<s>
A	O
molecular	B-Algorithm
logic	I-Algorithm
gate	I-Algorithm
is	O
a	O
molecule	O
that	O
performs	O
a	O
logical	O
operation	O
based	O
on	O
one	O
or	O
more	O
physical	O
or	O
chemical	O
inputs	O
and	O
a	O
single	O
output	O
.	O
</s>
<s>
Molecular	B-Algorithm
logic	I-Algorithm
gates	I-Algorithm
work	O
with	O
input	O
signals	O
based	O
on	O
chemical	O
processes	O
and	O
with	O
output	O
signals	O
based	O
on	O
spectroscopic	O
phenomena	O
.	O
</s>
<s>
The	O
concept	O
of	O
molecular	B-Algorithm
logic	I-Algorithm
gates	I-Algorithm
,	O
extending	O
the	O
applicability	O
of	O
logic	O
gates	O
to	O
molecules	O
,	O
aims	O
to	O
convert	O
chemical	O
systems	O
into	O
computational	O
units	O
.	O
</s>
<s>
Over	O
the	O
past	O
three	O
decades	O
,	O
the	O
field	O
has	O
evolved	O
to	O
realize	O
several	O
practical	O
applications	O
in	O
molecular	B-Algorithm
electronics	I-Algorithm
,	O
biosensing	O
,	O
DNA	B-Application
computing	I-Application
,	O
nanorobotics	O
,	O
and	O
cell	O
imaging	O
,	O
among	O
others	O
.	O
</s>
<s>
AND	O
,	O
OR	O
,	O
XOR	B-Application
,	O
NAND	O
,	O
NOR	O
,	O
XNOR	O
,	O
and	O
INH	O
are	O
two-input	O
logic	O
gates	O
.	O
</s>
<s>
The	O
AND	O
,	O
OR	O
,	O
and	O
XOR	B-Application
gates	O
are	O
fundamental	O
logic	O
gates	O
,	O
and	O
the	O
NAND	O
,	O
NOR	O
,	O
and	O
XNOR	O
gates	O
are	O
complementary	O
to	O
AND	O
,	O
OR	O
,	O
and	O
XOR	B-Application
gates	O
,	O
respectively	O
.	O
</s>
<s>
Figure	O
1	O
depicts	O
an	O
example	O
of	O
a	O
dual-input	O
molecular	B-Algorithm
logic	I-Algorithm
gate	I-Algorithm
with	O
metal	O
ions	O
as	O
inputs	O
(	O
input	O
"	O
1	O
"	O
)	O
and	O
fluorescence	O
emission	O
as	O
output	O
(	O
output	O
"	O
1	O
"	O
)	O
.	O
</s>
<s>
While	O
a	O
YES	O
molecular	B-Algorithm
logic	I-Algorithm
gate	I-Algorithm
,	O
as	O
described	O
previously	O
,	O
can	O
convert	O
signals	O
from	O
their	O
ionic	O
to	O
photonic	O
forms	O
(	O
hence	O
the	O
term	O
“	O
photoionic	O
”	O
)	O
,	O
they	O
are	O
singular-input-singular-output	O
systems	O
.	O
</s>
<s>
The	O
PET	O
is	O
quenched	O
upon	O
coordination	O
with	O
protons	B-Application
and	O
sodium	O
ions	O
,	O
respectively	O
,	O
for	O
the	O
two	O
receptors	O
,	O
and	O
would	O
lead	O
the	O
anthracene	O
unit	O
to	O
fluoresce	O
.	O
</s>
<s>
The	O
truth	O
table	O
for	O
an	O
AND	O
gate	O
was	O
completely	O
realized	O
as	O
the	O
system	O
would	O
exhibit	O
a	O
fluorescence	O
output	O
only	O
in	O
the	O
presence	O
of	O
both	O
protons	B-Application
and	O
sodium	O
ions	O
in	O
the	O
system	O
.	O
</s>
<s>
The	O
molecular	B-Algorithm
logic	I-Algorithm
gate	I-Algorithm
illustrated	O
in	O
Figure	O
5	O
demonstrates	O
the	O
advancement	O
from	O
redox-fluorescent	O
switches	O
to	O
multi-input	O
logic	O
gates	O
with	O
an	O
electrochemical	O
switch	O
.	O
</s>
<s>
This	O
two-input	O
AND	O
logic	O
gate	O
incorporates	O
a	O
tertiary	O
amine	O
proton	B-Application
receptor	O
and	O
a	O
tetrathiafulvalene	O
redox	O
