Silicon nanoparticles by the oxidation of [Si4]4-- and [Si9]4--containing Zintl phases and their corresponding yield

Article abstract of DOI:10.1021/ic5027398

The Zintl phases with nominal compositions Na₄Si₄, Rb₇NaSi₈, and A₁₂Si₁₇ (A = K, Rb, Cs) were utilized as precursors in the synthesis of silicon nanoparticles (Si NPs). The present study characterizes and compares the yields of Si NPs synthesized from Na₄Si₄, Rb₇NaSi₈, and A₁₂Si₁₇ (A = K, Rb, Cs). Na₄Si₄ and Rb₇NaSi₈ Zintl phases consist of anionic silicon tetrahedra stabilized by group I cations. The A₁₂Si₁₇ (A = K, Rb, Cs) Zintl phases that contain [Si₉]^4- and [Si₄]^4- clusters have been speculated to be more soluble than the A₄Si₄ (A = Na, Rb, Cs) Zintl phases that contain solely [Si₄]^4- clusters due to the lower charge density of the [Si₉]^4- cluster. The Zintl phases were reacted with NH₄Br in dimethylformamide (DMF) and subsequently capped with allylamine. The Si NPs were characterized by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), UV-vis, and photoluminescence (PL) spectrophotometry. Furthermore, the Si yields were characterized by inductively coupled plasma mass spectrometry (ICP-MS) to evaluate if the reactions of [Si₉]^4- cluster containing Zintl phases resulted in higher yields of Si NPs. The yield of Si increased with larger or mixed alkali metal Zintl phases, leading to the conclusion that Coulombic interactions between the cations and anions affect the Zintl phase's reactivity. The size of the Si NPs also increased with larger and mixed alkali metal cations, resulting in similar NP concentrations regardless of the starting material. With respect to ease of synthesis and yield, Na₄Si₄ remains the most practical precursor for the solution synthesis of Si NPs; however, the larger and mixed alkali metal precursors show promise for further development.

Full text of DOI:10.1021/ic5027398

Article
pubs.acs.org/IC
4
−
4−
Silicon Nanoparticles by the Oxidation of [Si ] - and [Si ] -
4
9
Containing Zintl Phases and Their Corresponding Yield
Bradley M. Nolan, Thomas Henneberger, Markus Waibel, Thomas F. Fassler,
†
‡
‡
‡
̈
,
†
and Susan M. Kauzlarich*
†
Department of Chemistry, University of California, One Shields Avenue, Davis, California 95616, United States
‡
Department of Chemistry, Technische Universitat
̈
̈
Munchen, Lichtenbergstraße 4, 85747 Garching, Germany
*
S Supporting Information
ABSTRACT: The Zintl phases with nominal compositions
Na Si , Rb NaSi , and A Si (A = K, Rb, Cs) were utilized as
4
4
7
8
12 17
precursors in the synthesis of silicon nanoparticles (Si NPs).
The present study characterizes and compares the yields of Si
NPs synthesized from Na Si , Rb NaSi , and A Si (A = K, Rb,
4
4
7
8
12 17
Cs). Na Si and Rb NaSi Zintl phases consist of anionic silicon
4
4
7
8
tetrahedra stabilized by group I cations. The A Si (A = K, Rb,
1
2
17
4−
4
−
Cs) Zintl phases that contain [Si9] and [Si4] clusters have
been speculated to be more soluble than the A Si (A = Na, Rb,
4
4
4
−
Cs) Zintl phases that contain solely [Si ] clusters due to the
lower charge density of the [Si9] cluster. The Zintl phases were reacted with NH Br in dimethylformamide (DMF) and
4
4
−
4
subsequently capped with allylamine. The Si NPs were characterized by transmission electron microscopy (TEM), energy-
dispersive spectroscopy (EDS), UV−vis, and photoluminescence (PL) spectrophotometry. Furthermore, the Si yields were
4−
characterized by inductively coupled plasma mass spectrometry (ICP-MS) to evaluate if the reactions of [Si ] cluster
9
containing Zintl phases resulted in higher yields of Si NPs. The yield of Si increased with larger or mixed alkali metal Zintl
phases, leading to the conclusion that Coulombic interactions between the cations and anions affect the Zintl phase’s reactivity.
The size of the Si NPs also increased with larger and mixed alkali metal cations, resulting in similar NP concentrations regardless
of the starting material. With respect to ease of synthesis and yield, Na Si remains the most practical precursor for the solution
4
4
synthesis of Si NPs; however, the larger and mixed alkali metal precursors show promise for further development.
