Properties Of Liquid Crystals Research Articles

Asymmetrical liquid crystals synthesis for effective sensing: Fluorescence investigations

Currently, a new set of asymmetrical dimeric molecules with a Schiff-base at one end and a chalcone alkali substitution by di-ether are made and their liquid crystal and fluorescence properties are investigated. The proposed chemical structure was confirmed by routine analytical methods using FT-IR and NMR spectroscopy. Additionally, polarized optical microscopy (POM); was used to assess the pointed compounds' liquid crystalline characteristics, while differential scanning calorimetry (DSC); was employed to confirm the compounds' transitions. The results report the length of the alkali chain at one end of the molecule is critical to the creation of the mesophase type. Compounds with medium-length chains exhibit nematic mesophases with moderate transition temperatures. The fluorescence of compounds was analyzed, with blue-emitting results indicating the presence of blue-light-emitting features. The 10a had higher ɛ; as well as red-shifted λmax; and Fmax; compared to the others and has blue light emission properties. Eventually; the expanding range of possible uses to include OLED material and fluorescent probes for sensing applications.

Effect of substituents on the properties of fluorine-containing polyphenyl liquid crystal compounds

In order to explore the influence of molecular structure on the properties of liquid crystal (LC) materials, the dielectric anisotropy, rotational viscosity coefficient and birefringence of different fluorine-containing polyphenyl LC compounds are measured experimentally. The effects of lateral substituents and terminal substituents are analyzed. The experimental results show that the substitution of fluorine substituents in lateral substituents or terminal substituents will lead to the decrease of rotational viscosity coefficient, whether it is fluorine-containing triphenyl LC compounds or fluorine-containing tetraphenyl LC compounds. The dielectric anisotropies of LC compounds (fluorine-containing tetraphenyl LC compounds ND-3 and ND-8, ND-4 and ND-9, and ND-1 and ND-10) in which the terminal isothiocyano substituents are substituted by fluorine substituents all show a downward trend, with the decreasing degrees of 41.3%, 20.7% and 19.2% respectively. In addition to the influence of the replacement of fluorine and isothiocyanato on the terminal substituents, the dielectric anisotropy is affected by different lateral substituents from large to small: fluorine, methyl, and ethyl. The lateral fluorine substitution impact of ND-3, with an increase of 9.4%, is the best among fluorine-containing tetraphenyl LC compounds when compared to the lateral ethyl substitution of ND-2. Besides, compared with -F, -NCS can effectively extend the π-electron conjugation length of the molecule and improve the birefringence of the LC. This research is of great help to improve the comprehensive properties of LC materials and provides data accumulation for the development and application of LC compounds.

Synthesis and characterisation of chiral liquid crystal compounds containing cholesterol and D(+)-camphoric acid

ABSTRACT Two series of chiral liquid crystal compounds were synthesised from benzoic acid containing cholesterol with different carbon-chain lengths and bisphenol monoester containing camphoric acid with different carbon-chain lengths, named BCP-C and DCP-C. The structure of the monomers is characterised by IR, 1H NMR and 13C NMR, which indicate that the synthesised molecule conforms to the molecular design. The textures of monomers were characterised by POM, and their selective reflection was studied. It was found that the synthesised liquid crystal compounds exhibited good liquid crystal and optical properties. The phase transition behaviour was characterised using DSC, and the results were consistent with those observed by POM. TGA showed that they had good thermal stability.

Synthesis and mesomorphic properties of bent liquid crystals containing triazole mesogenic unit with terminal flexible alkyl chain and laterally ethoxy substituted Schiff base

ABSTRACT A new series of bent-shaped liquid crystals containing a triazole ring were synthesised and characterised at ambient and elevated temperatures. The triazole-cored and bent liquid crystals possess a flexible alkyl chain at one terminal, while the other side of the core is connected by a laterally ethoxy Schiff base consisting of a CN-biphenyl moiety. The evaluation on optical and thermal properties was carried out by polarising optical microscope and differential scanning microscope which revealed the length of the alkyl chain, –CnH2n + 1, that influenced the mesophase and the related clearing temperatures (Tc). Whilst the compounds with higher number of n possess lower Tc points, the presence of SmA phase seemed to be more favourable for the compounds in which the alkyl chain length was n ≥ 12. This observation can be associated with its bending angle and charge distributions along the two arms of which the interaction between the opposite counterparts of both arms in these bent-liquid crystals would promote the formation of SmA phase. The computational calculations based on density functional theory were performed to further support the transition from non-mesomorphic to SmA phases upon the increase in alkyl chain length (n), dipole moment and polarity which contribute to its stability.

