Transcript Slide 1

Nanochemistry
NAN 601
Instructor:
Dr. Marinella Sandros
Lecture 16: Nanodiamonds
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Detonation nanodiamond (DND),
often also called ultradispersed
diamond (UDD), is diamond that
originates from a detonation.
When an oxygen-deficient
explosive mixture of
TNT/Hexogen is detonated in a
closed chamber, diamond
particles with a diameter of ca. 5
nm are formed at the front of
detonation wave in time of
several microseconds.
http://en.wikipedia.org/wiki/Detonation_nanodiamond
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The discovery of nanodiamond synthesis in 1963, followed by a
prolonged suspension of active study.
For several reasons, including the security measures in place in the USSR
and a lack of industrial interest in nanotechnology at the time, them
application of this nanodiamond (ND) remained unreported and underexploited until very recently.
Rediscovery of the synthesis in 1982–1993, with intensified study and
production of nanodiamonds simultaneously at several research centers
in the USSR. In this period, production potential exceeded the scale of
application.
Unprofitable production of small batches of nanodiamonds in 1993–
2003, leading to the closure of a number of research centers and the
termination of production.
Scheme of explosive technology
Inert gas
Ice or water shell
Explosives:
CH3
O 2N
Dry
product
collector
NO2
O2N
+
NO2
TNT
Wet
product
collector
N
N
NO2
N
NO2
Hexogen
Further acid purification
The detonation of
carbon-containing
explosives at high
temperature and
pressure with a
negative oxygen
balance results in the
condensation of the
free atomic carbon
products as diamond
or liquid carbon.
Phys. Sol. State, 2004 46, 611–615
•Theoretical calculations show that conditions for
diamond stability during this process are only conserved
for a very short time (sub-microsecond) and are closely
followed by conditions where graphite is the more stable
phase.
•This is due to a fast decrease in pressure while the
system is still at a high temperature, which favours a
diamond-to-graphite transformation.
•To obtain diamond, it is therefore important to control
the rate at which the system cools—faster cooling at
relatively high pressure results in a higher diamond
yield.
(i) Rapid decrease in pressure at
high temperatures facilitates
the diamond-to-graphite
transition.
(ii) Rapid cooling ensures that
diamond remains the most
stable phase and results in
higher yields of detonation
ND.
Phys. Sol. State, 2004 46, 611–615
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The most commonly used explosives for this process are mixtures of
trinitrotoluene (TNT) and hexogen or octogen. Explosion commonly takes
place in a sealed stainless steel chamber in the absence of oxygen.
Diamond yield increases with the quantity of coolant present in the
system; gases such as argon are commonly used, as well as water, waterbased foams and ice.
Optimal cooling rates after detonation are found to be 3000–4000 K min1. The products of detonation are a complex mix of ND particles of an
average size of 5 nm and other graphitic carbon forms, hence rigorous
cleaning stages are then employed to remove the nondiamond material.
The extent and method of cleaning depends on the source of the ND
powder, but generally includes either gaseous ozone treatment or
solution phase nitric acid oxidation to remove sp2 carbon and metallic
impurities.
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Produced by detonation from
carbon-containing precursors
such as TNT and hexogen,
resulting in nanoparticles with 2
wt% nitrogen and 1wt% of
hydrogen.
Nanodiamonds are unique
structures that have diverse
electronic properties depending
on their size and morphology.
The powder contains
diamond particles of very
narrow size distribution
averaging 5 nm but, as is
clear from the image, the
particles readily agglomerate
to form aggregates up to
several micrometres in
dimension.
Kulakova, I. I. 2004 Surface chemistry of nanodiamonds. Phys. Solid State 46, 636–643.
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The exact nature of the
outer layer remains
unclear, but two general
models
have emerged:
(i) an amorphous shell with
significant sp2 carbon
content or
(ii) an sp2 graphene-type
sheet, of a fullerene
structure, giving rise to a
structure described as
‘bucky-diamond’.
Heating ND particles to above 1000 K
in vacuum does result in laminates of
fullerene shells being formed around
the diamond core and ultimately to the
formation of ‘carbon onions’.
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The nature of the bonding sites of nitrogen in ND is
still the subject of debate; in some studies, FTIR
spectroscopy has shown the presence of NH2 groups
on the surface of the ND, while others demonstrate
that nitrogen atoms are only present within the core
of the ND.
It is probable that nitrogen groups present on the
surface have been introduced during the acid
cleaning stage, whereas substitutional core nitrogen
impurities come about during the detonation
process, as nitrogen is a component of most
explosives used.
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The hydrogenated surface is
part of a 0.6 nm-thick shell
of seven partially disordered
carbon layers that contain
61% of all C and mostly
produce higher-field 13C
NMR signals. Unpaired
electrons (indicated by red
arrows) occur with a density
of 40 per particle and are
located 0.4–1 nm from the
surface.
J. Am. Chem. Soc., 2009, 131, 1426–1435
Krueger A,Chem. Eur. J.14,1382–1390 (2008).
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Nitrogen is the most common impurity in
diamond , and is present in natural
specimens in various forms.
Nitrogen may be atomically incorporated
either as single isolated (substitutional)
impurities known as C centres, as pairs of
adjacent impurities known as A centres, or
in groups such as four substitutional
nitrogen atoms surrounding a vacancy
known as B centres.
