High-performance asymmetric supercapacitor made of NiMoO₄ nanorods@Co₃O₄ on a cellulose-based carbon aerogel

• Meixia Wang,
• Jing Zhang,
• Xibin Yi,
• Benxue Liu,
• Xinfu Zhao and
• Xiaochan Liu

Beilstein J. Nanotechnol. 2020, 11, 240–251, doi:10.3762/bjnano.11.18

• porous structure, the NiMoO4@Co3O4/CA ternary composite yields electrodes with an enhanced specific capacitance of 436.9 C/g at a current density of 0.5 A/g and an excellent rate capability of 70.7% capacitance retention at 5.0 A/g. Moreover, an advanced asymmetric supercapacitor (ASC) is assembled using

• the NiMoO4@Co3O4/CA ternary composite as the positive electrode and activated carbon as the negative electrode. The ASC device exhibits a large capacitance of 125.4 F/g at 0.5 A/g, a maximum energy density of 34.1 Wh/kg at a power density of 208.8 W/kg as well as a good cyclic stability (84% after

• 2000 cycles), indicating its wide applicability in energy storage. Finally, our results provide a general approach to the construction of CA and MOF-based composite materials with hierarchical porous structure for potential applications in supercapacitors. Keywords: carbon aerogel; hierarchically

Fabrication of Ag-modified hollow titania spheres via controlled silver diffusion in Ag–TiO₂ core–shell nanostructures

• Bartosz Bartosewicz,
• Malwina Liszewska,
• Bogusław Budner,
• Marta Michalska-Domańska,
• Krzysztof Kopczyński and
• Bartłomiej J. Jankiewicz

Beilstein J. Nanotechnol. 2020, 11, 141–146, doi:10.3762/bjnano.11.12

• obtained composite catalyst exhibits a synergistic effect between the anatase crystalline shell and the AuNPs as well as superb thermal and mechanical stability of the highly dispersed AuNPs. TiO2 HSs decorated with ultrasmall Ag nanocrystallites and exhibiting excellent photocatalytic properties were

Gold and silver dichroic nanocomposite in the quest for 3D printing the Lycurgus cup

• Lars Kool,
• Floris Dekker,
• Anton Bunschoten,
• Glen J. Smales,
• Brian R. Pauw,
• Aldrik H. Velders and
• Vittorio Saggiomo

Beilstein J. Nanotechnol. 2020, 11, 16–23, doi:10.3762/bjnano.11.2

• nanoparticles present in the glass. In this research we show the synthesis of dichroic silver nanoparticles and their embedding in a 3D printable nanocomposite. The addition of gold nanoparticles to the silver nanoparticle composite, gave a 3D printable nanocomposite with the same dichroism effect of the

Synthesis of amorphous and graphitized porous nitrogen-doped carbon spheres as oxygen reduction reaction catalysts

• Maximilian Wassner,
• Markus Eckardt,
• Andreas Reyer,
• Thomas Diemant,
• Michael S. Elsaesser,
• R. Jürgen Behm and
• Nicola Hüsing

Beilstein J. Nanotechnol. 2020, 11, 1–15, doi:10.3762/bjnano.11.1

• beneficial or disadvantageous. The degree of graphitization can be increased, e.g., by higher reaction temperatures or catalytic graphitization [31][32][33]. Previously, we had reported on core–shell titanium (oxy)nitride and tantalum (oxy)nitride@N-doped carbon composite spheres, which were based on a

• measurements under controlled electrolyte transport, employing a rotating ring disk electrode (RRDE) setup (section 2 in “Results and Discussion”). We will compare the ORR performance with those of the previously reported TiON@NCS and TaON@NCS composite materials. A more detailed account of the electrochemical

• the transport limited current cannot result from a transition from a 2-electron pathway to a 4-electron pathway with increasing overpotential. The N-doped carbon spheres investigated in the present study were previously used as conducting carbon cores for composite catalysts (summary of the results in

Advanced hybrid nanomaterials

• Andreas Taubert,
• Fabrice Leroux,
• Pierre Rabu and
• Verónica de Zea Bermudez

Beilstein J. Nanotechnol. 2019, 10, 2563–2567, doi:10.3762/bjnano.10.247

• for sensing or corrosion protection. To understand composite formation of a complex hybrid assembly, high quality characterization is paramount. An example is small angle X-ray scattering (SAXS), which was used in the work “Mechanism of silica–lysozyme composite formation unraveled by in situ fast

