Palaeococcus pacificus DY20341T, a hyperthermophilic archaeon from deep sea hydrothermal sediments, grows at temperature range from 50 to 90 ℃ (Topt = 80℃). To explore the molecular basis of its thermal adaptation, we identified six representative hyperthermostable proteins from its cytosolic fraction that remained soluble after a stringent in vitro heat treatment at 100 °C. MALDI-TOF mass spectrometry identified these as an inorganic pyrophosphatase (PPase), a 5’-methylthioadenosine phosphorylase (MTAP), and four putative transporter components (one TRAP and three ABC transporter solute-binding proteins). RT-qPCR analysis revealed that the transcription of all six corresponding genes was significantly upregulated when the growth temperature was elevated from 80 °C to 90 °C, suggesting a potential role in the cellular response to heat stress. Biochemical characterization of the recombinant PPase demonstrated remarkable thermostability and an optimal temperature of 90 °C. Kinetic analysis revealed high catalytic efficiency, with a maximal specific activity of 590 ± 30 U/mg and a strong substrate affinity ( K_m = 6.24 µM). Phylogenetic analysis of the identified thermostable MTAP (PAP_00250) revealed its evolutionary origin from hyperthermophilic archaea, distinguishing it clearly from a second MTAP homolog (PAP_07050) in the genome, which aligns with mesophilic bacteria. The structural stability of the identified ABC and TRAP transporter components hypothesizes that efficient nutrient scavenging remains critical at extreme temperatures. Together, these findings provide valuable insights into the stable molecular machinery and potential physiological strategies enabling P. pacificus to thrive in hydrothermal environments.
The ZnxCd1-xS nanocrystals with different Zn2+/Cd2+ratios were solvothermally incubated in water-soluble nanoreactors formed by inverse miniemulsion. Notably, Zn0.5Cd0.5S nanocrystals with larger grain sizes were obtained from polyacrylamide (PAM) nanoreactors, where the PAM solution served as a key component for precursor ripening. The miniemulsion-derived nanoreactors remained stable during nanocrystal incubation, with a size of approximately 160 nm. The obtained ZnxCd1-xS nanocrystals exhibited a cubic structure, and their band gap (Eg) was tunable from 3.83 eV (x= 1) to 2.64 eV (x= 0). The catalytic performance of the nanocrystals was optimized by adjusting both the Zn2+/Cd2+ratio and the PAM concentration in the nanoreactors. Specifically, Zn0.5Cd0.5S nanocrystals incubated in nanoreactors containing 10.0 mg g-1PAM achieved an enhanced grain size of 15 nm, displaying a tunable band gap of 2.58 eV and a weaker luminescence intensity. These nanocrystals exhibited the best catalytic degradation efficiency by balancing the light absorption and the photogenerated charge redox ability, thereby providing a selective strategy for the design of the advanced semiconductor materials.
Epitaxial CdSe/ZnSe submonolayer quantum dots (SMQDs), formed from CdSe coverages below one monolayer (ML), often exhibit a double-peak excitonic structure in their photoluminescence spectra. The narrower, higher-energy peak corresponds to excitons localized within the SMQDs. The lower-energy peak is broader, which is not typical of donor-bound excitons, and has therefore been attributed in previous studies to morphological features of the quantum dots. The identification of the origin of the low-energy peak is technologically relevant for quantum applications of the SMQDs. To clarify the origin of this excitonic structure, we grew several CdSe SMQDs samples with nominal coverages of 0.5 and 0.25 MLs embedded in both non-intentionally doped and Cl-doped ZnSe barriers. The heterostructures were systematically characterized by photoluminescence spectroscopy. A direct comparison of the excitonic properties of the CdSe SMQDs samples grown within ZnSe barriers with varyingn-type impurity doping clearly demonstrates that the relative intensity and line shape of the lower-energy peak depend strongly on donor concentration. These findings overturn the previous morphological interpretation and conclusively demonstrate that the lower-energy component originates from donor impurities. It corresponds to localized excitons bound to single or multiple neutral donors and/or to negative trions formed at low temperature. The intensity in both cases depends on donor doping level.
Aging-induced contact enhancement is a prominent natural phenomenon in materials science. However, it has often been overlooked in nanocrystalline films. Herein, we developed a NiOx/SnO2p-n heterojunction synaptic memristor based on NiOxand SnO2nanocrystals inks, where aging-driven nanocrystal boundary coalescence serves as the origin of improved memristive switching and synaptic emulation. SnO2nanocrystals with amorphous surfaces undergo gradually boundary coalescence after film formation to strengthen bonding between nanocrystals. The ITO/NiOx/SnO2/Ag device exhibits enhanced memristive behavior with aging time at room temperature, and thermal treatment accelerates this aging process. The device emulates synaptic functions of long-term potentiation/depression, excitatory/inhibitory postsynaptic current, and short-term/long-term memory. This work elucidates how aging-driven nanocrystalline evolution facilitates the low-cost fabrication of high-performance neuromorphic devices via solution processing and thermal acceleration.
