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Polyimide (PI) with excellent comprehensive properties has been extensively applied in electronic devices. The miniaturization and integration of electrical equipment put forward more stringent requirements for heat dissipation, so a composite with high thermal conductivity and low dielectric properties has become a critical factor. In this work, fluorinated graphene (FG) and boron nitride nanosheets modified with polydopamine (PDA@BNNS) were filled into the PI matrix as fillers to prepare FG/PDA@BNNS/PI composites. The mixed filling of FG and BNNS synergistically improves the dielectric and thermal conductivity, and this research breaks the balance barrier between dielectric and thermal conductivity. The resulting 4.99 wt % FG/PDA@BNNS/PI composite exhibited excellent comprehensive properties, including ultralow dielectric constant of 1.67, low loss of 0.013 at 1 MHz, and high thermal conductivity of 2.464 W m–1 K–1. In addition, the film also showed standout breakdown resistance (81.22 kV/mm) and mechanical properties such that the tensile strength reached 35.7 MPa. This report can inspire future development of composites for electronic packaging. [ABSTRACT FROM AUTHOR]

Single-particle inductively coupled plasma mass spectrometry (spICP-MS) has been used to characterize metallic nanoparticles (NPs) assuming that all NPs are spherical and composed of pure element. However, environmental NPs generally do not meet these criteria, suggesting that spICP-MS may underestimate their true sizes. This study employed a system hyphenating the atomizer (ATM), differential mobility analyzer (DMA), and spICP-MS to characterize metallic NPs in tap water. Its performance was validated by using reference Au nanoparticles (AuNPs) and Ag-shelled AuNPs. The hyphenated system can determine the actual size and metal composition of both NPs with additional heating after ATM, while stand-alone spICP-MS misidentified the Ag-shelled AuNPs as smaller individual AgNPs and AuNPs. Dissolved metal ions could introduce artifact NPs after heating but could be eliminated by centrifugation. The hyphenated system was applied to characterize Fe-containing and Pb-containing NPs resulting from the corrosion of plumbing materials in tap water. The mode sizes of Fe-containing and Pb-containing NPs were determined to be 110 and 100 nm and the particle number concentrations were determined to be 4.99 × 10 7 and 1.40 × 10 6 #/mL, respectively. Cautions should be paid to potential changes in particle size induced by heating for metallic NPs with a low melting point or a high organic content.

The high-throughput screening of chemically active substances has aroused widespread interest in recent years. The screening of drug carriers is usually ignored, although they interact directly with physiological barriers and target cells, and they determine the fate and efficacy of drugs in vivo. In this work, a series of polydiacetylene (PDA) vesicles (ca. 550 nm) that simulate the cell membrane are constructed to detect the membrane affinity of gene vectors. The surface potentials of vesicles are adjusted by changing the phospholipid composition using different charged compounds. All vesicles show the rapid color changes upon the addition of gene vectors by the naked eye within <5 min. The optimized 1,2-dimyristoyl- sn-glycero-3-phosphocholine (DMPC)-PDA vesicles display the most sensitive discoloration response to the commercially available gene vectors, including Lipofectamine 2000, Entranster-H4000, and polyethylenimine. The logarithm of transfection efficiency for green fluorescent protein plasmid (pGFP) mediated by these three vectors in L02 and HepG2 cells demonstrate an excellent linear correlation with the logarithm of membrane affinity (log K b ) of the gene vectors detected by DMPC-PDA vesicles. This rapid visualization method not only allows the in vitro membrane affinity prediction of gene vectors that greatly contributes to the gene transfection efficiency, but also offers a universal strategy for the potential high-throughput screening of various carrier materials featuring high cell affinity.