• ) was employed in “Topochemical engineering of composite hybrid fibers using layered double hydroxides and abietic acid” [27]. In this work, a composite hybrid was formed using cellulose fibers with LDH particles growing on their surface and then covered by abietic acid. The fibers were tested against

• a polymer shell armored with an inorganic layer (cerium oxide nanoparticles). CeO2 nanoparticles act as oxygen scavengers, protecting the organic fluorophore from molecular oxygen. A different approach to luminescent composite films is reported in “Towards rare-earth-free white light-emitting diode

Synthesis and acetone sensing properties of ZnFe₂O₄/rGO gas sensors

• Kaidi Wu,
• Yifan Luo,
• Ying Li and
• Chao Zhang

Beilstein J. Nanotechnol. 2019, 10, 2516–2526, doi:10.3762/bjnano.10.242

• about 600–1000 nm. The gas sensing test revealed that the introduction of rGO improved the performance of the sensing of acetone to low concentration, and the ZnFe2O4/rGO composite gas sensor containing 0.5 wt % of rGO exhibited a high sensitivity in sensing test using 0.8–100 ppm acetone at 200 °C. The

• rate of 5 °C/min to reduce GO to rGO [33][34], and five samples were obtained: hollow spheres of pure ZnFe2O4 and ZnFe2O4/rGO composite spheres with 0.1, 0.25, 0.5 and 1 wt % of rGO. Characterization methods The crystal phases of pure ZnFe2O4 and the ZnFe2O4/rGO composites were characterized by X-ray

• the 0.5 wt % ZnFe2O4/rGO composite. Furthermore, the composition of the sample was analyzed by high-angle annular dark-field imaging scanning transmission electron microscopy (HAADF-STEM) and EDS. The element mappings in Figure 6e reveal the existence of C, Zn, Fe and O in the 0.5 wt % ZnFe2O4/rGO

Formation of metal/semiconductor Cu–Si composite nanostructures

• Natalya V. Yumozhapova,
• Andrey V. Nomoev,
• Vyacheslav V. Syzrantsev and
• Erzhena C. Khartaeva

Beilstein J. Nanotechnol. 2019, 10, 2497–2504, doi:10.3762/bjnano.10.240

• 10.3762/bjnano.10.240 Abstract Molecular dynamics modelling of the formation of copper and silicon composite nanostructures was carried out by using the many-particle potential method. The dependences of the internal structure on the cooling rate and the ratio of elements were investigated. The

• content of 50 atom %. Additionally, an estimation of the effective experimental cooling rate was made. Keywords: composite nanoparticle; gas-phase synthesis; molecular dynamics modelling; Introduction In recent years, due to the development of various methods of synthesis, it has become possible to

• create composite Janus-like or core–shell nanoparticles. The size and the unique morphology at the nanoscale provide new optical, electronic, magnetic and surface properties to these nanoparticles [1][2]. In addition, it is possible to combine materials of which alloys do not exist in nature. The shell

Abrupt elastic-to-plastic transition in pentagonal nanowires under bending

• Sergei Vlassov,
• Magnus Mets,
• Boris Polyakov,
• Jianjun Bian,
• Leonid Dorogin and
• Vahur Zadin

Beilstein J. Nanotechnol. 2019, 10, 2468–2476, doi:10.3762/bjnano.10.237

• flexible polymer composite materials. Keywords: finite element method; mechanical properties; molecular dynamics; nanowires; Introduction Nanostructures comprised of noble metals with face centered cubic (FCC) crystal structure (Au, Ag and Cu according to the most common physical definition) prepared via

Polyvinylpyrrolidone as additive for perovskite solar cells with water and isopropanol as solvents

• Chen Du,
• Shuo Wang,
• Xu Miao,
• Wenhai Sun,
• Yu Zhu,
• Chengyan Wang and
• Ruixin Ma

Beilstein J. Nanotechnol. 2019, 10, 2374–2382, doi:10.3762/bjnano.10.228

• , enhancing composite resistance and reducing film defects. Ultimately, we achieved an outstanding photoelectric performance of the PVP-doped PSCs shown by a power conversion efficiency (PCE) of 15.19% and an average steady-state PCE of 14.55% under AM 1.5G simulated solar irradiation with a shadow mask of

