19 research outputs found
Design and Synthesis of IndazoleâIndole Hybrid via <i>tert</i>-Butyl Nitrite Mediated Cascade Diazotization/Isomerization/Cyclization
In this report, a tert-butyl nitrite
(TBN)-mediated
straightforward metal-free approach has been presented for the synthesis
of a diverse range of C-3-substituted indazoleâindole hybrids
using readily accessible 2-(indolin-3-ylidenemethyl)Âaniline
derivatives. This strategy is proposed to occur via a diazonium salt
intermediate that is capable of cascade isomerization and intramolecular
CâN bond formation through a 5-endo-dig cyclization
to achieve a wide variety of indazoleâindole hybrids in good
yields
Particle Deposition on Microporous Membranes Can Be Enhanced or Reduced by Salt Gradients
Colloidal particle deposition on
membranes is a continuing scientific
and technological challenge. In this paper we examine the role of
a previously unexplored phenomenonî¸diffusiophoretic particle
transport toward a membraneî¸in relation to fouling. Diffusiophoresis
is an electrokinetic transport mechanism that arises in salt gradients,
especially when the ions have different diffusion coefficients. Through
experiments conducted with salt diffusing across microdialysis membranes,
with no advection, we show experimentally that diffusiophoresis induces
colloidal deposition on the surface of microporous surfaces. We used
transient salt (NaCl, KCl, LiCl) gradients and fundamental electrokinetic
modeling to assess the role of diffusiophoresis in colloidal fouling.
Based on (i) difference in diffusion coefficients of ions, (ii) zeta
potential on the particles, and (iii) ionic gradient applied across
the walls of the membrane, colloidal fouling could be both quantitatively
and qualitatively predicted. Our understanding enabled us to stop
particle deposition by adding calcium carbonate outside the membrane,
which generates a stronger electric field in a direction opposite
to that created by salt diffusing from the membrane. We propose that
accounting for this diffusiophoretic mode of particle deposition is
important in understanding membrane fouling
Enhanced Transport into and out of Dead-End Pores
Dead-end micro- and nanoscale channels are ubiquitous in nature and are found in geological and biological systems subject to frequent disruptions. Achieving fluid flows in them is not possible through conventional pressure-driven mechanisms. Here we show that chemically driven convective flows leading to transport in and out of dead-end pores can occur by the phenomenon of âtransient diffusioosmosisâ. The advective velocity depends on the presence of an <i>in situ</i>-generated transient ion gradient and the intrinsic charge on the pore wall. The flows can reach speeds of 50 Îźm/s and cause extraction of otherwise-trapped materials. Our results illustrate that chemical energy, in the form of a transient salt gradient, can be transduced into mechanical motion with the pore wall acting as the pump. As discussed, the phenomena may underlie observed transport in many geological and biological systems involving tight or dead-end micro- and nanochannels
Enhanced Transport into and out of Dead-End Pores
Dead-end micro- and nanoscale channels are ubiquitous in nature and are found in geological and biological systems subject to frequent disruptions. Achieving fluid flows in them is not possible through conventional pressure-driven mechanisms. Here we show that chemically driven convective flows leading to transport in and out of dead-end pores can occur by the phenomenon of âtransient diffusioosmosisâ. The advective velocity depends on the presence of an <i>in situ</i>-generated transient ion gradient and the intrinsic charge on the pore wall. The flows can reach speeds of 50 Îźm/s and cause extraction of otherwise-trapped materials. Our results illustrate that chemical energy, in the form of a transient salt gradient, can be transduced into mechanical motion with the pore wall acting as the pump. As discussed, the phenomena may underlie observed transport in many geological and biological systems involving tight or dead-end micro- and nanochannels
Enhanced Transport into and out of Dead-End Pores
Dead-end micro- and nanoscale channels are ubiquitous in nature and are found in geological and biological systems subject to frequent disruptions. Achieving fluid flows in them is not possible through conventional pressure-driven mechanisms. Here we show that chemically driven convective flows leading to transport in and out of dead-end pores can occur by the phenomenon of âtransient diffusioosmosisâ. The advective velocity depends on the presence of an <i>in situ</i>-generated transient ion gradient and the intrinsic charge on the pore wall. The flows can reach speeds of 50 Îźm/s and cause extraction of otherwise-trapped materials. Our results illustrate that chemical energy, in the form of a transient salt gradient, can be transduced into mechanical motion with the pore wall acting as the pump. As discussed, the phenomena may underlie observed transport in many geological and biological systems involving tight or dead-end micro- and nanochannels
Enhanced Transport into and out of Dead-End Pores
