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Papers by Lance Moses

Research paper thumbnail of Non-native Co-, Mn-, and Ti-oxyhydroxide nanocrystals in ferritin for high efficiency solar energy conversion

Nanotechnology, 2014

Quantum dot solar cells seek to surpass the solar energy conversion efficiencies achieved by bulk... more Quantum dot solar cells seek to surpass the solar energy conversion efficiencies achieved by bulk semiconductors. This new field requires a broad selection of materials to achieve its full potential. The 12 nm spherical protein ferritin can be used as a template for uniform and controlled nanocrystal growth, and to then house the nanocrystals for use in solar energy conversion. In this study, precise band gaps of titanium, cobalt, and manganese oxyhydroxide nanocrystals within ferritin were measured, and a change in band gap due to quantum confinement effects was observed. The range of band gaps obtainable from these three types of nanocrystals is 2.19-2.29 eV, 1.93-2.15 eV, and 1.60-1.65 eV respectively. From these measured band gaps, theoretical efficiency limits for a multi-junction solar cell using these ferritin-enclosed nanocrystals are calculated and found to be 38.0% for unconcentrated sunlight and 44.9% for maximally concentrated sunlight. If a ferritin-based nanocrystal with a band gap similar to silicon can be found (i.e. 1.12 eV), the theoretical efficiency limits are raised to 51.3% and 63.1%, respectively. For a current matched cell, these latter efficiencies become 41.6% (with an operating voltage of 5.49 V), and 50.0% (with an operating voltage of 6.59 V), for unconcentrated and maximally concentrated sunlight respectively.

Research paper thumbnail of Fluorescence Imaging of Analyte Profiles in an Inductively Coupled Plasma with Laser Ablation as a Sample Introduction Source

Fluorescence Imaging of Analyte Profiles in an Inductively Coupled Plasma with Laser Ablation as ... more Fluorescence Imaging of Analyte Profiles in an Inductively Coupled Plasma with Laser Ablation as a Sample Introduction Source Lance Moses Department of Chemistry and Biochemistry, BYU Doctor of Philosophy Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has risen to among the top tier techniques for the direct analysis of solid samples. However, significant problems remain that must be solved to achieve the full analytical potential of LA-ICP-MS. Inefficient conversion of aerosol to ions within the ICP or transmission through the MS interface may decrease precision, sensitivity, and/or accuracy. Although fundamental mechanisms that govern ion production and transmission have been studied extensively in solution-nebulization (SN) ICP-MS instruments, significant gaps in our understanding remain. Furthermore, it is unclear to what extent differences between the aerosols generated during SN and LA influence either ion production or transmission. In this work, I in...

Research paper thumbnail of Evaluation of particle size distributions produced during ultra-violet nanosecond laser ablation and their relative contributions to ion densities in the inductively coupled plasma

Spectrochimica Acta Part B: Atomic Spectroscopy

Relative contributions to ion densities in the inductively coupled plasma (ICP) of particles of v... more Relative contributions to ion densities in the inductively coupled plasma (ICP) of particles of various sizes produced by laser ablation (LA) were investigated. Particles generated by 266 nm, ns LA of BaF 2 , CaF 2 , and a scandium aluminum alloy, characterized using SEM, consisted of hard and soft agglomerates, spherical particles, and irregularly-shaped particles. Although soft agglomerates and spherical particles were common to aerosols generated by LA in all cases, hard agglomerates appeared to be unique to the scandium aluminum alloy, while irregularly-shaped exfoliated particles were unique to the calcium and barium fluoride windows. The spatial distributions of Ca, Ba, and Sc ions in the ICP were determined from laserinduced fluorescence images taken with filters of pore sizes from 1-8 µm added in-line to the transport tube upstream from the ICP. In all cases, a significant fraction of the ions formed in the ICP originated from micron-sized particles. Differences in the penetration depths of nanometersized agglomerates and micron-sized particles were about 2 mm for Ca and 1 mm for Ba. Differences in the penetration depths of nanometer and micron-sized agglomerates observed in the case of aluminum scandium were much less significant. This suggests that micron-sized hard-agglomerates and nanometer-sized soft-agglomerates experience very similar vaporization patterns. Additionally, there was evidence that flow patterns in the transport tube affect the trajectories of particles entering the plasma.

