Type-II heterostructures of α-V2O5 nanowires interfaced with cadmium chalcogenide quantum dots: Programmable energetic offsets, ultrafast charge transfer, and photocatalytic hydrogen evolution.

We synthesized a new class of heterostructures by depositing CdS, CdSe, or CdTe quantum dots (QDs) onto α-V2O5 nanowires (NWs) via either successive ionic layer adsorption and reaction (SILAR) or linker-assisted assembly (LAA). SILAR yielded the highest loadings of QDs per NW, whereas LAA enabled better control over the size and properties of QDs. Soft and hard x-ray photoelectron spectroscopy in conjunction with density functional theory calculations revealed that all α-V2O5/QD heterostructures exhibited Type-II band offset energetics, with a staggered gap where the conduction- and valence-band edges of α-V2O5 NWs lie at lower energies (relative to the vacuum level) than their QD counterparts. Transient absorption spectroscopy measurements revealed that the Type-II energetic offsets promoted the ultrafast (10-12-10-11 s) separation of photogenerated electrons and holes across the NW/QD interface to yield long-lived (10-6 s) charge-separated states. Charge-transfer dynamics and charge-recombination time scales varied subtly with the composition of heterostructures and the nature of the NW/QD interface, with both charge separation and recombination occurring more rapidly within SILAR-derived heterostructures. LAA-derived α-V2O5/CdSe heterostructures promoted the photocatalytic reduction of aqueous protons to H2 with a 20-fold or greater enhancement relative to isolated colloidal CdSe QDs or dispersed α-V2O5 NWs. The separation of photoexcited electrons and holes across the NW/QD interface could thus be exploited in redox photocatalysis. In light of their programmable compositions and properties and their Type-II energetics that drive ultrafast charge separation, the α-V2O5/QD heterostructures are a promising new class of photocatalyst architectures ripe for continued exploration.

Hole Extraction by Design in Photocatalytic Architectures Interfacing CdSe Quantum Dots with Topochemically Stabilized Tin Vanadium Oxide.

Tackling the complex challenge of harvesting solar energy to generate energy-dense fuels such as hydrogen requires the design of photocatalytic nanoarchitectures interfacing components that synergistically mediate a closely interlinked sequence of light-harvesting, charge separation, charge/mass transport, and catalytic processes. The design of such architectures requires careful consideration of both thermodynamic offsets and interfacial charge-transfer kinetics to ensure long-lived charge carriers that can be delivered at low overpotentials to the appropriate catalytic sites while mitigating parasitic reactions such as photocorrosion. Here we detail the theory-guided design and synthesis of nanowire/quantum dot heterostructures with interfacial electronic structure specifically tailored to promote light-induced charge separation and photocatalytic proton reduction. Topochemical synthesis yields a metastable ß-Sn0.23V2O5 compound exhibiting Sn 5s-derived midgap states ideally positioned to extract photogenerated holes from interfaced CdSe quantum dots. The existence of these midgap states near the upper edge of the valence band (VB) has been confirmed, and ß-Sn0.23V2O5/CdSe heterostructures have been shown to exhibit a 0 eV midgap state-VB offset, which underpins ultrafast subpicosecond hole transfer. The ß-Sn0.23V2O5/CdSe heterostructures are further shown to be viable photocatalytic architectures capable of efficacious hydrogen evolution. The results of this study underscore the criticality of precisely tailoring the electronic structure of semiconductor components to effect rapid charge separation necessary for photocatalysis.

Implantable Tin Porphyrin-PEG Hydrogels with pH-Responsive Fluorescence.

Tetracarboxy porphyrins can be polymerized with polyethylene glycol (PEG) diamines to generate hydrogels with intense, near-infrared, and transdermal fluorescence following subcutaneous implantation. Here, we show that the high density porphyrins of the preformed polymer can be chelated with tin via simple incubation. Tin porphyrin hydrogels exhibited increasing emission intensities, ratios, and lifetimes from pH 1 to 10. Tin porphyrin hydrogel emission was strongly reversible and pH responsiveness was observed in the physiological range between pH 6 and pH 8. pH-sensitive emission was detected via noninvasive transdermal fluorescence imaging in vivo following subcutaneous implantation in mice.

Aminoalkanoic Acids as Alternatives to Mercaptoalkanoic Acids for the Linker-Assisted Attachment of Quantum Dots to TiO2.

