A self-aligned assembling terahertz metasurface microfluidic sensor for liquid detection.

This paper reports a new terahertz metasurface microfluidic sensor, which is actually a kind of reflective terahertz metasurface absorber with a microfluidic-channel structure located in the strong field energy region of the absorber. The metasurface structure is made on an ultra-thin quartz substrate as the cap layer, while a two-step structure is made on a silicon substrate as the pedestal layer. In order to precisely control the thickness of the microfluidic channel, the cap layer is self-aligned assembled with the pedestal layer to form the terahertz metasurface microfluidic sensor. The obtained sensor could enhance the light-matter interaction, resulting in high sensing performance. The measured results show that the sensor has a perfect absorption peak at 2.60 THz and a high Q-factor of 62.59, which are basically consistent with the simulated results. The sensitivity and FOM calculated based on the measured results of different liquids with different refractive indices is 0.733 THz per RIU and 16.4, respectively. Compared with some recently related work, the sensitivity is increased by about 40%, the Q-factor is increased by 3-5 times, and the FOM is increased by 5 times, which make the sensor have great application potential for solution detection in the terahertz frequency band.

Optical metasurfaces for multiplex high-performance grating-type structural colors.

Optical metasurfaces provide a significant approach for the production of structural colors due to their excellent optical control abilities. Herein, we propose trapezoidal structural metasurfaces for achieving multiplex grating-type structural colors with high comprehensive performance originating from the anomalous reflection dispersion in the visible band. Single trapezoidal metasurfaces with different x-direction periods can tune the angular dispersion regularly from 0.036 rad/nm to 0.224 rad/nm to generate various structural colors, and composite trapezoidal metasurfaces with three kinds of combinations can achieve multiplex sets of structural colors. The brightness can be controlled by adjusting the distance between the trapezoids in a pair accurately. The designed structural colors have higher saturation than traditional pigmentary colors, whose excitation purity can reach 1.00. The gamut is about 158.1% of the Adobe RGB standard. This research has application potential in ultrafine displays, information encryption, optical storage, and anti-counterfeit tagging.

Dimethyl 3,3'-[(4-nitro-phen-yl)methyl-ene]bis-(1H-indole-2-carboxyl-ate) ethanol hemisolvate.

There are two main molecules in asymmetric unit of the title compound, C27H21N3O6·0.5C2H5OH. In both, the indole ring systems are approximately perpendicular to each other, at dihedral angles of 69.3 (5) and 82.8(4)°. In the crystal, mol-ecules are linked by N-H⋯O and O-H⋯O hydrogen bonds into a three-dimensional supra-molecular architecture. The solvent ethanol mol-ecule acts as a donor, forming an O-H⋯O hydrogen bond, reinforcing the structure.

7,8-Dimethyl-11H-indeno-[1,2-b]quinoxalin-11-one.

In the title compound, C17H12N2O, the mean planes of the indene ring and quinoxaline system (r.m.s. deviations = 0.0131 and 0.0082 Å) are approximately parallel to one another, making a dihedral angle of 1.2 (5)°. This means that the indeno-[1,2-b]quinoxaline ring is almost in the same plane (r.m.s. deviation = 0.0181 Å).

11,11-Diphenyl-11H-indeno-[1,2-b]quinoxaline.

In the title compound, C27H18N2, the mean planes of the pendant benzene rings are approximately perpendicular to one another, making a dihedral angle of 79.3 (5)°; the indeno-[1,2-b]quinoxaline ring system (r.m.s. deviation = 0.1197 Å) is twisted with respect to the pendant benzene rings by 70.0 (4) and 67.6 (3)°. Weak aromatic π-π stacking [centroid-centroid separation = 3.628 (2) Å] and C-H⋯π inter-actions occur in the crystal.

Diethyl 3,3'-[(3-fluoro-phen-yl)methyl-ene]bis-(1H-indole-2-carboxyl-ate).

In the title compound, C29H25FN2O4, the mean planes of the indole ring systems are approximately perpendicular to one another [dihedral angle = 88.3 (4)°]. The benzene ring is twisted with respect to the indole ring systems by 49.8 (5) and 77.6 (3)°. In the crystal, pairs of N-H⋯O hydrogen bonds link the mol-ecules into the inversion dimers which are further linked into supra-molecular chains propagating along the [110] direction.

