Photoluminescent Ozone Sensor with Enhanced Sensitivity by Using CdSe/ZnS Quantum Dots Modified with Gold and Platinum

Abstract

We report photoluminescence-based ozone sensing using composite films composed of gold or platinum and red-emitting CdSe/ZnS core-shell quantum dots. The sensing efficiency of quantum dots is enhanced by the addition of noble metals. The composite films undergo reversible changes in photoluminescence intensity (measured at excitation/emission wavelengths of 365/652-659 nm) in the presence of ppm levels of ozone in air at 25°C and at atmospheric pressure. The sensitivity of the composite films does not saturate with ozone in the 0.5-200 ppm concentration range. When compared with a quantum dot-only film, the composite films show higher sensitivities to 0.5 ppm ozone of 27% (gold) and 43% (platinum). When compared with a quantum dot-only film, the photoluminescence of the gold-or platinum-palladium alloy-based film recovers faster after the removal of ozone in the surrounding atmosphere. Thus, platinum-or gold-conjugated quantum-dot films form sensor modules for the reversible and highly sensitivie detection of ozone under the tested ambient conditions.

Reversible sensing of nitrogen dioxide using photoluminescent CdSe/ZnS quantum dots and enhanced response by combination with noble metals

“…Thus, the SEM observation confirmed the particulate structure of the samples suggested by atomic force microscopy (AFM). 23) Figures 2(a)2(d) show SEM images of the QD-only film, Au-QD composite film, Pt-QD composite film, and Pt-Pd-QD composite film on a glass substrate, respectively. The bright part in the SEM images corresponds to the QD aggregates, while the dark part corresponds to gaps between the QD aggregates in the films.…”

“…These morphological features of the films were consistent with the results seen with AFM. 23) The sizes of QD aggregates in the films are considered to reflect the binding affinity of QD for each NM and glass substrate.…”

“…QD films with and without NMs were prepared in the following manner. 23) A QD film without any NM was prepared on a glass plate substrate (18 © 18 © 0.120.17 mm) (Micro Cover Glass, Matsunami Glass) by cast deposition of a decane solution containing homogeneously dispersed red-emitting CdSe/ZnS coreshell QDs (1 ¯M) capped with trioctylphosphine (TOP) and trioctylphosphine oxide (TOPO) (Q21721MP, Invitrogen TM , Thermo Fisher Scientific). The cast film was then dried in vacuum at room temperature by a portable aspirator (MDA-15, ULVAC KIKO).…”

“…For PL measurements, the sensor film samples were excited with UV light (wavelength = 365 nm; Spot Cure SP-7, Ushio Lighting) through a quartz optical fiber and an optical band-pass filter for 365 nm (MX0365, Asahi Spectra). 23) Artificial air [N 2 (78.5 vol.%) and O 2 (21.5 vol.%); Japan Fine Products] or artificial air containing 1, 10, and 100 ppm NO 2 (Sumitomo Seika Chemicals) was passed through the quartz optical gas cell at a constant flow rate of 100 mL/min. PL spectra of each film in air with NO 2 were measured after exposure to NO 2 -containing air for 12 min.…”

Enhanced Photothermal Therapy of Breast Cancer via Co-Loading With Autophagy Inhibitor

“…Compared to other surface-modi ed QDs, [38][39][40] PIFC NPs show an evident advantage in the photoluminescence of individual PIFC NPs, since many QDs are encapsulated in every nanoparticle, with relatively strong protection by the large polymer matrix without aggregation. Therefore, PIFC NPs could constitute a great probe for real-time optical cell imaging, which may be extremely useful for diagnosing and treating cancers.…”