INTRODUCTION
microwave-assisted aqueous synthesis of Si NPs produced by
the reduction of (3-aminopropyl)trimethoxysilane using
■
Subsequent to Canham’s seminal paper on the fluorescence of
nano-Si, silicon nanomaterials have received intense attention
within the scientific community. Synthesis, size/morphology,
photoemission, and surface functionalization have dominated
1
9,20
trisodium citrate.
Of the many synthetic methods known
1
in the literature to produce Si NPs, no route has yet been
established as synthetically superior. The use of pyrophoric
materials, HF, and high temperatures is evidence that a simple
synthetic route to colloidal Si remains elusive. Moreover, there
is a lack of information regarding the yield of Si NPs produced
by the various methods in the literature. When the mass of the
produced nanoparticles has been reported, little information
has been provided as to how this number was acquired: i.e.,
what percentage of the mass is attributed to silicon versus the
ligand or the percent yield relative to the initial silicon source.
Knowing the yield of Si NPs for a synthetic route is important,
considering the future industrial role that Si NPs are expected
to fulfill. The yield of Si NPs, along with the cost of synthesis,
will define the scope of the application for a particular synthesis.
Our investigation focuses on determining the yield of Si NPs as
produced by the oxidation of the Zintl phases Na Si , Rb NaSi ,
2
−10
silicon nanoparticle (Si NP) research.
Because silicon is an
inexpensive and abundant semiconductor material that is
already ubiquitous in technology, extending the applications
of bulk silicon to the nanoscale holds much appeal in areas
11−13
related to energy conversion and other optoelectronics.
Furthermore, Si NPs exhibit the advantageous size-dependent
quantum confinement effects of the group II−VI and group
III−V quantum dots without the inherent toxicity, making
8
,14−16
them desirable for bioapplications.
The syntheses of Si NPs include both top-down and bottom-
up approaches. The etching of silicon wafers is the most
notable top-down approach, while synthetic methods such as
the gas-phase decomposition of molecular silicon species,
reduction of silicon halides, oxidation of Zintl phase materials,
1
0,17,18
4
4
7
8
and others comprise the bottom-up approaches.
Two
and A Si (A = K, Rb, Cs) with NH Br.
12
17
4
recent examples of bottom-up synthetic routes are the thermal
processing of hydrogen silsesquioxane under a reducing
atmosphere, where the Si NPs are formed encapsulated in a
silica matrix and liberated by HF treatment, and a facile
Received: November 13, 2014
Published: December 8, 2014
©
2014 American Chemical Society
396
dx.doi.org/10.1021/ic5027398 | Inorg. Chem. 2015, 54, 396−401

Inorganic Chemistry
Article
The Zintl phases Na Si , K Si , and Mg Si have been
Rb
7
NaSi
8
was synthesized following a previously reported
4
4
4
4
2
3
4
method. According to this method stoichiometric quantities of Rb,
Na, and Si (6.23, 0.89, and 7.12 mmol, respectively) were loaded into a
tantalum tube, which was crimped shut in an argon-filled glovebox and
then sealed by an argon-filled arc welder. The tantalum tube was
further enclosed within an evacuated silica ampule. The ampule was
heated at 2 K/min to 600 °C, allowed to dwell for 10 h, and then
cooled to room temperature (0.2 K/min). The product was
characterized by powder X-ray diffraction to be phase pure.
previously explored as reactive precursors to synthesize Si
1
8,21−23
NPs.
However, the application of the heavier Zintl
phases Rb NaSi and A Si (A = K, Rb, Cs) toward Si NP
7
8
12 17
production has not been evaluated. The A Si (A = K, Rb, Cs)
1
2
17
Zintl phases are composed of two distinct silicon clusters
4
−
4−
present in a ratio of two [Si4] clusters to one [Si9] cluster
Figure 1). Isolating and characterizing the individual clusters
(
A Si (A = K, Rb, Cs) Zintl phases were synthesized following a
1
2
17
2
8,35
procedure similar to that previously reported.
The alkali metals
were mixed with Si powder (6.52 mmol of alkali metal, 9.24 mmol of
Si), sealed in a tantalum tube, and enclosed within an evacuated silica
ampule. The ampule was heated at 2 K/min to 900 °C, allowed to
dwell for 10 h, and then cooled to room temperature (0.5 K/min).
The products were characterized by powder X-ray diffraction. K Si
1
2
17
was phase pure, and A Si (A = Rb, Cs) were found to be primarily
12
17
the A Si phase.
4
4
Figure 1. [Si ]4 and [Si9]4− clusters that comprise the A Si (A = K,
Rb, Cs) Zintl phases.
−
Caution! Na Si , Rb NaSi , and A Si (A = K, Rb, Cs) Zintl phases
4 4 7 8 12 17
4
12 17
as well as the alkali metals K, Rb, and Cs are highly reactive to air and
moisture. These materials must be handled carefully under inert
atmosphere conditions.
