Vijay 8 Feb 2020 CRSI-VIT

“Phosphorene Quantum Dots:
Electrochemical Preparation, Doping and

Possible Applications”
26th CRSI National Symposium in Chemistry (NSC-26)

7-8 February 2020, Vellore Institute of Technology (VIT)
MATERIALS ELECTROCHEMISTRY: SOFT, HARD, INTELLIGENT,
STUPID, LIGHT, ULTRAHARD, ELECTRODES! - TOO DIVERSE!
Functionalized
Monolayer CNT and
Protected nano-
Self- Nanoclusters composites Graphene
assembled for PEM fuel GQDs
Monolayers cells 2D
Size and Electroche QUANTUM ...Teaching Materials Chemistry
shape mical DOTS
controlled
& Electrochemistry...
Power … CSIR-NCL
Nanostruct Sources
ures CSIR-CECR
Material (Physical too!) Transformations: 1990 to 2020...
My Group
Mr. Bhalchandra A. Kakade Mr. Kannan Ramaiyan
Mr. Bhaskar R. Sathe

Ms. Mahima Subhramannia
Dr. K. Vijayamohanan
(2007)
Ms. Meera Parthasarathy Mr. Sanjay patil
FUNDING SUPPORT
• CSIR/DST/MNRE
Mrs. Sneha A. Kulkarni • HONEYWELL, US Mr. Dhanraj Rathode

 Chemistry of 2D Materials
 Quantum Dots of 2D Materials
 Electrochemical Synthesis
 Phosphorene Quantum Dots
 N-doped PQDs – in situ & ambient T
 Applications as Electrocatalysts
• Nitrogen doping on PQDs: structural, optical and

electrochemical properties - Potential benefits of
applications ranging from electrocatalysts and
molecular electronics to chemical sensors
Functionalization of Carbon nanotubes
LONGITUDINAL OR HELICAL UNZIPPING – GNRs
TRANSVERSE – NONAQUEOUS MEDIA - GQDs
Nanoletters 3(2003)279
Angew. Chem. Int. Ed. 47 (2008)2653
Nanoletters 8(2008)2693
Chem. Eur. J. 39(2012) 12522
J. Am. Chem. Soc. 133(2011)4168
Angew. Chem. Int. Ed. 52 (2013) 2482
Science Reports 4(2014)4363
ACS Macroletters 3(2014)1064
Phys. Today.
9(2016)38
Strong in-plane covalent bonds and weak

out-of-plane van der Waals forces; 5-0 eV
gap,
More Efficient Device Applications
Superior performance in electrocatalytic
and energy storage applications due to
faster heterogeneous electron transfer,
shorter diffusion lengths
Alio-valent/iso-valent Doping
Functionalization to suit processing
Twistronics
Preparation of 2D Materials
1.Liquid phase exfoliation,
2. Chemical Vapor Deposition (CVD)
3. Mechanical cleavage
4. Electrochemical
5. Laser pulse exfoliation,
6. Microwave etc.
Phosphorene Quantum Dots:

Special Features
•Widely tunable band gap

•Strong in-plane anisotropy
•Anisotropic effective mass
•High carrier mobility
•Flexibility for functionalization
Applications: spanning from electronic, optoelectronic, and spintronic

devices to sensors, actuators, and thermo-electrics to energy conversion, and
storage devices
Energy Band Gap Engineering of Phosphorene
M Akhtar et al. npj 2D Materials and Applications(2017)
Schematic diagram of the top-down and
bottom-up methods for synthesizing GQDs
Adv. Mater., 2010, 22, 734.

Hydrothermal cutting of graphene sheets: blue and green emitting
Role of Structural Distortion in Stabilizing Electrosynthesized Blue-
Emitting Phosphorene Quantum Dots
Illustration of electrosynthesis of PQDs
Transmission electron micrographs
Bulk BP PQDs
Average size=7.8 ±1 .6 nm (N=50)

• Inherent in-plane anisotropy and
anisotropic effective mass
coupled with lattice strain
• potential applications in
optoelectronics, catalysis and
sensing
J. Phys. Chem. Let. 10(2019)973 10
Atomic Force Micrograph and
corresponding height profile of
PQDs
The AFM
topographic
images along with
their height
profiles. PQDs
show ~3-4 layers
based on an
interlayer distance
of 0.53 while lesser
number of layers
are noticed for
NPQDs (~1-2
layers)
(a) UV−visible spectrum of electrosynthesized PQDs (inset:
PQDs under 365 nm UV light along with blank electrolyte).
(b) UV−visible spectra of PQDs recorded after a few days.
X-ray diffraction patterns of BP and
(c) PL spectra of PQDs exhibiting excitation wavelength
electrochemically prepared PQDs
independence. (d) Time resolved fluorescence decay pattern
for PQDs recorded at an excitation wavelength of 370
12
nm
and emission wavelength of 42
ELECTROCHEMICAL SYNTHESIS OF N DOPED PQDs
Electric field
Time
Solvent
Temperature
Counter Ion
Oxidation
induced edge
state
functionalization
by P=O, P-O-P
functional
groups can be
minimized by
Reductive
exfoliation
Chem. Com. 54(2018)11733

