Copper (Cu2+) is physiologically essential, but
excessive Cu2+ may cause potential risk to plants and animals
due to the bioaccumulative properties. Hence, sensitive
recognition is crucial to avoid over intake of Cu2+, and visual
recognition is more favored for practical application. In this
work, a dual-emission ratiometric fluorescent nanoprobe was
developed possessing the required intensity ratio, which can
facilitate the sensitive identification of Cu2+ by the naked eye.
The probe hybridizes two fluorescence nanodots (quantum dots
(QDs) and carbon dots (CDs)). Although both of them can be
viable fluorescence probes for metal ion detection, rarely
research has coupled this two different kinds of fluorescence
material in one nanosensor to fabricate a selectively ratiometric
fluorescence probe for intracellular imaging. The red emitting
CdTe/CdS QDs were capped around the silica microsphere to serve as the response signal label, and the blue-emitting CDs,
which is insensitive to the analyte, were covalently attached to the QDs surface to act as the reference signal. This core−satellite
hybrid sphere not only improves the stability and brightness of QDs significantly but also decreases the cytotoxicity toward HeLa
cells tremendously. Moreover, the Cu2+ could quench the QDs emission effectively but have no ability for reduction of the CDs
emission. Accordingly, a simple, efficient, and precise method for tracing Cu2+ was proposed. The increase of Cu2+ concentration
in the series of 0−3 × 10−6 M was in accordance with linearly decrease of the F650/F425 ratio. As for practical application, this
nanosensor was utilized to the ratiometric fluorescence imaging of copper ions in HeLa cells.
Currently, environmental pollution caused by heavy metals
has become a severe problem due to the indestructibility
of these metals in addition to their toxic effects on living
organisms.1 Copper, which is one of the most vital transition
metals to the human body, is physiologically essential in several
aspects, such as bone formation, cellular respiration, and
connective tissue development, and serves as a significant
catalytic cofactor for various metallo-enzymes.2 However, an
excessive amount of copper may exhibit high toxicity and may
cause severe damage to the central nervous system, resulting in
disorders associated with neurodegenerative diseases (e.g.,
Wilson’s and Alzheimer’s diseases).3,4 According to the
guidelines for drinking-water quality of the World Health
Organization (WHO), copper is identified as a “significant
chemical element for health in drinking water.” The
recommended daily allowance of copper suggested by National
Research Council ranges from 1.5 to 3.0 mg for adults, 1.5 to
2.5 mg for children, and 0.4 to 0.6 mg for infants.5,6 Thus, the
identification and measurement of copper ions (Cu2+) in the
environmental matrix and biological fluids have become
increasingly important. During the past 2 decades, a large nu |