Powder X-ray Diffraction. Powder X-ray diffraction (PXRD)
patterns were collected on a Bruker D8 Advance diffractometer using
Cu radiation (Cu Kα: λ = 1.54 Å). Samples were ground with a mortar
and pestle and loaded into an airtight sample holder in an argon-filled
drybox. Powder diffraction patterns were collected in a 2θ range of
has been the focus of research on these Zintl phases. The
x−
solvate structure of the [Si9]2 cluster has been isolated with
4−28
charges of 2−, 3−, and 4−.
Moreover, the nine atomic
silicon cluster has been isolated as the complexes [Si −
9
8
−
3− 29,30
{
Ni(Co) )} −Si ] and [Si −Zn(C H )] .
While there
2
2
9
9
6
5
1
0−90° with a step size of 0.02°. However, because of poor signal-to-
are several reports in the literature of the isolation of both the
x−
noise ratios at low and high 2θ, only 20−60° 2θ is displayed. The
PXRD patterns are provided as Supporting Information.
solvate and coordinated [Si ] clusters, the only known
9
4−
4− 28
isolated structure of [Si4] is [Si (CuMes) ] . Recently, the
4
2
Synthesis of 3-Aminopropenyl-Capped Silicon Nanopar-
ticles. All reactions were performed under inert atmosphere
conditions on a Schlenk line. To maintain consistency within the
Zintl phase series, all reactions were performed with 2.55 mmol of Si
from the respective nominal composition Zintl phases. This quantity
corresponds to 0.64, 0.32, and 0.15 mmol of Na Si , Rb NaSi , and
first NMR signal of a bare silicide in solution was reported as
4
−
31
the [Si4] ion in liquid ammonia. The difficulty in isolating
4
−
the [Si4] cluster arises from the high charge per atom, which
causes Na Si , for example, to be nearly insoluble in all solvents.
4
4
The A Si (A = K, Rb, Cs) Zintl phases also exhibit low
12
17
4
4
7
8
solubility, but these materials can be solubilized in liquid
A12Si17 (A = K, Rb, Cs), respectively. In an argon-filled glovebox, the
Zintl phase was added to a three-neck round-bottom flask containing a
3
−
ammonia. In addition, the [Si −Zn(C H )]
complex
mentioned above was isolated from a pyridine solution and
9
6
5
magnetic stir bar along with 3.83 mmol of NH Br (Sigma-Aldrich,
4
2−
≥99.99%) and 150 mL of previously distilled dimethylformamide
the more oxidized [Si9] is soluble in DMF. Using a more
soluble Zintl phase precursor in the synthesis of Si NPs may
lead to a higher yield of Si NPs relative to what can be obtained
from Na Si .
(DMF) (Sigma-Aldrich, 99.8%). The reaction flask was closed with an
adapter and stopcock, glass stopper, and a rubber septum and
transferred to the Schlenk line. Once connected to the Schlenk line,
the glass stopper was replaced with a water-cooled reflux condenser.
4
4
Herein, we report a comparative study of Si NPs synthesized
from the A Si (A = K, Rb, Cs) Zintl phases to Si NPs
The mixture was heated to 150 °C for 12 h under an argon flow
36,37
1
2
17
(Scheme 1).
After 12 h of heating, the reaction mixture was cooled
4−
produced from the Zintl phases composed solely of [Si4]
to room temperature. While the reaction mixture was under air-free
conditions, 0.57 mL of allylamine (Sigma-Aldrich, 98%) was injected.
The reaction mixture was then heated at 150 °C for 4 h to produce 3-
aminopropenyl-capped Si NPs. The product consisted of a yellow
solution and a black precipitate. The black precipitate was determined
to be a mixture of amorphous and crystalline Si.
clusters (i.e., Na Si and Rb NaSi ). Inductively coupled plasma
4
4
7
8
mass spectrometry (ICP-MS) was used to quantify the silicon
concentration of each reaction. Transmission electron micros-
copy (TEM) provided information regarding the nanoparticle
size and morphology. The absorbance and photoluminescence
properties of the Si NPs synthesized from the various Zintl
phases were measured. Using the ICP-MS and TEM data, we
calculated the Si NP concentration in accordance with
previously reported values for the number of silicon atoms
Scheme 1. Reaction Scheme for the Synthesis of Amine-
Terminated Si NPs
17
contained within a Si NP with respect to the Si NP diameter.
EXPERIMENTAL SECTION
■
Synthesis of Na Si , Rb NaSi , and A Si (A = K, Rb, Cs).