Research paper thumbnail of The effects of He on ablation and inductively coupled plasma environment in ultra-violet, nanosecond laser ablation inductively coupled plasma mass spectrometry

Spectrochimica Acta Part B: Atomic Spectroscopy

The effects of helium gas on ablation and ICP processes were investigated. Differences in the siz... more The effects of helium gas on ablation and ICP processes were investigated. Differences in the size, shape, and abundance of aerosol particles generated in argon and helium atmosphere were studied off-line using SEM imaging of aerosol particles impacted on polycarbonate filter disks. In general, ablation in helium generated fewer large particles, and larger, more densely-packed softagglomerates. However, corresponding changes in the ion densities in the ICP, observed in high-resolution images obtained using LIF, were not always predictable. In all cases, higher He/Ar ratios led to lower ion densities in the ICP. This effect was attributed to increased rates of off-axis diffusion at higher He/Ar ratios. Differences in the ion densities produced during ablation in argon vs helium were highly dependent on sample type, the axial position of vaporization, and the He/Ar ratio. There was evidence that vaporization efficiencies of softagglomerates were less affectedthan micron-sized particles by particle acceleration at higher He/Ar ratios.

Research paper thumbnail of Tuning the band gap of ferritin nanoparticles by co-depositing iron with halides or oxo-anions

J. Mater. Chem. A, 2014

The substitution of alternate anions into the iron core of ferritin alters the mineral and change... more The substitution of alternate anions into the iron core of ferritin alters the mineral and changes the band gap of the resulting materials.

Research paper thumbnail of Fluorescence imaging of ion distributions in an inductively coupled plasma with laser ablation sample introduction

Spectrochimica Acta Part B: Atomic Spectroscopy, 2015

High-resolution images of the spatial distributions of Sc II, Ca II, and Ba II ion densities in t... more High-resolution images of the spatial distributions of Sc II, Ca II, and Ba II ion densities in the 10 mm upstream from the sampling cone in a laser ablationinductively coupled plasma-mass spectrometer (LA-ICP-MS) were obtained using planar laser induced fluorescence. Images were obtained for each analyte as a function of the carrier gas flow rate with laser ablation (LA) sample introduction and compared to images with solution nebulization (SN) over the same range of flow rates. Additionally, images were obtained using LA at varying fluences and with varying amounts of helium added to a constant flow of argon gas. Ion profiles in SN images followed a pattern consistent with previous work: increasing gas flow caused a downstream shift in the ion profiles. When compared to SN, LA led to ion profiles that were much narrower radially and reached a maximum near the sampling cone at higher flow rates. Increasing the fluence led to ions formed in the ICP over greater axial and radial distances. The addition of He to the carrier gas prior to the ablation cell led to an upstream shift in the position of ionization and lower overall fluorescence intensities.

Research paper thumbnail of Non-native Co-, Mn-, and Ti-oxyhydroxide nanocrystals in ferritin for high efficiency solar energy conversion

Nanotechnology, 2014

Quantum dot solar cells seek to surpass the solar energy conversion efficiencies achieved by bulk... more Quantum dot solar cells seek to surpass the solar energy conversion efficiencies achieved by bulk semiconductors. This new field requires a broad selection of materials to achieve its full potential. The 12 nm spherical protein ferritin can be used as a template for uniform and controlled nanocrystal growth, and to then house the nanocrystals for use in solar energy conversion. In this study, precise band gaps of titanium, cobalt, and manganese oxyhydroxide nanocrystals within ferritin were measured, and a change in band gap due to quantum confinement effects was observed. The range of band gaps obtainable from these three types of nanocrystals is 2.19-2.29 eV, 1.93-2.15 eV, and 1.60-1.65 eV respectively. From these measured band gaps, theoretical efficiency limits for a multi-junction solar cell using these ferritin-enclosed nanocrystals are calculated and found to be 38.0% for unconcentrated sunlight and 44.9% for maximally concentrated sunlight. If a ferritin-based nanocrystal with a band gap similar to silicon can be found (i.e. 1.12 eV), the theoretical efficiency limits are raised to 51.3% and 63.1%, respectively. For a current matched cell, these latter efficiencies become 41.6% (with an operating voltage of 5.49 V), and 50.0% (with an operating voltage of 6.59 V), for unconcentrated and maximally concentrated sunlight respectively.

Research paper thumbnail of Fluorescence Imaging of Analyte Profiles in an Inductively Coupled Plasma with Laser Ablation as a Sample Introduction Source

Fluorescence Imaging of Analyte Profiles in an Inductively Coupled Plasma with Laser Ablation as ... more Fluorescence Imaging of Analyte Profiles in an Inductively Coupled Plasma with Laser Ablation as a Sample Introduction Source Lance Moses Department of Chemistry and Biochemistry, BYU Doctor of Philosophy Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has risen to among the top tier techniques for the direct analysis of solid samples. However, significant problems remain that must be solved to achieve the full analytical potential of LA-ICP-MS. Inefficient conversion of aerosol to ions within the ICP or transmission through the MS interface may decrease precision, sensitivity, and/or accuracy. Although fundamental mechanisms that govern ion production and transmission have been studied extensively in solution-nebulization (SN) ICP-MS instruments, significant gaps in our understanding remain. Furthermore, it is unclear to what extent differences between the aerosols generated during SN and LA influence either ion production or transmission. In this work, I in...