In addition to this, diamond can contain a
variety of other ‘color centres’ based on
the combination of impurity atoms and
their vacancy complexes
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NDs defect comprises of a single nitrogen
impurity in a substitutional position directly
adjacent to a lattice vacancy.
This defect is of interest in the field of
nanomedicine as it is fluorescent, with an
unusually high quantum yield.
The energy level structure of the N–V defect in
diamond has a ground state and excited states
forming an electron spin triplet with 3A and 3E,
and due to the spin–spin interaction in the
diamond crystal, the ground state is split into
(ms = 0) and (ms = ±1) sub-levels. A transition
between these states may be excited with light
of ultraviolet wavelength (<400 nm).
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One of the attractive properties of ND is its ability to
fluoresce when excited with light of ultraviolet
wavelength (< 400 nm).
The emission of 5 nm detonation diamond is dominated
by a broad band in the visible region, from 390 to
650 nm.
The mechanism of photoluminescence has been variously
assigned to the emission from impurity sites (e.g.
dopants) within the core, defects in the diamond lattice
or sp2 clusters on the ND surface.
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Some lower energy (red) emissions were found to
vary between ND samples and also to decrease
after heating, indicating an association with the
amount of sp2 carbon on the surface of the ND.
However, when thicker layers of graphite were
formed on the surface, photoluminescence
intensity was found to decrease dramatically,
demonstrating that graphite itself was not
responsible for this emission and it was
conjectured that sp2 clusters embedded in a sp3
matrix may be responsible
Schematic of available energy levels within the diamond
band gap capable of undergoing excitation and
photoluminescence.
Holt K B Phil. Trans. R. Soc. A 2007;365:2845-2861
©2007 by The Royal Society
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Another ND fluorescence process of note is that resulting
from excitation of the negatively charged nitrogen–vacancy
(N–V)− centre, which absorbs strongly at 560 nm and emits
efficiently at 700 nm.
This type of fluorescence has been reported in 1b (nitrogencontaining) diamond particles of 35 and 100 nm that have
been irradiation damaged to create defects.
Irradiation with an electron beam creates a vacancy in the
lattice and the sample is then annealed to bring the vacancy
close to the nitrogen atom; this (N–V)− centre acts as an ion
embedded in a solid matrix. As this fluorescence arises from
defects deep within the ND core, it is unaffected by the
surface chemistry of the ND.
Diamond Relat. Mater., 2009, 18, 567–573
(A) bright-field image
(B) epifluorescence image
(C) time traces of the
nanodiamonds and 100
nm green fluorescent
polystyrene beads excited
under the same conditions
(mercury lamp: λex = 450–
490 nm) and the resulting
fluorescence was collected
over the wavelength range
of 505–545 nm.
Diamond Relat. Mater., 2009, 18, 567–573
Scheme for separation and purification of the recombinant protein from Escherichia coli cells using
adsorption of proteins onto detonation ND (using the procedure described by Bondar et al. 2004).
Holt K B Phil. Trans. R. Soc. A 2007;365:2845-2861
©2007 by The Royal Society
Nanodiamonds easily internalized into cells for drug release. A – E. Confocal
images of fluorescently (FITC)-labeled nanodiamonds incubated with RAW
264.7 macrophages. F. Transmission electron microscope image of ND–DOX
complexes within the cytoplasm of macrophage cells. Scale bars represent
20 nm.
Layer-by-layer deposition process: sequential 2 x 2
μm AFM scans of (A) glass, (B) poly-l-lysine and (C)
ND thin film layer.
ACS Nano, 2008, 2(2), 203-12.
A.
B.
Schematic depiction of the
construction of
nanodiamond-parylene
microfilms. Nanodiamonds
are sandwiched between a
thick base layer and thin
variable non-conformal
layer of parylene, which
allows for controllable
release.
Resultant microfilms can be
of varied size and are
flexible.
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B.
Fluorescence spectra of 35-nm FNDs
suspended in water (1 mg ml- 1 each),
prepared with either 40-keV He+ or
3-MeV H+ irradiation. Inset:
Fluorescence image of a 35-nm FND
suspension excited by 532-nm laser
light.
Fluorescence intensities of FNDs as a
function of particle size at three
different laser powers. Inset:
Fluorescence time trace (intensity
normalized) of a 25-nm FND.
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Helium atoms are chemically inert, and embedding
these atoms in a diamond lattice through
neutralization of the stopped He+ ions does not
appreciably change the photophysical properties of
the FNDs produced.
40-keV He+ ion can create 40 vacancies as it
penetrates diamond
high-fluence 40-keV He+ beams can be readily
generated by radio-frequency ion sources. The
current is more than two orders of magnitude
higher than that of a 3-MeV H+ beam emanating
from a tandem particle accelerator.
(A)
(B)
Bright-field and epifluorescence (red pseudocolour) images of the
cell after fluorescent nanodiamond uptake.
Three-dimensional reconstruction (left panel), showing the
boundaries of the nucleus and the cytoplasm of the cell. Threedimensional trajectory (shown in pseudo-colour, right panel) and
displacements of a single fluorescentnanodiamond (labeled with a
yellow box in (A)) inside the cell over a time span of 200 s.
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How are NDs made?
NDs emission at 700 nm is attributed to
what?
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NDs are made from the detonation of
carbon-containing precursors such as TNT
and hexogen under inert atmosphere in a
closed chamber.
Arise from the N–V defect.