4
4
7
8
12 17
Na Si was purchased from SiGNa Chemistry, Inc. (80%) and used as
4
4
32
received. Powder X-ray diffraction showed the presence of both Na
and Si, along with Na Si . Sodium and potassium were purified from
4
4
impurities such as alkali metal oxides by liquating, i.e., melting and
careful decanting the alkali metal melt. This process was repeated
3
3
twice. Rubidium was distilled as previously reported. Cesium
ABCR, 99.98%) and silicon (Wacker Chemie AG, 99.9%) were
used without further purification.
(
3
97
dx.doi.org/10.1021/ic5027398 | Inorg. Chem. 2015, 54, 396−401

Inorganic Chemistry
Article
Purification of Silicon Nanoparticles. To separate the bulk
silicon precipitate from the yellow solution, the DMF mixture was
centrifuged for 40 min. The supernatant was decanted and the black
solid discarded. The yellow solution contains the alkylamine-capped Si
nanoparticles, which were further purified and characterized
accordingly. The DMF supernatant was exchanged for 18 MΩ cm
nanopure water by successively concentrating and diluting the solution
multiple times using a rotary evaporator. The final aqueous solution
was characterized by UV−vis, photoluminescence, TEM, EDS, and
ICP-MS.
Spectrophotometry. UV−vis data were collected for aqueous
samples on a Shimadzu UV-1700 spectrophotometer with a sampling
interval of 1.0 nm and a fixed slit width of 1.0 nm. Samples were
analyzed in 18 MΩ cm nanopure water. Photoluminescence (PL)
spectra were acquired on a Jobin Yvon Horiba FluoroMax-P
spectrophotometer. The scan increment was set to 1.00 nm with an
integration time of 1.00 s. The excitation and emission slit widths were
fixed at 5.00 nm. The spectra are provided in the Supporting
Information.
Si NPs capped with allylamine were prepared by Schlenk line
synthesis using the Zintl phase precursors according to Scheme
1
. The reactions produced air-stable NP dispersions in DMF
that were subsequently exchanged into an aqueous solvent.
UV−vis and photoluminescence spectra were acquired for the
Si NPs synthesized from each of the respective Zintl phase
precursors (Figure S2 (Supporting Information)). The average
emission wavelength of the Si NPs synthesized from Na Si was
4 4
430 ± 5 nm. The photoluminescence emission maxima of the
Rb NaSi and nominal A Si (A = K, Rb, Cs) Zintl phases
7
8
12 17
ranged between 421 and 434 nm (Table 1). These data are in
Table 1. Emission Maxima of the Silicon NPs Synthesized
from the Corresponding Zintl Phases
Zintl phase
K Si
12 17
Rb NaSi8
Rb Si
12 17
Cs Si
12 17
4
Na Si4
7
TEM Imaging/EDS Spectroscopy. TEM samples were prepared
by drop-casting the Si NP solution onto a holey carbon grid (SPI). Si
NPs were imaged on a 200 kV JEOL 2500SE TEM. Energy-dispersive
spectra were collected on a Thermo Corporation EDS spectrometer
coupled to the TEM. Gatan Digital Micrograph software was used to
collect the images acquired on the TEM. The histograms are provided
in the Supporting Information.
ICP-MS. Quantitative silicon concentrations were acquired by
inductively coupled plasma mass spectrometry (ICP-MS). Silicon
samples from individual reactions were each concentrated to a volume
of 10 mL. From the 10 mL silicon nanoparticle solution, 200, 400, and
λem (nm)
429
434
427
429
421
agreement with literature values of the reported emission
maxima for Si NPs synthesized from the reaction of Na Si with
4
4
4
NH Br. A recent study on the origin of red and blue
4
photoluminescence of Si NPs best explains the observed
photoluminescence.
that trace amounts of nitrogen and oxygen were responsible for
producing defects in the Si NPs, which give rise to blue
photoluminescence. Further investigation into the role of
surface groups determined that the Si NP photoluminescence
could be tuned across the visible spectrum by carefully selecting
the surface ligand.
The presence of the Si NPs from K Si was confirmed by
energy-dispersive spectroscopy (EDS) (Figure 2) with the
presence of the characteristic Si Kα peak. The Cu Kα is
attributed to the copper grid on which the sample was
prepared.
3
9,40
In that paper the authors concluded
6
00 μL aliquots were diluted to 5 mL in 3% trace element HNO . The
3
prepared samples were analyzed by the Interdisciplinary Center for
Plasma Mass Spectrometry at the University of California, Davis
41
(
ICPMS.UCDavis.edu), using an Agilent 7500CE ICP-MS (Agilent
12
17
Technologies, Palo Alto, CA). The samples were introduced using a
MicroMist Nebulizer (Glass Expansion, 4 Barlow’s Landing Road,
Unit 2A, Pocasset, MA 02559, USA) into a temperature-controlled
spray chamber with He as the collision cell gas. Instrument standards
were diluted from Certiprep ME 2A (SPEX CertiPrep, 203 Norcross
Avenue, Metuchen, NJ 08840, USA) to 50, 100, 250, 500, and 1000
ppb and from Certiprep ME4 to 50, 100, 250, 500, and 1000 ppb,
respectively, in 3% trace element HNO (Fisher Scientific) in 18.2 MΩ
3
cm water. A standard consisting of ME 2A and ME4 with a
concentration of 100 ppb was analyzed every 12th sample as a quality
control.
