47 research outputs found
Dopamine/Silica Nanoparticle Assembled, Microscale Porous Structure for Versatile Superamphiphobic Coating
Artificial superamphiphobic surfaces,
which could repel both water
and low surface tension organic liquids, have been limited to particular
kinds of materials or surfaces thus far. In this work, a kind of microscale
porous coating was developed. Taking dopamine and hydrophilic fumed
silica nanoparticles as initial building blocks, microscale porous
coating was constructed <i>via</i> ice templation. Polydopamine
bound silica nanoparticles together to form a porous structure network
and rendered the coating to have potential for further postfunctionalization.
After two-step CVD, the microscale porous coating changes from superhydrophilic
to superamphiphobic, exhibiting super-repellency to droplets with
surface tension of 73–23 mN/m. The influences of concentration
of initial dopamine, hydrophilic fumed silica nanoparticles, and dry
conditions on the formation of the porous structure have been studied
to optimize the conditions. Coatings with different pore sizes and
pore heights have been fabricated to discover the relationship between
the structure parameters and the repellency of the porous coatings.
Only with optimal pore size and pore height can the porous coating
display superamphiphobicity. Compared with nanoscale, the microscale
structure favors the achievement of superamphiphobicity. Given the
outstanding adhesive ability of polydopamine, the superamphiphobic
coatings have been successfully applied to various materials including
artificial materials and natural materials
Thickening of the Immobilized Polymer Layer Using Trace Amount of Amine and Its Role in Promoting Gelation of Colloidal Nanocomposites
Immobilized polymer layers surrounding
nanoparticles are proposed
to be of essentially vital importance for the reinforcement of nanofiller
to polymer matrices, but there is still a need to clarify its contribution
to diverse rheological performance like colloidal stability and gelation.
In this study, we find for the first time that introducing a trace
amount of secondary/tertiary amine efficiently thickens the immobilized
glassy layer in hydrophilic fumed silica (FS) filled polypropylene
glycol (PPG) from 1.5 to 4.5 nm, which simultaneously promotes gelation
of the liquid-like dispersion even containing extremely low contents
of FS (<2 vol %). By coordinately using modulated differential
scanning calorimetry and rheology methods, we find strong evidence
that (1) the amine-promoted gelation is due to thickening and easy-percolation
of the inner glassy layer converted from an outer uncrystallizable
layer, and (2) the dispersion rheology could be well normalized within
the framework of a two-phase model incorporating effective volume
fraction of nanoparticles plus the glassy layers. We also highlight
the importance of the surface chemistry of FS for adjusting the polymer
immobilization and dispersion rheology
Study of Polyelectrolyte Complex Nanoparticles as Novel Templates for Biomimetic Mineralization
Needle-like water-soluble polyelectrolyte complex nanoparticles
(PEC NPs), consisting of sodium carboxylmethyl cellulose (CMCNa) and
polyÂ(methacryloxyethyl trimethyl ammonium chloride) (PDMC), were studied
as novel templates for biomimetic mineralization. Barium acetate and
sodium sulfate solutions were added simultaneously into CMCNa/PDMC
polyelectrolyte complex (PEC) solutions as BaSO<sub>4</sub> precursors.
Spherical BaSO<sub>4</sub> crystals with unique annual ring cross
section were synthesized in different concentrations of PEC solution.
Energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform
infrared spectroscopy, and thermogravimetric analysis (TGA) showed
that these crystals were composed of ca. 90–95 wt % BaSO<sub>4</sub> and 5–10 wt % PEC NPs. Study of ionic strength effect
on PEC mineralization revealed that the rigid needle-like structure
of PEC is responsible for BaSO<sub>4</sub> morphology. In addition,
the mineralization differences between CMCNa and CMCNa/PDMC PEC are
discussed
Rarefaction curves.
<p>Based on A: nucleotide sequences; B: amino acid sequences. Cutoff values are selected as 1%, 3% and 10% for nucleotide sequences, and 1%, 3% and 5% for amino acid sequences.</p
The community composition in each station.
