Controlling Band Gap Energies in Cluster-Assembled Ionic Solids through Internal Electric Fields

Chaki, Nirmalya K.; Mandal, Sukhendu; Reber, Arthur C.; Qian, Meichun; Saavedra, Héctor M.; Weiss, Paul S.; Khanna, Shiv N.; Sen, Ayusman

doi:10.1021/nn101640r

Cited by 77 publications

(77 citation statements)

References 43 publications

(64 reference statements)

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“…Changing the assembly from a 0D to a 2D architecture is generally expected to decrease the band gap energy through increased band broadening due to larger coordination; however, we generally observe an increase in band gap energy, as seen in Figure 1. 30 The symbols in Figure 1 mark the character of the cluster building block, and the gold-linked, Zn-and Cd-linked, and M(CO) 3 -bound clusters all show an increase in the band gap energy as the dimensionality of the assembly increases. , but changing the cation results in 0D (5) and 2D (6À8) architectures (Figure 4).…”

Section: Band Gap Energy Tuning: Role Of Internal Electric Fieldmentioning

confidence: 99%

Controlling the Band Gap Energy of Cluster-Assembled Materials

et al. 2013

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C luster-assembled materials combine the nanoscale size and composition-dependent properties of clusters, which have highly tunable magnetic and electronic properties useful for a great variety of potential technologies. To understand the emergent properties as clusters are assembled into hierarchical materials, we have synthesized 23 clusterassembled materials composed of As 7 3À -based motifs and different countercations and measured their band gap energies. We found that the band gap energy varies from 1.09 to 2.21 eV. In addition, we have carried out first principles electronic structure studies to identify the physical mechanisms that enable control of the band gap edges of the cluster assemblies.The choice of counterion has a profound effect on the band gap energy in ionic cluster assemblies. The top of the valence band is localized on the arsenic cluster, while the conduction band edge is located on the alkali metal counterions. Changing the counterion changes the position of the conduction band edge, enabling control of the band gap energy. We can also vary the architecture of the ionic solid by incorporating cryptates as counterions, which provide charge but are separated from the clusters by bulky ligands. Higher dimensionality typically decreases the band gap energy through band broadening; however band gap energies increased upon moving from zero-dimensional (0D) to two-dimensional (2D) assemblies. This is because internal electric fields generated by the counterion preferentially stabilize the adjacent lone pair orbitals that mark the top of the valence band. Thus, the choice of the counterion can control the position of the conduction band edge of ionic cluster assemblies. In addition, the dimensionality of the solid via internal electric fields can control the valence band edge.Through covalently linking arsenic clusters into composite building blocks, we have also been able to tune the band gap energy. We used a theoretical description based on cluster orbital theory to provide microscopic understanding of the electronic character of the composite building blocks and the observed variations in the band gap energy. Also, we have shown how dimeric linkers can be used to control the band gap energy. Lastly, we also investigated the effects of charge transfer complexes of M(CO) 3 on the band gap energy.

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Section: Band Gap Energy Tuning: Role Of Internal Electric Fieldmentioning

confidence: 99%

Controlling the Band Gap Energy of Cluster-Assembled Materials

et al. 2013

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“…I n superlattices and heterostructures, the Coulombic interaction between adjacent atomic layers of (nominally) charged and/or neutral planes can create internal electric fields [1][2][3] that induce or alter many functional electronic, ferroic and optical properties [4][5][6][7][8][9] . In the majority of atomically layered oxides explored to date, however, the heterostructures are constructed by interleaving two or more bulk materials, often perovskite 'blocks' with well-defined three-dimensional connectivity [10][11][12][13][14][15] .…”

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“…Rarely are the starting oxides natural heterostructures themselves, for example, Aurivillius, Dion-Jacobson or the RuddlesdenPopper (RP) phases. The latter (ABO 3 ) n /(AO) (also denoted as A n þ 1 B n O 3n þ 1 ) RP structure has n ABO 3 perovskite blocks stacked along the [001] direction with an extra sheet of AO rocksalt layers interleaved every n perovskite layers. This geometry disconnects the BO 6 octahedra along one direction and imposes severe constraints on the nearest-neighbour interactions 16 , promoting anisotropy in the structure-derived electronic, transport and magnetic properties, which contrasts sharply with the 3D perovskite analogues [17][18][19][20] .…”

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Massive band gap variation in layered oxides through cation ordering

Balachandran

Rondinelli

2015

Nat Commun

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The electronic band gap is a fundamental material parameter requiring control for light harvesting, conversion and transport technologies, including photovoltaics, lasers and sensors. Although traditional methods to tune band gaps rely on chemical alloying, quantum size effects, lattice mismatch or superlattice formation, the spectral variation is often limited to o1 eV, unless marked changes to composition or structure occur. Here we report large band gap changes of up to 200% or B2 eV without modifying chemical composition or use of epitaxial strain in the LaSrAlO 4 Ruddlesden-Popper oxide. First-principles calculations show that ordering electrically charged [LaO] 1 þ and neutral [SrO] 0 monoxide planes imposes internal electric fields in the layered oxides. These fields drive local atomic displacements and bond distortions that control the energy levels at the valence and conduction band edges, providing a path towards electronic structure engineering in complex oxides.

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“…[42] In cluster-assembled materials, we found that the dimensionality of these hierarchical materials could change the band-gap energy through the position of the counterions. [5] This may occur because the field could increase or decrease the energy of the frontier orbitals of the cluster and change the band-gap energy, similarly to what is seen in crystalfield splitting. This internal electric field could cause the band-gap energy of a CAM to be larger than that of the free cluster.…”

Section: Introductionmentioning

confidence: 98%

The Effects of Alkaline‐Earth Counterions on the Architectures, Band‐Gap Energies, and Proton Transfer of Triazole‐Based Coordination Polymers

et al. 2015

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Increased thermal or mechanical stability of DNA duplexes is desired for many applications in nanotechnology or ‐medicine where DNA is used as a programmable building block. Modifications of pyrimidine bases are known to enhance thermal stability and have the advantage of standard base‐pairing and easy integration during chemical DNA synthesis. Through single‐molecule force spectroscopy experiments with atomic force microscopy and the molecular force assay we investigated the effect of pyrimidines harboring C‐5 propynyl modifications on the mechanical stability of double‐stranded DNA. Utilizing these complementary techniques, we show that propynyl bases significantly increase the mechanical stability if the DNA is annealed at high temperature. In contrast, modified DNA complexes formed at room temperature and short incubation times display the same stability as non‐modified DNA duplexes.

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Controlling Band Gap Energies in Cluster-Assembled Ionic Solids through Internal Electric Fields

Cited by 77 publications

References 43 publications

Controlling the Band Gap Energy of Cluster-Assembled Materials

Controlling the Band Gap Energy of Cluster-Assembled Materials

Massive band gap variation in layered oxides through cation ordering

The Effects of Alkaline‐Earth Counterions on the Architectures, Band‐Gap Energies, and Proton Transfer of Triazole‐Based Coordination Polymers

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