlled intercalation allows for large PL modulations. The introduced
electrochemically controlled PL will find significant applications in future chemical and bio-optical sensors as well as optical modulators/switches.
Over the past decade, the interest in aluminum composites reinforced with carbon nanotubes has gr... more Over the past decade, the interest in aluminum composites reinforced with carbon nanotubes has grown significantly. Studies have been carried
out to overcome problems with uniform dispersion, interfacial bonding, void formation and carbide formation of the composites. In the present work,
multi-wall carbon nanotubes (MWCNTs) aluminum composites were produced. High-energy ball milling with the aim at developing well-dispersed
MWCNTs Al composites was followed by cold compaction, sintering, and hot extrusion at 500 ºC. Different amounts of stearic acid as
processing control agent (PCA) is used in order to minimize cold welding of the Al particles, and to produce finer particles. Differential scanning
calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were employed
to analyze the MWCNTs, the aluminum powder, and the composites’ microstructural behavior. The hardness and tensile properties of
the composites are also evaluated. The results showed 500% increase in yield stress after the addition of 1 wt% MWCNTs in Al-MWCNTs
based composite. The ball-milling time of 4 h is found to be sufficient as excessive milling time destroys a vast number of MWCNTs.
Group-15 elements phosphorus, arsenic, antimony and bismuth offer the prospect of serving as func... more Group-15 elements phosphorus, arsenic, antimony and bismuth offer the prospect of serving as functional
alloying elements for developing high-capacity alloy anodes for sodium-ion batteries (NIBs). Here
we obtain concentration-dependent electrochemical properties of sodium (Na) alloys with group-15
elements using first principles calculations. Since Na intercalation in these alloys is accompanied by a
substantial volume expansion that can lead to mechanical failure and loss of capacity, we have also
obtained a full set of concentration-dependent elastic properties for a single crystal as well as a polycrystalline
microstructure. We find that sodiation of these alloys results in their significant elastic
softening by as large as 60%. In contrast to the group-14 alloys that are also being explored as anodes of
NIBs, the elastic softening in group-15 alloys varies in a non-monotonic manner with Na concentration,
and more importantly, the maximum degradation of elastic properties does not necessarily occur at full
sodiation. Our results provide crucial insights into the electrochemical and mechanical response of these
alloys to Na intercalation, thus contributing to the design of failure-resistant architectures of high capacity
NIBs.
Identifying suitable layered materials as electrodes with desirable electrochemical properties re... more Identifying suitable layered materials as electrodes with desirable electrochemical properties remains a
key challenge for rechargeable Na-ion batteries (NIBs). Using first principles methods, here we examine
the efficacy of layered molybdenum disulphide (MoS2) as a host electrode material for NIBs. We identify
various low energy Na adsorption sites and evaluate the stability of the hexagonal and tetragonal polytypes
of MoS2 upon Na intercalation. Our results illustrate a moderately strong binding between Na and
MoS2 that is thermodynamically favorable against the cluster formation and phase separation of Na. We
find that while Na intercalation in MoS2 results in a phase transformation from the hexagonal phase to
the tetragonal phase, it gives rise to a maximum theoretical capacity of 146 mAh g1 and a low average
electrode potential in the range of 0.75e1.25 V. Our calculations of Na diffusion kinetics indicates a
moderately fast mobility of Na in the van derWaals interlayer spaces of MoS2. These results highlight the
promise of MoS2 as an appealing negative electrode (anode) for rechargeable NIBs.
Accurate description of the mechanical behavior of crystalline Na alloys is essential in establis... more Accurate description of the mechanical behavior of crystalline Na alloys is essential in establishing their
electrochemical performance as well as their viability as anodes in Na-ion batteries. Using first principles
simulations, we have investigated the intrinsic elastic properties of crystalline NaeM (M¼ Sn, Pb, Si and
Ge) phases observed during Na intercalation. We have obtained the complete set of concentrationdependent
anisotropic elastic constants as well as the average macroscopic elastic moduli of polycrystalline
structures. We find that sodiation of pure M phases leads to a remarkable elastic softening
that results in up to 75% deterioration of the elastic moduli. Our analysis of the electronic charge
distribution demonstrates that the elastic softening during sodiation originates from a transition to
weaker ionic interatomic bonding. Our results highlight the significance of the concentration dependence
of the elastic moduli for the analysis of deformation behavior of Na alloy anodes of Na-ion
batteries during sodiation and desodiation.
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Papers by Majid Mortazavi
(2D) semiconductor compounds is desirable for
many applications. Here, by electrochemically intercalating
lithium into 2D molybdenum disulfide (MoS2) nanoflakes,
plasmon resonances in the visible and near UV wavelength
ranges are achieved. These plasmon resonances are controlled
by the high doping level of the nanoflakes after the
intercalation, producing two distinct resonance peak areas
based on the crystal arrangements. The system is also
benchmarked for biosensing using bovine serum albumin.