• characterization methods show that PVP was effective in inhibiting the recombination of carriers, enhancing the composite resistance, reducing film defects, and boosting the photoelectric performance of the PSCs. With a PCE of 15.19% and an average steady-state PCE of 14.55% under AM 1.5G simulated solar

• five devices is reduced. A higher level of Rrec relates to a larger arcs in the figure, which suggests a smaller number of composite centers in the solar cell [35]. When the amount of PVP additive is 0.5 and 1 mg/mL, the Rrec value is greater than that of devices without PVP. In contrast, when 2 or 3

Design and facile synthesis of defect-rich C-MoS₂/rGO nanosheets for enhanced lithium–sulfur battery performance

• Chengxiang Tian,
• Juwei Wu,
• Zheng Ma,
• Bo Li,
• Pengcheng Li,
• Xiaotao Zu and
• Xia Xiang

Beilstein J. Nanotechnol. 2019, 10, 2251–2260, doi:10.3762/bjnano.10.217

• composite with both large surface area and high porosity for the use as advanced electrode material in lithium–sulfur batteries. Double modified defect-rich MoS2 nanosheets are successfully prepared by introducing reduced graphene oxide (rGO) and amorphous carbon. The conductibility of the cathodes can be

• improved through the combination of amorphous carbon and rGO, which could also limit the dissolution of polysulfides. After annealing at different temperatures, it is found that the C-MoS2/rGO-6-S composite annealed at 600 °C yields a noticeably enhanced performance of lithium–sulfur batteries, with a high

• . However, the capacity of carbon and sulfur composite cathodes generally fades rapidly during long-term cycling, because the carbon materials can provide only inferior physical adsorption to the polar Li2Sn [16]. Once Li2Sn is solvated, it dissolves easily in the electrolyte from the electrode surface and

A novel all-fiber-based LiFePO₄/Li₄Ti₅O₁₂ battery with self-standing nanofiber membrane electrodes

• Li-li Chen,
• Hua Yang,
• Mao-xiang Jing,
• Chong Han,
• Fei Chen,
• Xin-yu Hu,
• Wei-yong Yuan,
• Shan-shan Yao and
• Xiang-qian Shen

Beilstein J. Nanotechnol. 2019, 10, 2229–2237, doi:10.3762/bjnano.10.215

• to the D and the G band of carbon, respectively. The ratio of the two peaks reflects the degree of graphitization. This kind of composite not only benefits the flexibility of the fibers, but also grants good conductivity to the fibers, which is crucial for the preparation of free-standing electrodes

• , this all-fiber-based LiFePO4//Li4Ti5O12 full battery can be cycled at 1C for 800 times. Figure S2 (Supporting Information File 1) shows a photo and SEM pictures of the LiFePO4 and Li4Ti5O12 fiber membrane electrodes after the charge–discharge cycles. It can be seen that the composite electrodes still

• /Max2500X-ray diffractometer was used to determine the crystalline structure of the composite fibers. A JSM-5600LV scanning electron microscope and a JEOL JEM2010 transmission electron microscope were used to observe the morphology and microstructures of the fibers. The electrochemical performance of the

Targeted therapeutic effect against the breast cancer cell line MCF-7 with a CuFe₂O₄/silica/cisplatin nanocomposite formulation

• B. Rabindran Jermy,
• Vijaya Ravinayagam,
• Widyan A. Alamoudi,
• Dana Almohazey,
• Hatim Dafalla,
• Lina Hussain Allehaibi,
• Abdulhadi Baykal,
• Muhammet S. Toprak and
• Thirunavukkarasu Somanathan

Beilstein J. Nanotechnol. 2019, 10, 2217–2228, doi:10.3762/bjnano.10.214

• Chemistry, School of Basic Sciences, Vels Institute of Science, Technology and Advanced Studies (VISTAS), Chennai 600117, India 10.3762/bjnano.10.214 Abstract The combination of magnetic nanoparticles with a porous silica is a composite that has attracted significant attention for potential multifunctional

• –vis analysis revealed the functionalization of cisplatin in tetrahedral and octahedral coordination in the CuFe2O4/HYPS composite. Compared to other supports such as mesocellular foam and silicalite, the release of cisplatin using the dialysis membrane technique was found to be superior when CuFe2O4