Introduction of CdSe/ZnS Quantum Dots into Liquid Crystalline Matrix

An important aspect of modern materials science, namely the possibility of combining inorganic nanoparticles and liquid crystals in composite materials is discussed. These systems make it possible to combine liquid crystal properties of matrix and luminescent properties of quantum dots. A five-component mixture consisting mainly of 4-cyanobiphenyl derivatives used as a matrix. The substitution of ligands formed during the synthesis of quantum dots with derivatives of organic acids is shown. Using two new optically active ligands, the chiralization of the nematic matrix was demonstrated by introducing quantum dots into it.

A hybrid ionic liquid crystal comprising imidazolium surfactant-graphene oxide

ABSTRACT To produce graphene oxide liquid crystal composites with better controllability, imidazolium surfactant with biphenyl mesogenic core (CBphCM) has been synthesised and used to modify the negatively charged surface of graphene oxide (GO) to obtain a hybrid ionic liquid crystal (CBphCM-GO). The process of GO and CBphCM recombination was monitored by various experimental techniques such as FT-IR, Uv-vis, Raman and XPS. The experimental results indicated that the C=O bonds on GO sheets are all reduced and C−O bonds are partially reduced due to the imidazolium units being electrically active and nitrogen-rich, and the presence of the N−O bonds indicates that a new hybrid is formed between CBphCM and GO. The recombination destroys the electrostatic repulsion balance among the GO lattices, and the CBphCM-GO is observed a fluffy appearance by TEM. The liquid crystal properties of CBphCM and CBphCM-GO were investigated by DSC, polarised optical microscopy (POM) and variable temperature X-ray diffraction, respectively. As an ionic liquid crystal, CBphCM has SmA as well as the rare SmC phases exhibits de Vries-like behaviour with a layer shrinkage. The liquid crystal properties of CBphCM-GO are derived from CBphCM, and the layer shrinkage behaviour from SmA to SmC phase has also been observed.

Exceptional points and lines and Dirac points and lines in magnetoactive cholesteric liquid crystals

We investigated the properties of cholesteric liquid crystals (CLCs) being in external static magnetic field directed along the helix axis. We have shown that in the case of the wavelength dependence of magneto-optic activity parameter, and in the presence of absorption new features appear in the optics of CLCs. We have shown that in this case new photonic band gaps (PBGs) appear. This new PBG is sensitive to the polarization of the incident light. But if the chirality sign of the polarization of the incident diffracting light for the basic PBG (which exist also at the absence of external magnetic field) is determined only by the chirality sign of the CLC helix, then for the second one it is determined by the external magnetic field direction (i.e., on whether the directions of the external magnetic field and the incident light are parallel, or they are antiparallel). We have shown that in this case besides Dirac points there appear also Dirac lines as well as exceptional points and exceptional lines. And moreover, near some of these points and lines the narrow bands or wide bands of magnetically induced transparency, and magnetically induced absorption appear, and near the others a wide coherent perfect absorption band appears that is insensitive to incident light polarization. And finally at some wavelength the same reflection, transmission and absorption takes place for any polarization of incident light, although it is not Dirac point nor exceptional point. This system can apply as tunable narrow-band or broad-band filters and mirrors, a highly tunable broad/narrow-band coherent perfect absorber, transmitter, ideal optical diode, and other devices.

Dynamic tunable narrow-band perfect absorber for fiber -optic communication band based on liquid crystal

At present, most of the reported metasurface structure absorbers show that its working band cannot be regulated actively. In this study, a dynamic tunable narrow-band perfect absorption structure for fiber-optic communication band based on liquid crystal (LC) is proposed and studied. The structure is mainly composed of two effective tiers. The top tier gold array and the bottom tier reflective gold film, which are separated by a SiO2-LC dielectric medium interlayer to form a metal–dielectric–metal structure. Due to the unique optical properties of LCs, its index of refraction can be changed by adjusting the bias voltage and temperature, so as to adjust the resonance wavelength actively. The designed structure is analyzed by finite element method and the coupled mode theory is used to verify the analysis results. The designed structure has a 99.92% absorption effect in the most commonly used band of fiber-optic communication. Due to the symmetry of the absorber structure, the device is not sensitive to the polarization state of the excitation source. Moreover, the absorber exhibits an unusual dependence on the incident angle, which can be attributed to the anisotropy of the LC. Based on the dependence of incident angle, a plasma optical switch with large ON/OFF ratio (η) of 27.395 dB and nearly flawless modulation depth of 99.818% can be realized. It is believed that this structure can provide a method for the dynamic control of near infrared electromagnetic waves, and to be applied in electromagnetic energy absorption, filtering and plasma optical switch system.