This work provides a foundation for developing future 2D
MoS2 based biological and optical units.
offer unique electronic and optical properties, which are significantly
different from their bulk counterparts. It is known that the electronic
structure of 2D MoS2, which is the most popular member of the family, depends
on the number of layers. Its electronic structure alters dramatically at near
atomically thin morphologies, producing strong photoluminescence (PL).
Developing processes for controlling the 2D MoS2 PL is essential to efficiently
harness many of its optical capabilities. So far, it has been shown that this PL
can be electrically or mechanically gated. Here, we introduce an electrochemical approach to actively control the PL of liquid-phase-exfoliated 2D MoS2
nanoflakes by manipulating the amount of intercalated ions including Liþ, Naþ, and Kþ into and out of the 2D crystal structure. These ions are selected as
they are crucial components in many bioprocesses. We show that this controlled intercalation allows for large PL modulations. The introduced
electrochemically controlled PL will find significant applications in future chemical and bio-optical sensors as well as optical modulators/switches.
out to overcome problems with uniform dispersion, interfacial bonding, void formation and carbide formation of the composites. In the present work,
multi-wall carbon nanotubes (MWCNTs) aluminum composites were produced. High-energy ball milling with the aim at developing well-dispersed
MWCNTs Al composites was followed by cold compaction, sintering, and hot extrusion at 500 ºC. Different amounts of stearic acid as
processing control agent (PCA) is used in order to minimize cold welding of the Al particles, and to produce finer particles. Differential scanning
calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were employed
to analyze the MWCNTs, the aluminum powder, and the composites’ microstructural behavior. The hardness and tensile properties of
the composites are also evaluated. The results showed 500% increase in yield stress after the addition of 1 wt% MWCNTs in Al-MWCNTs
based composite. The ball-milling time of 4 h is found to be sufficient as excessive milling time destroys a vast number of MWCNTs.
alloying elements for developing high-capacity alloy anodes for sodium-ion batteries (NIBs). Here
we obtain concentration-dependent electrochemical properties of sodium (Na) alloys with group-15
elements using first principles calculations. Since Na intercalation in these alloys is accompanied by a
substantial volume expansion that can lead to mechanical failure and loss of capacity, we have also
obtained a full set of concentration-dependent elastic properties for a single crystal as well as a polycrystalline
microstructure. We find that sodiation of these alloys results in their significant elastic
softening by as large as 60%. In contrast to the group-14 alloys that are also being explored as anodes of
NIBs, the elastic softening in group-15 alloys varies in a non-monotonic manner with Na concentration,
and more importantly, the maximum degradation of elastic properties does not necessarily occur at full
sodiation. Our results provide crucial insights into the electrochemical and mechanical response of these
alloys to Na intercalation, thus contributing to the design of failure-resistant architectures of high capacity
NIBs.
key challenge for rechargeable Na-ion batteries (NIBs). Using first principles methods, here we examine
the efficacy of layered molybdenum disulphide (MoS2) as a host electrode material for NIBs. We identify
various low energy Na adsorption sites and evaluate the stability of the hexagonal and tetragonal polytypes
of MoS2 upon Na intercalation. Our results illustrate a moderately strong binding between Na and
MoS2 that is thermodynamically favorable against the cluster formation and phase separation of Na. We
find that while Na intercalation in MoS2 results in a phase transformation from the hexagonal phase to
the tetragonal phase, it gives rise to a maximum theoretical capacity of 146 mAh g1 and a low average
electrode potential in the range of 0.75e1.25 V. Our calculations of Na diffusion kinetics indicates a
moderately fast mobility of Na in the van derWaals interlayer spaces of MoS2. These results highlight the
promise of MoS2 as an appealing negative electrode (anode) for rechargeable NIBs.
electrochemical performance as well as their viability as anodes in Na-ion batteries. Using first principles
simulations, we have investigated the intrinsic elastic properties of crystalline NaeM (M¼ Sn, Pb, Si and
Ge) phases observed during Na intercalation. We have obtained the complete set of concentrationdependent
anisotropic elastic constants as well as the average macroscopic elastic moduli of polycrystalline
structures. We find that sodiation of pure M phases leads to a remarkable elastic softening
that results in up to 75% deterioration of the elastic moduli. Our analysis of the electronic charge
distribution demonstrates that the elastic softening during sodiation originates from a transition to
weaker ionic interatomic bonding. Our results highlight the significance of the concentration dependence
of the elastic moduli for the analysis of deformation behavior of Na alloy anodes of Na-ion
batteries during sodiation and desodiation.