Dead-end micro- and nanoscale channels are ubiquitous in nature and are found in geological and biological systems subject to frequent disruptions. Achieving fluid flows in them is not possible through conventional pressure-driven mechanisms. Here we show that chemically driven convective flows leading to transport in and out of dead-end pores can occur by the phenomenon of âtransient diffusioosmosisâ. The advective velocity depends on the presence of an <i>in situ</i>-generated transient ion gradient and the intrinsic charge on the pore wall. The flows can reach speeds of 50 Îźm/s and cause extraction of otherwise-trapped materials. Our results illustrate that chemical energy, in the form of a transient salt gradient, can be transduced into mechanical motion with the pore wall acting as the pump. As discussed, the phenomena may underlie observed transport in many geological and biological systems involving tight or dead-end micro- and nanochannels
Enhanced Transport into and out of Dead-End Pores
Dead-end micro- and nanoscale channels are ubiquitous in nature and are found in geological and biological systems subject to frequent disruptions. Achieving fluid flows in them is not possible through conventional pressure-driven mechanisms. Here we show that chemically driven convective flows leading to transport in and out of dead-end pores can occur by the phenomenon of âtransient diffusioosmosisâ. The advective velocity depends on the presence of an <i>in situ</i>-generated transient ion gradient and the intrinsic charge on the pore wall. The flows can reach speeds of 50 Îźm/s and cause extraction of otherwise-trapped materials. Our results illustrate that chemical energy, in the form of a transient salt gradient, can be transduced into mechanical motion with the pore wall acting as the pump. As discussed, the phenomena may underlie observed transport in many geological and biological systems involving tight or dead-end micro- and nanochannels
Enhanced Transport into and out of Dead-End Pores
Dead-end micro- and nanoscale channels are ubiquitous in nature and are found in geological and biological systems subject to frequent disruptions. Achieving fluid flows in them is not possible through conventional pressure-driven mechanisms. Here we show that chemically driven convective flows leading to transport in and out of dead-end pores can occur by the phenomenon of âtransient diffusioosmosisâ. The advective velocity depends on the presence of an <i>in situ</i>-generated transient ion gradient and the intrinsic charge on the pore wall. The flows can reach speeds of 50 Îźm/s and cause extraction of otherwise-trapped materials. Our results illustrate that chemical energy, in the form of a transient salt gradient, can be transduced into mechanical motion with the pore wall acting as the pump. As discussed, the phenomena may underlie observed transport in many geological and biological systems involving tight or dead-end micro- and nanochannels
Enhanced Transport into and out of Dead-End Pores
Dead-end micro- and nanoscale channels are ubiquitous in nature and are found in geological and biological systems subject to frequent disruptions. Achieving fluid flows in them is not possible through conventional pressure-driven mechanisms. Here we show that chemically driven convective flows leading to transport in and out of dead-end pores can occur by the phenomenon of âtransient diffusioosmosisâ. The advective velocity depends on the presence of an <i>in situ</i>-generated transient ion gradient and the intrinsic charge on the pore wall. The flows can reach speeds of 50 Îźm/s and cause extraction of otherwise-trapped materials. Our results illustrate that chemical energy, in the form of a transient salt gradient, can be transduced into mechanical motion with the pore wall acting as the pump. As discussed, the phenomena may underlie observed transport in many geological and biological systems involving tight or dead-end micro- and nanochannels
Self-Generated Diffusioosmotic Flows from Calcium Carbonate Micropumps
Calcium carbonate particles, ubiquitous in nature and
found extensively
in geological formations, behave as micropumps in an unsaturated aqueous
solution. The mechanism causing this pumping is diffusioosmosis, which
drives flows along charged surfaces. Our calcium carbonate microparticles,
roughly âź10 Îźm in size, self-generate ionic gradients
as they dissolve in water to produce Ca<sup>2+</sup>, HCO<sub>3</sub><sup>â</sup>, and OH<sup>â</sup> ions that migrate
into the bulk. Because of the different diffusion coefficients of
these ions, spontaneous electric fields of roughly 1â10 V/cm
arise in order to maintain electroneutrality in the solution. This
electric field drives the diffusiophoresis of charged tracers (both
positive and negative) as well as diffusioosmotic flows along charged
substrates. Here we show experimentally how the directionality and
speed of the tracers can be engineered by manipulating the tracer
zeta potential, the salt gradients, and the substrate zeta potential.
Furthermore, because the salt gradients are self-generated, here by
the dissolution of solid calcium carbonate microparticles another
manipulated variable is the placement of these particles. Importantly,
we find that the zeta potentials on surfaces vary with both time and
location because of the adsorption or desorption of Ca<sup>2+</sup> ions; this change affects the flows significantly