Changes in molecular relaxations and network properties of a triaromatic liquid crystal epoxy resin with nonterminal functional groups

AbstractTwo types of liquid crystal epoxy precursors and corresponding epoxy‐amine networks are investigated in this paper. The epoxy groups are non‐terminal in one of the monomers (NTEM) and terminal in the other one (MU22). Both monomers contain the same mesogen and exhibit liquid crystal properties. Structural differences between the carbon chains affect physical properties of the monomers and the products of curing, which involves a typical diamine—DDM (4,4′‐diaminodiphenylmethane). Phase transition temperatures, conditions of the curing reaction and glass transition temperatures in the cured products are determined through differential scanning calorimetry (DSC), optical observations (POM) and broadband dielectric spectroscopy (BDS). The modification of the carbon chains affects the phase transition temperatures, dielectric response, and the glass transition in the cured products. The dielectric response of NTEM monomer reveals two relaxation processes (β and γ) associated with molecular motions of polar groups in the mesogen (β‐process) and in the carbon chains (γ‐process). In contrast, MU22 only displays a similar β‐process. A segmental α‐process related to structural reorientation (connected with glass transition) appears in both cured products, but in NTEM the glass transition temperature is significantly lower. Local relaxations in the epoxy networks match the corresponding processes in their respective precursors.

The relaxation dynamics and dielectric properties of cyanobiphenyl-based nematic tripod liquid crystals

We present a detailed investigation of the phase behaviour, molecular relaxation dynamics, rheology and dielectric properties of two cyanobiphenyl-based liquid crystal (LC) tripods, differing only in the length of their spacer units (6 or 9 carbons). These LC tripods combine properties of low molecular weight LCs and LC polymers, resulting in a range of advantageous properties including a wide nematic range (ΔT>90 K) and a large birefringence (0.3 at T−TNI=-80 K for the 6 spacer tripod). Using broadband dielectric relaxation spectroscopy, calorimetry, oscillatory and steady state shear rheology, we identified four molecular relaxation processes: the structural (α) relaxation (defining the glass transition temperature, Tg); the δ relaxation (reorientation of the mesogen unit around its short axis); the β relaxation (reorientation around its long axis); and the γ relaxation (internal tripod arm fluctuations). The β and γ relaxations follow Arrhenius temperature dependencies in the glass, whereas the α and δ relaxations merge above, but near Tg, where they follow a non-Arrhenius VFT behaviour. For higher temperatures, the two relaxations separate and for T>T⁎, where T⁎ marks a dynamic crossover, the α relaxation transitions from VFT to Arrhenius behaviour. For the two tripods, ratios of T⁎/Tg=1.14 and T⁎/Tg=1.13 were observed respectively, consistent with the ratio observed for many side-chain LC polymers (and other LC systems), and consistent with the ratio where a dynamic crossover is typically observed also for non-LC glass-formers. However, for non-LC systems, the transition to Arrhenius behaviour happens at significantly higher temperatures relative to Tg and the dynamic crossover at T⁎ is typically observed as a transition between two different VFT behaviours. We argue that for the tripods these differences arise from differences in the molecular relaxation mechanisms induced by the LC order. Finally, for temperatures where δ and α relaxations are separated, we find that ion conductivity decouples from the α relaxation, instead following the δ relaxation; this demonstrates that the ion transport properties for the tripods can be tuned by the design of the tripod mesogen arm.