RESULTS AND DISCUSSION
■
As described above, Na Si and Rb NaSi are composed of
4
4
7
8
isolated silicon tetrahedra, whereas the A Si (A = K, Rb, Cs)
1
2
17
Zintl phases contain both tetrahedra and nine-atom mono-
capped-square-antiprismatic silicon clusters. Powder X-ray
diffraction of Na Si obtained from SiGNa displayed the
4
4
expected Na Si phase (monoclinic space group, C2/c) along
4
4
with Si and Na impurities. The calculated PXRD reflections for
Rb NaSi (cubic space group, Pa) confirmed that the product
7
8
was phase pure. Due to the larger unit cell, complex structure,
and disorder of K Si , the K Si PXRD pattern showed poor
Figure 2. EDS spectrum of silicon nanoparticles synthesized from
12
17
12 17
diffraction intensities; however, no other products were
K
12Si17. The image of the analyzed area is shown in the inset.
3
8
identified. The synthesis of the Rb Si and Cs Si Zintl
1
2
17
12 17
phases did not yield a phase pure product. Both Rb Si and
12
17
Cs Si showed mainly reflections of A Si . While reflections of
TEM showed that the NPs have a spherical morphology with
12
17
4
4
Rb Si can be found in the Rb sample, it was not possible to
diameters of 3.1 ± 0.8, 3.7 ± 1.2, 4.5 ± 1.9, 4.2 ± 1.4, and 4.0 ±
1.1 nm for Si NPs synthesized from Zintl phases with the
nominal compositions Na Si , K Si , Rb NaSi , Rb Si , and
12
17
determine if Cs Si was present in the Cs sample, due to the
12
17
high background and weak reflections. The experimental PXRD
4
4
12 17
7
8
12 17
patterns of the SiGNa Na Si and the as-prepared Rb NaSi ,
Cs Si , respectively (Figure 3 and Figure S2 (Supporting
4
4
7
8
12 17
K Si , Rb Si , and Cs Si Zintl phases are provided in
Figure S1 (Supporting Information).
Information)). All of the TEM images show NPs, and Figure
3C displays additional amorphous material, which is attributed
12
17
12 17
12 17
3
98
dx.doi.org/10.1021/ic5027398 | Inorg. Chem. 2015, 54, 396−401

Inorganic Chemistry
Article
of Si from the Zintl phases were calculated on the basis of the
purity of the precursor. With the calculated initial moles of Si
and the yield of Si determined by ICP-MS, the percent yields of
each Zintl phase reaction were calculated. Consistent with the
literature, we expected that the lower charge density of the
[
Si9]4 cluster should increase the solubility of the Zintl phase
−
in DMF and lead to a higher yield of Si. However, comparison
of the Si yields from the Rb NaSi and K Si precursors
7
8
12 17
showed that the reactions from the K Si Zintl phase
1
2
17
containing [Si9]4 clusters had a lower Si yield than reactions
−
4
−
from Rb NaSi , which contains only [Si ] clusters. Both Rb-
7
8
4
containing precursors Rb NaSi and the nominal composition
7
8
Rb Si had nearly the same yield. This observation was not
12
17
unexpected, as the nominal Rb Si was primarily indexed as
12
17
Rb Si by PXRD. The insolubility of the highly charged Zintl
4
4
phases in DMF explains the overall low yield of the reaction,
but not the increasing amount of Si yielded by the reaction with
larger and mixed alkali metal containing Zintl phases. The
cation size is more important to the chemical reactivity than the
Si anionic clusters in these Zintl phases. Smaller cations (e.g.,
sodium) will have more stabilizing Coulombic interactions with
the anionic clusters and therefore be less reactive toward
NH Br. This conjecture is supported by comparing the yield of
4
Si between Na Si and Rb NaSi , where both phases contain
4
4
7
8
only [Si4]4 clusters. The Rb NaSi Zintl phase produced ∼2.5
−
7
8
times more Si in solution in comparison to Na Si . The larger
4
4
Rb cation will disrupt the Coulombic interactions and increase
the reactivity of the mixed metal containing phase, leading to a
higher yield of Si.
