Mid-Infrared Plasmonic Platform Based on n-Doped Ge-on-Si: Molecular Sensing with Germanium Nano-Antennas on Si

CMOS-compatible, heavily-doped semiconductor films are very promising for applications in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in this wavelength range. In this work we investigate n-type doped germanium epilayers grown on Si substrates. We design and realize Ge nanoantennas on Si substrates demonstrating the presence of localized plasmon resonances, and exploit them for molecular sensing in the mid-infrared

Acoustically controlled enhancement of molecular sensing to assess oxidative stress in cells

We demonstrate a microfluidic platform for the controlled aggregation of colloidal silver nanoparticles using surface acoustic waves (SAWs), enabling surface enhanced Raman scattering (SERS) analysis of a cell based model for oxidative damage. We show that by varying the frequency and the power of the acoustic energy, it is possible to modulate the aggregation of the colloid within the sample and hence to optimise the SERS analysis

Graphene-coated holey metal films: tunable molecular sensing by surface plasmon resonance

We report on the enhancement of surface plasmon resonances in a holey bidimensional grating of subwavelength size, drilled in a gold thin film coated by a graphene sheet. The enhancement originates from the coupling between charge carriers in graphene and gold surface plasmons. The main plasmon resonance peak is located around 1.5 microns. A lower constraint on the gold-induced doping concentration of graphene is specified and the interest of this architecture for molecular sensing is also highlighted.Comment: 5 pages, 4 figures, Final version. Published in Applied Physics Letter

A photonic crystal cavity-optical fiber tip nanoparticle sensor for biomedical applications

We present a sensor capable of detecting solution-based nanoparticles using an optical fiber tip functionalized with a photonic crystal cavity. When sensor tips are retracted from a nanoparticle solution after being submerged, we find that a combination of convective fluid forces and optically-induced trapping cause an aggregation of nanoparticles to form directly on cavity surfaces. A simple readout of quantum dot photoluminescence coupled to the optical fiber shows that nanoparticle presence and concentration can be detected through modified cavity properties. Our sensor can detect both gold and iron oxide nanoparticles and can be utilized for molecular sensing applications in biomedicine.Comment: 13 pages, 5 figure

Pt (Ⅱ) complexes-based assays for small biomolecules detection in aqueous media

Supramolecular principles such as self-assembly, stimuli-responsiveness, and adaptiveness are widely utilized concepts for developing advanced functional materials. Particularly, they have also significantly impacted analytical science development. In the last two decades, countless supramolecular binders, molecular probes, and chemosensors combined with innovative assays have led to a revolution in molecular sensing and medical diagnostics. Nevertheless, most of these molecular sensing systems are still suffering from either low-binding affinity or low-selectivity or decomposition in complex media such as biofluids, which are the main obstacles limiting their further practical applications. Therefore, the development of new molecular sensing systems that can reach practical requirements is still one of the frontiers in supramolecular chemistry. So far, traditional chromatography-based techniques, e.g., HPLC-MS, are often used for molecular sensing, which are reliable but usually time- and cost-intensive, difficult to do parallel analysis, and require trained personnel. Spectroscopic method-based chemosensors and probes may thus become more suitable for practical applications because of cost-effectiveness, ease of handling, and high-throughput screening ability. Herein, the self-assembling probe (SAP)-based molecular sensing concept is described. By combining molecular reactions and supramolecular interactions, both the high-selective and the high-binding affinity are achieved for the identification and quantification of analytes by utilizing SAP. Beginning with fundamental photophysical knowledge in luminescence, a general introduction of this thesis is given in Chapter 1. As primary candidates for constructing the self-assembling probes (SAPs), transition metal complexes, particularly platinum(II) complexes, are briefly reviewed, including their basic photophysics and applications. In addition, current molecular sensing concepts are introduced and discussed, providing the essential background for the proposed sensing concept in the following text. Small-emitting water-soluble fluorophores are in demand in many application fields, such as fluorescent labels in in-vivo research, indicator dyes in molecular sensing systems, and test cases for theoretical computation studies. In this context, a size-record breaking green-emissive fluorophore 3-hydroxy-isonicotinic aldehyde (HINA, 128 g/mol, λex = 525 nm) is investigated in Chapter 2. Furthermore, HINA also serves as the model case for demonstrating problems that molecular probes face, and it functions as a suitable indicator moiety in the construction of the SAPs. In Chapter 3, the self-assembling probe (SAP)-based molecular sensing concept is described, where time- and spectra-resolved information is observed for the distinction and quantification of target analytes. Due to the combination of the supramolecular and molecular interactions, thirteen tested structural similar analytes can be distinguished by merely using one probe, which overcame the low-selectivity problem of other current molecular sensing concepts. In addition, the potential application of SAPs in human biofluids is explored. As an extension of Chapter 3, Chapter 4 explores the mechanism of the high-selective SAP systems, which is essentially the supramolecular self-assembling of the SAP-analyte conjugates driven by the non-covalent interactions between the adjacent molecules. Therefore, the SAP concept was also applied for chirality sensing as the chiral analyte created a chiral environment and enhanced the chiral signal of the SAP-analyte conjugate. Finally, the conclusion of this thesis is given in Chapter 5. Outlook and suggestions regarding the further investigation of the SAP concepts are included as well

Molecular Sensing by Nanoporous Crystalline Polymers

Chemical sensors are generally based on the integration of suitable sensitive layers and transducing mechanisms. Although inorganic porous materials can be effective, there is significant interest in the use of polymeric materials because of their easy fabrication process, lower costs and mechanical flexibility. However, porous polymeric absorbents are generally amorphous and hence present poor molecular selectivity and undesired changes of mechanical properties as a consequence of large analyte uptake. In this contribution the structure, properties and some possible applications of sensing polymeric films based on nanoporous crystalline phases, which exhibit all identical nanopores, will be reviewed. The main advantages of crystalline nanoporous polymeric materials with respect to their amorphous counterparts are, besides a higher selectivity, the ability to maintain their physical state as well as geometry, even after large guest uptake (up to 10–15 wt%), and the possibility to control guest diffusivity by controlling the orientation of the host polymeric crystalline phase. The final section of the review also describes the ability of suitable polymeric films to act as chirality sensors, i.e., to sense and memorize the presence of non-racemic volatile organic compounds