Linear aminoalkanoic acids (AAAs) and mercaptoalkanoic acids (MAAs) were characterized as bifunctional ligands to tether CdSe QDs to nanocrystalline TiO2 thin films and to mediate excited-state electron transfer (ET) from the QDs to TiO2 nanoparticles. The adsorption of 12-aminododecanoic acid (ADA) and 12-mercaptododecanoic acid (ADA) to TiO2 followed the Langmuir adsorption isotherm. Surface adduct formation constants (Kad) were ∼10(4) M(-1); saturation amounts of the ligands per projected surface area of TiO2 (Γ0) were ∼10(-7) mol cm(-2). Both Kad and Γ0 differed by 20% or less for the two linkers. CdSe QDs adhered to ADA- and MDA-functionalized TiO2 films; data were well modeled by the Langmuir adsorption isotherm and Langmuir kinetics. For ADA- and MDA-mediated assembly values of Kad were (1.8 ± 0.4) × 10(6) and (2.4 ± 0.4) × 10(6) M(-1), values of Γ0 were (1.6 ± 0.3) × 10(-9) and (1.2 ± 0.1) × 10(-9) mol cm(-2), and rate constants were (14 ± 5) and (60 ± 20) M(-1) s(-1), respectively. Thus, the thermodynamics and kinetics of linker-assisted assembly were slightly more favorable for MDA than for ADA. Steady-state and time-resolved emission spectroscopy revealed that electrons were transferred from both band-edge and surface states of CdSe QDs to TiO2 with rate constants (ket) of ∼10(7) s(-1). ET was approximately twice as fast through thiol-bearing linker 4-mercaptobutyric acid (MBA) as through amine-bearing linker 4-aminobutyric acid (ABA). Photoexcited QDs transferred holes to adsorbed MBA. In contrast, ABA did not scavenge photogenerated holes from CdSe QDs, which maximized the separation of charges following ET. Additionally, ABA shifted electron-trapping surface states to higher energies, minimizing the loss of potential energy of electrons prior to ET. These trade-offs involving the kinetics and thermodynamics of linker-assisted assembly; the driving force, rate constant, and efficiency of ET; and the extent of photoinduced charge separation can inform the selection bifunctional ligands to tether QDs to surfaces.

Photoinduced electron transfer from quantum dots to TiO2: elucidating the involvement of excitonic and surface states.

Colloidal semiconductor quantum dots (QDs) exhibit excitonic and surface states, both of which may participate in charge-transfer processes relevant to solar energy conversion. To explore this inherent complexity of the charge-transfer mechanisms of QDs, we used steady-state and time-resolved emission measurements to characterize excited-state electron transfer (ET) from core-only CdSe QDs and core/shell CdSe/ZnS QDs to TiO2 nanoparticles (NPs). Core-only QDs transferred electrons from both excitonic and surface states to TiO2 with rate constants of ET (ket) of approximately (1-3) × 10(8) s(-1) and (4-7) × 10(7) s(-1), respectively. Efficiencies of ET (ηet) from excitonic and surface states were approximately 71-82% and 64-76%, respectively. Thus, trapping of electrons lowered their potential energy but did not greatly affect the efficiency of their transfer to TiO2. Photogenerated holes were transferred from core-only CdSe QDs to adsorbed 3-mercaptopropionic acid (MPA), which linked the QDs to TiO2. We characterized core/shell CdSe/ZnS QDs as alternatives to core-only QDs. The ZnS shell eliminated the undesirable trapping of electrons and transfer of photogenerated holes to MPA. We measured ket of approximately (1-3) × 10(8) s(-1) and ηet of approximately 66-85% for ET from excitonic states of core/shell CdSe/ZnS QDs to TiO2 NPs. The insensitivity of ket to the presence of the ZnS shell may have arisen from increased cross-linking of core/shell QDs to TiO2. Our results highlight the involvement of surface states in excited-state ET processes of core-only QDs and, for the heterostructures reported here, the improved performance of core/shell CdSe/ZnS QDs relative to core-only CdSe QDs.

Endometriosis: A Review of Clinical Diagnosis, Treatment, and Pathogenesis.

Endometriosis is a condition that affects women of reproductive age, and it is distinguished by the development of endometrial-like tissue outside the uterine cavity. It is frequently accompanied by persistent pelvic discomfort and infertility. This investigation looks into recent findings on clinical manifestation to help doctors and improve women's health. PubMed and Google Scholar were used to review on clinical diagnosis of endometriosis. The search strategy contained the terms "endometriosis" and "clinical diagnosis." All research articles published between 1960 and 2021 were included in the search. The findings were then categorized to summarize the evidence. There was a total of 29 instances of endometriosis discovered. The patients' ages varied from 20 to 45 years old, with a median of 28.8 years and a mean of 29.4±7.7 years. Dysmenorrhea is a common disorder among adolescent girls experiencing various physical and emotional symptoms which have a detrimental influence on their quality of life. In this study, scar endometriosis was shown to be the more common variety of endometriosis, with 50% of cases predominantly developing at the lower segment cesarean section (LSCS) scar site. As a result, women with endometriosis are more likely to have miscarriages, and the quality of their embryos declines as a result.

Causes of Infertility: Diagnosis and Management With Microfluidic Sperm Sorter.

This case study refers to a three-and-a-half-year married couple who visited an infertility clinic and are facing infertility for two-and-a-half years. They started in vitro fertilization/assisted reproduction technology (IVF/ART) procedures from December 2021. In 2019, the couple underwent infertility therapy in Wardha, India, including three intra-uterine insemination (IUI) treatments which failed. The couple was then recommended the intracytoplasmic sperm injection (ICSI) procedure in which the semen sample was separated using a microfluidic sperm sorter for separating good quality sperms. There was no past medical history of both of the partners. Since she was infertile, the desire to have a child was extremely strong. Sadness, helplessness, bewilderment, and frustration are all common feelings associated with infertility. The left fallopian tube delays spillage in females and oligoasthenozoospermia in males; women were detected with secondary infertility and male sperm samples were sorted using a microfluidic sperm sorter and fertilized frozen oocytes for ICSI. As the male partner, in this case, had oligoasthenozoospermia, he was prescribed multivitamins and other medications. After ICSI, the blastocyst formation was good with the use of a microfluidic sperm sorter.