To approximate the NP concentration, we related the
average NP size to the number of Si atoms necessary to form
the nanoparticle along with the yield of Si determined by ICP-
17
MS. In contrast to the trend of increasing Si yield with larger
cation size, the concentrations of NPs were similar, ranging
between 0.137 μM (Rb NaSi ) and 0.208 μM (Cs sample)
Figure 3. Silicon nanoparticles synthesized from (A) Na Si , (B)
4
4
7
8
K Si (C) Rb NaSi , (D) Rb Si , and (E) Cs Si . The scale bar is
12
17,
7
8
12 17
12 17
(
Table 3). Na Si yielded the least Si and produced on average
4 4
100 nm.
the smallest nanoparticles; however, due to the exponential
increase in Si atoms with increasing NP size, the Si NP
concentrations from Na Si and the nominal Cs Si sample
to an organic polymer byproduct of hydrosilylation that was not
4
4
4
12 17
completely removed during the purification of the solution.
are comparable.
ICP-MS measurements show an increase in Si concentrations
as the mass of the alkali metal in the Zintl phase increases
CONCLUSIONS
(
Figure 4, Table 2). To account for non phase pure starting
■
Si NPs from the oxidation of a variety of Zintl phases
materials, upper and lower boundary limits of the initial moles
4
−
4−
containing [Si4] and [Si9] clusters have been characterized.
The optical properties of the Si NPs produced from Rb NaSi
7
8
and A Si (A = K, Rb, Cs) are similar to the properties of Si
12
17
NPs synthesized from the previously studied Na Si , with
4
4
emission wavelengths ranging from 421 to 434 nm. ICP-MS
results show that, from millimolar quantities of the Zintl phase
precursors, micromolar Si yields were achieved. A comparison
4−
of the Si yield from the oxidation reaction of the [Si ] -
4
containing Rb NaSi and the oxidation reaction of the mixed
7
8
4−
4−
[
Si ] - and [Si ] -containing K Si did not support the
4
9
12 17
4
−
hypothesis that the [Si9] cluster was more soluble in DMF. In
fact, Rb NaSi produced more than double the Si yield in
7
8
comparison with K Si when both initial precursor quantities
12
17
contained the same amount of Si. The Si yield also increased
with larger and heavier alkali metal containing Zintl phases. The
trend of increasing Si yield for the heavier alkali metal Zintl
phases is best explained by decreasing Coulombic interactions
of the anionic silicon clusters with the group I countercations
going down the group. The high yield of Si for the mixed metal
Rb NaSi phase further supports this hypothesis. The Si NP
Figure 4. Silicon yields related to the respective alkali metal Zintl
phase precursor.
7
8
3
99
dx.doi.org/10.1021/ic5027398 | Inorg. Chem. 2015, 54, 396−401

Inorganic Chemistry
Article
Table 2. ICP-MS Data Quantifying the Silicon Yield from the Corresponding Zintl Phase
a
b
c
SiGNa Na Si
Rb sample
Cs sample
Cs Si
12 17
4
4
Na Si
80% Na Si
K Si
12 17
Rb NaSi8
7
Rb Si4
Rb Si
Cs Si4
4
4
4
4
4
12 17
4
molar mass (g/mol)
amt of Si (mmol)
mass (g)
204.30
2.55
204.30
2.04
946.63
2.55
845.95
2.55
454.21
1.99
1503.07
2.55
643.98
1.93
2072.37
2.55
0.130
0.104
0.142
0.270
0.226
0.226
0.311
0.311
yield of Si (μmol)
yield (%)
1.22 ± 0.10
0.060
1.96 ± 0.12
0.077
3.19 ± 0.13
0.125
3.13 ± 0.21
3.38 ± 0.12
0.048
0.157
0.123
0.175
0.133
a
b
The experimentally acquired Si yield from SiGNa Na Si (80% pure) was used to extrapolate a theoretical percent yield of pure Na Si . Rb Si and
4
4
4
4
4
4
c
Rb Si represent the boundary limits of the initial mmol of Si and the percent yield. Cs Si and Cs Si represent the boundary limits of the initial
12
17
4
4
12 17
mmol of Si and the percent yield.
Table 3. Calculated Silicon Nanoparticle Concentrations
Na Si
4
K Si
12 17
Rb NaSi8
7
Rb Si
12 17
Cs Si
12 17
4
NP size (nm)
Si atoms
3.1 ± 0.8
759
3.7 ± 1.2
1290
4.5 ± 1.9
2321
4.2 ± 1.4
1887
4.0 ± 1.1
1630
Si yield (μmol)
1.22 ± 0.10
0.161 ± 0.013
1.96 ± 0.12
0.152 ± 0.009
3.19 ± 0.13
0.137 ± 0.005
3.13 ± 0.21
0.166 ± 0.011
3.38 ± 0.12
0.208 ± 0.007
[Si NP] (μM)
size increased with the size of the alkali metal cation. When the
NP average size was considered, an approximate NP
concentration was calculated to be near the micromolar regime
per reaction. The overall low yield of Si NPs, which varied
between 0.137 and 0.208 μM, is attributed to the low solubility
of the Zintl phases in DMF, limiting these reactions to the
surface of the material. Therefore, increasing the surface area of
the Zintl phase, reducing Coulombic attractions through metal
(5) Biesta, W.; van Lagen, B.; Gevaert, V. S.; Marcelis, A. T. M.;
Paulusse, J. M. J.; Nielen, M. W. F.; Zuilhof, H. Chem. Mater. 2012, 24,
4
(
311−4318.