donor	O
.	O
</s>
<s>
constructed	O
an	O
OR	O
molecular	B-Algorithm
logic	I-Algorithm
gate	I-Algorithm
using	O
an	O
aza-crown	O
ether	O
receptor	O
and	O
sodium	O
and	O
potassium	O
ions	O
as	O
the	O
inputs	O
.	O
</s>
<s>
Fluorescence	O
of	O
the	O
highly-emissive	O
boradiazaindacene	O
(	O
input	O
“	O
1	O
”	O
)	O
was	O
found	O
to	O
be	O
quenched	O
in	O
the	O
presence	O
of	O
either	O
a	O
zinc	B-Application
salt	O
[	O
Zn(II )	O
]	O
or	O
trifluoroacetic	O
acid	O
(	O
TFA	O
)	O
.	O
</s>
<s>
De	O
Silva	O
and	O
McClenaghan	O
designed	O
a	O
proof-of-principle	O
arithmetic	O
device	O
based	O
on	O
molecular	B-Algorithm
logic	I-Algorithm
gates	I-Algorithm
.	O
</s>
<s>
Likewise	O
,	O
addition	O
of	O
protons	B-Application
causes	O
a	O
bathochromic	O
shift	O
(	O
red	O
shift	O
)	O
,	O
and	O
when	O
both	O
cations	O
are	O
in	O
the	O
water	O
,	O
the	O
net	O
result	O
is	O
absorption	O
at	O
the	O
original	O
390	O
nm	O
wavelength	O
.	O
</s>
<s>
This	O
system	O
represents	O
an	O
XNOR	O
logic	O
gate	O
in	O
absorption	O
and	O
an	O
XOR	B-Application
logic	O
gate	O
in	O
transmittance	O
.	O
</s>
<s>
In	O
another	O
XOR	B-Application
logic	O
gate	O
system	O
,	O
the	O
chemistry	O
is	O
based	O
on	O
the	O
pseudorotaxane	B-Algorithm
depicted	O
in	O
Figure	O
11	O
.	O
</s>
<s>
In	O
organic	O
solution	O
the	O
electron-deficient	O
diazapyrenium	O
salt	O
(	O
rod	O
)	O
and	O
the	O
electron-rich	O
2	O
,	O
3-dioxynaphthalene	O
units	O
of	O
the	O
crown	O
ether	O
(	O
ring	O
)	O
self-assemble	O
by	O
formation	O
of	O
a	O
charge	B-Algorithm
transfer	I-Algorithm
complex	I-Algorithm
.	O
</s>
<s>
In	O
compound	O
B	O
in	O
Figure	O
10	O
B	O
,	O
the	O
bottom	O
section	O
contains	O
a	O
tertiary	O
amino	O
group	O
,	O
also	O
capable	O
of	O
binding	O
to	O
protons	B-Application
.	O
</s>
<s>
When	O
both	O
receptors	O
are	O
bound	O
to	O
calcium	O
ions	O
and	O
protons	B-Application
respectively	O
,	O
both	O
PET	O
channels	O
are	O
shut	O
off	O
.	O
</s>
<s>
An	O
enhanced	O
fluorescence	O
signal	O
is	O
observed	O
only	O
in	O
the	O
presence	O
of	O
excess	O
protons	B-Application
,	O
zinc	B-Application
and	O
sodium	O
ions	O
through	O
interactions	O
with	O
their	O
respective	O
amine	O
,	O
phenyldiaminocarboxylate	O
,	O
and	O
crown	O
ether	O
receptors	O
.	O
</s>
<s>
A	O
molecular	B-Algorithm
logic	I-Algorithm
gate	I-Algorithm
can	O
processes	O
modulators	O
much	O
like	O
the	O
setup	O
seen	O
in	O
de	O
Silva	O
’s	O
proof-of-principle	O
,	O
but	O
incorporating	O
different	O
logic	O
gates	O
on	O
the	O
same	O
molecule	O
is	O
challenging	O
.	O
</s>
<s>
When	O
monitored	O
at	O
two	O
different	O
wavelengths	O
,	O
565	O
and	O
660	O
nm	O
,	O
XOR	B-Application
and	O
INHIBIT	O
logic	O
gates	O
operations	O
are	O
realized	O
at	O
the	O
respective	O
wavelengths	O
.	O
</s>
<s>
Over	O
the	O
years	O
,	O
the	O
utility	O
of	O
molecular	B-Algorithm
logic	I-Algorithm
gates	I-Algorithm
has	O
been	O
explored	O
in	O
a	O