Synthesis and characterization of biowaste-based porous carbon nanoparticle-polymer dispersed ferroelectric liquid crystal composites

Herein, porous carbon nanoparticles (PCNPs) were synthesized using magnolia champaca seed pods and studied their doping effect on the polymer-dispersed ferroelectric liquid crystal (PDFLC) properties. The effect of PCNPs concentration (≤0.75 wt.%) on the morphology of PDFLC, polarization, and permittivity are investigated in thin sample cells. Field emission scanning electron microscope image results indicate the spherical shape of PCNPs of particle size ∼27 nm diameter. Temperature-dependent electro-optic and dielectric properties are also investigated in the wide SmC* phase and near transition temperature of SmC*-SmA*. Polarising optical microscope textures confirm the non-homogeneity of FLC molecules in the polymer matrix as a function of PCNPs concentration. Thespontaneous polarization and anchoring energy coefficients increase with increasing the doping amount of PCNPs.The phase transition temperature is found unaffected by PCNP doping in all prepared samples. In PDFLC and PCNPs doped PDFLC composites, usualbehaviourof permittivity as a function of temperature is observed. Fluorescence spectra show an enhanced two-fold increase in emission intensity peak at 412 nm wavelength for 0.5 wt.% PCNPs doped PDFLC while concentration-dependent quenching and slight redshift have been observed for the 0.75 wt.% PCNPs doped PDFLC. The enhanced electro-optic and dielectric properties observed in the composites suggest potential applications in displays, sensors, and optical devices. The findings open doors for further exploration and utilization of these functional materials in advanced electronic and photonic technologies.

Thermomechanical Coupling in Polydomain Liquid Crystal Elastomers

Abstract Liquid crystal elastomers (LCEs) are made of liquid crystal molecules integrated with rubber-like polymer networks. An LCE exhibits both the thermotropic property of liquid crystals and the large deformation of elastomers. It can be monodomain or polydomain in the nematic phase and transforms to an isotropic phase at elevated temperature. These features have enabled various new applications of LCEs in robotics and other fields. However, despite substantial research and development in recent years, thermomechanical coupling in polydomain LCEs remains poorly studied, such as their temperature-dependent mechanical response and stretch-influenced isotropic-nematic phase transition. This knowledge gap severely limits the fundamental understanding of the structure-property relationship, as well as future developments of LCEs with precisely controlled material behaviors. Here, we construct a theoretical model to investigate the thermomechanical coupling in polydomain LCEs. The model includes a quasi-convex elastic energy of the polymer network and a free energy of mesogens. We study the working conditions where a polydomain LCE is subjected to various prescribed planar stretches and temperatures. The quasi-convex elastic energy enables a “mechanical phase diagram” that describes the macroscopic effective mechanical response of the material, and the free energy of mesogens governs their first-order nematic-isotropic phase transition. The evolution of the mechanical phase diagram and the order parameter with temperature is predicted and discussed. Unique temperature-dependent mechanical behaviors of the polydomain LCE that have never been reported before are shown in their stress-stretch curves. These results are hoped to motivate future fundamental studies and new applications of thermomechanical LCEs.

Composite stability and electro-optical properties of carbon nanotubes/5CB-based nematic hybrid liquid crystals

ABSTRACT This study examined the impact of different concentrations of carbon nanotubes (CNTs) on five nematic hybrid liquid crystals (LCs) based on 5CB. Electro-optical properties of the composite were tested, and the interaction between CNTs and LCs was theoretically analysed by first principles. Experimental results showed the effect of CNTs on electro-optical properties of hybrid LCs depended on the groups contained in monomer LCs. LCs with polar groups at the end increased the dielectric anisotropy of the composite, while the impact of CNTs on hybrid LCs containing non-polar terminal monomers was the opposite. The same variation was reflected in splay elastic constants and clearing points. Meanwhile, dielectric anisotropy, splay elastic constant, and rotational viscosity coefficients all changed with CNTs doping concentrations, reflecting the order of binding stability between representative groups and CNTs, and the variation of threshold voltage and response time reflected the order of binding stability between LC molecules and CNTs, consistent with theoretical calculations. Conductivity tests showed the additive of CNTs increased the conductivity of the composite and revealed the impact of CNTs on threshold voltage. Dielectric tests showed the incorporation of CNTs increased dielectric real and imaginary parts in low-frequency regions and increased relaxation frequency in high-frequency regions.