(2D) semiconductor compounds is desirable for
many applications. Here, by electrochemically intercalating
lithium into 2D molybdenum disulfide (MoS2) nanoflakes,
plasmon resonances in the visible and near UV wavelength
ranges are achieved. These plasmon resonances are controlled
by the high doping level of the nanoflakes after the
intercalation, producing two distinct resonance peak areas
based on the crystal arrangements. The system is also
benchmarked for biosensing using bovine serum albumin.
This work provides a foundation for developing future 2D
MoS2 based biological and optical units.
offer unique electronic and optical properties, which are significantly
different from their bulk counterparts. It is known that the electronic
structure of 2D MoS2, which is the most popular member of the family, depends
on the number of layers. Its electronic structure alters dramatically at near
atomically thin morphologies, producing strong photoluminescence (PL).
Developing processes for controlling the 2D MoS2 PL is essential to efficiently
harness many of its optical capabilities. So far, it has been shown that this PL
can be electrically or mechanically gated. Here, we introduce an electrochemical approach to actively control the PL of liquid-phase-exfoliated 2D MoS2
nanoflakes by manipulating the amount of intercalated ions including Liþ, Naþ, and Kþ into and out of the 2D crystal structure. These ions are selected as
they are crucial components in many bioprocesses. We show that this controlled intercalation allows for large PL modulations. The introduced
electrochemically controlled PL will find significant applications in future chemical and bio-optical sensors as well as optical modulators/switches.
out to overcome problems with uniform dispersion, interfacial bonding, void formation and carbide formation of the composites. In the present work,
multi-wall carbon nanotubes (MWCNTs) aluminum composites were produced. High-energy ball milling with the aim at developing well-dispersed
MWCNTs Al composites was followed by cold compaction, sintering, and hot extrusion at 500 ºC. Different amounts of stearic acid as
processing control agent (PCA) is used in order to minimize cold welding of the Al particles, and to produce finer particles. Differential scanning
calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were employed
to analyze the MWCNTs, the aluminum powder, and the composites’ microstructural behavior. The hardness and tensile properties of
the composites are also evaluated. The results showed 500% increase in yield stress after the addition of 1 wt% MWCNTs in Al-MWCNTs
based composite. The ball-milling time of 4 h is found to be sufficient as excessive milling time destroys a vast number of MWCNTs.
alloying elements for developing high-capacity alloy anodes for sodium-ion batteries (NIBs). Here
we obtain concentration-dependent electrochemical properties of sodium (Na) alloys with group-15
elements using first principles calculations. Since Na intercalation in these alloys is accompanied by a
substantial volume expansion that can lead to mechanical failure and loss of capacity, we have also
obtained a full set of concentration-dependent elastic properties for a single crystal as well as a polycrystalline
microstructure. We find that sodiation of these alloys results in their significant elastic
softening by as large as 60%. In contrast to the group-14 alloys that are also being explored as anodes of
NIBs, the elastic softening in group-15 alloys varies in a non-monotonic manner with Na concentration,
and more importantly, the maximum degradation of elastic properties does not necessarily occur at full
sodiation. Our results provide crucial insights into the electrochemical and mechanical response of these
alloys to Na intercalation, thus contributing to the design of failure-resistant architectures of high capacity
NIBs.
key challenge for rechargeable Na-ion batteries (NIBs). Using first principles methods, here we examine
the efficacy of layered molybdenum disulphide (MoS2) as a host electrode material for NIBs. We identify
various low energy Na adsorption sites and evaluate the stability of the hexagonal and tetragonal polytypes
of MoS2 upon Na intercalation. Our results illustrate a moderately strong binding between Na and
MoS2 that is thermodynamically favorable against the cluster formation and phase separation of Na. We
find that while Na intercalation in MoS2 results in a phase transformation from the hexagonal phase to
the tetragonal phase, it gives rise to a maximum theoretical capacity of 146 mAh g1 and a low average
electrode potential in the range of 0.75e1.25 V. Our calculations of Na diffusion kinetics indicates a
moderately fast mobility of Na in the van derWaals interlayer spaces of MoS2. These results highlight the
promise of MoS2 as an appealing negative electrode (anode) for rechargeable NIBs.
electrochemical performance as well as their viability as anodes in Na-ion batteries. Using first principles
simulations, we have investigated the intrinsic elastic properties of crystalline NaeM (M¼ Sn, Pb, Si and
Ge) phases observed during Na intercalation. We have obtained the complete set of concentrationdependent
anisotropic elastic constants as well as the average macroscopic elastic moduli of polycrystalline
structures. We find that sodiation of pure M phases leads to a remarkable elastic softening
that results in up to 75% deterioration of the elastic moduli. Our analysis of the electronic charge
distribution demonstrates that the elastic softening during sodiation originates from a transition to
weaker ionic interatomic bonding. Our results highlight the significance of the concentration dependence
of the elastic moduli for the analysis of deformation behavior of Na alloy anodes of Na-ion
batteries during sodiation and desodiation.