• layers in the mixed metal oxide spinel composite. CuFe2O4 composite formation with activated carbon was reported using the co-precipitation technique [12][13]. Herein, we have prepared a nanocomposite comprised of CuFe2O4 and monodispersed spherical hydrophilic silica (HYPS) particles (Scheme 1) for

Use of data processing for rapid detection of the prostate-specific antigen biomarker using immunomagnetic sandwich-type sensors

• Camila A. Proença,
• Tayane A. Freitas,
• Thaísa A. Baldo,
• Elsa M. Materón,
• Flávio M. Shimizu,
• Gabriella R. Ferreira,
• Frederico L. F. Soares,
• Ronaldo C. Faria and
• Osvaldo N. Oliveira Jr.

Beilstein J. Nanotechnol. 2019, 10, 2171–2181, doi:10.3762/bjnano.10.210

• antigen-enriched calf serum were added to the composite bioconjugate complex mixture. The mixture was then incubated at 37 °C for 30 min, and dilutions were required to decrease the protein concentration. The devices were also evaluated with real samples, including culture medium of cancerous and control

Improved adsorption and degradation performance by S-doping of (001)-TiO₂

• Xiao-Yu Sun,
• Xian Zhang,
• Xiao Sun,
• Ni-Xian Qian,
• Min Wang and
• Yong-Qing Ma

Beilstein J. Nanotechnol. 2019, 10, 2116–2127, doi:10.3762/bjnano.10.206

• performance. Li et al. synthesized composites of mesoporous (001)-TiO2 and C applying a one-pot hydrothermal strategy in the presence of glucose and hydrofluoric acid (HF). The composites an exhibited excellent visible-light-driven photocatalytic performance [14]. Chen et al. synthesized a composite of g-C3N4

• -generated carriers, improve cycle stability and enhance the visible light response [17][18]. In addition to the composite two-phase approach described above, several groups reported elemental substitution in (001)-TiO2 with the aim of improving its photocatalytic performance. For example, a theoretical

Review of advanced sensor devices employing nanoarchitectonics concepts

• Katsuhiko Ariga,
• Tatsuyuki Makita,
• Masato Ito,
• Taizo Mori,
• Shun Watanabe and
• Jun Takeya

Beilstein J. Nanotechnol. 2019, 10, 2014–2030, doi:10.3762/bjnano.10.198

• composite of Co3O4 nanoparticles in black phosphorous thin films [86]. The composite structures were engineered by functionalization of black phosphorous nanosheets with branched polyethylenimine to which Co3O4 nanoparticles were included with a hydrothermal process. The sensor composite structures showed

• important targets in biosensor technology. Someya and co-workers developed a highly flexible organic amplifier to detect weak biosignals [107]. A highly conductive biocompatible gel composite made from multiwalled carbon nanotubes and aqueous hydrogel was integrated into a two-dimensional organic amplifier

Optimization and performance of nitrogen-doped carbon dots as a color conversion layer for white-LED applications

• Tugrul Guner,
• Hurriyet Yuce,
• Didem Tascioglu,
• Eren Simsek,
• Umut Savaci,
• Aziz Genc,
• Servet Turan and
• Mustafa M. Demir

Beilstein J. Nanotechnol. 2019, 10, 2004–2013, doi:10.3762/bjnano.10.197

• , Eskisehir Technical University, Eskisehir, Turkey Department of Metallurgy and Materials Engineering, Bartın University, Bartın, Turkey 10.3762/bjnano.10.197 Abstract In this study, green-emitting nitrogen-doped carbon dots (N-CDots) were synthesized and incorporated into drop-cast composite films for use

• as color conversion layers in a white-LED configuration to generate white light. In order to resolve the red deficiency of this configuration, a commercial red phosphor was integrated into the system. Moreover, the N-CDots were also processed into polymer/N-CDot composite fibers, for which we

• determined the amount of N-CDots that yielded adequate white-light properties. Finally, we showed that white light with excellent properties could be generated by employing both of the fabricated N-CDot composites either as drop-cast films or composite fibers. Hence, N-CDots provide a promising alternative

Porous silver-coated pNIPAM-co-AAc hydrogel nanocapsules

• William W. Bryan,
• Riddhiman Medhi,
• Maria D. Marquez,
• Supparesk Rittikulsittichai,
• Michael Tran and
• T. Randall Lee