Novel star-shaped liquid crystal macromolecules based on conjugated structures of azo and Schiff bases: synthesis and properties

ABSTRACT In this paper, a series of novel liquid crystal units (ASE-n, n = 4, 6, 8) of azo Schiff bases with sulphonic acid (-SO3H) as terminal substituents and different alkyl chain lengths were designed and synthesised. Nine star-shaped liquid crystal macromolecules with different central groups (ASE-P-n, ASE-T-n, ASE-G-n, n = 4, 6, 8) were synthesised by esterification of three novel azo Schiff base liquid crystal units (ASE-n, n = 4, 6, 8) with phloroglucinol, pentaerythritol and glucose. The structure of the synthesised compounds were analysed by infrared spectroscopy and 1H NMR. The results showed that all the compounds were consistent with the molecular structure design. The properties of liquid crystal such as phase transition temperature and liquid crystal mesophase range were characterised by POM and DSC. The effects of alkyl chain length and branched degree on the properties of liquid crystal were studied. The maximum absorption spectrum of the compound was determined by UV-Vis spectrophotometry. The photoisomerisation reaction of the compound was also studied. Under ultraviolet light (λ = 365 nm) irradiation, the effect of different duration on the cis-absorption percentage of azo (-N=N-) bond in the compound was studied.

Thermoresponsive cholesteric liquid–crystal systems doped with terpenoids as drug delivery systems for skin applications

Stimuli-responsive and tunable soft-matter systems are an advanced class of materials applicable for drug delivery. Liquid crystals (LCs) are promising candidates as multifunctional materials that can respond to temperature, light or magnetic field. Particularly, ordering and physical properties of thermoresponsive LCs depend predominantly on temperature as external trigger. The current work addresses an elegant strategy to implement the anisotropic properties of thermoresponsive LCs with a view to extending their application for drug delivery. We firstly fabricated novel compositions with a thermotropic core based on natural products – cholesteryl esters and mono-/bicyclic terpenoids. The distinctive feature of aforementioned systems is their temperature-induced switchability of drug release by transition to the LC state, depending on the skin temperature. Their mesomorphic and optical behavior was characterized via differential scanning calorimetry and polarizing optical microscopy. Furthermore, we describe the dependence of helical pitch on LC formulation for various ternary cholesteric systems doped with terpenoids, suggesting that these stimuli-responsive chiral dopants are nominally untwisting. Data from fluorescence probe technique indicate that cholesteryl esters and terpenoids as essential components of those LC systems jointly disrupt the tight structure of phospholipid bilayer packing enabling the facilitated penetration of drugs. The potential of LC formulations was explored for several model drugs with diverse physicochemical properties by in vitro and ex vivo penetration tests using artificial membranes and full human skin. Our findings confirm the potential of LC systems for various applications in skin drug delivery.

Hydrogen bond ferroelectric liquid crystal for tripartite temperature sensor: Experimental and computational (DFT) studies

The mesogenic behavior and electronic properties of hydrogen bond ferroelectric liquid crystal (HBFLC) complex are studied using experimental and theoretical techniques. HBFLC complex is synthesized from mesogenic 4-hexyloxy benzoic acid (6O BA) as the proton donor and nonmesogenic chiral DL-tartaric acid (DLTA) as the proton acceptor through intermolecular hydrogen bonding. Molecular geometry of DLTA+6O BA HBFLC complex is optimized by density functional theory (DFT) calculation. An interesting observation is that polarizing optical microscope (POM) study confirms that the HBFLC complex exhibits thermochromic behavior in chiral nematic (N[Formula: see text] along with induced nontitled smectic G* phases. Another noteworthy observation is the manifestation of tripartite temperature stages. Fourier-transform infrared spectroscopy (FTIR) and natural bond orbital (NBO) analysis elucidate the intermolecular hydrogen bond between mesogenic (6O BA) and nonmesogenic (DLTA) compounds. Further, frontier molecular orbital (FMO) study and electrostatic potential (ESP) analysis explore the reactivity sites, intermolecular charge transfer and electronic behavior of HBFLC complex.

Dirac points, new photonic band gaps, and effect of magnetically induced transparency in dichroic cholesteric liquid crystals with wavelength-dependent magneto-optical activity parameter.

We investigated the properties of cholesteric liquid crystals (CLCs) being in an external static magnetic field directed along the helix axis. We considered a dichroic CLC, that is, CLC with parameters ReΔ=Reɛ_{1}-Reɛ_{2}/2=0 and ImΔ=Imɛ_{1}-Imɛ_{2}/2≠0, where ɛ_{1,2} are the principal values of the local dielectric permittivity tensor. We have shown that in the case of the wavelength dependence of the magneto-optic activity parameter, new features appear in the optics of dichroic CLCs, in particular, in this case new Dirac points appear. Dirac points are points where there is an intersection of any two wave vector curves (they degenerate) and a linear law of the wave vector dependence on the frequency near these points. And moreover, at some Dirac points photonic band gaps (PBGs) appear; at others, lines of magnetically induced transparency (MIT), that is, a full transmission band appears, in an absorbing medium. In this case a polarization-sensitive transmission band appears too. At certain values of the helix pitch of the CLC and of the magnitude of the external magnetic field, three PBGs of different nature appear: a transmittance band, two narrow lines of MIT, and at others a broadband MIT, etc. This system is nonreciprocal, and the nonreciprocity changes over a wide range. It is observed both for reflection and transmittance and for absorption. The soft-matter nature of CLCs and their response to external influences lead to easily tunable multifunctional devices that can find a variety of applications. They can be applied as tunable narrow-band or broadband filters and mirrors, a highly tunable broad/narrow-band coherent perfect absorber, transmitter, ideal optical diode, and in other devices.