The average diameter
of PQDs 8 nm -
lattice fringes with a
spacing of 0.23 nm
assigned to (041) plane
of orthorhombic BP
A slightly smaller
average size is noticed
for NPQDs ~6 nm.
P-P distances of 0.16
and 0.23 nm are
calculated from x and z
directions
inter planar distances
calculated from the
lattice fringes 0.17 nm
and 0.22 nm for x and z
direction,
14
Voltammograms of BP before and after exfoliation at 100 mV/s in
propylene carbonate containing 0.1 wt % LiClO4
Electroreduction, P-P
bond cleaves and a
reversible radical
phosphido anion
[P4].- by a 1-e (peak
at -2.0 V). A broad
anodic peak around
0.2 V
polymerization? k
features of PQDs but
with more kinetic
reversibility.
• OCV change of 670 mV supports the thermodynamic feasibility (free energy

change is calculated to be -63 kJ/mol)
• Area Enhancement due to Exfoliation
NPQDs are
more likely to be
dominated by
zigzag edges
while the blue
shift observed
for PQDs due
to armchair
edges
Both PQDs and NPQDs contain P=O and P-
OH, P-NH2 stretching and P-NH bending
vibrational modes around 3400 and 1600 cm-
1 are noticed for NPQDs. P-N stretching
vibration - specially relevant to compare
PQDs of various surface functionalization18
Properties PQDs NPQDs
Interlayer distance 0.53 nm 0.63 nm
In-plane P-P bond

slightly elongated Slightly contracted
length
Raman spectral Red shift with emergence of D

Blue shift from BP
features modes
PL Quantum
83 % 88 %
Efficiency
PL life time 956 ps 875 ps
Radiative decay
8.6 x 108 s-1 10 x 108 s-1
constant
Non-radiative decay
1.77 x 108 s-1 1.0 x 108 s-1 19
constant
CONCLUSIONS
• N doping at room temperature using solvent or supporting
electrolyte
Changes P-P bond length and electronic structure - XRD,
XPS, and the excitation-independent PL - B, F, N, P, and S
Electrocatalysis/nanoelectronics, optimum oxygen content -

Generic for many two-dimensional materials – stretchable,
bendable power sources
New opportunities for making interesting van der Waals

hetero-structures
Acknowledgements
O V Manila, Subbiah Alwarappan CSIR-CECRI
P.M Ajayan, Rice University Houston, USA & DR. Shaijumon – IISER
Tvm
Prof. Amitav Patra, IACS, Kolkatta
ACKNOWLEDGEMENTS
Manju
Harikrishnan
Jayakrishnan
LEARNT ELECTROCHEMISTRY FROM
TAUGHT ELECTROCHEMISTRY
Dr. M.P. Vinod; Dr. Krishnau Bandyopadhyay
Dr. Varsha Choudhary; Dr. Mohammed Aslam
Dr. Niranajan Ramgir; Dr. Vadivel Murugan
Dr. Nirmalya Chaki; Dr. Jadab Sharma
Dr. Trupti Maddani; Dr. Sneha Kulkarni;
Dr. Mahima Dr. Bhalchandra Kakade
Dr. Meera Parthasarathy Dr. Bhasker Sathe
Dr. R. Kannan Dr. Dhanraj Shide
Dr. Joyashish
Dr. Sumana Kundu Dr. Jaison
Dr.Muniahah Dr. Manila
THANK
THANK YOU
YOU ALL
ALL

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“Phosphorene Quantum Dots:

Electrochemical Preparation, Doping and

26th CRSI National Symposium in Chemistry (NSC-26)

Mr. Bhaskar R. Sathe

Ms. Meera Parthasarathy Mr. Sanjay patil

Mrs. Sneha A. Kulkarni • HONEYWELL, US Mr. Dhanraj Rathode

• Nitrogen doping on PQDs: structural, optical and

Strong in-plane covalent bonds and weak

Phosphorene Quantum Dots:

•Widely tunable band gap

Applications: spanning from electronic, optoelectronic, and spintronic

Adv. Mater., 2010, 22, 734.

Average size=7.8 ±1 .6 nm (N=50)

Chem. Com. 54(2018)11733

• OCV change of 670 mV supports the thermodynamic feasibility (free energy

Interlayer distance 0.53 nm 0.63 nm

In-plane P-P bond

Raman spectral Red shift with emergence of D

PL life time 956 ps 875 ps

Electrocatalysis/nanoelectronics, optimum oxygen content -

New opportunities for making interesting van der Waals

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