Beilstein J. Nanotechnol. 2019, 10, 1973–1982, doi:10.3762/bjnano.10.194

• . The morphology and composition of the composite nanoparticles were characterized by SEM, TEM, and FTIR, respectively. UV–vis spectroscopy was used to characterize the optical properties. Keywords: hydrogels; nanocapsules; photothermal delivery; poly(NIPAM); porous silver shells; Introduction

Facile synthesis of carbon nanotube-supported NiO//Fe₂O₃ for all-solid-state supercapacitors

• Shengming Zhang,
• Xuhui Wang,
• Yan Li,
• Xuemei Mu,
• Yaxiong Zhang,
• Jingwei Du,
• Guo Liu,
• Xiaohui Hua,
• Yingzhuo Sheng,
• Erqing Xie and
• Zhenxing Zhang

Beilstein J. Nanotechnol. 2019, 10, 1923–1932, doi:10.3762/bjnano.10.188

• . deposited iron oxide on CNTs by atomic layer deposition (ALD) and the obtained CNTs@Fe2O3 presented a specific capacitance of 580.6 F·g−1 at 5 A·g−1 [21]. Zhang et al. used magnetron sputtering to prepare sandwich-like CNT@Fe2O3@C structures, and the composite exhibited a specific capacitance of 787.5 F·g−1

• to C–O and Ni–O, respectively [36]. The XPS results strongly support XRD and Raman results and confirm that NiO formed on the CC-CNT substrate, suggesting the universality of this aqueous reduction method to prepare CNT-based metal oxide composite. The electrochemical performance of the CC-CNT@NiO

Prestress-loading effect on the current–voltage characteristics of a piezoelectric p–n junction together with the corresponding mechanical tuning laws

• Wanli Yang,
• Shuaiqi Fan,
• Yuxing Liang and
• Yuantai Hu

Beilstein J. Nanotechnol. 2019, 10, 1833–1843, doi:10.3762/bjnano.10.178

• been investigated by Dai et al. [24] and Yang and co-workers [25]. The mechanical behavior of composite fibers with piezoelectric dielectrics and non-piezoelectric semiconductors have also been studied by Cheng et al. [26] and Luo and co-workers [27]. For piezoelectric p–n junctions, it becomes

Nanoarchitectonics meets cell surface engineering: shape recognition of human cells by halloysite-doped silica cell imprints

• Elvira Rozhina,
• Ilnur Ishmukhametov,
• Svetlana Batasheva,
• Farida Akhatova and
• Rawil Fakhrullin

Beilstein J. Nanotechnol. 2019, 10, 1818–1825, doi:10.3762/bjnano.10.176

• eukaryotic cells [3]. In particular, nanostructured composite shells (both hard and soft) deposited onto live cells have been shown to render the cells with novel mechanic and chemical functionalities [4][5][6]. In line with the concepts of nanoarchitectonics, cell surface engineering relies on the self

• of various functional composite materials [26]. The anisotropic shape (hollow tubules having lengths from 300 nm to 1–2 µm, 50–70 nm diameter, and 20 nm lumen) and surface chemistry (outer surface of SiO2, inner surface of Al2O3) make these nanotubes ideal carriers for novel catalysts, polymer

• comparable sizes such as yeast cells. Results and Discussion Our experimental strategy is schematically depicted in Figure 1. Following the nanoarchitectonics paradigm [35], we produced composite inorganic shells around human HeLa cells, using a polyelectrolyte nanolayer as a means to facilitate the

Growth dynamics and light scattering of gold nanoparticles in situ synthesized at high concentration in thin polymer films

• Corentin Guyot,
• Philippe Vandestrick,
• Ingrid Marenne,
• Olivier Deparis and
• Michel Voué

Beilstein J. Nanotechnol. 2019, 10, 1768–1777, doi:10.3762/bjnano.10.172

• in the composite less than 1%, the effect of doping is usually not detected experimentally using MG-EMA when the optical measurements are carried out out-of-resonance. This effect has been modeled in Supporting Information File Supporting Information File 1. Moreover, going from standard ellipsometry

TiO₂/GO-coated functional separator to suppress polysulfide migration in lithium–sulfur batteries