<p>The community composition in each station.</p
Boundary Lubrication by Associative Mucin
Mucus
lubricants are widely distributed in living organisms. Such
lubricants consist of a gel structure constructed by associative mucin.
However, limited tribological studies exist on associative mucin fluids.
The present research is the first to investigate the frictional behavior
of a typical intact vertebrate mucin (loach skin mucin), which can
recover the gel structure of mucus via hydrophobic association under
physiological conditions (5–10 mg/mL loach skin mucin dissolved
in water). Both rough hydrophobic and hydrophilic polydimethylsiloxane
(PDMS) rubber plates were used as friction substrates. Up to 10 mg/mL
loach skin mucin dissolved in water led to a 10-fold reduction in
boundary friction of the two substrates. The boundary-lubricating
ability for hydrophilic PDMS decreased with rubbing time, whereas
that for hydrophobic PDMS remained constant. The boundary-lubricating
abilities of the mucin on hydrophobic PDMS and hydrophilic PDMS showed
almost similar responses toward changing concentration or sodium dodecyl
sulfate (SDS). The mucin fluids reduced boundary friction coefficients
(μ) only at concentrations (<i>c</i>) in which intermucin
associations were formed, with a relationship shown as μ ∼ <i>c</i><sup>–0.7</sup>. Destroying intermucin associations
by SDS largely impaired the boundary-lubricating ability. Results
reveal for the first time that intermolecular association of intact
mucin in bulk solution largely enhances boundary lubrication, whereas
tightly adsorbed layer plays a minor role in the lubrication. This
study indicates that associated mucin should contribute considerably
to the lubricating ability of biological mucus in vivo
Map of the ECS showing the locations of the sampling stations.
<p>Map of the ECS showing the locations of the sampling stations.</p
Image_2_A Virus Infecting Marine Photoheterotrophic Alphaproteobacteria (Citromicrobium spp.) Defines a New Lineage of ssDNA Viruses.TIF
<p>In recent metagenomic studies, single-stranded DNA (ssDNA) viruses that infect bacteria have been shown to be diverse and prevalent in the ocean; however, there are few isolates of marine ssDNA phages. Here, we report on a cultivated ssDNA phage (vB_Cib_ssDNA_P1) that infects Citromicrobium bathyomarinum RCC1878 (family Sphingomonadaceae), and other members of the genus. This is the first ssDNA phage reported to infect marine alphaproteobacteria, and represents a newly recognized lineage of the Microviridae infecting members of Sphingomonadaceae, the Amoyvirinae. The ∼26 nm diameter polyhedral capsid contains a 4,360 bp genome with 6 open reading frames (ORFs) and a 59.3% G+C content. ORF1 encodes the capsid protein and ORF3 encodes the replication initiator protein. The replication cycle is ∼5 h, followed by a burst releasing about 180 infectious particles. The closest relative of vB_Cib_ssDNA_P1 is a prophage within the genome of Novosphingobium tardaugens strain NBRC16725. Phylogenetic analysis indicates that the vB_Cib_ssDNA_P1 phage and two related prophages, as well as an environmental sequence, form a novel group within the Microviridae. Our results indicate that this is a previously unknown lineage of ssDNA viruses which also supplies a new model system for studying interactions between ssDNA phages and marine bacteria.</p
Relationship between the overall GC versus GC3 of <i>psbA</i> squences.
<p>A. The partitioning characteristics for all communities (data from ECS). <i>Synechococcus</i>: y = 2.5655x - 0.7067 (R<sup>2</sup> = 0.9265); Synechomyovirus: y = 2.463x - 0.6944 (R<sup>2</sup> = 0.8566). B. The partitioning characteristics for <i>Synechococcus</i> and Synechomyovirus (data from GOS database). C. The partitioning characteristics for different <i>Synechococcus</i> clades. D. The partitioning characteristics for different Synechomyovirus clades.</p