Bidirectional photoswitching of molecular materials under ambient condition is of significant importance. Herein, we present for the first time that a core-shell UCNP-SCO nanosphere (UCNP = upconversion nanophosphor, SCO = spin crossover), which was composed of a UCNP core (NaYF 4 : 20 mol % Yb 3+ , 1 mol % Er 3+ ) and an SCO iron(II) shell ([Fe(H 2 Bpz) 2 (bipy-COOH)], H 2 Bpz = dihydrobis(1-pyrazolyl)borate, bipy-COOH = 4,4'-dicarboxy-2,2'-bipyridine), can be reversibly photoswitched between the high-spin and low-spin states at room temperature in the solid state, via alternating irradiation with near-infrared (λ = 980 nm) and ultraviolet (λ = 310 nm) light. What's more, this reversible spin-state switching was accompanied by a variation of fluorescent spectrum and dielectric constants. The strategy here, that is, integrating the SCO iron(II) complex into a UCNP-SCO nanosphere for molecular photoswitching, may open a new area in the development of photocontrolled molecular devices.

A thermal-induced dielectric switching has been realized in two ion-pair crystal [C 2 H 6 N 5 ] + ·[H 2 PO 4 ] - (1, C 2 H 6 N 5 = 3,5-diamino-1,2,4-triazolinium) through single-crystal-to-single-crystal phase transition (SCSC-PT). Upon cooling from room temperature, the 1D cation stripes that are composed of [C 2 H 5 N 5 ] + cations have undergone a 90° sharp rotation around the c axis, accompanied by the transition of crystal stacking from loose unparallel (dynamic state) to compression parallel (static state) and reorientation of dipoles on the [C 2 H 5 N 5 ] + cation, which thus resulted in high dielectric state to low dielectric state transformation. While on the warming run, the reverse process was rather sluggish, resulting in a reversible dielectric switching with ultralarge (about 40K wide) hysteresis loop near room temperature. It is thought that the large-sized polar cation stripes have a predominant influence on the switching properties of 1.

The organometallic cation 1 (Fe(bipy-NH 2 ) 3 2+ , bipy-NH 2 = 4,4'-diamino-2,2'-bipyridine), which was constructed in situ in solution, can bind CO 2 from air effectively with a stoichiometric ratio of 1:4 (1/CO 2 ), through the formation of "H-bonded CO 2 " species: [CO 2 -OH-CO 2 ] - and [CO 2 -CO 2 -OH] - . These two species, along with the captured individual CO 2 molecules, connected 1 into a novel 3D (three-dimensional) architecture, that was crystal 1·2(OH - )·4(CO 2 ). The adsorption isotherms, recycling investigations, and the heat capacity of 1 have been investigated; the results revealed that the organometallic cation 1 can be recycled at least 10 times for the real-world CO 2 capture applications. The strategies presented here may provide new hints for the development of new alkanolamine-related absorbents or technologies for CO 2 capture and sequestration.

Sustainability urgently demands low dielectric loss and low elastic modulus as fostering high permittivity (Hi-K) conductor/polymer composites. This work introduces a ternary composite system, consisting of acrylic resin elastomer (AR), chemically modified polyaniline (HBSiPA), and the thermally reduced graphene oxides (TrGOs), for applying to actuators, of which AR was fabricated by free radical polymerization. The unique hybridized graphene (HBSiPA-TrGO) was prepared by a two-step procedure, including the doped polyaniline modified by the hyperbranched polysiloxane via a ring opening reaction, followed by the decoration of HBSiPA on the surface of TrGO, the conductivity of which is desired to be the same as that of graphene. Afterward, diverse filler contents of HBSiPA-TrGO were put into the AR matrix to fabricate composites with the solution casting method and TrGO/AR composites were fabricated as well for comparison. Unlike TrGO, HBSiPA has plenty of polyaniline chain segments that ensure better dispersion of graphene hybrids in the AR, and thus the composites inherit the excellent electrical property of graphene. The permittivity and dielectric loss of the HBSiPA-TrGO/AR composite at 100 Hz are 3.5 and 0.27 times that of the TrGO/AR composite, respectively, when the loading of fillers approaches the percolation threshold (f c ), which originates from the HBSiPA anchored onto the graphene serving as spacer and thus decreases the leakage currents induced by the contact of graphene sheets. Besides, the elastic modulus of 2.83 vol % HBSiPA-TrGO/AR composite was lower than 5 MPa.