• Ning Liu,
• Lu Wang,
• Taizhe Tan,
• Yan Zhao and
• Yongguang Zhang

Beilstein J. Nanotechnol. 2019, 10, 1726–1736, doi:10.3762/bjnano.10.168

• but suffer from poor cyclic performance due to the dissolution of intermediate polysulfides. Herein, a lightweight nanoporous TiO2 and graphene oxide (GO) composite is prepared and utilized as an interlayer between a Li anode and a sulfur cathode to suppress the polysulfide migration and improve the

• capacity of 843.4 mAh g−1, which corresponds to a capacity retention of 76.48% at a current rate of 0.2 C. Moreover, the Li/S battery with the TiO2/GO-coated separator showed superior cyclic performance and excellent rate capability, which shows the promise of the TiO2/GO composite in next-generation Li/S

• batteries. Keywords: dealloying; functional separator; lithium–sulfur batteries; TiO2/GO composite; Introduction The portability of handheld electronic products and successful realization of next-generation electric vehicles urgently require advanced energy storage devices with higher storage capacity and

High-temperature resistive gas sensors based on ZnO/SiC nanocomposites

• Vadim B. Platonov,
• Marina N. Rumyantseva,
• Alexander S. Frolov,
• Alexey D. Yapryntsev and
• Alexander M. Gaskov

Beilstein J. Nanotechnol. 2019, 10, 1537–1547, doi:10.3762/bjnano.10.151

• composite nanomaterials using highly dispersed silicon carbide (SiC). The unique physical and chemical properties of silicon carbide – wide band gap (Eg = 2.4–3.2 eV), high Debye temperature 1400 K, high thermal conductivity of 4.9 W/cm·K, low reactivity to oxygen and water vapor – ensure the stability of

• composite materials with respect to temperature, radiation, chemical and mechanical effects [6][7]. It has been shown that in MO/SiC nanocomposites containing metal oxide (MO) and nanostructured SiC, the presence of silicon carbide inhibits the growth of MO crystallites at high temperatures [8]. The

• difference in the adsorption properties, reactivity and electrical behavior of semiconductor oxides and silicon carbide, as well as possible chemical interactions on their interface, cause changes in the sensor performance of composite materials. The SiC-based materials in the form of planar Pt/MO/SiC

Flexible freestanding MoS₂-based composite paper for energy conversion and storage

• Florian Zoller,
• Jan Luxa,
• Thomas Bein,
• Dina Fattakhova-Rohlfing,
• Daniel Bouša and
• Zdeněk Sofer

Beilstein J. Nanotechnol. 2019, 10, 1488–1496, doi:10.3762/bjnano.10.147

• flexible MoS2-based composite paper by high-energy shear force milling and simple vacuum filtration. This composite material combines high flexibility, mechanical strength and good chemical stability. Chronopotentiometric charge–discharge measurements were used to determine the capacitance of our paper

• and delivers specific capacity of 740 mA·h·g−1 at a current density of 0.1 A·g−1. After 40 cycles at this current density the material still reached a capacity retention of 91%. Our findings show that this composite material could find application in electrochemical energy storage and generation

• active material and the current collector upon bending deformation [10]. However, there are promising reports on freestanding MoS2/carbonaceous composite electrodes which have demonstrated attractive electrochemical performance [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Beside

Magnetic segregation effect in liquid crystals doped with carbon nanotubes

• Danil A. Petrov,
• Pavel K. Skokov,
• Alexander N. Zakhlevnykh and
• Dmitriy V. Makarov

Beilstein J. Nanotechnol. 2019, 10, 1464–1474, doi:10.3762/bjnano.10.145

• intensity of the impurity subsystem. The optical phase lag between ordinary and extraordinary rays of light transmitted through a layer of a liquid crystal composite is calculated. The possibility of changing the nature of the Fréedericksz transition from second order to first order is shown. This

• composite materials capable of spontaneous ordering are interesting due to the fact that their properties are determined by the interactions between the embedded nanoparticles and the carrier matrix. The properties of LC mixtures with nanoparticles substantially depend on the material of the particles

• , their shape, size, and concentration. Anisometric particles are oriented in the LC matrix, which leads to significant changes in the electro- and magneto-optical response of the composite material. Nanoparticles placed in an LC enhance many physical properties, such as susceptibility to external fields