Research paper thumbnail of Evaluation of particle size distributions produced during ultra-violet nanosecond laser ablation and their relative contributions to ion densities in the inductively coupled plasma

Spectrochimica Acta Part B: Atomic Spectroscopy

Relative contributions to ion densities in the inductively coupled plasma (ICP) of particles of v... more Relative contributions to ion densities in the inductively coupled plasma (ICP) of particles of various sizes produced by laser ablation (LA) were investigated. Particles generated by 266 nm, ns LA of BaF 2 , CaF 2 , and a scandium aluminum alloy, characterized using SEM, consisted of hard and soft agglomerates, spherical particles, and irregularly-shaped particles. Although soft agglomerates and spherical particles were common to aerosols generated by LA in all cases, hard agglomerates appeared to be unique to the scandium aluminum alloy, while irregularly-shaped exfoliated particles were unique to the calcium and barium fluoride windows. The spatial distributions of Ca, Ba, and Sc ions in the ICP were determined from laserinduced fluorescence images taken with filters of pore sizes from 1-8 µm added in-line to the transport tube upstream from the ICP. In all cases, a significant fraction of the ions formed in the ICP originated from micron-sized particles. Differences in the penetration depths of nanometersized agglomerates and micron-sized particles were about 2 mm for Ca and 1 mm for Ba. Differences in the penetration depths of nanometer and micron-sized agglomerates observed in the case of aluminum scandium were much less significant. This suggests that micron-sized hard-agglomerates and nanometer-sized soft-agglomerates experience very similar vaporization patterns. Additionally, there was evidence that flow patterns in the transport tube affect the trajectories of particles entering the plasma.

Research paper thumbnail of The effects of He on ablation and inductively coupled plasma environment in ultra-violet, nanosecond laser ablation inductively coupled plasma mass spectrometry

Spectrochimica Acta Part B: Atomic Spectroscopy

The effects of helium gas on ablation and ICP processes were investigated. Differences in the siz... more The effects of helium gas on ablation and ICP processes were investigated. Differences in the size, shape, and abundance of aerosol particles generated in argon and helium atmosphere were studied off-line using SEM imaging of aerosol particles impacted on polycarbonate filter disks. In general, ablation in helium generated fewer large particles, and larger, more densely-packed softagglomerates. However, corresponding changes in the ion densities in the ICP, observed in high-resolution images obtained using LIF, were not always predictable. In all cases, higher He/Ar ratios led to lower ion densities in the ICP. This effect was attributed to increased rates of off-axis diffusion at higher He/Ar ratios. Differences in the ion densities produced during ablation in argon vs helium were highly dependent on sample type, the axial position of vaporization, and the He/Ar ratio. There was evidence that vaporization efficiencies of softagglomerates were less affectedthan micron-sized particles by particle acceleration at higher He/Ar ratios.

Research paper thumbnail of Tuning the band gap of ferritin nanoparticles by co-depositing iron with halides or oxo-anions

J. Mater. Chem. A, 2014

The substitution of alternate anions into the iron core of ferritin alters the mineral and change... more The substitution of alternate anions into the iron core of ferritin alters the mineral and changes the band gap of the resulting materials.

Research paper thumbnail of Fluorescence imaging of ion distributions in an inductively coupled plasma with laser ablation sample introduction

Spectrochimica Acta Part B: Atomic Spectroscopy, 2015

High-resolution images of the spatial distributions of Sc II, Ca II, and Ba II ion densities in t... more High-resolution images of the spatial distributions of Sc II, Ca II, and Ba II ion densities in the 10 mm upstream from the sampling cone in a laser ablationinductively coupled plasma-mass spectrometer (LA-ICP-MS) were obtained using planar laser induced fluorescence. Images were obtained for each analyte as a function of the carrier gas flow rate with laser ablation (LA) sample introduction and compared to images with solution nebulization (SN) over the same range of flow rates. Additionally, images were obtained using LA at varying fluences and with varying amounts of helium added to a constant flow of argon gas. Ion profiles in SN images followed a pattern consistent with previous work: increasing gas flow caused a downstream shift in the ion profiles. When compared to SN, LA led to ion profiles that were much narrower radially and reached a maximum near the sampling cone at higher flow rates. Increasing the fluence led to ions formed in the ICP over greater axial and radial distances. The addition of He to the carrier gas prior to the ablation cell led to an upstream shift in the position of ionization and lower overall fluorescence intensities.