10 research outputs found
Room Temperature, Multiphasic Detection of Explosives, and Volatile Organic Compounds Using Thermodiffusion Driven Soret Colloids
Achieving a label-free spectroscopic platform for multiphasic analytical detection in real-time, ambient conditions is extremely challenging due to the fundamental dichotomy between ultrahigh sensitivity and reliability of detection. Addressing these challenges, we demonstrate a versatile surface-enhanced Raman scattering (SERS) platform capable of multiphasic, reliable detection with ultrahigh sensitivity. The SERS platform is extremely sensitive and relies on vapor molecules present at the solid-vapor or liquid-vapor interface for reliable detection in ambient conditions (298 K, 1 atm). We observe that metal nanoparticles, subjected to a temperature gradient, migrate and self-assemble into precise nanoparticle assemblies, in a nanoscale analogue of Soret effect. The formation and monodispersity of these nanoparticles assemblies, termed Soret colloids (SCs), is kinetically controllable using the thermal gradient. Soret colloids exhibit excellent size uniformity (monodispersity index, MDI similar to 0.8) and strong interplasmon coupling to generate uniform and intense electromagnetic hot-spots enabling multiphasic, reliable (relative standard deviation, RSD < 5%), instantaneous (<60 s), ambient (298 K, 1 atm) and spectroscopic detection through SERS. Thereby, we demonstrate SERS detection of analytes with a wide range of vapor pressures (10(-9)-10(-1) atm) such as 2,4,6 trinitrotoluene (TNT) and volatile organic compounds (VOCs). Besides, extremely reliable (RSD< 5%), liquid-state SERS detection is also enabled with SCs over a broad concentration range (10(-16) - 10(-6) M) extending to single-molecular sensitivity. Besides fundamentally overcoming the trade-off between high sensitivity and reliability, the vapor-phase detection protocol and platform demonstrated here presents transformative opportunities for real-time detection of explosives, medical diagnostics by breath-analysis and pollution monitoring
Room Temperature, Multiphasic Detection of Explosives, and Volatile Organic Compounds Using Thermodiffusion Driven Soret Colloids
Achieving a label-free
spectroscopic platform for multiphasic analytical
detection in real-time, ambient conditions is extremely challenging
due to the fundamental dichotomy between ultrahigh sensitivity and
reliability of detection. Addressing these challenges, we demonstrate
a versatile surface-enhanced Raman scattering (SERS) platform capable
of multiphasic, reliable detection with ultrahigh sensitivity. The
SERS platform is extremely sensitive and relies on vapor molecules
present at the solid–vapor or liquid–vapor interface
for reliable detection in ambient conditions (298 K, 1 atm). We observe
that metal nanoparticles, subjected to a temperature gradient, migrate
and self-assemble into precise nanoparticle assemblies, in a nanoscale
analogue of Soret effect. The formation and monodispersity of these
nanoparticles assemblies, termed Soret colloids (SCs), is kinetically
controllable using the thermal gradient. Soret colloids exhibit excellent
size uniformity (monodispersity index, MDI ∼ 0.8) and strong
interplasmon coupling to generate uniform and intense electromagnetic
hot-spots enabling multiphasic, reliable (relative standard deviation,
RSD < 5%), instantaneous (<60 s), ambient (298 K, 1 atm) and
spectroscopic detection through SERS. Thereby, we demonstrate SERS
detection of analytes with a wide range of vapor pressures (10<sup>–9</sup>–10<sup>–1</sup> atm) such as 2,4,6
trinitrotoluene (TNT) and volatile organic compounds (VOCs). Besides,
extremely reliable (RSD< 5%), liquid-state SERS detection is also
enabled with SCs over a broad concentration range (10<sup>–16</sup> – 10<sup>–6</sup> M) extending to single-molecular
sensitivity. Besides fundamentally overcoming the trade-off between
high sensitivity and reliability, the vapor-phase detection protocol
and platform demonstrated here presents transformative opportunities
for real-time detection of explosives, medical diagnostics by breath-analysis
and pollution monitoring
Scalable Approach to Highly Efficient and Rapid Capacitive Deionization with CNT-Thread As Electrodes
A scalable
route to highly efficient purification of water through capacitive
deionization (CDI) is reported using CNT-thread as electrodes. Electro-sorption
capacity (<i>q</i><sub>e</sub>) of 139 mg g<sup>–1</sup> and average salt-adsorption rate (ASAR) of 2.78 mg g<sup>–1</sup>min<sup>–1</sup> achieved here is the highest among all known
electrode materials and nonmembrane techniques, indicating efficient
and rapid deionization. Such exceptional performance is achieved with
feedstock concentrations (≤1000 ppm) where conventional techniques
such as reverse osmosis and electrodialysis prove ineffective. Further,
both cations (Na<sup>+</sup>, K<sup>+</sup>, Mg<sup>2+</sup>, and
Ca<sup>2+</sup>) and anions (Cl<sup>–</sup>, SO<sub>4</sub><sup>2–</sup> and NO<sub>3</sub><sup>–</sup>) are removed
with equally high efficiency (∼80%). Synergism between electrical
conductivity (∼25 S cm<sup>–1</sup>), high specific
surface area (∼900 m<sup>2</sup> g<sup>–1</sup>), porosity
(0.7 nm, 3 nm) and hydrophilicity (contact angle ∼25°)
in CNT-thread electrode enable superior contact with water, rapid
formation of extensive electrical double layer and consequently efficient
deionization. The tunable capacitance of the device (0.4–120
mF) and its high specific capacitance (∼27.2 F g<sup>–1</sup>) enable exceptional performance across a wide range of saline concentrations
(50–1000 ppm). Facile regeneration of the electrode and reusability
of the device is achieved for several cycles. The device demonstrated
can desalinate water as it trickles down its surface because of gravity,
thereby eliminating the requirement of any water pumping system. Finally,
its portable adaptability is demonstrated by operating the device
with an AA battery