Optical
control and readout of electron spin and spin currents
in thin films and nanostructures have remained attractive yet challenging
goals for emerging technologies designed for applications in information
processing and storage. Recent advances in room-temperature spin polarization
using nanometric chiral molecular assemblies suggest that chemically
modified surfaces or interfaces can be used for optical spin conversion
by exploiting photoinduced charge separation and injection from well-coupled
organic chromophores or quantum dots. Using light to drive photoexcited
charge-transfer processes mediated by molecules with central or helical
chirality enables indirect measurements of spin polarization attributed
to the chiral-induced spin selectivity effect and of the efficiency
of spin-dependent electron transfer relative to competitive relaxation
pathways. Herein, we highlight recent approaches used to detect and
to analyze spin selectivity in photoinduced charge transfer including
spin-transfer torque for local magnetization, nanoscale charge separation
and polarization, and soft ferromagnetic substrate magnetization-
and chirality-dependent photoluminescence. Building on these methods
through systematic investigation of molecular and environmental parameters
that influence spin filtering should elucidate means to manipulate
electron spins and photoexcited states for room-temperature optoelectronic
and photospintronic applications.
The combination of photonics and
spintronics opens new ways to transfer and process information. It
is shown here that in systems in which organic molecules and semiconductor
nanoparticles are combined, matching these technologies results in
interesting new phenomena. We report on light induced and spin-dependent
charge transfer process through helical oligopeptide–CdSe nanoparticles’
(NPs) architectures deposited on ferromagnetic substrates with small
coercive force (∼100–200 Oe). The spin control is achieved
by the application of the chirality-induced spin-dependent electron
transfer effect and is probed by two different methods: spin-controlled
electrochemichemistry and photoluminescence (PL) at room temperature.
The injected spin could be controlled by excitation of the nanoparticles.
By switching the direction of the magnetic field of the substrate,
the PL intensity could be alternated.
Spin-dependent
photoluminescence (PL) quenching of CdSe nanoparticles
(NPs) has been explored in the hybrid system of CdSe NP purple membrane,
wild-type bacteriorhodopsin (bR) thin film on a ferromagnetic (Ni-alloy)
substrate. A significant change in the PL intensity from the CdSe
NPs has been observed when spin-specific charge transfer occurs between
the retinal and the magnetic substrate. This feature completely disappears
in a bR apo membrane (wild-type bacteriorhodopsin in which the retinal
protein covalent bond was cleaved), a bacteriorhodopsin mutant (D96N),
and a bacteriorhodopsin bearing a locked retinal chromophore (isomerization
of the crucial C13=C14 retinal double bond was prevented by
inserting a ring spanning this bond). The extent of spin-dependent
PL quenching of the CdSe NPs depends on the absorption of the retinal,
embedded in wild-type bacteriorhodopsin. Our result suggests that
spin-dependent charge transfer between the retinal and the substrate
controls the PL intensity from the NPs.
The availability of robust superhydrophobic materials with the ability to withstand harsh environments are in high demand for many applications. In this study, we have presented a simple method to fabricate superhydrophobic materials from TiO2 nanotube arrays (TNTAs) and investigated the resilience of the materials when they are subjected to harsh conditions such as intense cavitation upon ultrasonication, corrosion in saline water, water-jet impact, and abrasion. The TNTAs were prepared by anodization of Ti foil in buffered aqueous electrolyte containing fluoride ions. The hydrophilic TNTAs were functionalized with octadecylphosphonic acid (ODPA) or 1H, 1H′, 2H, 2H′-perfluorodecyl phosphonic acid (PFDPA) to form a self-assembled monolayer on the TNTA surface to produce superhydrophobic ODPA@TNTA or PFDPA@TNTA surfaces. The superhydrophobic ODPA@TNTA and PFDPA@TNTA have contact angles of 156.0° ± 1.5° and 168° ± 1.5°, and contact angle hysteresis of 3.0° and 0.8°, respectively. The superhydrophobic ODPA@TNTA and PFDPA@TNTA were subjected to ultrasonication, corrosion in saline water, and water-jet impact and abrasion, and the resilience of the systems was characterized by electrochemical impedance spectroscopy (EIS), contact angle (CA) measurements, diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and field-emission scanning electron microscopy (FESEM). The results presented here show that superhydrophobic ODPA@TNTA and PFDPA@TNTA are robust and resilient under the harsh conditions studied in this work, and indicate the potential of these materials to be deployed in practical applications.
This
report describes the synthesis of thiol-protected Pd nanoparticles
(NPs) (Pd-MUA) (MUA = 11-mercaptoundecanoic acid) supported
on oxidized charcoal (OC-Pd-MUA) at room temperature.
The Pd-MUA NPs and OC-Pd-MUA nanocomposites
(NCs) were characterized with Fourier transform infrared (FTIR) spectroscopy,
transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry
(EDX), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller
(BET) techniques. The size distribution curve revealed that the diameter
of the nanoparticles was in the range of ∼8–12 nm, and
the surface area of the NCs was found to be 138.449 m2/g.
The as-prepared OC-Pd-MUA NCs were used as a catalyst
for the cross dehydrogenative coupling (CDC) of two different heteroarenes.
Remarkably, the catalyst was found to be very efficient in activating
various heteroarenes under mild reaction conditions. Most importantly,
no homocoupled or other byproducts were observed during the heterocoupling
reactions. Moreover, the catalyst can be potentially used for the
homocoupling reaction of various heteroarenes. It is noteworthy that
only 0.22 mol % catalyst loading was required to activate a broad
substrate scope with large functional group tolerance. Notwithstanding,
the efficacy of the catalyst was found to be retained even after six
reaction cycles. The reusability and hot filtration tests validated
the heterogeneous nature of the catalysis. In addition, the experimental
and computational studies collectively suggested that thiophene derivatives
react to produce energetically stable products compared with other
heteroarenes during the reaction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.