Crystal structure of diethyl 3,3'-[(2,4-di-chloro-phen-yl)methyl-idene]bis-(1H-indole-2-carboxyl-ate).

In the title compound, C29H24Cl2N2O4, the mean planes of the two indole ring systems (r.m.s. deviations = 0.1249 and 0.0075 Å) are approximately perpendic-ular to one another, with a dihedral angle of 80.9 (5)° between them. The benzene ring is inclined to the mean planes of the two indole ring systems by 76.1 (3) and 78.3 (4)°. Weak intra-molecular C-H⋯π inter-actions affect the mol-ecular conformation. In the crystal, pairs of N-H⋯O hydrogen bonds link the mol-ecules into inversion dimers which are further linked into supra-molecular chains by N-H⋯O hydrogen bonds and short Cl-Cl contacts.

Crystal structure of diethyl 3,3'-[(4-nitro-phen-yl)methyl-ene]bis-(1H-indole-2-carboxyl-ate).

In the title compound, C29H25N3O6, the mean planes of the two indole ring systems (r.m.s. deviations = 0.0115 and 0.0082 Å) are approximately perpendic-ular to one another, making a dihedral angle of 89.7 (5)°; the benzene ring is twisted with respect to the two indole ring systems by 52.6 (4) and 88.2 (3)°. In the crystal, pairs of N-H⋯O hydrogen bonds link the mol-ecules into the inversion dimers, which are further linked into supra-molecular chains along the b-axis direction. Weak C-H⋯O hydrogen bonds and C-H⋯π inter-actions are also observed in the crystal.

Crystal structure of diethyl 3,3'-[(2-fluoro-phen-yl)methyl-idene]bis-(1H-indole-2-carboxyl-ate).

In the title compound, C29H25FN2O4, the mean planes of the two indole ring systems (r.m.s. deviations = 0.1392 and 0.0115 Å) are approximately perpendicular to one another, subtending a dihedral angle of 86.0 (5)°; the benzene ring is twisted with respect to the mean planes of the two indole ring systems by 83.3 (2) and 88.1 (4)°, respectively. In the crystal, pairs of N-H⋯O hydrogen bonds link the mol-ecules into centrosymmetric dimers, which are further linked by N-H⋯O hydrogen bonds into supra-molecular chains propagating along the [101] direction.

Crystal structure of dimethyl 3,3'-[(4-fluoro-phen-yl)methyl-ene]bis-(1H-indole-2-carboxyl-ate).

In the title compound, C27H21FN2O4, the mean planes of the indole ring systems (r.m.s. deviations = 0.0263 and 0.0160 Å) are approximately perpendic-ular to one another, making a dihedral angle of 84.0 (5)°; the fluoro-benzene ring is twisted with respect to the mean planes of the two indole ring systems at 89.5 (5) and 84.6 (3)°. In the crystal, pairs of N-H⋯O hydrogen bonds link the mol-ecules into inversion dimers, which are further linked by N-H⋯O hydrogen bonds into supra-molecular chains propagated along the b-axis direction. Weak C-H⋯π inter-actions are observed between neighbouring chains.

Crystal structure of dimethyl 3,3'-[(4-chloro-phen-yl)methyl-ene]bis-(1H-indole-2-carboxyl-ate).

In the title compound, C27H21ClN2O4, the mean planes of the two indole ring systems (r.m.s. deviations = 0.021 and 0.024 Å) are approximately perpendicular to one another, with a dihedral angle of 79.54 (12)°. The benzene ring is twisted with respect to the mean planes of the two indole ring systems at angles of 80.14 (15) and 86.30 (15)°. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds, forming inversion dimers with an R (2) 2(18) ring motif. The dimers are linked by a further N-H⋯O hydrogen bond, forming chains along [100]. There are intra- and inter-molecular C-H⋯π inter-actions present, the latter linking the chains to form a three-dimensional supra-molecular structure.

Crystal structure of dimethyl 3,3'-[(3-nitro-phen-yl)methyl-ene]bis-(1H-indole-2-carboxyl-ate) ethanol monosolvate.

