108 research outputs found
Visualization of the Eigen-structure Updating of Three-Dimensional Random Tensor
This image visualizes the structural relationship between the higher order singular value decomposition (HOSVD) of a three-dimensional random tensor (above) of size 20x15x10 and a partial three-dimensional tensor (below) of size 7x10x5, which is extracted from the original random tensor (above). The relative position of the new tensor within the old tensor is highlighted in yellow. Their higher order singular value decompositions are shown on the right, which consist of core tensors (red and blue), and two sets of loading matrices (shown in colored images). In this research in UIC, we discovered the structural relationship between the HOSVDs of those two tensors, and developed fast updating and downdating algorithms for re-calculating of HOSVDs. These algorithms are applicable to many areas of research involving tensor-form data. Specifically, we applied these algorithms in dynamic updating and downdating of video and motion trajectory databases
External Heavy-Atom Activated Phosphorescence of Organic Luminophores in a Rigid Fluid Matrix
Growing attention has been paid to pure organic room-temperature
phosphorescence (RTP). Although an insufficient population and fast
nonradiative decay of triplet excitons are avoided in recent endeavors,
complicated synthesis and limited universality still hinder its development.
Further, fluid RTP materials are more difficult to design because
of faster nonradiative relaxation. Herein, a deep eutectic mixture
of glucose and choline, a stable supercooled liquid at room temperature,
is employed as a matrix. Direct transformation from commercial fluorescent
dyes to RTP fluid is realized by doping without modifications. The
excited triplet states are generated by an external heavy atom, while
the rigid noncovalent network stabilizes them with both functions
intrinsic to the liquid matrix. Modulation of matrix components also
results in nearly white light emission of a single dye. This study
presents a general strategy to design fluid RTP materials starting
from the vast library of fluorophores
Controllable Self-Assembling of Gold Nanorods via On and Off Supramolecular Noncovalent Interactions
5,15-BisÂ(4-sulfonatophenyl)Âporphyrin (<b>DPPS</b>) with a
planar conjugated system and two negative charges was found to be
able to engender the self-assembling of CTAB-<b>GNR</b>s due
to the electrostatic interaction between <b>DPPS</b> and CTAB
together with the π–π intermolecular interaction
of <b>DPPS</b>, while its bulky supramolecular pseudo[3]Ârotaxane
included by β-cyclodextrin prevented such self-assembling due
to the interruption of the above noncovalent interactions
Amorphous 2‑Bromocarbazole Copolymers with Efficient Room-Temperature Phosphorescent Emission and Applications as Encryption Ink
The
development of metal-free organic room-temperature phosphorescent
(RTP) materials is promising but challenging, because spin–orbit
coupling is less efficient without heavy metals such as platinum and
palladium. Here, we present a novel amorphous copolymer composed of
2-bromocarbazole phosphor and acrylamide on its side chains, which
can engender blue–purple phosphorescence emission with high
quantum yield at room temperature. The polymer matrices of acrylamide
and the hydrogen bonding in the polymeric chain system can effectively
help to inhibit nonradiative transition process and, hence, strengthen
the phosphorescent emission. The molar ratio of the 2-bromocarbazole
phosphor and acrylamide remarkably influences the RTP emission intensities
and quantum yields of the polymers. The high amount of phosphor will
weaken the rigidity of the polymers and the shielding effect from
oxygen, thus leading to a decrease in their RTP emission, while a
low concentration of the phosphor will also weaken their RTP emission
intensity. Furthermore, RTP intensity of the amorphous polymer is
responsive to humidity, because the hydrogen bonding in the polymeric
chain system can be broken by water, which makes it applicable in
the area of encryption