6) Shiohara, A.; Hanada, S.; Prabakar, S.; Fujioka, K.; Lim, T. H.;
Yamamoto, K.; Northcote, P. T.; Tilley, R. D. J. Am. Chem. Soc. 2009,
32, 248−253.
7) Romero, J. J.; Llansola-Portoles
Rodrıguez, H. B.; Moore, A. L.; Gonzalez, M. C. Chem. Mater. 2013,
1
(
́
, M. J.; Dell’Arciprete, M. L.;
́
2
5, 3488−3498.
cations, and employing a metathesis reaction with SiX (X = Cl,
4
(8) Gupta, A.; Swihart, M. T.; Wiggers, H. Adv. Funct. Mater. 2009,
9, 696−703.
Br, I) may be more promising routes for achieving higher yields
of Si NPs.
1
(9) Buriak, J. M. Chem. Mater. 2014, 26, 763−772.
(
10) Hessel, C. M.; Henderson, E. J.; Veinot, J. G. C. Chem. Mater.
2
(
006, 18, 6139−6146.
ASSOCIATED CONTENT
■
11) Pi, X. D.; Li, Q.; Li, D. S.; Yang, D. R. Sol. Energy Mater. Sol.
*
S
Supporting Information
Cells 2011, 95, 2941−2945.
Figures of the PXRD patterns of the starting materials, the
UV−vis and photoluminescence spectra, and TEM NP
histograms for each reaction. This material is available free of
charge via the Internet at http://pubs.acs.org.
(12) Mastronardi, M. L.; Henderson, E. J.; Puzzo, D. P.; Chang, Y.;
Wang, Z. B.; Helander, M. G.; Jeong, J.; Kherani, N. P.; Lu, Z.; Ozin,
G. A. Small 2012, 8, 3647−3654.
(
13) Cho, E. C.; Park, S.; Hao, X.; Song, D.; Conibeer, G.; Park, S.
C.; Green, M. A. Nanotechnology 2008, 19, 245201.
14) Shiohara, A.; Prabakar, S.; Faramus, A.; Hsu, C.-Y.; Lai, P.-S.;
Northcote, P. T.; Tilley, R. D. Nanoscale 2011, 3, 3364−3370.
15) Bhattacharjee, S.; Rietjens, I. M. C. M.; Singh, M. P.; Atkins, T.
(
AUTHOR INFORMATION
■
(
Corresponding Author
M.; Purkait, T. K.; Xu, Z.; Regli, S.; Shukaliak, A.; Clark, R. J.; Mitchell,
B. S.; Alink, G. M.; Marcelis, A. T. M.; Fink, M. J.; Veinot, J. G. C.;
Kauzlarich, S. M.; Zuilhof, H. Nanoscale 2013, 5, 4870−4883.
(16) McVey, B. F. P.; Tilley, R. D. Acc. Chem. Res. 2014, 47, 3045−
*E-mail for S.M.K.: smkauzlarich@ucdavis.edu.
Notes
The authors declare no competing financial interest.
3
051.
17) Zou, J.; Sanelle, P.; Pettigrew, K. A.; Kauzlarich, S. M. J. Cluster
Sci. 2006, 17, 565−578.
18) Pettigrew, K. A.; Liu, Q.; Power, P. P.; Kauzlarich, S. M. Chem.
(
ACKNOWLEDGMENTS
■
(
(
This work was supported by the National Science Foundation
CHE-1035468) and the Bavaria California Technology Center
BaCaTeC-Precursor Methods for Silicon based Materials). We
(
Mater. 2003, 15, 4005−4011.
(19) Hessel, C. M.; Reid, D.; Panthani, M. G.; Rasch, M. R.;
Goodfellow, B. W.; Wei, J.; Fujii, H.; Akhavan, V.; Korgel, B. A. Chem.
Mater. 2011, 24, 393−401.
thank Joel Commisso from the Interdisciplinary Center of
Plasma Mass Spectrometry for ICP-MS. Furthermore, we thank
Dr. Oliver Janka and Dr. Elayaraja Muthuswamy for many
insightful discussions.