In the title compound, C27H21N3O6·C2H5OH, the indole ring systems are approximately perpendicular to each other, with a dihedral angle of 89.3 (5)°; the plane of the benzene ring is oriented with respect to the indole ring systems at 49.9 (5) and 73.4 (3)°. In the crystal, mol-ecules are linked by N-H⋯O and O-H⋯O hydrogen bonds and weak C-H⋯π inter-actions into a three-dimensional supra-molecular architecture. A void of 33.0 (7) Å(3) is observed in the crystal structure. The solvent ethanol molecule acts as a donor, forming an O-H⋯O hydrogen bond, reinforcing the framework structure.

2-(1-Benzo-thio-phen-2-yl)-4H-1,3,4-oxa-diazin-5(6H)-one.

In the title compound, C11H8N2O2S, the oxadiazinone ring is nearly planar [maximum deviation = 0.016 (4) Å], and is approximately coplanar with the benzo-thio-phene ring system [dihedral angle = 3.1 (5)°]. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds, forming chains running along the b-axis direction.

Crystal structure of dimethyl 3,3'-[(3-fluoro-phenyl)methyl-ene]bis-(1H-indole-2-carboxyl-ate).

In the title compound, C27H21FN2O4, the mean planes of the two indole ring systems (r.m.s. deviations = 0.0166 and 0.0086 Å) are approximately perpendic-ular to one another, making a dihedral angle of 87.8 (5)°; the fluorobenzene ring is twisted with respect to the mean planes of the two indole ring systems at 82.7 (5) and 85.5 (3)°. In the crystal, pairs of N-H⋯O hydrogen bonds link the mol-ecules into the inversion dimers, which are further linked by N-H⋯O hydrogen bonds into supra-molecular chains propagating along the b-axis direction. Weak C-H⋯π inter-actions are observed between neighbouring chains.

Dimethyl 3,3'-(phenyl-methyl-ene)bis-(1H-indole-2-carboxyl-ate).

In the title compound, C27H22N2O4, the two indole ring systems are approximately perpendicular to each other, with a dihedral angle of 84.5 (5)° between their planes; the benzene ring is twisted with respect to the two indole ring systems at angles of 78.5 (5) and 86.5 (3)°. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds, weak C-H⋯O and C-H⋯N hydrogen bonds, and C-H⋯π inter-actions into a three-dimensional supra-molecular architecture.

3-Chloro-2,4,5-trifluoro-benzoic acid.

The title compound, C7H2ClF3O2, was prepared by the chlorination of 3-amino-2,4,5-trifluoro-benzoic acid. The carboxyl group is twisted relative to the benzene ring by 6.8 (1)°. In the crystal, pairs of O-H⋯O hydrogen bonds link mol-ecules into typical centrosymmetric carb-oxy-lic acid dimers. These dimers are arranged into sheets parallel to (-103).

Diethyl 3,3'-(phenyl-methyl-ene)bis-(1H-indole-2-carboxyl-ate).

In the title compound, C(29)H(26)N(2)O(4), the benzene ring is twisted by 73.5 (5) and 84.9 (3)° with respect to the mean planes of the two indole ring systems; the mean planes of the indole ring systems are oriented at a dihedral angle of 82.0 (5)°. In the crystal, mol-ecules are linked by pairs of N-H⋯O hydrogen bonds into chains.

N-[(2S)-2-Chloro-propano-yl]glycine.

The title compound, C(5)H(8)ClNO(3), was prepared by the nucleophilic substitution reaction of (2S)-2-chloro-propanoyl chloride with glycine. The acetate group forms a dihedral angle of 84.6 (1)° with the mean plane of the C-NH-C=O fragment. In the crystal, the molecules are linked by N-H⋯O and O-H⋯O hydrogen bonds, generating a three-dimensional network, which consolidates the crystal packing.

N-[4-(4-Fluoro-phen-yl)-5-hy-droxy-methyl-6-isopropyl-pyrimidin-2-yl]-N-methyl-methane-sulfonamide.

In the title compound, C(16)H(20)FN(3)O(3)S, the pyrimidine and benzene rings are oriented at a dihedral angle of 38.8 (3)°. An intra-molecular C-H⋯O hydrogen bond occurs. The crystal structure is stabilized by O-H⋯N hydrogen bonds. In addition, C-H⋯O inter-actions are also present.

1-Butyl-3-(1-naphtho-yl)-1H-indole.

In the title mol-ecule, C(23)H(21)NO, the dihedral angle between the planes of the indole ring and naphthalene ring system is 68.8 (5)°.