مجال
التميز
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تميز دراسي وبحثي وإبداع علمي
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البحوث المنشورة
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البحث (1):
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عنوان البحث:
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Self-Assembly of Charged Bodipy Dyes To
Form Cassettes That Display Intracornplex Electronic Energy Transfer and
Accrete into Liquid Crystals
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رابط إلى البحث:
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here
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تاريخ النشر:
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2012
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موجز عن البحث:
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Red- and blue-absorbing boron dipyrromethene dyes,
bearing opposite electronic charges, associate in solution to form a 1:2
complex having a stability constant of ca. 1017 M–2. The complex can be
dismantled by addition of a large excess of tetra-N-butylammonium cations.
The same complex displays liquid crystalline properties on heating from rt to
above 150 °C, as characterized by various experimental techniques. Highly
efficient electronic energy transfer from the red to the blue dye occurs in
both the initial complex and the subsequent mesomorphic state.
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البحث (2):
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عنوان البحث:
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Fluorescent molecular rotors under
pressure: synergistic effects of an inert polymer
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رابط إلى البحث:
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تاريخ النشر:
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2012
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موجز عن البحث:
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Sterically unhindered boron
dipyrromethene dyes bearing aryl hydrocarbons at the mesoposition
can function as fluorescent probes for monitoring changes in rheology of the
surrounding environment. The key aspect of such behaviour relates to the ease
of rotation of the aryl ring, which is set in part by frictional forces with
nearby solvent molecules. For the target dye under consideration here,
gyration of the meso-phenylene ring shows a pronounced temperature
dependence but only a modest ensitivity towards applied pressure. Changing
the specific viscosity of the solvent by adding a linear polymer has but a
small effect on the fluorescence yield of the dye under ambient conditions
and thereby indicates that there is little contact between dye and polymer.
Under pressure in the presence of polymer, the fluorescence yield increases
dramatically and allows design of an effective fluorescence-based pressure
sensor. The simplest explanation of this phenomenon has the polymer wrapping
around the dye under pressure and curtailing the rotary action. In addition,
it has to be considered that the inert polymer renders the chloroform solvent
more susceptible to a pressure-induced increase in density by minimising
electrostatic repulsion between chlorine lone pairs. In this respect, the
polymer acts as a lubricant for compression of chloroform under pressure.
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البحث (3):
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عنوان البحث:
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Nanomechanical properties of
molecular-scale bridges as visualised by intramolecular electronic energy
transfer
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رابط إلى البحث:
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تاريخ النشر:
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17 Oct 2012
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موجز عن البحث:
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A series of molecular dyads has been synthesized and
fully characterised. These linear, donor–spacer–acceptor compounds comprise
terminal dyes selected to exhibit intramolecular electronic energy transfer
(EET) along the molecular axis. The spacer is built by accretion of
ethynylene–carborane units that give centre-to-centre separation distances of
38, 57, 76, 96, and 115 Å respectively along the series. The probability of
one-way EET between terminals depends on the length of the spacer but also on
temperature and applied pressure. Throughout the series, the derived EET
parameters are well explained in terms of through-space interactions but the
probability of EET is higher than predicted for the fully extended
conformation except in a glassy matrix at low temperature. The implication is
that these spacers contract under ambient conditions, with the extent of
longitudinal contraction increasing under pressure but decreasing as the
temperature is lowered. Longer bridges are more susceptible to such
distortion, which is considered to resemble a concertina effect caused by
out-of-plane bending of individual subunits. The dynamics of EET can be used
to estimate the strain energy associated with molecular contraction, the
amount of work done in effecting the structural change and the Young’s
modulus for the bridge.
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البحث (4):
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عنوان البحث:
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Influence of Applied Pressure on the Probability
of Electronic Energy Transfer across a Molecular Dyad
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رابط إلى البحث:
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تاريخ النشر:
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20/2/2013
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موجز عن البحث:
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A pair of covalently linked molecular dyads is
described in which two disparate boron dipyrromethene dyes are separated by a
tolane-like spacer. Efficient electronic energy transfer (EET) occurs across
the dyad; the mechanism involves important contributions from both
Förster-type coulombic interactions and Dexter-type electron exchange
processes. The energy acceptor is equipped with long paraffinic chains that
favor aggregation at high concentration or at low temperature. The aggregate
displays red-shifted absorption and emission spectral profiles, relative to
the monomer, such that EET is less efficient because of a weaker overlap
integral. The donor unit is insensitive to applied pressure but this is not
so for the acceptor, which has extended π-conjugation associated with
appended styryl groups. Here, pressure reduces the effective π-conjugation
length, leading to a new absorption band at higher energy. With increasing
pressure, the overall EET probability falls but this effect is nonlinear and
at modest pressure there is only a small recovery of donor fluorescence. This
situation likely arises from compensatory phenomena such as restricted
rotation and decreased dipole screening by the solvent. However, the
probability of EET falls dramatically over the regime where the π-conjugation
length is reduced owing to the presumed conformational exchange. It appears
that the pressure-induced conformer is a poor energy acceptor.