(
20) Zhong, Y.; Peng, F.; Bao, F.; Wang, S.; Ji, X.; Yang, L.; Su, Y.;
Lee, S.-T.; He, Y. J. Am. Chem. Soc. 2013, 135, 8350−8356.
21) Mayeri, D.; Phillips, B. L.; Augustine, M. P.; Kauzlarich, S. M.
(
Chem. Mater. 2001, 13, 765−770.
REFERENCES
■
(22) Bley, R. A.; Kauzlarich, S. M. J. Am. Chem. Soc. 1996, 118,
12461−12462.
(
(
(
(
1) Canham, L. T. Appl. Phys. Lett. 1990, 57, 1046−1048.
2) Batu, G.; Naoto, S. Sci. Technol. Adv. Mater. 2014, 15, 014207.
3) Veinot, J. G. C. Chem. Commun. 2006, 4160−4168.
(23) Cho, B.; Baek, S.; Woo, H.-G.; Sohn, H. J. Nanosci. Nanotechnol.
2014, 14, 5868−5872.
(24) Goicoechea, J. M.; Sevov, S. C. Inorg. Chem. 2005, 44, 2654−
2658.
4) Atkins, T. M.; Louie, A. Y.; Kauzlarich, S. M. Nanotechnology
2
012, 23, 294006.
4
00
dx.doi.org/10.1021/ic5027398 | Inorg. Chem. 2015, 54, 396−401

Inorganic Chemistry
Article
(
25) Goicoechea, J. M.; Sevov, S. C. J. Am. Chem. Soc. 2004, 126,
860−6861.
26) Joseph, S.; Suchentrunk, C.; Kraus, F.; Korber, N. Eur. J. Inorg.
Chem. 2009, 2009, 4641−4647.
27) Joseph, S.; Suchentrunk, C.; Korber, N. Z. Naturforsch. B 2010,
6
(
(
6
(
5, 1059−1065.
28) Waibel, M.; Kraus, F.; Scharfe, S.; Wahl, B.; Fas
Chem., Int. Ed. 2010, 49, 6611−6615.
29) Joseph, S.; Hamberger, M.; Mutzbauer, F.; Har
̈
sler, T. F. Angew.
(
̈
tl, O.; Meier, M.;
Korber, N. Angew. Chem., Int. Ed. 2009, 48, 8770−8772.
30) Goicoechea, J. M.; Sevov, S. C. Organometallics 2006, 25, 4530−
536.
31) Neumeier, M.; Fendt, F.; Gar
Korber, N.; Gschwind, R. M. Angew. Chem., Int. Ed. 2013, 52, 4483−
486.
32) SiGNa Chemistry, Inc., Davis, CA, 2013.
33) Brauer, G. Handbuch der Praparativen Anorganischen Chemie, 3rd
ed.; Ferdinand Enke Verlag: Stuttgart, Germany, 1975.
34) Goebel, T.; Prots, Y.; Ormeci, A.; Pecher, O.; Haarmann, F. Z.
Anorg. Allg. Chem. 2011, 637, 1982−1991.
35) Waibel, M.; Benda, C. B.; Wahl, B.; Fas
011, 17, 12928−12931.
36) Neiner, D.; Chiu, H. W.; Kauzlarich, S. M. J. Am. Chem. Soc.
006, 128, 11016−11017.
37) Zhang, X.; Neiner, D.; Wang, S.; Louie, A. Y.; Kauzlarich, S. M.
Nanotechnology 2007, 18, 095601.
38) Queneau, V.; Todorov, E.; Sevov, S. C. J. Am. Chem. Soc. 1998,
20, 3263−3264.
39) Dasog, M.; Yang, Z.; Regli, S.; Atkins, T. M.; Faramus, A.; Singh,
(
4
(
̈ ̈
tner, S.; Koch, C.; Gartner, T.;
4
(
(
̈
(
(
̈
sler, T. F. Chem. Eur. J.
2
(
2
(
(
́
1
(
M. P.; Muthuswamy, E.; Kauzlarich, S. M.; Tilley, R. D.; Veinot, J. G.
C. ACS Nano 2013, 7, 2676−2685.
(
40) Fuzell, J.; Thibert, A.; Atkins, T. M.; Dasog, M.; Busby, E.;
Veinot, J. G. C.; Kauzlarich, S. M.; Larsen, D. S. J. Phys. Chem. Lett.
013, 4, 3806−3812.
41) Dasog, M.; De los Reyes, G. B.; Titova, L. V.; Hegmann, F. A.;
Veinot, J. G. C. ACS Nano 2014, 8, 9636−9648.
2
(
4
01
dx.doi.org/10.1021/ic5027398 | Inorg. Chem. 2015, 54, 396−401