Multicolor Photoluminescence of a Hybrid Film via the Dual-Emitting Strategy of an Inorganic Fluorescent Au Nanocluster and an Organic Room-Temperature Phosphorescent Copolymer
Achieving
multicolor photoluminescence, especially white-light
emission, under mild conditions based on hybrid organic–inorganic
materials has attracted growing attention. A novel system, via a histidine
modified Au nanocluster (AuNC@histidine) with bluish green fluorescence
and a 4-bromo-1,8-naphthalic anhydride derivative polymer (poly-BrNpA)
with orange room-temperature phosphorescence (RTP) emission, was designed
and prepared. White-light emission could be achieved by adjusting
the proportions of the two components. The hydrogen bond enhanced
the RTP emission of such copolymer systems through suppressing the
nonradiative relaxation process by the well-formed and highly cross-linked
network. By introducing fluorescence compounds (AuNC@histidine) which
were insensitive to environmental humidity, this fluorescence-phosphorescence
dual-emitting hybrid system could also be used as a humidity responsive
material, since the hydrogen bonds in poly-BrNpA chains could be broken
by environmental humidity. The color switching could be well conducted
in a polyÂ(vinyl alcohol) (PVA) matrix, which was good for forming
a processable and humidity responsive film
A Total Synthesis of the Antifungal Deoxyaminocyclitol Nabscessin B from l‑(+)-Tartaric Acid
Aminocyclitol <b>2</b>, a recently isolated and notable antifungal
agent, was prepared from homochiral Îł-hydroxycyclohexenone <b>4</b>, which is itself available in six steps from l-(+)-tartaric
acid (<b>3</b>). The well-defined rigidifying effect arising
from the 1,2-diacetal protecting group associated with compound <b>4</b> and its derivatives allows for high levels of regio- and
stereo-chemical control in the manipulation of the cyclitol framework
Total Synthesis of the Marine Alkaloid Discoipyrrole C via the MoOPH-Mediated Oxidation of a 2,3,5-Trisubstituted Pyrrole
A total synthesis of the marine alkaloid
discoipyrrole C (<b>3</b>) is described. In the pivotal step,
the 2,3,5-trisubstituted
pyrrole <b>19</b> was treated with MoOPH in the presence of
MeOH, and the resulting methoxylated 1,2-dihydro-3<i>H</i>-pyrrol-3-one <b>20</b> subjected to reaction with potassium
carbonate in MeOH then trifluoroacetic acid and H<sub>2</sub>O. This
gave a mixture of target <b>3</b> and its dehydration product,
and the structure of the former compound was confirmed by single-crystal
X-ray analysis
Total Synthesis of the Marine Alkaloid Discoipyrrole C via the MoOPH-Mediated Oxidation of a 2,3,5-Trisubstituted Pyrrole
A total synthesis of the marine alkaloid
discoipyrrole C (<b>3</b>) is described. In the pivotal step,
the 2,3,5-trisubstituted
pyrrole <b>19</b> was treated with MoOPH in the presence of
MeOH, and the resulting methoxylated 1,2-dihydro-3<i>H</i>-pyrrol-3-one <b>20</b> subjected to reaction with potassium
carbonate in MeOH then trifluoroacetic acid and H<sub>2</sub>O. This
gave a mixture of target <b>3</b> and its dehydration product,
and the structure of the former compound was confirmed by single-crystal
X-ray analysis
Total Syntheses of the Resorcylic Acid Lactones Paecilomycin F and Cochliomycin C Using an Intramolecular Loh-Type α‑Allylation Reaction for Macrolide Formation
Subjection of the resorcylic ester <b>16</b> to a Nozaki–Hiyama–Kishi
reaction afforded the 12-membered lactone <b>17</b>, while treatment
of it under the Loh-type α-allylation conditions using indium
metal gave the isomeric, 14-membered macrolide <b>18</b>. Compound <b>18</b> was readily elaborated to the resorcylic acid lactone type
natural products paecilomycin F and cochliomycin C
Visible-Light-Dependent Photocyclization: Design, Synthesis, and Properties of a Cyanine-Based Dithienylethene
A cyanine-based dithienylethene is
developed. Its photoisomerization shows that (1) the irradiation of
visible light can induce cyclization while the cycloreversion takes
place upon irradiation with UV light and (2) the addition of CN<sup>–</sup> can lead to cyclization and cycloreversion upon irradiation
of UV light and visible light, respectively
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