Multicomponent structural color membrane based on soft lithography array for high-sensitive Raman detection

Inspired by ordered photonic crystals and structural color materials in nature, we successfully prepared hydroxypropyl cellulose (HPC) photonic films with ordered surface arrays by double-imprint soft lithography. Then we introduced another important material of the cellulose family, cellulose nanocrystals (CNC), which has liquid crystal nature and birefringent properties of the particles, into the system to realize the single-point shrinkage of the film array and the control of structural color. Through multi-component doping and concentration control, we further optimized the multi-scale structure of the materials, and obtained HPC/CNCs composite photonic films with excellent properties in color, stability and flexibility, whose elastic modulus and tensile properties are significantly higher than those of single-component. Further loading of SiO2@PDA enhances the color saturation and realizes the in-situ reduction of metal ions on the film surface. This plasma film can track a variety of substances with high sensitivity and long-term stability, showing potential application prospects in the field of surface-enhanced Raman scattering (SERS), which provides a potential possibility for chiral structures to be used in the field of biosensor detection and circularly polarized luminescence.

The effect of surfaces on the structural properties of liquid crystals

The effect of the surface microrelief on the structural properties of both the nematic and smectic A (SmA) phases, and the effect of the emerging smectic structure induced by the surface at temperatures close to the second-order nematic-SmA (NA) phase transition temperature TNA, on the Freedericksz threshold voltage for homogeneously aligned polar liquid crystals, is theoretically analyzed.It is shown that the orientation distortion of the director field caused by the wave-like microrelief on solid surfaces exponentially decays in the bulk of both phases. Since in the case of the SmA phase, the characteristic depth of deformation is comparable to the length of the molecule, then when the period of undulating relief passes several micrometers, the depth of penetration of the deformation is several tens of micrometers. This is two orders of magnitude greater than the penetration length of the distortion in the case of the nematic phase.The effect of the surface-induced SmA phase on the threshold voltage, for homogeneously aligned of polar liquid crystals is discussed from the energy point of view. It is shown that the Freedericksz critical voltage, for 4-n-octyl-4′-cyanobiphenyl, in a very thin cell near the second-order nematic-SmA (NA) phase transition temperature, exhibits an anomalous increase with decreasing of temperature T towards TNA.

Liquid crystal biosensor based on AuNPs signal amplification for detection of human chorionic gonadotropin

The detection of human chorionic gonadotropin (HCG) allows for the determination of pregnancy and is thus crucial during early pregnancy testing. This study introduces a novel liquid crystal (LC) biosensor that employs Au nanoparticles (AuNPs) for signal amplification, thus enabling the detection of the HCG antigen in a micro, efficient, and cost-effective manner. The sensor design capitalizes on the unique properties of LC to facilitate the detection of HCG. In this research, the surface of the base substrate was first modified with material from DMOAP and APTES, and EDC/sulfo-NHS was used to couple AuNPs and β-hCG to form an AuNP-β-hCG conjugate that improves the coupling rate. The carboxyl group of the antibody was reacted with the aldehyde group of glutaraldehyde, which helps to fix the β-hCG antibody to the surface of the substrate. The HCG sample is immobilized on the surface of the substrate via antigen-antibody immunobinding. As signal amplifiers, the AuNPs can have a significant effect on the topology of the interface and the vertical order of the LC molecules, thus reducing the limit of detection. Finally, the limit of detection was calculated using the SPSS system, and the relationship between grey values and concentrations was also obtained. The detection limit for HCG can be as low as 1.916 × 10−3 mIU·mL−1 under ideal conditions. Compared to other detection methods for HCG, this structure provides a detection pathway with excellent sensitivity, low detection limits, and better specificity, thus offering a new idea for HCG or any other target requiring trace detection.