wide	O
range	O
of	O
fields	O
such	O
as	O
chemical	O
and	O
biological	O
detection	O
,	O
the	O
pharmaceutical	O
and	O
food	O
industries	O
,	O
and	O
the	O
emerging	O
fields	O
of	O
nanomaterials	O
and	O
chemical	B-Device
computing	I-Device
.	O
</s>
<s>
Wen	O
and	O
coworkers	O
also	O
designed	O
an	O
INHIBIT	O
molecular	B-Algorithm
logic	I-Algorithm
gate	I-Algorithm
with	O
Fe3+	O
and	O
EDTA	O
as	O
the	O
inputs	O
and	O
a	O
fluorescence	O
output	O
for	O
the	O
detection	O
of	O
ferric	O
ions	O
in	O
solutions	O
.	O
</s>
<s>
Heavy	B-Operating_System
metal	I-Operating_System
ions	O
provide	O
a	O
persistent	O
threat	O
to	O
human	O
health	O
because	O
of	O
their	O
inherent	O
toxicity	O
and	O
low	O
degradability	O
.	O
</s>
<s>
The	O
molecule	O
works	O
as	O
a	O
photodynamic	O
agent	O
upon	O
irradiation	O
at	O
660	O
nm	O
under	O
conditions	O
of	O
relatively	O
high	O
sodium	O
and	O
proton	B-Application
ion	O
concentrations	O
by	O
converting	O
triplet	O
oxygen	O
to	O
cytotoxic	O
singlet	O
oxygen	O
.	O
</s>
<s>
The	O
concept	O
of	O
DNA	B-Application
computing	I-Application
came	O
about	O
as	O
a	O
way	O
to	O
address	O
storage	O
density	O
issues	O
because	O
of	O
the	O
exploding	O
volumes	O
of	O
data	O
information	O
.	O
</s>
<s>
Theoretically	O
,	O
a	O
gram	O
of	O
single-stranded	O
DNA	O
is	O
capable	O
of	O
storing	O
over	O
400	O
exabytes	B-Application
(	O
order	O
of	O
1020	O
bytes	B-Application
)	O
of	O
data	O
at	O
a	O
density	O
of	O
two	O
bits	O
per	O
nucleotide	O
.	O
</s>
<s>
Recently	O
,	O
molecular	B-Algorithm
logic	I-Algorithm
gate	I-Algorithm
systems	O
have	O
been	O
utilized	O
in	O
DNA	B-Application
computing	I-Application
models	O
.	O
</s>
<s>
Massey	O
and	O
coworkers	O
constructed	O
photonic	O
DNA	O
molecular	O
logic	O
circuits	O
using	O
cascades	O
of	O
AND	O
,	O
OR	O
,	O
NAND	O
,	O
and	O
NOR	O
molecular	B-Algorithm
logic	I-Algorithm
gates	I-Algorithm
.	O
</s>
<s>
on	O
demonstrating	O
NOT	O
,	O
AND	O
,	O
OR	O
,	O
and	O
XNOR	O
logic	O
systems	O
based	O
on	O
DNA	O
crossover	O
tiles	O
,	O
Bader	O
and	O
co	O
.	O
on	O
manipulating	O
the	O
DNA	O
G-quadruplex	O
structure	O
to	O
realize	O
YES	O
,	O
AND	O
,	O
and	O
OR	O
logic	O
operations	O
,	O
and	O
Chatterjee	O
and	O
coworkers	O
on	O
constructing	O
logic	O
gates	O
using	O
reactive	O
DNA	O
hairpins	O
on	O
DNA	O
origami	O
surfaces	O
are	O
some	O
examples	O
that	O
mark	O
the	O
progress	O
in	O
the	O
field	O
of	O
logic	O
gate-based	O
DNA	B-Application
computing	I-Application
.	O
</s>
<s>
Molecular	B-Algorithm
logic	I-Algorithm
gate	I-Algorithm
systems	O
can	O
theoretically	O
overcome	O
the	O
problems	O
arising	O
when	O
semiconductors	O
approach	O
nano-dimensions	O
.	O
</s>
<s>
Molecular	B-Algorithm
logic	I-Algorithm
gates	I-Algorithm
are	O
more	O
versatile	O
than	O
their	O
silicon	O
counterparts	O
,	O
with	O
phenomena	O
such	O
as	O
superposed	O
logic	O
unavailable	O
to	O
semiconductor	O
electronics	O
.	O
</s>