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البحث (5)
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عنوان البحث:
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Fluorescent molecular rotors based on
the BODIPY motif: effect of remote substituents
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رابط إلى البحث:
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Click
here
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تاريخ النشر:
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Accepted 28th July 2014
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موجز عن البحث:
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The ability of an unconstrained boron dipyrromethene
dye to report on changes in local viscosity is improved by appending a single
aryl ring at the lower rim of the dipyrrin core. Recovering the symmetry by
attaching an identical aryl ring on the opposite side of the lower rim
greatly diminishes the sensory activity, as does blocking rotation of the
meso-aryl group. On the basis of viscosity- and temperature dependence
studies, together with quantum chemical calculations, it is proposed that a
single aryl ring at the 3-position extends the molecular surface area that
undergoes structural distortion during internal rotation. The substitution
pattern at the lower rim also affects the harmonic frequencies at the bottom
of the potential well and at the top of the barrier. These effects can be
correlated with the separation of the H1,H7 hydrogen atoms.
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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Younger Members Symposium 2012
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تاريخ الإنعقاد:
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Jun 2012
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بلد
ومكان الإنعقاد:
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Nottingham, UK
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طبيعة المشاركة:
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Poster
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عنوان المشاركة:
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Electronic Energy Transfer in
Self-Assembled Clusters and Liquid Crystals Containing BODIPY Dyes
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ملخص المشاركة:
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Over the past few decades, a large
variety of elaborate molecular architectures has been synthesized and
examined in terms of their ability to demonstrate intramolecular electronic
energy transfer. Although many exotic chemical systems have been reported they
are not so useful from a practical point-of-view since the synthesis is
demanding and time consuming. As an alternative we have investigated a system
whereby ionic self-assembly leads to formation of 1:2 adducts that themselves
associate into liquid-crystalline materials that are stable over a wide
temperature range. In contrast to covalent entities, much less attention has
been given to using electrostatic interactions to build superstructures with
logically sited reactants displaying highly efficacious energy transfer. A
further benefit this approach is that the emergent mesophase has the
potential to function as a superior light-harvesting array for silicon-based
solar cells.
Here, we describe the photophysical
properties of the individual units before and after self-assemblage. The
results are interpreted in terms of electronic energy transfer and can be
used to measure stability of the assembly and its dismantlement with
competing cations. In particular, we consider the effects of temperature, polarity,
concentration, and added cation. Comparison is made with the analogous
covalently linked dyad.
The target compound, which comprises a
yellow-absorbing BODIPY as energy donor and two blue-absorbing BODIPY dyes as
acceptor, was synthesized by the group of Dr Raymond Ziessel in Strasbourg
while the photophysical properties have been measured in Newcastle.
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المؤتمر (2):
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عنوان المؤتمر:
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The 4th international advances in applied physics
and material science congress and exhibition
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تاريخ الإنعقاد:
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24-27
April 2014
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مكان
الإنعقاد:
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Fethiye, Mugla, Turkey
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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An intelligent artificial solar concentrator
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ملخص المشاركة:
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A new molecular triad, constructed from a soluble
diketopyrrolopyrrole (DDP) unit linked to two disparate boron dipyrromethene
(Bodipy) fluorophores, has been synthesized, characterized and subjected to
photophysical examination. The terminal Bodipy dyes differ by virtue of the
strength of the donor group situated at the outer periphery of the conjugated
pathway, which causes a marked variation in colour, this varying from blue
(B) to green (G), with the latter dye being susceptible to protonation.
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جوائز التكريم:
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الجائزة (1):
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مسمى الجائزة:
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E-On poster best prize
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الجهة المانحة:
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The Royal Society of Chemistry
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تاريخ منح الجائزة:
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June 2012
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مجال التكريم:
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Younger Members Symposium 2012
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الجائزة (2):
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مسمى الجائزة:
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Best Oral Presentation
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الجهة المانحة:
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The 7th Saudi Students conference (SSC
2014)
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تاريخ منح الجائزة:
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01-02/02/2014
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مجال التكريم:
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Best Oral
Presentation entitled : Switching the Direction of Intramolecular Electronic
Energy Transfer in Functional Molecular Triads
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